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Computerized Control of Glass Container Process
COMPUTERIZED CONTROL OF GLASS CONTAINER PROCESS
R.A. DA~Y DALY
H. W. J. CECJLJGIiWELL CROUGHWELL 8~HART CClRPORATIUN CORPORATION El·1HAR: BLOOMFIELD, CCJNNECTICLJT CONNECTICUT
BLOCJXFIE~J,
ABSTRACT
Inspecting for quality Packing for shipment
Computerized control is considered for a machine that forms molten glass into rigid containers. The operation is concerned with two interrelated thermodynamic cycles - parison shaping and container molding. The traditional machine cycle is established and maintained via a mechanical controller; setup and operating adjustments may be made, but the procedure requires "artisan" knowhow. State-of-theart advancements in control technology and equipment now permit automated control in which the glass container forming is considered as a series of thermodynamic events rather than a sequence of mechanical operations. Such automation of glass forming advances the concept of overall glass container process control. INTRODUCTION The manufacture of glass containers is a sequence of thermodynamic events whereby raw materials of the earth are transformed to the glassy state as molded vessels. Control of the events, be it automatic or otherwise, is paramount to the production of quality glassware. The first part of this paper will describe the forming of molten glass into rigid containers on machines with the traditional mechanical controller. The second part will consider computerized control of the forming process. GLASS CONTAINER MANUFACTURE Forty billio~ billion glass containers were produced in the United States during 1972 by plants that operated 24 hours a day, 77 days a week. Today, thousands of tons of raw material will flow into production lines that create their own hostile environment of heat, contaminants and noise. The continuous in-line .. hich are segmented operation tas has sequential stages ·which by purpose and associated equipment and oontrols. controls. The stages of a typioal typical prod'~ction production operation in a glass plant are shown in Figure Fig;~re 1. 3atching Batching of raw materials Charging into furnace 11elti"g liq~id state Melting to liquid Conditioning as to temperature Feedinz as individual glass charges Feeding Formin~ into containers Forming cOutainers Annealing in the lehr
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Forming Stage Forming, the most dynamic stage, is critical in terms of energy exchange, glass handling and cycle time. There is heat transfer from the glass to the molds and reheat within the glass surfaces between molding steps. The various heat profiles are significant to the shaping and handling of the glass. The energy exchanges take place quite rapidly and, so, achieving a desired degree of exchange is a matter of critical timing. Forming in each section of the multi-section forming machine, is accomplished as indicated in Figure 2. The gob is delivered from the feeder and passes down through the loading funnel and into the blank mold. The baffle is brought down onto the funnel, and settle blow air is applied through the baffle to pack the glass down into the finish cavity (top of bottle) formed by the neck ring and plunger. Then the baffle, funnel and plunger are retracted and the baffle brought down again to form (with the blank mold) the molding cavity for the parison. During this time and before counter blow, the glass which was in contact with the plunger (corkage glass) reheats. When adequate corkage reheat has occurred, the counter blow air is turned on to come up past the retracted plunger and blow the glass into the hollow parison shape. After sufficient glass to mold contact, the counter blow is turned off and the baffle and split blank mold are removed from contact with the parison. Opening of the blank mold commences a period of reheat for all the glass except that which is in contact with the neck ring. Reheat continues through the inverting transfer of the parison to the blow r.wld mold and until the final blow air comes on. Before final blow can occur, the split neck ring must open, releasing the parison to the blow mOld, mold, and start its return to the blank station. When the neck ring mechanism is out of the way, the final blow head can move down onto the blow mold which with parison. '.i th the bottom plate, encloses the pari son. Final blow air at the required pressure expands the parison to contact the mold. At the end of the necessary contact period, the final blow is shut off and the out tongs blow head and mold removed so that the take takeout
can move in i n to remove r emove the newly newl y formed bottle from the bottom plate. plate . Opening of the blow b l ow mold commences a period of rere heat and cooling at the end of which wh ich the container container must be rigid enough to be conveyed away on its own base. During this per period, i od , the bottle is carried by takeout tongs to a suspended position over ove r a dead plate for cooling and a nd at a selected time released r eleased to stand on the dead pl plate ate before befor e being transferred to the synchronized conveyor. conveyor .
state of the glass. glass . For example, if the corkage reheat is too short, short , he can lengthen it by moving one button. button . In the case of too short a settle blow, blow , however, he must move 4 buttons and he must move them in a particular order or or he may cause mechamechanisms to collide. collide . Challenge The opportunity for f or advancement in control in glass container co ntainer manufacturing manufacturin g is emphasized by the fact that an average of only 85 percent of o f attempted production is packed and shipped from plants. In accepting the challenge Emhart elected elec ted to start with the most dynamic element in the production sequence, that is, is , the control cont rol of the I.S. Forming Machine. Machine .
Thermodynamic Thermodynami c Functions The sequence described for a machine section can be broken down into thermodynamic functions for the two phases of forming. I. I . Parison Shaping 1. 1.
Loading
2.
blow Settle blow
3. 3.
Corkage reheat
4. 4.
Counter blow
5.
Reheat
CO~TROL DIRECT DIGITAL CONTROL
r ms of direct dire c t digital control devices While many fo forms past , recent advances in the have existed in the past, speed , miniaturization and economy of inherently speed, di g ital controllers have accurate programmable digital approp r iate for a wide variety of appliappli made them appropriate c ati ons. cations. Characteristics There are several functional characteristics of programmable digital controllers which make them applicable to the specific type of control system control . First, First , which is required in glass plant control. tech the wide variety of specialized programming techniques and the availability of standard external devices for operator and process interaction ease effort . And, digital hardware the system design effort. has the ability to retain accurate histories of conditions over long intervals and works with great repeatability . Thus, the digital concon speed and repeatability. troller has the potential for becoming a valuable tool in the task of optimizing the glass container process . process.
