TABULATED RESULTS
Insert actual values in the relevant boxes
The range value, R, is the maximum minus the minumum, taken from the seven steps.
Melt cushion Dosing time Screw end position Injection time Injection pressure P hyd max Inection pressure PN hydraulic Changeover stroke Standard deviation (16 shots) 1 mean R 2 mean R 3 mean R 4 mean R 5 mean R 6 mean R 7 mean R
Can you see a trend?
Which step had the greatest effect on the consistency of the moulding?
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STEP EIGHT
Optimising the clamp force
Reduce the clamp force by steps of 50 kN (100 kN for machines over 100 tonnes) using the settings far optimised in the seven steps above.
Allow the process to stabilise each time and then weigh five mouldings.
Tabulate your results below and plot a graph of tonnage against part weight.
Does the mould require the expected clamp force?
What are the advantages of running at reduced tonnage?
STEP EIGHT RESULTS
Insert actual values in the relevant boxes
Enter results in XL spreadsheet. Print out graph. Weight 1 Weight 2 Weight 3 Weight 4 Weight 5 Mean weight Clamp force Required clamp force kN 22
STEP NINE
Set injection pressure
Until now the injection pressure has been set to the machine’s maximum value. From the Process Statistcs page it can be seen that the machine does not need all that pressure to fill the mould.
Gradually decrease the set injection pressure until the injection time starts to increase. Increase the pressure again until the previous injection time is established with a consistency of 0.08 s or better – preferably 0.02 to 0.03 s variation.
What is the purpose of limiting the injection pressure?
STEP NINE RESULTS Actual peak injection pressure Set injection pressure bar bar 23
Appendix 1
TYPICAL PROCESS TOLERANCES
Shot-weight deviation Plasticising time Injection time Cycle time Screw position, dosing stop Melt cushion Melt temperature Mould temperature Barrel temperature Feed zone temperature Hot runner temperature Hydraulic oil temperature Room temperature Mould cavity pressure Pressure integral Injection filling pressure Holding pressure Back pressure Filling differences (Balance of fill for each cavity) on multi-cavity tools Mould breathe Change over pressure (Pn Value) Screw surface speed Melt temperature peak value Melt temperature value at changeover 0.05% ± 0.04s ± 0.02s ± 0.5% ± 0.1mm ± 0.1mm ± 2°C ± 1°C ± 1°C ± 1°C ± 1°C ± 1°C ± 2°C ± 3 bar ± 200 ± 1 bar ± 1 bar ± 0.5 bar ± 1% 0.01mm ± 1 bar ± 10mms ± 0.3oC ± 0.3oC -10.1% ± 0.06s ± 0.02s ± 0.5% ± 0.1mm ± 0.1mm ± 2°C ± 1°C ± 1°C ± 2°C ± 2°C ± 1°C ± 2°C ± 4 bar ± 300 ± 2 bar ± 1 bar ± 0.5 bar ± 1% 0.01mm ± 2 bar ± 15mms ± 0.4oC ± 0.4oC -10.2% 0.08s ± 0.04s ± 1% ± 0.2mm ± 0.2mm ± 3°C ± 2°C ± 2°C ± 3°C ± 3°C ± 2°C ± 3°C ± 6 bar ± 600 ± 3 bar ± 1.5 bar ± 1 bar ± 2% 0.02mm ± 3 bar ± 20mms ± 0.5oC ± 0.5oC -10.4% 0.13s ± 0.06s ± 1% ± 0.3mm ± 0.3mm ± 5°C ± 4°C ± 4°C ± 4°C ± 4°C ± 2°C ± 4°C ± 8 bar ± 900 ± 4 bar ± 2 bar ± 1 bar ± 5% 0.04mm ± 4 bar ± 30mms ± 0.6oC ± 0.6oC -1 The achievable part quality is much influenced by the condition of the material processed.
It is important that moisture content, proportion of regrind and proportion of colour (masterbatch) are constant.
Acceptable tolerances of principal injection moulding processing
parameters
Bichler:Abt 9601- May 88 Updated Feb 01
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