Injection Molding EPDM Rubber Insert Molding
Elastimold, Inc.
Albuquerque, New Mexico
Before Using Sensonetics:
"We had a high level of rejects, and had to adjust machine injection pressures from 3-6 times each shift, on each of our DESMA 4-Station Rotary and Lewis Vertical Machines, to control the Fill/Flash Balance to minimize rejects,"
After using Sensonetics Nozzle Pressure Transducers For Melt Pressure Control:
"The machines run without rejects and without adjustments for weeks at a time. We only make about 3 very minor adjustments in 10 weeks. We have installed 15 to date, and will order 50 more units for this plant, plus additional quantities for the Ackettstown, New Jersey and Asian Plants."
Annual Savings: Over $30,000 Per Machine
Pay Back: 1.5 Months
George Havlena
Measuring Pressure Fluctations in the Nozzle Area of a Hydraulic Pressure Transducer Controlled Machine
Machine: 250 Ton Hydraulic Machine with pressure multiplier factor of 10, Operating with a hydraulic Pressure Transducer at 2,000 psi max, for a theoretica; Ppeak-max of 20,000 psi
Monitor: Silicon on Sapphire Nozzle Pressure and Temperature Sensor with Nicolet Process Monitor
Mold: 32 Cavity Cap/Closure Mold, Molding HDPE Resin, 1.5 Grams/Part
Monitored Conditions:
| Shot-to-Shots Monitored: | 4,000 |
| Ppeak/Melt at Nozzle, High Reading: | 14,400 PSI |
| Ppeak/Melt at Nozzle, Low Reading: | 13,560 PSI |
| Variation, Ppeak at Nozzle: | 420 PSi, +/- 3.0% |
| Hold Pressure at Nozzle, High Reading: | 7,710 PSI |
| Hold Pressure at Nozzle Low Reading: | 7,370 PSI |
| Variation, Phold at Nozzle: | 170 PSI, +/- 2.2% |
| Melt Temperature, Max/Min: | 227/225 C |
Conclusions:
This example shows that excessive pressure variations of 420 psi are normally encountered at the nozzle with traditional hydraulic transducer control. This machine can benefit from Silicon on Sapphire Nozzle Melt Pressure Control to 20-30 Psi Accompanied by a significant reduction in rejects with less routine machine adjustments.
Why measuring Nozzle Pressire & Temperature is important:
1. Defines condition and Uniformity of Plastic Melt
2. Basically, Peak and Pack Pressures Control Shot Weight
3. Quality Depends on melt pressure repeatability & Temp Uniformity
4. Hydraulic Pressure is not an indication of Nozzle pressure
5. Barrel Temperatures do not indicate melt temperature
6. Alerts operators to improper plastic molding conditions
7. LVDT Position transducers do not directly control shot weight
8. Best closed loop control method is with Silicon on Sapphire Melt Pressure
Why Sensonetics Silicon on Sapphire Transducers
Pressure Transducers are best:
1. Best Linear accuracy and repeatability, 30-40 psi vs 300-450 psi
2. No Hysteresis, No Dead-Bands, No Ambient Temperature Effects
3. Measures Both Pressure and Temperature in one Melt Penetration
4. No Mold Transducers to Hook-Up for every mold set-up
5. Impervious to wear-out by abrasive fillers
6. Impervious to fatigue >10,000,000 Cycles Flex Life
7. Fast Pressure Response Time, <500 uSEC.
8. Fast Temperature Response, <200 mSEC.
9. Sensonetics contains no hazardous mercury OR NaK
10 Sensonetics is best for ISO-9000 Processes
11 Potential for Zero Rejects, 0.002%, 6-Sigma Shot Weight Control
12 Best Control for "After Dark" Molding Operations
13 Sensonetics Prices Are Lowest on a lifetime
Basis
Requirements for Injection Molding Data Acquisition Systems:
1. Signal Reception of 0-10 vdc
2. Windows Operating System
3. 2-8 channels of Acquisition
4. 1-4 mS Sampling Rate of Melt Pressure
5. 100-500 mS Sampling Rate for Melt Temperature
6. Statistical Data Analysis and SPC
7. Pressure Cycle Plot Every 1-10 Shots
8. Portability for Pressure Side Usage
9. No Special Sensors or Hardware
10. Functionality vs Objectives
Data Acquisition/Injection Machine
Control Systems
| Manufacturer | Op Systems | Signal | Resp Time |
| Allen Bradley | 0-10V | 2 mS | |
| Barber Coleman | 0-33 mV | 2 mS | |
| Cinn-Milacron 486 | 0-10 V | ? | |
| Hunkar Labs | DOS | 0-14.7 mV | ? |
| Mattec | DOS | 0-10 V | ? |
| Nicollet P.E. | Windows | 0-10 V | ? |
| Proshot | Windows | 0-10 V | 2 mS |
| RJG | DOS | 0-5 V | 10 mS |
| Shotscope | Windows | 0-10 V | ? |
| Van Dorn | 0-10 V | 2 mS |
Why Measuring Extrusion Pressure
and
Temperature Is Important:
1. Defines Condition and Uniformity of Plastic Melt
2. Fundamentally, Pressure Controls Output Rate
3. Quality Depends on Melt Pressure & Uniformity
4. Barrel Temperatures Do Not Indicate Melt Temperature
5. Alerts Operators To Unsafe or Improper Conditions
6. Best Closed Loop Control Method Is Silicon On Sapphire Melt Pressure
Why Sensonetics Silicon on Sapphire Diaphragm Transducers Are the Best!
1. Best Accuracy, Linearity and Repeatability
2. No Hystersis, Dead-Bands, No Ambient Temperature Effects
3. Measures Both Pressure & Temperature in a one device
4. Faster Response Time, <100 uSEC, 200 Times Faster
5. Sensonetics has No Pushrods to Stick or Jam
6. One-Piece, all Stainless Steel Construction
7. Sensonetics Is Ideal For ISO-9000 Plants & Processes
8. Potential for CpK = 10 in Dimensional Control
9. Impervious to Wear-out from Abrasive Fillers, Fiber-Glass, Etc.
10. Impervious to Fatigue; >30,000,000 Cycles vs 1,000,000 & Still Going
11. Sensonetics Contains No Hazardous Mercury or NaK Liquids
12. Sensonetics Prices are Competitively priced
13. Sensonetics Pressure Transducer
Cost is lowest on a lifetime basis
The Proper Care of Plastic Melt Pressure Transducers:
1. Always Stop The Machine Before Removing a transducer
2. Always remove a transducers from a hot/warm machine, never from a cold machine to prevent diaphgram displacement >3. Always Clean the Removed Transducer While Hot
4. Clean Transducer with a terry cloth, solvent brass brush
5. Never use wire wheel steel brushes, Salt Baths, Blow Torches, Etc to clean a transducer
6. Clean the machine mounting well after plastic stops to ooze out.
7. It is okay to install transducer into a warm or cold machine
8. Always Clean and Inspect the Mounting Well with the Proper Tools (Even Brand new machines have been known to have improper mounting wells)
9. Blue Machinist's dye must transfer from the 45 degree shoulder, or the transducer is not seated properly
10. Remember a transducer is a delicate instrument, not a bolt!!
11. Keep the protective cover on the tip at all times to prevent tip damage if dropped.
12. Before installing, bench calibrate the transducer using the zero and 80% R-Cal values with the machine's pressure indicators or Controllers
13. Install the transducer using the recommended torque(Usually 40-50 inch-pounds).Do not overtorque and damage the diaphgram.
14. Heat the machine to operating temperature
15. Reset the zero at the operating temperature.
16. Never reset the span when the machine is warm or hot!!!
17. Jog the drive several times to be sure that all the plastic is molten before operating
18. For best accuracy where precision is required, run some plastic through the machine, then stop it and reset zero again, in case the melt temperature is different than the barrel temperature
19. The Transducer and machine is ready to operate
20. Routine re-calibration is not necessary because sapphire diaphragms do not stretch or fatigue like do not stretch do not stretch or fatigue like stainless steel ones