11. Container Shaping l. 1.
Final blow
2.
Dead plate cooling
The way in which the machine operator can control var iables is by means of the timing the therrr.al variables cont r ols for the various var ious actions of the section. controls dampIt should be noted that there are adjustable dampers in the cooling air supplies for dead plate and mold cooling. cool i ng . Timing
Focal Point - Forming
Each section of the forming machine has its own mechanical timing drum such as that illustrated 3 . In I n the 21 tracks of the drum are in Figure 3. adjustable On and Off buttons which position related air valves open or closed as the drum section . rotates and thereby time the actions of the section. operator , principally in job setup, setup , To assist the operator, the drum is graduated in 5° increments.
seen , the process for the manufacture As we have seen, of glass gldss containers consists of a series of segsegments . In designing a control system for this ments. process process,, a focal point has been chosen which will provide the greatest economy as a result of autocontrol . The shaping of the container is matic control. subsy stem in the process and, the most dynamic subsystem c ritical control. therefore, requires the most critical Also, economic justification for an alternate cont r ol system is more readily r ead ily evident in the formform control ing machine than in the substantially more stable segments of the process at this time. Expansion to ot her process segments can and will be include other requir e d . Therefore, Therefore , the choice accomplished when required. of control equipment must be made with this future futur e mind . expansion in mind.
Ope ration Operation Operation may be considered to consist of two p r oduction. modes; job setup and production. Job setup involves setting of the controls of the feeder , forming machine and conveyor forehearth, feeder, for the particular container to be made. When timed , synchronized synch r onized and production is the units are timed, on - stream the machine mach i ne operator takes over from the on-stream prosetup crew. The operator commonly maintains proth r ough modification of the feeder duction quality through operation, changes in timing of the machine sections ai r . and adjusting of cooling air.
FOR"1ING t4ACHIlIE CONTROL - TIMING DRUM ALTERNATE FOR~ING t1ACHIIIE The first step of the development of an automatic forming machine control has been the implementation of an alternate to the timing drum. Both a hard wired system and a version employing a digital computer realized. compute r have been realiz ed . The functions of these two systems system s are similar. Basically, Basically , there
Timing changes are usually made because a thermal function is too long or too short for the particular
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are four functional blocks in an I. S. machine mac hine timing control system as a s shown on Figure 4.
time or or setting in the machine mac h ine cycle at which a given switching action takes place is held constant until such operator suc h time as the ope rator changes the setting. The setting Th e control unit is capable capabl e of accepting acc epting sett ing changes while the machine is cycling. cyc l ing .
Sync hron ization: First, there must be a means for f or Synchronization: interrelating the motions mo ti ons of the feeder, fe e de r, forming mac hine, and take-away t ake -away conveyor. conveyor . A unit uni t has been machine, coupled designed which is coupl e d directly dire ctly to the feeder of the forming drive to provide synchronization of fo rmin g Synchromachine to tthe h e supply ooff gglass lass charges. Synchr on izing the conveyor drive to the feeder drive will nizing synchronouss be done as it is now with either the synchronou ele ctr ic motor system or the direct mechanical mec hanical electric drive arrangement.
Special Design: This I. S. timing control control has been dig ital implemented with a specially designed digital electronic circuit. The relationships between the setting storage and the various registers and arithmetic logic units are fixed. The setting storage is alterable, and iiss accessed by the operator via a spec ially designed des i gned panel pane l and hardwired har dwi red circuitry. specially Since, for fo r simple simpl e machine sequencing, sequen cing, the t he desired of the th e unit is known such a design desi gn ade quatefunction of adequately performs per fo r ms the t he tasks of I. S. S . machine timing.
Control Co ntrol Unit: Next, Next , there must be a controller. Thee ccontroller Th ontrol ler receives r ece ives synchronizing signals from generator the pulse pu ls e gene r a t or and produces timing timin g signals to the machine control ddevices. evice s.
Machine Control Contr ol Devices: The machine control dede vices v ices are special electro-pneumatic valve valv e blocks which of air wh ich control the supply of ai r to the various mamachine mec mechanisms hanisms and are entirely compatible compa tible with existing ex ist ing forming f ormin g sections. Direct interfacing int erfacing is controller provided between the cont r oll er and the valve blocks. Operator will Operat or Panel: The operator wi ll be given g iven access acces s to the control contr ol unit via a specially designed de signed operator panel.. In this panel is tthe ope rator panel he very important man machine interface. The operator will derive de rive from it an understanding unders tanding of of the operation ope rati on of the ent entire system. ire sys tem.
Programmable Programmab le Controller: Control ler : In I n programmable prograrrmabl e digital d igi tal controllers co ntroller s the internal transfers trans fers of data are specified by means of a progr program storedd in memory. mean s of am store This programmable pr ogrammable unit also stores the timing timi ng setset i n memory. Operation of an I. S. machine in tings in a simple timing control mode has been achieved ac hieved with this controll controller. Several scheder. Seve ral standard standar d task scheduling techn techniques employed i ques have been emp loyed to t o optimize the control contro l function and has resulted in free proce ssor time without sacrificing fine setting cessor resolution r esolution and the potential for multiple mu lt iple machine control. This free time and the ease of programt he addit ion of features featur es to the ming will allow the addition system at minimal expense. minima l expen se .
