STEP SIX
Optimise decompression
Find the decompression speed which gives best screw stroke and melt cushion consistency. Set a decompression stroke of 5mm.
Check that you still achieve 95-98% fill.
Take sixteeen consecutive mouldings and determine the standard deviation of the weights.
Print out:
Page 21 Dosing Profiles Page 50 Process Statistics
What has happened to the screw stop position?
What is happening to the check ring?
17
STEP SIX RESULTS
Insert actual values in the relevant boxes Weight without holding pressureWeight with holding pressure Percentage fill Standard deviation (16 shots) Melt cushion (mean and range)Dosing time (mean and range)Mean value Rangeminmax %g Screw stop position (mean and range) Injection time (mean and range) Peak injection pressure, P inj. max Injection pressure at changeover, PN press. Changeover stroke 18
STEP SEVEN
Optimise holding pressure profile
Use the Holding Profile page to set a holding pressure profile which ensures a smooth transition from injection to the holding pressure phase and use a high enough pressure to pack the part properly.
Add a step which reduces holding pressure gradually to zero.
Take sixteeen consecutive mouldings and determine the standard deviation of the weights.
Print out:
Page 24 MWE
Page 27 Holding Profile Page 50 Process Statistics
Why do you need a smooth transition from injection to holding pressure?
Why bother to reduce the pressure gradually if the gate has already frozen?
19
STEP SEVEN RESULTS
Insert actual values in the relevant boxes Weight without holding pressureWeight with holding pressure Percentage fill Standard deviation (16 shots) Melt cushion (mean and range)Dosing time (mean and range)Mean value Rangeminmax %g Screw stop position (mean and range) Injection time (mean and range) Peak injection pressure, P inj. max Injection pressure at changeover, PN press. Changeover stroke 20