Strange surface defect when packing ASA with high pressure
Strange surface defect when packing ASA with high pressure
(OP)
This defect happens mostly when working with ASA in molds with satin surface finishes.
When we raise the packing pressure in order to eliminate sink marks there comes a point where marks start to appear in the seen face. The marks appear just where the ejector pins, slides and logos are, and have the same size and shape of the pins, slides, etc.
We have left the logos out of the question because there is a change in the thickness, a very small one though. The pins have been checked and they are flush with the cavity wall.
We thought that maybe it was due to a different heat transfer coefficient of the pins and slides. Changed one of the pins for a copper plug and the defect disappeared in that area.
Anybody knows of the name of this defect? We are puzzled about the origin of this but cannot find any information about it because we do not know the name of it.
I’m sorry I can’t provide photos of this, due to the difficulty of capturing them in a photo and confidentiality issues.
Thanks in advance.
Eduardo
When we raise the packing pressure in order to eliminate sink marks there comes a point where marks start to appear in the seen face. The marks appear just where the ejector pins, slides and logos are, and have the same size and shape of the pins, slides, etc.
We have left the logos out of the question because there is a change in the thickness, a very small one though. The pins have been checked and they are flush with the cavity wall.
We thought that maybe it was due to a different heat transfer coefficient of the pins and slides. Changed one of the pins for a copper plug and the defect disappeared in that area.
Anybody knows of the name of this defect? We are puzzled about the origin of this but cannot find any information about it because we do not know the name of it.
I’m sorry I can’t provide photos of this, due to the difficulty of capturing them in a photo and confidentiality issues.
Thanks in advance.
Eduardo





RE: Strange surface defect when packing ASA with high pressure
Chris DeArmitt
Expert consulting & training
www.phantomplastics.com
RE: Strange surface defect when packing ASA with high pressure
RE: Strange surface defect when packing ASA with high pressure
A light spray of release agent on the ejection side cavity for a few shots may also give clues if it is the above.
H
www.tynevalleyplastics.co.uk
It's ok to soar like an eagle, but weasels don't get sucked into jet engines.
RE: Strange surface defect when packing ASA with high pressure
thank you for your answers.
It is very difficult to capture the defect in a photo as you have to turn the part around to properly see the defect. I'll try to take a photo that I can share.
The marks appear in the front side while the ejectors and slides are on the back side of the part. As if the marks were some kind of "reflection" of the opposite face.
Eduardo
RE: Strange surface defect when packing ASA with high pressure
H
www.tynevalleyplastics.co.uk
It's ok to soar like an eagle, but weasels don't get sucked into jet engines.
RE: Strange surface defect when packing ASA with high pressure
RE: Strange surface defect when packing ASA with high pressure
This is the best photo that I could get, not very good though.
I still have to try heating them. I'll let you know of my findings.
RE: Strange surface defect when packing ASA with high pressure
www.tynevalleyplastics.co.uk
It's ok to soar like an eagle, but weasels don't get sucked into jet engines.
RE: Strange surface defect when packing ASA with high pressure
I think that the ejector stressed can be ruled out. A colleague inspected a part just opening the mold, no ejection, and the marks were already there. :-/
RE: Strange surface defect when packing ASA with high pressure
RE: Strange surface defect when packing ASA with high pressure
www.tynevalleyplastics.co.uk
It's ok to soar like an eagle, but weasels don't get sucked into jet engines.