Each of the four system components is critical to the machine operation. ma c hine op eration. All have been designed to environment withstand the hostile envi ronment of the glass gl as s plant. plant . The major features feat ures of both the hardwired incorporating system and the one inc orporat ing a programmable programmab le logic unit are ddiscussed iscussed in the following descripdescri pon of the systems sys tem s is described de scribed in t ion. Operati tion. Operation the dis discussion of control panels. cussion of
glasss plant pl ant environment env ironment is i s not suitable for f or the t he The glas s urvival of of sophisticated sophisticat ed electr oni c circuitry. survival electronic The configuration options available opti ons avail able for both types of of units are: a re: 1) to locate l ocate the th e controller con troller at the machine and put it in enclosure; i n a suitable enc l osure ; or 2) to put it in a rroom oom with wi th a controlled control led environment environm e nt in a remote r emote location. While I-Ihile the th e prototype programprogrammable unit is contained in an air conditioned enenclosur e it has pr ovis i on for remote remot e location. l ocat i on . closure provision
Synchronizing Unit
Valve Block
A pu lse generator ocated pulse generator has been designed to be llocated thee feeder thee mechanical feeder at th feed er and coupled to th fe ede r drive apparatus directly. Due to the ssevere evere condition st at the feeder, feeder , the th e pulse ditionss which exi exist generator uses magnetic sensors to count gear generator tee th. The gear t ly driv en by the feeder teeth. gear is direc directly driven at an appropriate spe ed relationship relati onship (e.g. a sixsix speed sec ti on machine would require requ ire a six-to-one six - to- one speed section reduction as the feeder cycle corresponds to the shearing cyclee of one sect section sheari ng cycl ion and the period of the pulse pul se generator generat or cycle must be that of the comcomplete machine). ple t e mach i ne) .
un i t switches power to linear l i near motion mot i on The control control unit solenoi ds in the valve blocks. b l ocks. These solenoi ds vent solenoids solenoids supply supp ly air ai r to the machine's mach ine 's mechanisms. me chan isms. Manual overrides, both mechanical mechani cal and eelectrical, lectric al , are proprovided to allow application appli cation of air to a given mechmech anism. an ism. The solenoid so leno id valve block is mounted mounte d in place of of the existing timing drum actuated va valves. l ves . The speed control devices are identical for fo r both. Control Co ntr ol Panels Panel s
pane l s provide nachine macnlne controls, controls , section The control panels he running controls and timing controls in both tthe hardwired programmable hardwir ed and the pro gr~~abl e controller contrcller designs. desi gns . 'Chr re is i s a separate sepa r at e panel p anel area for each eaC!1 control Th~re segment as shown in Fi Figure gur e 6 for the th e programmable unit. un it.
There are two pulse trains fr om the synchronizer from pulses to the th e controller; con troll er; the timing puls es and a reset re set pul s e. The number of timing pulses generated per pulse. cycle is fi xe d and is i s dete r mined by the degree degr ee of fixed determined desired. signal occurs resolution de sired . The reset signal occu rs once ffor or each forming machine cycle aand nd establishes es tab lishe s the th e zero ze ro point in the cycle.
Xachine Controls: Cc ntrol s: The Main Power switch and a Machine l~aster Emergency Stop button !~a ster Er.1ergency but ton are located in the t he machine panel.. As a safety feature, the machi ne control panel t he solenoid sol en oid drivers dr ivers is put under the power to the operator control ope rator contr ol via this emergency emer gency switch. swi tc!1 . In pn~e r this addition to interrupting the supply of pn~er t s actuation. button notifies the controller of iits wnen this t his signal signa l is received, r ece ived, all outputs are put pu t
Control Cont r ol Unit
The control unit uni t per forms the task of switching performs powe r o- pneumatic valves which in turn tur n powerr to the elect electro-pneumatic me chani sms. The switch air pressure to the machine mechanisms.
220
1. 1.
22.. FUN CTIONAL DIAGRAM FUNCTIONAL DIAGRAM OF OF THE THE FORMATION FORMATION OF OF PARISON PARISON AND AND BOTTLE BOTTLE
STAGES OF OF AA TYPICAL TYPICAL PRODUCTION PRODUCTION OPERATION OPERATION STAGES
'~.H~ III
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INSPECTION INSPECTION
PACKING PACKING
4. Air operating line and valvenameplales A"operalong line and valve numbers
I.S - BLOCK DIAGRAM I.S.. TIMING SYSTEM SYSTEM-BLOCK
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1.5. TIMING CONTROL I.S.
-----1
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FORMING STAGE STAGE FORMING
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in the off condition; the removal of power is a precaution in the event of controller failure. The Machine Emergency Stop affects all the solenoid machine . valves on the machine.
setting must be checked (i.e. (i . e . it cannot exceed 360°). Then an appropriate point in the cycle must be awaited before insertion of the new setting.
Section Running Controls: One Emergency Stop button is provided for each section of the machine. When actuated, this switch performs the same function on the associated section that the Master Emergency Stop performs on the entire machine. Again, power is removed from the solenoids to put the section in a passive state. In addition to the emergency stop facility, the operator is given access to the r~n r~n ning of the individual individual machine sections via Start/ Start / Stop buttons and to the delivery of glass to individindivid ual sections via Delivery Enable buttons. These functions are designed to give the operator a concon venient, semi-automatic semi - automatic means of temporarily stopstop ping a given section for whatever purpose. When the section is stopped, pressing the Start/Stop button puts the control of that section in a Start Up state for two cycles. During these two cycles, control signals are applied app l ied to the solenoid valves and section operation begins, but the gob Delivery Enable is ineffective. This provides two dry cycles to insure synchronization. A cycle is begun when the pulse count reaches the Start/Stop value. If the Start/Stop button is pushed again before the delivery is enabled, the section will stop as soon as the Start/Stop valve is reached. reached . Once two cycles have been completed after starting up, the control of the section goes into a Run state. At this time, the gob delivery may be enabled by pressing the button for that section. If the gob has been enabled, even if it is subsequently disabled, pushpush ing the Start/Stop button while in the Run state causes the control to go to a Shutdown state. In this state, the delivery is disabled automaticalautomatical ly and two cycles are performed to clear the glass out of the machine. When the Start/Stop valve is reached after these two cycles the control signals are no longer changed for that section by the concon mech trol program, and the motions of the section mechcease . anisms cease.
