TWO-SHOT PRESSURE TRANSDUCER FOR INJECTION MOLDING QUALITY CONTROL

By: Sam Berry and Josh Holcomb

Faculty Mentor: Muralidhar Ghantasala

Industry Mentor: Tony Crespo

Sponsor: Summit Polymers Inc. – Plant 18

OVERVIEW

  Current state of art

  Motivation-need for improved quality control

  Present process vs. Proposed solution

  Simulation

  Implementation of Two-Shot Pressure sensor control

  Steps Involved

  Where we stand today

  Project completion-further steps

  Conclusion

CURRENT STATE OF ART

  Basic Plastic Injection Molding consists of five major steps   Step 1. Mold closes   Step 2. Injection Process begins   Step 3. Cooling/Packing of the part  Step 4. Plasticizing the resin  Step 5. Mold opens, ejection of part and

runner  Repeat the process

  During production, the injection unit will stay in place. The injection unit is retracted away from the tool when the machine is not in use.

FULL PRESS VIEW FOR TWO-SHOT KRAUSS MAFFEI WITH ROTARY TABLE

TWO-SHOT PROCESS

  Same process as a traditional plastic injection molding machine except add in an extra plastic injection unit and a rotary table.

  Once the injection process is complete, the mold opens, ejects the finished part and then rotates the live side of the mold 180 ̊, so the bottom cavity will be injected with the second shot.

  The rotary table actuates between 0 ̊ and 180 ̊. It will rotate 180 ̊ clockwise, complete the injection molding process, then it will rotate 180 ̊ counterclockwise.

MOTIVATION-NEED FOR IMPROVED QUALITY CONTROL

  Summit Polymers Inc. – Plant 18 is currently operating a Krauss Maffei Two-Shot press that produces a product for General Motors. This product is assembled into a 2021 Chevrolet Silverado 2500 for the Upper Steering Colum.

  It consists of two materials. The plastic portion is Polypropylene (PPR .0590) and the rubber portion is Ethylene Propylene Diene Monomer (EPDM) that is a Thermoplastic Elastomer (TPE).

  The part is a ‘Shoot-and-Ship’. Once it comes out of the machine, it is packed into a shipping tote and sent to a GM facility for assembly.

§ Summit Polymers Inc. – Plant 18 has received multiple complaints, from GM, about the part not being fully complete (a Short Shot).

WHAT IS A SHORT SHOT

  A “short shot” is when the mold stops short of completely filling the mold cavity, leaving voids or thin areas, and creating a deficient product. These holes are commonly found in very thin areas of the mold or at the edges of the final product – the last places a mold would normally fill.

  Many different factors during the molding process can result in a short shot.   Reduced cavity pressure  Filling speed of injection unit  Shot size   Flow restriction from blocked gates

  Filling speed, Shot size, mold temperature, and barrel temperature are all fixed variables during the molding process. Cavity pressure is not monitored in the current process.

PRESENT PROCESS VS. PROPOSED PROCESS

PRESENT PROCESS VS. PROPOSED PROCESS

  Current process does not monitor the pressure inside of the mold cavities

  The proposed process involves a pressure transducer in each of the four cavities of the mold.   Cavity pressure is measured by placing a strain button sensor (Pressure Transducer) behind

the ejector pins. The force produced on the head of the ejector pin will translate to the pressure transducer.

  The pressure transducer will be able to read live pressure inside of the mold cavity in order to produce a quality part every time.

  The pressure transducers will be wired directly into the HMI (Human Machine Interface) box.   The HMI box will consist of a Programable Logic Controller (PLC), an input/output

module, sensor conditioners, wire terminal blocks, as well as a touch screen display on the outside to view all the data.

CAVITY PRESSURE CURVE IN A GENERAL MOLD

SIMULATION

Mold Flow simulation for the fill time needed to fill the TPE section of the mold cavity.

This simulation shows us the necessary location of where the sensors should be placed inside the mold cavity.

SIMULATIONS

Pressure inside the molding cavity for the TPE section of the mold cavity.

The sensors should be placed in two regions. The end of fill region or in the post gate region.

One sensor will be in each cavity, so the end of fill region will benefit us most for implementation.

IMPLEMENTATION OF TWO-SHOT SENSOR CONTROL

  Have DME sensors (pressure transducers) placed into mold

  Simple sensor junction box for quick connect and disconnect while installing tool into the press

  HMI box built along with the PLC programming done

  Have correct wiring through the rotary table for sensors

  Have power routed from press to HMI box

  Have signal cable routed from robot to HMI box for good part/bad part signal

SENSOR PLACEMENT IN THE MOLD

SENSOR PLACEMENT IN THE MOLD

ROTARY TABLE

STEPS INVOLVED

  Finding the region to place the pressure sensors.

  How to read the sensors correctly and how it will communicate with the press and robot.

  Wiring diagram of the HMI box.

  Where to correctly route wires safely in the press.

  Programming for the sensors to display live pressure values and target pressure values for a complete part.

  Mounting HMI box on press for ease of trouble shooting.

