ME-542 Manufacturing with Non-metallic Materials

VAN DORN H-300 PLUNGER-STYLE INJECTION MOLDING MACHINE

The injection molding process involves rapid pressure filling of a specific mold cavity with a fluid material, followed by the solidification of the material into a product. The process is used for thermoplastics, thermosetting resins, and rubbers. This is a manual for a plunger type Van Dorn large injection molding machine, where Van Dorn is just one of many manufacturers of injection molding machines. Actual pictures are inserted throughout the manual.

Included within this manual is a guide on:

• CARE OF THE MACHINE
• BEFORE OPERATION STEPS
• MACHINE ADJUSTMENTS
• HINTS FOR BETTER MOLDING
• MOUNTING MOLDS
• A List of DON'TS
• HYDRAULIC TROUBLE SHOOTING
• SEQUENCE OF OPERATION
• TEST RUN

When operating the Van Dorn Large Injection Molding Machine, located at San Diego State University, College of Engineering, there are a few things that are worth documenting that were discovered while making the machine operate. First one must have a little knowledge between the DIFFERENCES of the two types of injection molding machines, screw and plunger type. Keeping in mind that the Van Dorn is a plunger type.

This particular machine does not require water lines to be hooked up, so when referencing an original manual and it mentions the water lines being connected, it can be ignored.

On the front left of the machine is a panel with hinges that can easily be opened. Within this panel are two switches that need to be tripped, if this is not done the power will not be supplied to the machine. This is not mentioned anywhere in the manual so one must adhere to this procedure.

Lastly, only one person should be operating the machine at any time, it is a very unforgiving machine! One should also be fully aware of the STOP buttons, in case of an emergency.

CARE OF THE MACHINE

LUBRICATION

Hydraulic units are all self-lubricated and require no attention. Strainers on intake line in tank prevent foreign matter from entering the hydraulic system and should be cleaned twice a year. If hydraulic oil should become contaminated, drain tank and system. Flush tank and system with a compatible solvent and clean. Refill to correct level with new Hydraulic oil recommended by Vickers Hydraulic system sheet.

The plunger housing and cylinder platen ways should be lubricated with oil.

The safety door rollers and the cam follower should be kept oiled to insure free operation of the safety door.

Give the entire lubrication system a periodic inspection to insure getting grease to all points. Check should include broken, leaky and clogged lines.

WATER COOLING

Hydraulic oil is cooled by water, circulated through a heat exchanger and controlled with a globe valve on the outlet line using sufficient water to keep oil temperature within oil manufacturer's limits.

Shut off cocks are installed to control water to injection plunger and heater collar.

HYDRAULIC SYSTEM RESERVOIR

The reservoir on all Van Dorn Injection Molding Machines is of sufficient capacity to insure trouble free operation. The tank interior is coated with a glyptol oil resistant paint to prevent scale or other foreign matter from tank to contaminate oil.

The reservoir should be filled to high mark on oil level gage with a high quality hydraulic oil of the M.S. (Maximum Severity) type. Viscosity range 220 to 275 S.S. U. @ 100 F. (Sinclair Rubilene HD-10w) or (Mobil D.T.E. Medium hydraulic turbine oil) or equivalent.

DO NOT USE OLD OR CONTAMINATED FLUIDS OF UNKNOWN QUALITIES.

RESERVOIR CAPACITIES

H-270 - 55 Gallons

H-300 - 55 Gallons

H-400 - 80 Gallons

H-800 - 120 Gallons

The filter for models H-270 and H-300 are located inside the tank, on models H-400 and H-800 the external or Rosean Filter is used.

It is important that these filters are cleaned approximately every week for the first month of operation, once a month for the next three months of operation and after that approximately twice a year.

Be sure that fluid level is maintained and should be checked daily.

The fluid is further protected by a Kebby Tank Trapper Magnet suspended into the oil. This device traps and holds minute ferrous metallic particles that could pass through the filter and cause excessive pump wear. The magnet should be removed twice weekly for the first six weeks of operation and thereafter twice a year.

