ABS PC cracking after few days assembly
ABS PC cracking after few days assembly
(OP)
Dear All,
We are current have the problem with the plastic cracking issue after few days assembling, we don't know the cause of this issue, attached the some picture, hope some experts can answer my question.
- Plastic we are using is PC/ABS C2950, Brand: Sabic
- Drying material time: 3.5 hrs
- Dry material temperature: 95 degree
- injection machine temperate: 220-240 degree
- Injection pressure: 86, 60,85,70
- Injection speed(mm/s): 28,15,45,25
- injection position (mm): 88, 86.5, 65,0
- Packing pressure: 85
- Packing time: 2
- Back pressure : 15%
- Cooling time (s): 18
If you know any cause and solution, please email me: cwu0518@gmail.com, Thanks for your help in advance!!
Cheers
Cindy





RE: ABS PC cracking after few days assembly
Paul Kuklych
http://www.improve-your-injection-molding.com
RE: ABS PC cracking after few days assembly
Thanks for your quick response.
This is a water proof product, seal with silicon o-ring insert and screw, screw size is M2*4.5, screw head diameter=5.0mm, silicon insert outer diameter 4.5mm, inter diameter 2mm. thickness 1.5mm. We found the plastic got a lot of stress from the screw areas. We are thinking if the silicon insert size is improper with this screw as well.
Attached picture for your reference.
Many thanks for your help in advance.
Cheers
Cindy
RE: ABS PC cracking after few days assembly
Chris DeArmitt PhD FRSC
President
Plastic materials consultant to the Fortune 100
www.phantomplastics.com
RE: ABS PC cracking after few days assembly
If those are pan head screws with a flat underside, is there a proper o-ring gland that contains the o-ring and controls crush on the o-ring? If not, the o-ring might be contacting the inside of the hole and applying what is essentially an internal pressure. To a first order approximation, the o-ring can be treated like an incompressible liquid.
Are you controlling torque during assembly?
Are the cracks consistantly in the same places? Are they at an internal feature like a web or gusset?
Rick Fischer
Principal Engineer
Argonne National Laboratory
RE: ABS PC cracking after few days assembly
I would suspect it's not a weld line either. Position seems wrong for that - I would expect one crack.
I get fed up with getting designs which show countersunk screw holes! And these are from "professional" design houses!
H
www.tynevalleyplastics.co.uk
It's ok to soar like an eagle, but weasels don't get sucked into jet engines.
RE: ABS PC cracking after few days assembly
RE: ABS PC cracking after few days assembly