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TWO-SHOT PRESSURE TRANSDUCER FOR INJECTION MOLDING

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Text of TWO-SHOT PRESSURE TRANSDUCER FOR INJECTION MOLDING

By: Sam Berry and Josh Holcomb
Faculty Mentor: Muralidhar Ghantasala
Industry Mentor: Tony Crespo
OVERVIEW
  Simulation
  Steps Involved
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 - PARTS Cavity Pressure BOM List
Item Vendor Part Number Price Quantity Total C-more EA9 series HMI Automation Direct EA9-T7CL-R $ 499.00 1 499 Click PLC Automation Direct C0-01DD2-D $ 105.00 1 105 Click Analog Module Automation Direct C0-4AD2DA-2 $ 165.00 1 165 Electrical Enclosure McmasterCarr 7865K42 $69.10 1 69.1 Click Output Module Automation Direct C0-04DA-2 $132.00 1 132 Enclosure 10x10x6 Allied Electronics 70147961 $52.41 1 52.41 Terminal Block - Orange Allied Electronics 70330122 $ 2.86 6 17.16 Terminal Block - Blue Allied Electronics 70169238 $ 2.67 6 16.02 Terminal Block - Green Allied Electronics 70169239 $ 8.51 3 25.53 End Cover Allied Electronics 70169221 $ 0.88 2 1.76 End Bracket Allied Electronics 70169103 $ 1.15 2 2.3 Terminal Block Bridge - 2 Allied Electronics 70169212 $ 0.58 5 2.9 Terminal Block Bridge - 5 Allied Electronics 70169215 $ 2.63 4 10.52 Signal 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
pressure.https://na.dmecomp any.com/Catalog/Catalog.asp x?CatalogId=DME&CatalogD
etailId=1128 $ 664.99 3 1994.97
Cavity Pressure Sensor
CatalogDetailId=1128 $ 721.51
Amphenol Plug - Female (Crimp) Allied Electronics 70143474 $ 53.79 5 268.95
Amphenol Plug - Male (Crimp) Allied Electronics 70143472 $ 61.72 5 308.6 Total= 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
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