Gloss variation

[Paolo]

Hi,

I'm working on a process right now, and we are with a defect in the part. Our gloss is higher than the nominal value. The process was stable but now we have this issue and what it is confusing me is that gloss doesn't come due to surface finish or mold temp (50ºC ). I think it is a burn gloss (if I can call it like this), its like air get between the skin part and surface mold. Is this possible? The part looks good but when we measure the gloss it's a litle higher and our client does not accept as I said before.

btw we have 10mm (20mm/s) decompress after dosing due to drool.

When we clean the mold parts get better again.

Mold Temp. 50ºC both parts
Nozzle Temp . 240ºC
Material: ASA
Inj speed. 30 mm/s
backpressure: 20bar
Screw rotation: 120 rpm

Thank you for your time guys!!

Paolo

[rickbatey]

Paolo what's the mold finish measure? I bet the gloss of the mold steel is too high. Have it reduced to fix issue. ASA mimics the tool finish very well.
Rick.

[Paolo]

Paolo what's the mold finish measure? I bet the gloss of the mold steel is too high. Have it reduced to fix issue. ASA mimics the tool finish very well.
Rick.

Rick,

I can't find the mold finish measure in the 2D draw, the only thing that I can tell you is "Finish : Grain type k31 (VW)" not sure this can help.. but I found out we're having problems relate to gloss from the begining but only a few months ago they noticed better results after cleaning the mold surface.

I think you'are right about the mold finish measure I just don't understand why we get good parts after the cleaning.

Paolo

[rickbatey]

Paolo,
The cleaning of the mold probably removed volatiles left in the mold grain from the melt or the tool isn't being sprayed with mold saver when pulled and properly cleaned when installed in the press prior to start up. I think a mold cleaner like Slide Products Resin remover might work on ASA. You can spray the mold and run parts throwing the next 5-6 shots out. The heat of the resin makes the volatiles stick in the next few molded parts cleaning out the grain. Just be careful when you try this the first time. I used it where I'm at and the tool has large slides in it. I was out so someone else used it, sprayed the mold too heavy, and the slides stuck down!!
Rick.