Since, in a multi-section multi - section machine, the various section cycles are phase shifted with respect to one another the setting which the operator requests aqd enters will be relative to a zero reference for that section. This section zero point is related to the pulse generator zero point by a phase angle for each section. The setting is modified by this value as it is read from or entered into the setting table. Thus, the operator can think in terms of similar setting values for the same valves on each section. The operator is given access to the phase angle via the panel to correct for delivery time variations. Setup Run Mode: The setup man may elect an assisassis tance feature by specifying the mode of operation called Setup Run. In this mode, the operator does not enter new settings but rather jogs the existing settings by one unit of resolution at a time. This allows him to gradually change the timing very accurately and quickly, watching the effect on the ware as he does. does . Individual valve settings are jogged to allow the setup man to bring the machine into a well timed condition. A safety feature of the jog function lies in the fact that a seriously erroneous change can not be made (e.g. setting in 60° when 260° is meant). The setup man can have the assistance of jogging and also free to make large changes in settings at job change timp. by specifying the appropriate mode of operation. operation .
Timing Controls: The following is a discussion of the timing control features as they exist in the progr ammable controller. These features are catagocatagoprogrammable rized by the mode of operation which they represent Setup , in the control system. The modes are: I) Setup, character2) Setup Run, and 3) Operator Jog. The characteristics of both the setup and setup run modes in the programmable controller are incorporated in the hardwired controller design. The programmable controller incorporates certain additional operator assistance features which would be difficult to realize economically in the hardwired scheme.
Operator Jog Mode: The distinction of the Operator Jog mode is that the jogging of settings does not effect single mechanical motions. The event number entered specifies instead of a valve number, a group of valve numbers for timing events which occur between thermal functions. Since it is the therther mal intervals that the operator is concerned with, he is thus relieved of the bother of changing all algoof these settings individually. The control algobe rithm has the definition of these relationships between the thermal intervals and timing built in and a jog modifies all of the timing settings for the events associated with a given function. A good example would be the motions which occur between settle blow and counter blow in readying the funnel and baffle for counter blow. There are four timing eVents in this change. change . If the operator wishes to events extend settle blow at the expense of corkage reheat, numb e r he would jog the associated function setting number e ve nt s and all corresponding to these four timing events together . four timing settings would shift together. Special Features: The timing control panel has programseveral additional functions with the programc o ntroller system. system . One is the maintenance mable controller t h ermal of a minimum interval between the various thermal functions. These intervals are entered by the setup man using the Interval Set. When in the Operator Jog mode, changes made to the thermal cor intervals are checked to be certain that the corresponding interval is not violated.
Setup Mode: Settings are displayed by the operator by his specifying the desired section and valve by number. He must specify whether ~e wants the On appro setting or the Off setting by pressing the appropriate button (refer to Figure 6). If a new setting is to be made, it is keyed in and shown in an intermediate display to allow the operator to verify con his entry. The new setting is passed to the controller by pressing a Load button. Various checks and considerations are made automatically before o f the the setting is accepted. First, validity of
A second function which the setup man may use is the Fill feature. At setup time, the setting settingss
222
5. 5. I.S.. TIMING SYSTEM-PICTORIAL I.S SYSTEM - PICTORIAL VIEW
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for one section are transposed to the other machine sections by actuating the Fill button. This means that the setup man need set up only one section via the setting entry procedure in setting up the entire machine. (Note: the hardwired version also incorporates a Fill function) Also, the settings for any section may be read from an external storage medium via a Load button.
of hot end inspection, perhaps even new forming methods will require the careful control of the variety of systems for heat exchange and handling that will always be present in the glass forming process. Typically, one controller will be assigned to each I. S. machine. MUltiple Multiple controller installations may have one additional special controller per furnace which may be assigned other tasks and would be capable of substituting for any other timing system. The supplemental system would perform the various control activities now carried out by separate controllers. The fact that all of the control features share a common origin, will greatly facilitate eventual total system integration. As the level of forming machine performance is improved and when future economic justification allows, the entire process may be brought under a single, multi-dimensional control strategy.
The storing of all the current settings of a particular section is done via a Save button. The settings are put on either paper tape or magnetic cassettes and may, therefore, be directly recalled for future setup of the job. In addition to the tape output, a printer may be connected and used to record all the machine's settings. The storage of operating settings provides a means for correlating performance with operating conditions. An example of the print-out format incorporated in the Emhart programmable controller system is shown in Figure 7.
CONCLUSION
The I. S. machine control systems, as described, are essentially sequencing systems. The design of both systems was done emphasizing compatibility with the glass plant environment and utility to the hot end operator. The features incorporated in the system are those which were considered to be most advantageous to the glass plant. With the programmable controller, additional or different features can be developed and incorporated easily. The digital controller, although essentially a binary device, is not limited to turning signals on and off in response to digital inputs. The field of analog to digital and digital to analog conversion techniques has arrived at the point where the inclusion of these devices in a system does not represent prohibitive expense. Much of the full range of analog signal processing techniques can either be performed by the controller or can be added in conventional ways to the control scheme. On going development of several direct digital control schemes for the I. S. machine is currently underway. In addition, other areas of the process are being considered for the potential economies to the glass plant of putting them under direct digital control. Incorporating these in the overall plant control strategy will replace the separate, isolated analog control loops which exist today.