WIRING SCHEMATIC FOR HMI

CLICK PLC

  The Click PLC programming is used for the complete analysis of the pressure transducers signals from inside of the mold cavity. The PLC programming will determine if a good/bad part is produced, and then communicates with the robot to either place the good part on the conveyor belt or to put the bad part in the quality sort bin.

  We are using Click PLC because of its cheaper price and easy ladder programing.   It is compatible with the Whitman Robot and Krauss Maffei Press.  Uses the same programming as the Electronic Bead Board used for the

conveyor belt and Mattech Program for viewing tooling jobs progress.  Open Peripheral input and output selections on press for cavity pressure

monitoring of the PLC to communicate between Press, Robot, and PLC.

PRESSURE TRANSDUCER AND PLC MODULE

DME 500lb pressure transducer. Two different sensors for the length of cable needed to lead the connection point to outside of the tool. There is a 12-inch lead and a 36-inch lead needed for the tool.

Click PLC module that will be used for the sensor monitoring of the system.

COST ANALYSIS - PARTSCavity Pressure BOM List

Item Vendor Part Number Price Quantity TotalC-more EA9 series HMI Automation Direct EA9-T7CL-R $ 499.00 1 499Click PLC Automation Direct C0-01DD2-D $ 105.00 1 105Click Analog Module Automation Direct C0-4AD2DA-2 $ 165.00 1 165Electrical Enclosure McmasterCarr 7865K42 $69.10 1 69.1Click Output Module Automation Direct C0-04DA-2 $132.00 1 132Enclosure 10x10x6 Allied Electronics 70147961 $52.41 1 52.41Terminal Block - Orange Allied Electronics 70330122 $ 2.86 6 17.16Terminal Block - Blue Allied Electronics 70169238 $ 2.67 6 16.02Terminal Block - Green Allied Electronics 70169239 $ 8.51 3 25.53End Cover Allied Electronics 70169221 $ 0.88 2 1.76End Bracket Allied Electronics 70169103 $ 1.15 2 2.3Terminal Block Bridge - 2 Allied Electronics 70169212 $ 0.58 5 2.9Terminal Block Bridge - 5 Allied Electronics 70169215 $ 2.63 4 10.52Signal Conditioner Module Youngblood Automation 1781-7B30-01 $ 240.00 4 960

Signal Conditioner Base Youngblood Automation 1782-7BAS $ 110.57 4 442.28

Cavity Pressure Sensor

DME - See link for correct part number for caivty

pressure.https://na.dmecompany.com/Catalog/Catalog.aspx?CatalogId=DME&CatalogD

etailId=1128 $ 664.99 3 1994.97

Cavity Pressure Sensor

DME - See link for correct part number for caivty pressure.https://na.dmecompany.com/Catalog/Catalog.aspx?CatalogId=DME&

CatalogDetailId=1128$ 721.51

2 1443.02

Amphenol Plug - Female (Crimp) Allied Electronics 70143474 $ 53.79 5 268.95

Amphenol Plug - Male (Crimp) Allied Electronics 70143472 $ 61.72 5 308.6Total= 6516.52

COST ANALYSIS

  Total amount for custom setup is approximately $6500 for all major components.

  RJG total of components would cost approximately $3200 for new sensors and $3700 for computing system Edart.  Approximately $6900 for major components but not including a monitor,

stand, and signal conditioning modules needed.  Total RJG package would cost around $9000 for all components.

WHERE WE STAND TODAY

  Due to pandemic related global supply chain restraints, estimated time of completion is July 1st.

  Installation of components will need to be scheduled around production times.

  Components are designed to be compatible with system for smooth programming.

PROJECT COMPLETION-FURTHER STEPS

  Upon full installation, data will be obtained through daily production.

  Quality tracking will be done over the course of two weeks.

  Trial runs will be performed to analyze best vs. worst products produced.

  Accuracy analysis will be executed.

  Data obtained will be compared to annual data to evaluate improvement.

CONCLUSION

  Analysis of the cavity pressure will allow for molding accurate parts consistently with good quality control, obviating the need for further examination.

  The PLC programming will analyze every part molded and determine if the pressure is within a set tolerance. This will determine if the part will have any defects.

  This will save time, money, and the reputation of Summit Polymers Inc. –Plant 18 with the delivery of quality parts to the customer more consistently.

  From the cost analysis of buy and create, creating a custom set-up would benefit the company in cost savings.

REFERENCES

  https://www.aireplastics.com/basic-injection-molding-process/

  https://www.paulsontraining.com/skillbuilder/

  https://additivemanufacturingindia.blogspot.com/2018/12/embedding-conformal-cooling-channels-in.html?m=0

  https://www.simtec-silicone.com/two-shot-lsr-expertise-and-experience/

  https://www.tech-pol.com/de/bimaterial_spritzguss_techpol.php

  Troubleshooting Short Shot in Plastic Injection Molding - Midstate Mold

ACKNOWLEDGEMENTS

  We would like to thank:  Summit Polymers Inc. – Plant 18 for funding our project  Industry mentor: Tony Crespo  Manufacturing Engineer: Brain Dorman  Tooling Technician: Tony Hudson  Faculty mentor: Muralidhar Ghantasala

DISCUSSION

Any Questions?