BEFORE OPERATION STEPS

DIRECTION OF MOTORS ROTATION

Before operating the press, check the direction of rotation of the motor. Push pump "Start" button to start motor and operate pump. The motor should rotate counter-clockwise when viewed from the pump end. A red arrow painted on the motor also indicates correct direction of motor rotation. If the motor runs in the wrong direction change the polarity of any two motor power lines at the disconnect switch.

CAUTION: Running a motor in reverse direction will result in serious damage to the hydraulic pump.

Open plunger speed control and leave die speed control closed. When pump is running in proper direction the full system pressure will be indicated on gauge. Be sure pump rotates in direction indicated by arrows on pump. Pump can be immediately ruined by running in either direction without oil and can also be ruined by running in the wrong direction with oil. WARNING - jog motor as little as possible to determine pump direction.

WATER SUPPLY

Water supply averages three to six gallons per minute depending on seasons., working conditions and temperatures of supply.

OIL SUPPLY

Hydraulic systems require a very high grade hydraulic oil capable of withstanding severe conditions and long service.

Oil level gage on front of machine indicates oil levels and should never be allowed to drop below LOWER level. When machine is operated oil level will drop

from UPPER level as oil is required to fill system.

MACHINE ADJUSTMENTS

1. Adjusting link end

SHORTENING MOLD STROKE

A stroke shortening arrangement is located at the end of mold cylinder comprising a

screw adjustment and yoke.

MOLD SPACE ADJUSTMENT

This can be done by adjusting toggle mechanism. Loosen clamp on tie bar nuts and

spin nuts back if more space is needed. By use of the hand crank on the left hand

end of machine, linkage can be adjusted as required. Spin tie bar nuts to toggle

platen and make hand tight. Set locking clamps on nuts.

2. Adjusting Injection End

NOZZLE ADJUSTMENT

Nozzle positioning control lever on front of machine moves injection housing in

either direction. Bring nozzle against sprue bushing as lightly as possible, to avoid

damage to contacting parts, by jogging control lever. Leave control lever open

during machine operation as pressure to cylinder is required during each shot to

keep heater nozzle against its seat when injecting plastic.

HINTS FOR BETTER MOLDING

VOLUMETRIC FEED

A yoke fastened to two supporting rods has passing through it a threaded rod

coming from the feed piston. The amount the feed piston can travel forward is

controlled by a stop dog on the threaded rod. To increase quantity of material into

heating cylinder move by screwing stop dog away from cylinder and to decrease,

move dog nearer to cylinder.

Between the feed cylinder and hopper, a slide controls the opening through which

material flows. This slide can be used to control amount of flow and will shut off

flow entirely so that material may be changed.

An adjustable dam at the front of feed cylinder should be adjusted to control or

shut off material, particularly when material is changed from virgin to reground material. Reground material has a greater tendency to "pack" and can jam the feed piston.

HEATING CYLINDER

Heat to plasticize thermoplastic material is furnished with electrical resistance elements around the heating cylinder and is controlled automatically with pyrometers in control panel. Thermocouples are connected to the pyrometers which control electrical circuits as heat is required. The pyrometers maintain temperatures and are adjustable to narrow margins.

Three groups of heating elements "Front heater", "Center heater", and "Rear heater" are each controlled with its own pyrometer. Two groups on H-300 and H-270 presses "Front Zone" and "Rear Zone".

Specialized temperature control is possible for each zone and should be added to provide the best plasticizing combination of plastic material, mold design, etc. Your material supplier will give you temperature and other information pertinent to the material you are to use.

Efficiency of a new "first-time-mold" can best be obtained by first setting the three zones to a temperature just above plasticizing temperature of material. Allow heater to reach temperature setting before feeding in material. Expel contaminated material and bring heater nozzle up against mold for several trial shots to indicate condition of molded product.

Increase "Front heater" heat by increments until maximum quality and cycle are obtained. Repeat with "Center heater", then with "Rear heater" until best performance and quality are obtained.

For nozzle replacement, use a box wrench on hex, giving a sharp blow to wrench handle to loosen it. When installing a nozzle, make sure the threads in heater and on nozzle are clean, dry and free of marks or nicks that will prevent seats from making a perfect seal. Use suitable lubricant on threads. Several commercial preparations are on the market for this type of condition, one of them being FELPRO. Do not use oil or grease as the heat will cause it to burn out. Any difficulty experienced other than above, the assembly should be returned to the factory.