The forming machine is the focal point of this control scheme for the glass container forming process. Improving the operation of the machine begins by giving the operator a better timing system. Machine sequencing systems have been implemented with both specially designed circuitry, and a programmable controller. The flexibility of the programmable unit allows the addition of operator assistance features and is entirely compatible with the total system concept of overall process control. ACKNOWLEDGEMENT The authors wish to acknowledge the technical assistance of Mr. G. D. Mylchreest of the Central Research and Development Staff of Emhart and Mr. F. Wythe of the Hartford Division's Research and Special Projects group. 7. PRINT- OUT FORMAT I~FCOkn I~FCOkn
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R.A. DA~Y DALY
H. W. J. CECJLJGIiWELL CROUGHWELL 8~HART CClRPORATIUN CORPORATION El·1HAR: BLOOMFIELD, CCJNNECTICLJT CONNECTICUT
BLOCJXFIE~J,
ABSTRACT
Inspecting for quality Packing for shipment
Computerized control is considered for a machine that forms molten glass into rigid containers. The operation is concerned with two interrelated thermodynamic cycles - parison shaping and container molding. The traditional machine cycle is established and maintained via a mechanical controller; setup and operating adjustments may be made, but the procedure requires "artisan" knowhow. State-of-theart advancements in control technology and equipment now permit automated control in which the glass container forming is considered as a series of thermodynamic events rather than a sequence of mechanical operations. Such automation of glass forming advances the concept of overall glass container process control. INTRODUCTION The manufacture of glass containers is a sequence of thermodynamic events whereby raw materials of the earth are transformed to the glassy state as molded vessels. Control of the events, be it automatic or otherwise, is paramount to the production of quality glassware. The first part of this paper will describe the forming of molten glass into rigid containers on machines with the traditional mechanical controller. The second part will consider computerized control of the forming process. GLASS CONTAINER MANUFACTURE Forty billio~ billion glass containers were produced in the United States during 1972 by plants that operated 24 hours a day, 77 days a week. Today, thousands of tons of raw material will flow into production lines that create their own hostile environment of heat, contaminants and noise. The continuous in-line .. hich are segmented operation tas has sequential stages ·which by purpose and associated equipment and oontrols. controls. The stages of a typioal typical prod'~ction production operation in a glass plant are shown in Figure Fig;~re 1. 3atching Batching of raw materials Charging into furnace 11elti"g liq~id state Melting to liquid Conditioning as to temperature Feedinz as individual glass charges Feeding Formin~ into containers Forming cOutainers Annealing in the lehr
218
Forming Stage Forming, the most dynamic stage, is critical in terms of energy exchange, glass handling and cycle time. There is heat transfer from the glass to the molds and reheat within the glass surfaces between molding steps. The various heat profiles are significant to the shaping and handling of the glass. The energy exchanges take place quite rapidly and, so, achieving a desired degree of exchange is a matter of critical timing. Forming in each section of the multi-section forming machine, is accomplished as indicated in Figure 2. The gob is delivered from the feeder and passes down through the loading funnel and into the blank mold. The baffle is brought down onto the funnel, and settle blow air is applied through the baffle to pack the glass down into the finish cavity (top of bottle) formed by the neck ring and plunger. Then the baffle, funnel and plunger are retracted and the baffle brought down again to form (with the blank mold) the molding cavity for the parison. During this time and before counter blow, the glass which was in contact with the plunger (corkage glass) reheats. When adequate corkage reheat has occurred, the counter blow air is turned on to come up past the retracted plunger and blow the glass into the hollow parison shape. After sufficient glass to mold contact, the counter blow is turned off and the baffle and split blank mold are removed from contact with the parison. Opening of the blank mold commences a period of reheat for all the glass except that which is in contact with the neck ring. Reheat continues through the inverting transfer of the parison to the blow r.wld mold and until the final blow air comes on. Before final blow can occur, the split neck ring must open, releasing the parison to the blow mOld, mold, and start its return to the blank station. When the neck ring mechanism is out of the way, the final blow head can move down onto the blow mold which with parison. '.i th the bottom plate, encloses the pari son. Final blow air at the required pressure expands the parison to contact the mold. At the end of the necessary contact period, the final blow is shut off and the out tongs blow head and mold removed so that the take takeout
can move in i n to remove r emove the newly newl y formed bottle from the bottom plate. plate . Opening of the blow b l ow mold commences a period of rere heat and cooling at the end of which wh ich the container container must be rigid enough to be conveyed away on its own base. During this per period, i od , the bottle is carried by takeout tongs to a suspended position over ove r a dead plate for cooling and a nd at a selected time released r eleased to stand on the dead pl plate ate before befor e being transferred to the synchronized conveyor. conveyor .
state of the glass. glass . For example, if the corkage reheat is too short, short , he can lengthen it by moving one button. button . In the case of too short a settle blow, blow , however, he must move 4 buttons and he must move them in a particular order or or he may cause mechamechanisms to collide. collide . Challenge The opportunity for f or advancement in control in glass container co ntainer manufacturing manufacturin g is emphasized by the fact that an average of only 85 percent of o f attempted production is packed and shipped from plants. In accepting the challenge Emhart elected elec ted to start with the most dynamic element in the production sequence, that is, is , the control cont rol of the I.S. Forming Machine. Machine .
Thermodynamic Thermodynami c Functions The sequence described for a machine section can be broken down into thermodynamic functions for the two phases of forming. I. I . Parison Shaping 1. 1.
Loading
2.
blow Settle blow
3. 3.
Corkage reheat
4. 4.
Counter blow
5.
Reheat
CO~TROL DIRECT DIGITAL CONTROL
r ms of direct dire c t digital control devices While many fo forms past , recent advances in the have existed in the past, speed , miniaturization and economy of inherently speed, di g ital controllers have accurate programmable digital approp r iate for a wide variety of appliappli made them appropriate c ati ons. cations. Characteristics There are several functional characteristics of programmable digital controllers which make them applicable to the specific type of control system control . First, First , which is required in glass plant control. tech the wide variety of specialized programming techniques and the availability of standard external devices for operator and process interaction ease effort . And, digital hardware the system design effort. has the ability to retain accurate histories of conditions over long intervals and works with great repeatability . Thus, the digital concon speed and repeatability. troller has the potential for becoming a valuable tool in the task of optimizing the glass container process . process.
11. Container Shaping l. 1.
Final blow
2.
