graemeian
17th January 2014, 02:24 PM
I am new to the world of injection molding. I have a Boy 15s that I retrofitted with a PLC. The PLC allowed me to add features such as having a motor spin to release threaded parts. I am using PVC. Between parts, I get about an inch of ooze. My first concern is the nozzle. The bore of the nozzle is large (0.109"). My sprue bushing starts at about 0.15". My machine shot size is 36 cm3. My part is about 14 cm3.
Can I use a smaller nozzle bore? What would be the minimum bore?
I fabricated the die with gearing to unscrew a pair of plastic parts
My parts are perfect but I want to optimize my system.
Having never seen this model of machine in operation, I only have you tube videos for dynamic reference.
I used the original German/English processing schematic to make my steps. I may be doing something wrong. Here are my process steps. Please feel free to comment.
1. Mold is open and an open switch is triggered.
2. Motor spins and unscrews the part.
3. Drop chute is now triggered by hand or by part dropping.
4. Mold closes and close switch is triggered.
5. High pressure clamp is activated.
6. Nozzle is driven into mold and a switch is triggered.
7. Injector cylinder injects about 40% of a shot into mold.
7a. A switch is triggered to let PLC know that the Injector reached about 35%.
8. Injector pressure is held for a few seconds to complete fill.
9. Injector pressure is released.
10. Auger spins and reloads to the point of setting a switch.
11. High pressure clamp is released.
12. Mold opens and nozzle retracts from sprue to return limit switch. (Nozzle retracts about an inch. Any more is wasted material. Any less will build up around the sprue bushing.)
13. After open limit switch on mold and retract limit switch on nozzle carriage are set, ejector motor spins.
Goto #3
Should I add any more steps?
I considered adding a dwell time after #10 to allow for the pressure to relax. I did not see one the original bilingual schematics.
Since the parts are small, I plan to play with the order by injecting the resin and then using the high pressure clamp to "coin" the part.
Since I am using PVC, I have to purge the system with PE after I stop for the day and spray all of the exposed parts with oil. It can take a couple of hours to get the machine flowing with PVC again. Therefore, I do not have time to try a new idea every day.
Without adding a nozzle valve, I am considering machining a 1/16" (1.5mm) bore nozzle out of D2 steel. I could then possibly retract the nozzle only a few mm.
Any thoughts?
Thank you in advance.
Can I use a smaller nozzle bore? What would be the minimum bore?
I fabricated the die with gearing to unscrew a pair of plastic parts
My parts are perfect but I want to optimize my system.
Having never seen this model of machine in operation, I only have you tube videos for dynamic reference.
I used the original German/English processing schematic to make my steps. I may be doing something wrong. Here are my process steps. Please feel free to comment.
1. Mold is open and an open switch is triggered.
2. Motor spins and unscrews the part.
3. Drop chute is now triggered by hand or by part dropping.
4. Mold closes and close switch is triggered.
5. High pressure clamp is activated.
6. Nozzle is driven into mold and a switch is triggered.
7. Injector cylinder injects about 40% of a shot into mold.
7a. A switch is triggered to let PLC know that the Injector reached about 35%.
8. Injector pressure is held for a few seconds to complete fill.
9. Injector pressure is released.
10. Auger spins and reloads to the point of setting a switch.
11. High pressure clamp is released.
12. Mold opens and nozzle retracts from sprue to return limit switch. (Nozzle retracts about an inch. Any more is wasted material. Any less will build up around the sprue bushing.)
13. After open limit switch on mold and retract limit switch on nozzle carriage are set, ejector motor spins.
Goto #3
Should I add any more steps?
I considered adding a dwell time after #10 to allow for the pressure to relax. I did not see one the original bilingual schematics.
Since the parts are small, I plan to play with the order by injecting the resin and then using the high pressure clamp to "coin" the part.
Since I am using PVC, I have to purge the system with PE after I stop for the day and spray all of the exposed parts with oil. It can take a couple of hours to get the machine flowing with PVC again. Therefore, I do not have time to try a new idea every day.
Without adding a nozzle valve, I am considering machining a 1/16" (1.5mm) bore nozzle out of D2 steel. I could then possibly retract the nozzle only a few mm.
Any thoughts?
Thank you in advance.