FLASHING - CAUSES

1. Temperature too high; 2. Injection pressure too high; 3. Mold not properly vented; 4. Locking pressure insufficient; 5. Mold faces not parallel.

Adjust machine or heat controllers for flashing except venting which must be corrected by mold maker. An indication of improper venting is repeated flashing at one cavity while another fails to fill.

FEED-AMOUNT

Too much material fed into the heater will not cause flash, other conditions being right. Feed adjustment is provided that "shots" of various amounts can be produced under uniform conditions. "Packing" of plunger indicates too much feed. This is the difference between when plunger stops injecting plastic and its "bottom" position. Molding is usually done with a 1/8" to 1/4" "Pack" and feed adjustments should be regulated to keep within these limits. If weightfeeder is used see proper instructions.

FILL-FAILURE OF MOLD

Heater temperature too low. Injection pressure too low or injection interval too short. Mold not properly vented.

TEMPERATURES

Temperature of material affects of molding. The higher the temperature, the greater the plasticity, the easier it becomes to mold, but takes more time to cool in mold. Therefore, keep temperature as low as permissible for good molding practice. If material is forced rapidly through heater, more heat is required to plasticize it.

INJECTION or BOOSTER PRESSURE

This occurs when the Booster Timer is running and pressure is determined by setting the booster pressure valve located on front of machine.

COOLING

This system takes off excessive heat from heater collar, plunger, oil cooler and mold when required. Drain lines should be warm to the touch. If they are cold too much water is being used.

MOUNTING MOLDS

The 4" hole in ring located in the stationary mold platen is accurately bored to locate a mold correctly. The H-270 has a 2" dia. locating ring. A corresponding boss or spree bushing mast fit this hole. The sprue bushing must have a concave radius corresponding to the radius of the nozzle and is to be such that a leak proof joint will be formed to prevent leakage of hot plastic under high pressure.

Ejection of parts from the mold is accomplished by means of one or more rods incorporated in the mold which hits against the fixed ejector platen when mold-opens. Drawing also gives dimensions from the face of movable mold platen to ejector platen when in "OPEN" position and size and location of holes drilled in movable mold platen. Ejection of molded parts should start before platen reaches the "OPEN" position. Design of mold determines exact amount.

To avoid damage to mold, heater nozzle or seat, put machine on "MANUAL" control and move mold platen to back position. DO NOT have machine on "Semi" or "Automatic" cycle as pressure is against spree bashing when injecting plastic and movable mold will move in if trial of action of mold look-up etc. is made.

To obtain correct mold space, adjust toggle mechanism as follows: Loosen clamps

on tie bar nuts and spin nuts back if more space is needed. By use of the hand

crank on the left hand end of machine, linkage should be adjusted to a dimension

slightly more than thickness of' mold. Spin tie bar nuts up to toggle platen. Set locking clamps on nuts. Movable mold platen can be shifted to "OPEN" position for maximum mounting space. Mold can now be installed starting with the stationary half. Insert the four inch diameter sprue in hole In platen and clamp in place. Use screw holes nearest mold for maximum leverage on mold clamps. With stationary half of mold securely mounted, next place movable half on the guiding dowels and put ejector pins into position. Bring movable platen against mold slowly, and clamp in place in same manner as stationary half was mounted.

Check the closing action of toggles which develops little or no locking pressure at this point. Open mold, loosen clamps and tighten tie rod nuts about ten graduations each, making sure it in the same for each nut. Check locking pressure.

Should toggle close promptly, repeat previous routine using about four graduations this time. Locking pressure is a matter of judgment and previous routine should be repeated until required locking pressure is accomplished. WARNING - Be sure to set locking clamps on nuts each time. Parallelism of mold faces can be checked by feelers while mold faces are slightly cracked open. Mold faces out of parallel will set up unequal stresses on the tie bars and links leading to excessive wear and possible breakage.