Dead plate cooling
The way in which the machine operator can control var iables is by means of the timing the therrr.al variables cont r ols for the various var ious actions of the section. controls dampIt should be noted that there are adjustable dampers in the cooling air supplies for dead plate and mold cooling. cool i ng . Timing
Focal Point - Forming
Each section of the forming machine has its own mechanical timing drum such as that illustrated 3 . In I n the 21 tracks of the drum are in Figure 3. adjustable On and Off buttons which position related air valves open or closed as the drum section . rotates and thereby time the actions of the section. operator , principally in job setup, setup , To assist the operator, the drum is graduated in 5° increments.
seen , the process for the manufacture As we have seen, of glass gldss containers consists of a series of segsegments . In designing a control system for this ments. process process,, a focal point has been chosen which will provide the greatest economy as a result of autocontrol . The shaping of the container is matic control. subsy stem in the process and, the most dynamic subsystem c ritical control. therefore, requires the most critical Also, economic justification for an alternate cont r ol system is more readily r ead ily evident in the formform control ing machine than in the substantially more stable segments of the process at this time. Expansion to ot her process segments can and will be include other requir e d . Therefore, Therefore , the choice accomplished when required. of control equipment must be made with this future futur e mind . expansion in mind.
Ope ration Operation Operation may be considered to consist of two p r oduction. modes; job setup and production. Job setup involves setting of the controls of the feeder , forming machine and conveyor forehearth, feeder, for the particular container to be made. When timed , synchronized synch r onized and production is the units are timed, on - stream the machine mach i ne operator takes over from the on-stream prosetup crew. The operator commonly maintains proth r ough modification of the feeder duction quality through operation, changes in timing of the machine sections ai r . and adjusting of cooling air.
FOR"1ING t4ACHIlIE CONTROL - TIMING DRUM ALTERNATE FOR~ING t1ACHIIIE The first step of the development of an automatic forming machine control has been the implementation of an alternate to the timing drum. Both a hard wired system and a version employing a digital computer realized. compute r have been realiz ed . The functions of these two systems system s are similar. Basically, Basically , there
Timing changes are usually made because a thermal function is too long or too short for the particular
219
are four functional blocks in an I. S. machine mac hine timing control system as a s shown on Figure 4.
time or or setting in the machine mac h ine cycle at which a given switching action takes place is held constant until such operator suc h time as the ope rator changes the setting. The setting Th e control unit is capable capabl e of accepting acc epting sett ing changes while the machine is cycling. cyc l ing .
Sync hron ization: First, there must be a means for f or Synchronization: interrelating the motions mo ti ons of the feeder, fe e de r, forming mac hine, and take-away t ake -away conveyor. conveyor . A unit uni t has been machine, coupled designed which is coupl e d directly dire ctly to the feeder of the forming drive to provide synchronization of fo rmin g Synchromachine to tthe h e supply ooff gglass lass charges. Synchr on izing the conveyor drive to the feeder drive will nizing synchronouss be done as it is now with either the synchronou ele ctr ic motor system or the direct mechanical mec hanical electric drive arrangement.
Special Design: This I. S. timing control control has been dig ital implemented with a specially designed digital electronic circuit. The relationships between the setting storage and the various registers and arithmetic logic units are fixed. The setting storage is alterable, and iiss accessed by the operator via a spec ially designed des i gned panel pane l and hardwired har dwi red circuitry. specially Since, for fo r simple simpl e machine sequencing, sequen cing, the t he desired of the th e unit is known such a design desi gn ade quatefunction of adequately performs per fo r ms the t he tasks of I. S. S . machine timing.
Control Co ntrol Unit: Next, Next , there must be a controller. Thee ccontroller Th ontrol ler receives r ece ives synchronizing signals from generator the pulse pu ls e gene r a t or and produces timing timin g signals to the machine control ddevices. evice s.
Machine Control Contr ol Devices: The machine control dede vices v ices are special electro-pneumatic valve valv e blocks which of air wh ich control the supply of ai r to the various mamachine mec mechanisms hanisms and are entirely compatible compa tible with existing ex ist ing forming f ormin g sections. Direct interfacing int erfacing is controller provided between the cont r oll er and the valve blocks. Operator will Operat or Panel: The operator wi ll be given g iven access acces s to the control contr ol unit via a specially designed de signed operator panel.. In this panel is tthe ope rator panel he very important man machine interface. The operator will derive de rive from it an understanding unders tanding of of the operation ope rati on of the ent entire system. ire sys tem.
Programmable Programmab le Controller: Control ler : In I n programmable prograrrmabl e digital d igi tal controllers co ntroller s the internal transfers trans fers of data are specified by means of a progr program storedd in memory. mean s of am store This programmable pr ogrammable unit also stores the timing timi ng setset i n memory. Operation of an I. S. machine in tings in a simple timing control mode has been achieved ac hieved with this controll controller. Several scheder. Seve ral standard standar d task scheduling techn techniques employed i ques have been emp loyed to t o optimize the control contro l function and has resulted in free proce ssor time without sacrificing fine setting cessor resolution r esolution and the potential for multiple mu lt iple machine control. This free time and the ease of programt he addit ion of features featur es to the ming will allow the addition system at minimal expense. minima l expen se .
