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Suhas
31st July 2012, 05:54 PM
Hello All,
I am curious to find out how are you optimizing the screw recovery speeds? For example, let us say I am processing Acetal.
Thanks,
Suhas

rickbatey
31st July 2012, 11:02 PM
Suhas,
It depends on a few variables. 1-The cycle time required. 2-The residence time/shot volume between the mold and injection unit. 3-The back pressure I need for this resin/tool combination.
I try to use 6.9 B or 100 psi of back pressure at a minimum. I expect to get the screw charged and decompression finished about five seconds prior to cooling timer expiration. But I also know too slow a screw rotation speed and I will fight a process for no reason.

Rick.

brentb
1st August 2012, 01:38 AM
Hello All,
I am curious to find out how are you optimizing the screw recovery speeds? For example, let us say I am processing Acetal.
Thanks,
Suhas

Well, in general it depends on if the resin being processed is S.C. or amorphous. Then it can get even more specific with the resin and things Rick mentions. Now if you are making closures at a 3 second cycle!!!!

KOM
brent

moldingppm
1st August 2012, 02:07 PM
A lot of times I'll just go by the specs the manufacturer gives me

Suhas
2nd August 2012, 04:55 PM
Thanks guys. Any 'newer' ideas ?
Regards,
Suhas

brentb
3rd August 2012, 02:23 AM
Thanks guys. Any 'newer' ideas ?
Regards,
Suhas

How new do you want? New ideas or good new ideas?
For a really new idea, buy a copy of your book and read pages 108 and 137
Then KOM
brent

Suhas
3rd August 2012, 07:25 AM
Good One Brent! The book is now 'old' :) Need the second edition!
Thanks,
Suhas

pjhall
8th August 2012, 07:30 PM
I set the recovery to be about 3 -5 seconds shorter than cooling time. If the cooling time is very long I will use a screw rotate delay then recover. I would rather have the delay at the beginnig of the cooling time and not at the end. Back pressure varies with material and I like the slowest scew speed possible.

skyhew
9th August 2012, 02:14 AM
Screw speed will very much depends on screw size. Normally I use the "Screw Surface Speed (SSS)" for reference. It is distance of a particular point of the screw traveled per second (mm/sec) to obtain an OPTIMAL MELT for a particular material. “Speed required to get the optimal friction”.

Scientific study has been done for most of the popular polymer grade to obtain best SSS.

I am here to share the table: 5.

Regards,
Sky Hew
skyhew(at)gmail.com