Water cooling for mold can be had by connecting flexible hose from water source.

Perfectly made molds fill completely and allow the product to be readily ejected. Minor difficulties frequently result because mold perfection is hard to attain. For instance, product sticking in mold so it will not eject; cavities do not fill or wall sections too thin; complicated design is difficult to keep in order; sharp inside corners instead of fillets. All these conditions affect the productivity and allowances must be made.

DON'TS

1. Don't have motor running when working between mold platens. Shut if off.

2. Don't neglect oil leaks. Leaks in high pressure oil lines get worse. Tighten

immediately.

3. Don't try to clear nozzle by heat or pressure if some foreign matter clogs it. Remove nozzle and clean it out.

4. Don't increase unloading valve setting. Excess heating of oil and extra motor overload is the product of increasing unloading valve setting.

5. Don't leave heat on when not using machine. Continue to operate machine with current off until plastic starts to cool.

6. Don't operate machine when hydraulic oil goes over 150 degrees F. Stop machine and investigate. Clogged water line or back pressure in drain line or extra motor load may be reason for too high a temperature.

7. Don't change setting of high pressure relief valve on pump. Maximum allowable pressure is shown on drawing of hydraulic circuit.

8. Don't decide that a bearing is worn if pump starts to make a rattling noise.

The cause may be an air leak in pump gasket or oil intake lines or the oil screens

in tank are clogged.

9. Don't risk injury. Make daily inspection of all safety devices such as safety

door, guide rails, rollers, and cam surfaces which engage limit switches (See Step

21 in TEST RUN).

HYDRAULIC TROUBLE SHOOTING

NOISY PUMP

1) Plugged or dirty filter- Remove and clean.

2) Insufficient oil- Check oil level and add if necessary.

3) Air leak in pump intake line- Using a heavy oil in suitable spouted container, supply to all threaded joints of intake line assembly, one at a time, if noise ceases momentarily the last joint tested should be dismantled, threads checked and re-assembled with a suitable thread seal.

4) Air inclusions in oil- Remove tank cover and check tank drops if they have broken off or have loosened up or for any sharp stream of oil hitting surface of oil, causing it to airiate, tighten or replace lines.

5) Overheated oil- Check oil temperature. Should nor exceed 140 F. Check if sufficient cool water is passing through heat exchanger.

PUMP WEAR

1) Wrong grade of oil- Have oil analyzed by local oil company, follow Vickers recommendation of their bulletin 286-S.

2) Check oil for dirt and fine suspended particles. Replace pump cartridge and clean and flush tank, replace with clean new oil of proper viscosity.

3) Normal pump wear must be expected, and in time pump cartridge will have to be replaced. It is a good practice to have replacement parts of pump on hand.

LOSS OF INJECTION AND CLAMP PRESSURE

1) Check low pressure close limit switch to be sure its roller has cleared operating cam.

2) Check relief valve by inserting gap in port and checking pressure. If pressure is not

indicated, screw setting handle full out allow oil to flush through seat for approximately 15

seconds and then set to proper pressure. If loss of pressure persists and if gage is fluctuating

wildly it indicates dirt on seat of adjusting cone. Remove adjusting portion of valve, check cone

and seat, and replace. If no pressure is indicated, the trouble could be in one of the remote relief

valves. Repeat above operation except use gage in front of machine. We have found that 90%

of loss of pressure is due to dirt on cone and seats on one of the above valves.

LOSS OF CLAMP AND HOLDING PRESSURE, "BOOST" NORMAL

1) This would indicate that low pressure pump is operating properly and that relief valves are

okay. However, the trouble could possibly a broken shaft in a pump. Remove plug in reducing

"TEE" located above pump, the breaks siphoning action in intake line and allows pump and

pump manifold to catch oil that will be in pump and lines. Remove 3/4" line that runs from

pump manifold. Remove (4) hex bolts in head end pump and pull pump forward, check pump shaft. If broken, remove pump and replace or rebuild pump.

CAUTION!

Be sure to replace pipe plug into reducing "TEE" before starting up machine.