Each of the four system components is critical to the machine operation. ma c hine op eration. All have been designed to environment withstand the hostile envi ronment of the glass gl as s plant. plant . The major features feat ures of both the hardwired incorporating system and the one inc orporat ing a programmable programmab le logic unit are ddiscussed iscussed in the following descripdescri pon of the systems sys tem s is described de scribed in t ion. Operati tion. Operation the dis discussion of control panels. cussion of
glasss plant pl ant environment env ironment is i s not suitable for f or the t he The glas s urvival of of sophisticated sophisticat ed electr oni c circuitry. survival electronic The configuration options available opti ons avail able for both types of of units are: a re: 1) to locate l ocate the th e controller con troller at the machine and put it in enclosure; i n a suitable enc l osure ; or 2) to put it in a rroom oom with wi th a controlled control led environment environm e nt in a remote r emote location. While I-Ihile the th e prototype programprogrammable unit is contained in an air conditioned enenclosur e it has pr ovis i on for remote remot e location. l ocat i on . closure provision
Synchronizing Unit
Valve Block
A pu lse generator ocated pulse generator has been designed to be llocated thee feeder thee mechanical feeder at th feed er and coupled to th fe ede r drive apparatus directly. Due to the ssevere evere condition st at the feeder, feeder , the th e pulse ditionss which exi exist generator uses magnetic sensors to count gear generator tee th. The gear t ly driv en by the feeder teeth. gear is direc directly driven at an appropriate spe ed relationship relati onship (e.g. a sixsix speed sec ti on machine would require requ ire a six-to-one six - to- one speed section reduction as the feeder cycle corresponds to the shearing cyclee of one sect section sheari ng cycl ion and the period of the pulse pul se generator generat or cycle must be that of the comcomplete machine). ple t e mach i ne) .
un i t switches power to linear l i near motion mot i on The control control unit solenoi ds in the valve blocks. b l ocks. These solenoi ds vent solenoids solenoids supply supp ly air ai r to the machine's mach ine 's mechanisms. me chan isms. Manual overrides, both mechanical mechani cal and eelectrical, lectric al , are proprovided to allow application appli cation of air to a given mechmech anism. an ism. The solenoid so leno id valve block is mounted mounte d in place of of the existing timing drum actuated va valves. l ves . The speed control devices are identical for fo r both. Control Co ntr ol Panels Panel s
pane l s provide nachine macnlne controls, controls , section The control panels he running controls and timing controls in both tthe hardwired programmable hardwir ed and the pro gr~~abl e controller contrcller designs. desi gns . 'Chr re is i s a separate sepa r at e panel p anel area for each eaC!1 control Th~re segment as shown in Fi Figure gur e 6 for the th e programmable unit. un it.
There are two pulse trains fr om the synchronizer from pulses to the th e controller; con troll er; the timing puls es and a reset re set pul s e. The number of timing pulses generated per pulse. cycle is fi xe d and is i s dete r mined by the degree degr ee of fixed determined desired. signal occurs resolution de sired . The reset signal occu rs once ffor or each forming machine cycle aand nd establishes es tab lishe s the th e zero ze ro point in the cycle.
Xachine Controls: Cc ntrol s: The Main Power switch and a Machine l~aster Emergency Stop button !~a ster Er.1ergency but ton are located in the t he machine panel.. As a safety feature, the machi ne control panel t he solenoid sol en oid drivers dr ivers is put under the power to the operator control ope rator contr ol via this emergency emer gency switch. swi tc!1 . In pn~e r this addition to interrupting the supply of pn~er t s actuation. button notifies the controller of iits wnen this t his signal signa l is received, r ece ived, all outputs are put pu t
Control Cont r ol Unit
The control unit uni t per forms the task of switching performs powe r o- pneumatic valves which in turn tur n powerr to the elect electro-pneumatic me chani sms. The switch air pressure to the machine mechanisms.
220
1. 1.
22.. FUN CTIONAL DIAGRAM FUNCTIONAL DIAGRAM OF OF THE THE FORMATION FORMATION OF OF PARISON PARISON AND AND BOTTLE BOTTLE
STAGES OF OF AA TYPICAL TYPICAL PRODUCTION PRODUCTION OPERATION OPERATION STAGES
'~.H~ III
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INSPECTION INSPECTION
PACKING PACKING
4. Air operating line and valvenameplales A"operalong line and valve numbers
I.S - BLOCK DIAGRAM I.S.. TIMING SYSTEM SYSTEM-BLOCK
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1.5. TIMING CONTROL I.S.
-----1
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FORMING STAGE STAGE FORMING
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in the off condition; the removal of power is a precaution in the event of controller failure. The Machine Emergency Stop affects all the solenoid machine . valves on the machine.
setting must be checked (i.e. (i . e . it cannot exceed 360°). Then an appropriate point in the cycle must be awaited before insertion of the new setting.
Section Running Controls: One Emergency Stop button is provided for each section of the machine. When actuated, this switch performs the same function on the associated section that the Master Emergency Stop performs on the entire machine. Again, power is removed from the solenoids to put the section in a passive state. In addition to the emergency stop facility, the operator is given access to the r~n r~n ning of the individual individual machine sections via Start/ Start / Stop buttons and to the delivery of glass to individindivid ual sections via Delivery Enable buttons. These functions are designed to give the operator a concon venient, semi-automatic semi - automatic means of temporarily stopstop ping a given section for whatever purpose. When the section is stopped, pressing the Start/Stop button puts the control of that section in a Start Up state for two cycles. During these two cycles, control signals are applied app l ied to the solenoid valves and section operation begins, but the gob Delivery Enable is ineffective. This provides two dry cycles to insure synchronization. A cycle is begun when the pulse count reaches the Start/Stop value. If the Start/Stop button is pushed again before the delivery is enabled, the section will stop as soon as the Start/Stop valve is reached. reached . Once two cycles have been completed after starting up, the control of the section goes into a Run state. At this time, the gob delivery may be enabled by pressing the button for that section. If the gob has been enabled, even if it is subsequently disabled, pushpush ing the Start/Stop button while in the Run state causes the control to go to a Shutdown state. In this state, the delivery is disabled automaticalautomatical ly and two cycles are performed to clear the glass out of the machine. When the Start/Stop valve is reached after these two cycles the control signals are no longer changed for that section by the concon mech trol program, and the motions of the section mechcease . anisms cease.