OIL LEAK-CYLINDER PACKING

Remove gland cap of cylinder, using one of the packing shims provided with machine, cut an angle from O.D. to I.D. Place over rod and re-assemble gland cap. Do not use more than one shim at a time.

LEAKING FITTINGS

Using proper size wrench pull up hex nut at tubing until tight.

CAUTION!

Do not over tighten.

SEQUENCE OF OPERATION FOR

Model H-270

Model H-300

Model H-400

Model H-800

AUTOMATIC CYCLE

(Machine is OFF. Gate is OPEN. Plunger is BACK.)

1) Turn OPERATION switch to AUTO position;

PLUNGER ADVANCE selector switch to OFF position;

PLUNGER-FORWARD-OFF-REVERSE selector switch to REVERSE position;

MOLD-OPEN-CLOSE selector switch to OPEN position.

2) Depress PUMP START push button.

3) Close SAFETY GATE manually. Cycle starts.

4) Cycle is complete and will automatically repeat itself when MOLD OPEN TIMER times

out.

MANUAL OPERATION

1) Turn OPERATION switch to MANUAL position.

2) Close SAFETY GATE manually.

3) To close mold , turn MOLD SELECTOR SWITCH to CLOSED position.

4) To advance plunger, turn PLUNGER SELECTOR SWITCH to FORWARD position.

5) To retract plunger, turn PLUNGER SELECTOR SWITCH to REVERSE position.

6) To open mold, turn MOLD SELECTOR SWITCH to OPEN position.

GENERAL

A. Plunger Advance

1) In AUTO or SEMI cycle, turn PLUNGER ADVANCE selector to ON position.

2) Cycle will operate as mentioned in AUTO or SEMI cycle.

3) Plunger win remain at this forward position through the rest of the cycle, and the

beginning of the next cycle, up to the point where the plunger advances.

The rest of the cycle will function normally.

NOTE: When the MOLD CLOSE STOP or CORE PULL features are incorporated,

a double solenoid, spring centered valve must be use for the clamp. This caused

slight deviation from our normal operation in one feature of the cycle. Normally

when the safety gate is opened or anytime the MOLD CLOSE SOLENOID is

de-energized, the mold would open immediately. Now with the spring center

solenoid, if the safety gate is opened, or if MOLD CLOSE SOLENOID is de-

energized, the mold will stop and remain in that position.

SEMI CYCLE

1) The sequence is the same as in AUTOMATIC CYCLE except cycle does not repeat until safety gate is opened and closed again.

2) MOLD OPEN TIMER, T4, does not operate.

MANUAL CYCLE

1) Turn OPERATION selector to MANUAL position.

2) MANUAL CORE selector will operate the core.

TEST RUN

The following steps should be adhered to before production is attempted to insure correct operation of all units and me

Step 1. The movable mold platen is in the closed position and the plunger is back when machine leaves factory. The selector knob should be in "closed" position and "Plunger Selector" knob in reversed position. Put cycle selector knob on "Manual" and heater switches "OFF".

Step 2. Turn cooling water supply "ON" to heater housing and hydraulic system cooler.

Step 3. Make sure plunger speed control valve is open. Recheck motor rotation. Check oil temperature, not to be less than 50 degrees and oil must be above lower level.

Step 4. All preceding steps being complete, JOG motor until up to normal speed and allow to run until system is free of air. Pump noise at the start is harmless and is caused by oil rushing into the vacuum created by the pump vanes.

Step 5. After opening mold speed "Control Valve"., move mold platen to "Open" position. Use "Mold" lever on control station. Air in hydraulic system will cause platen to pause temporarily.

Step 6. 1250 P.S.I. H-400, 1800 P.S.I. E-300., (2000 P.S.I. on the H-2706& H-800) should be registered on machine oil pressure gage. Check.

Step 7. Turn heater selector switch "ON". Set pyrometers to about 350 degrees for testing. Continue with next steps until heater reaches testing heat.

Step 8. Adjust mold platen speed to maximum by turning speed control hand-wheel. Stop motor to receive pressure when control hand-wheel becomes difficult to move.

Step 9. When pyrometers have reached 3500 F plunger movement may be tested by shifting selector knob. Note: Dies have to be closed before plunger can be moved. To vary stroke of feed plunger adjust stop dog on feed screw from maximum to minimum. Note operation of hopper feed and action of slide controlling the opening between hopper and feed cylinder.

Step 10. Care of Safety Door - You will note that the mold platen will not move when its control lever is shifted if the safety door or mold platen is open. Observe how the cam on bottom of the safety door operates the limit switch levers as door is closed or opened. One limit switch is underneath and to the right and the other is underneath and to the left of the safety door. Inspect this entire mechanism daily for perfect operation to insure operator's safety. Opening safety door will open mold platen any time during the cycle preventing accidental closing of mold platen when removing product., inspecting or cleaning mold surfaces.

Step 11 Check to ascertain if the heating cylinder is up to the temperature for which pyrometers were set. The electric current should be off and will be indicated by the red lights being off on the pyrometers. Action of the pyrometers can be observed by moving the temperature setting position slightly below that of the temperature indicating needle, thus creating a condition similar to actual operation.

Step 12. For semi-automatic operation, open the safety gate., turn the cycle

selector switch to "SEMI", the mold selector switch to "OPEN", and the plunger

selector switch to "REVERSE". Set the "Plunger Forward" timer and the "MOLD

CLOSE" timer to approximately three seconds each. No time need be put on the

"Booster" timer as during this test run the machine will not be injecting plastic. Close the safety gate to start the cycle. The mold will close., then the plunger will go in and remain in until the "Plunger Forward" timer times out. Plunger will return to out position and mold will remain closed until "Die Close" timer times out. To re-cycle simply open and close safety door.

Step 13. Set the "Mold Open" timer to three seconds. Turn selector switch to "Auto" and the machine will re-cycle automatically.

Step 14. Note the cycle is interrupted when safety gate is opened., and the movable mold platen returns to the "Open" position. Close the safety gate and cycle is re d, Hand control may be switched from automatic or semi-automatic by turning cycle selector to

Step 15. Pre-pack is accomplished by setting the counter t o the required number of strokes, During ""Semi" or "Automatic" operation the plunger will retract in the normal way. On reaching the full "Out" position it will immediately go in again and stop and reverse when it actuates the f d limit switch. This action will repeat for the number of strokes, set on the counter. Pre-pack takes place during the cure position of the cycle so sufficient time must be set on the "Mold Close" timer to allow for the pre-pack strokes.

Step 16. Plunger advance.. Turn "Plunger Advance" switch to "On" position. "Semi" or "Automatic" operation the plunger will retract in the normal way after an injection stroke and immediately advance to the forward limit switch. The plunger will remain in this position until the cycle is completed and the movable platen opens and closes. The plunger will then advance to make an injection stroke and retract the action outlined above.

Step 17. Mold space adjustment is made by releasing the clamps on the tie bar nuts and swinging them out of the way to spin tie bar nuts back. By turning ratchet on left hand end of machine, link assembly may be moved back and forth. When mold space is adjusted spin tie bar nuts up hand tight against the link cylinder platen and be sure to set nut clamps before operating press. Always remove ratchet wrench from pinion before operating press.

Step 18, Inspect the machine for possible leaks in hydraulic., water and lubrication lines which may have developed and tighten with suitable wrenches.

Step 19, Test is completed. Shut down machine by pushing "Pump Stop" button, and "Heater Off" button and close water cooling valve.

The working order and knowledge of the machine and its controls have been acquired with this Test Run.. Machine is ready to operate.

DIFFERENCES

HYDRAULIC TYPE

Injection molding machines were initially of the plunger/torpedo type. They sometimes involve separate plastication (screw) and injection (piston) functions, and are then referred to as "pre-plasticator screw machines."

SCREW TYPE

At the plastication stage, the feed unit operates much as an extruder, melting and homogenizing the material in the screw/barrel system. The screw is allowed to retract, to make room for the molten material in a space at the cylinder head, referred to as the material "reservoir". At the injection stage, the screw is used as a ram for the rapid transfer of the molten material from the reservoir to the cavity between the two halves of the closed mold.

The screw type is the most modern of the two (hydraulic and screw) and is the most widely used.