Since, in a multi-section multi - section machine, the various section cycles are phase shifted with respect to one another the setting which the operator requests aqd enters will be relative to a zero reference for that section. This section zero point is related to the pulse generator zero point by a phase angle for each section. The setting is modified by this value as it is read from or entered into the setting table. Thus, the operator can think in terms of similar setting values for the same valves on each section. The operator is given access to the phase angle via the panel to correct for delivery time variations. Setup Run Mode: The setup man may elect an assisassis tance feature by specifying the mode of operation called Setup Run. In this mode, the operator does not enter new settings but rather jogs the existing settings by one unit of resolution at a time. This allows him to gradually change the timing very accurately and quickly, watching the effect on the ware as he does. does . Individual valve settings are jogged to allow the setup man to bring the machine into a well timed condition. A safety feature of the jog function lies in the fact that a seriously erroneous change can not be made (e.g. setting in 60° when 260° is meant). The setup man can have the assistance of jogging and also free to make large changes in settings at job change timp. by specifying the appropriate mode of operation. operation .
Timing Controls: The following is a discussion of the timing control features as they exist in the progr ammable controller. These features are catagocatagoprogrammable rized by the mode of operation which they represent Setup , in the control system. The modes are: I) Setup, character2) Setup Run, and 3) Operator Jog. The characteristics of both the setup and setup run modes in the programmable controller are incorporated in the hardwired controller design. The programmable controller incorporates certain additional operator assistance features which would be difficult to realize economically in the hardwired scheme.
Operator Jog Mode: The distinction of the Operator Jog mode is that the jogging of settings does not effect single mechanical motions. The event number entered specifies instead of a valve number, a group of valve numbers for timing events which occur between thermal functions. Since it is the therther mal intervals that the operator is concerned with, he is thus relieved of the bother of changing all algoof these settings individually. The control algobe rithm has the definition of these relationships between the thermal intervals and timing built in and a jog modifies all of the timing settings for the events associated with a given function. A good example would be the motions which occur between settle blow and counter blow in readying the funnel and baffle for counter blow. There are four timing eVents in this change. change . If the operator wishes to events extend settle blow at the expense of corkage reheat, numb e r he would jog the associated function setting number e ve nt s and all corresponding to these four timing events together . four timing settings would shift together. Special Features: The timing control panel has programseveral additional functions with the programc o ntroller system. system . One is the maintenance mable controller t h ermal of a minimum interval between the various thermal functions. These intervals are entered by the setup man using the Interval Set. When in the Operator Jog mode, changes made to the thermal cor intervals are checked to be certain that the corresponding interval is not violated.
Setup Mode: Settings are displayed by the operator by his specifying the desired section and valve by number. He must specify whether ~e wants the On appro setting or the Off setting by pressing the appropriate button (refer to Figure 6). If a new setting is to be made, it is keyed in and shown in an intermediate display to allow the operator to verify con his entry. The new setting is passed to the controller by pressing a Load button. Various checks and considerations are made automatically before o f the the setting is accepted. First, validity of
A second function which the setup man may use is the Fill feature. At setup time, the setting settingss
222
5. 5. I.S.. TIMING SYSTEM-PICTORIAL I.S SYSTEM - PICTORIAL VIEW
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for one section are transposed to the other machine sections by actuating the Fill button. This means that the setup man need set up only one section via the setting entry procedure in setting up the entire machine. (Note: the hardwired version also incorporates a Fill function) Also, the settings for any section may be read from an external storage medium via a Load button.
of hot end inspection, perhaps even new forming methods will require the careful control of the variety of systems for heat exchange and handling that will always be present in the glass forming process. Typically, one controller will be assigned to each I. S. machine. MUltiple Multiple controller installations may have one additional special controller per furnace which may be assigned other tasks and would be capable of substituting for any other timing system. The supplemental system would perform the various control activities now carried out by separate controllers. The fact that all of the control features share a common origin, will greatly facilitate eventual total system integration. As the level of forming machine performance is improved and when future economic justification allows, the entire process may be brought under a single, multi-dimensional control strategy.
The storing of all the current settings of a particular section is done via a Save button. The settings are put on either paper tape or magnetic cassettes and may, therefore, be directly recalled for future setup of the job. In addition to the tape output, a printer may be connected and used to record all the machine's settings. The storage of operating settings provides a means for correlating performance with operating conditions. An example of the print-out format incorporated in the Emhart programmable controller system is shown in Figure 7.
CONCLUSION
The I. S. machine control systems, as described, are essentially sequencing systems. The design of both systems was done emphasizing compatibility with the glass plant environment and utility to the hot end operator. The features incorporated in the system are those which were considered to be most advantageous to the glass plant. With the programmable controller, additional or different features can be developed and incorporated easily. The digital controller, although essentially a binary device, is not limited to turning signals on and off in response to digital inputs. The field of analog to digital and digital to analog conversion techniques has arrived at the point where the inclusion of these devices in a system does not represent prohibitive expense. Much of the full range of analog signal processing techniques can either be performed by the controller or can be added in conventional ways to the control scheme. On going development of several direct digital control schemes for the I. S. machine is currently underway. In addition, other areas of the process are being considered for the potential economies to the glass plant of putting them under direct digital control. Incorporating these in the overall plant control strategy will replace the separate, isolated analog control loops which exist today.
The forming machine is the focal point of this control scheme for the glass container forming process. Improving the operation of the machine begins by giving the operator a better timing system. Machine sequencing systems have been implemented with both specially designed circuitry, and a programmable controller. The flexibility of the programmable unit allows the addition of operator assistance features and is entirely compatible with the total system concept of overall process control. ACKNOWLEDGEMENT The authors wish to acknowledge the technical assistance of Mr. G. D. Mylchreest of the Central Research and Development Staff of Emhart and Mr. F. Wythe of the Hartford Division's Research and Special Projects group. 7. PRINT- OUT FORMAT I~FCOkn I~FCOkn
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