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rotate
09-05-2006, 02:48 PM
I'm curious as to how the texture is created on mold for plastic. The fine grain structure looks too detailed for CNC to create. Is it done using some sand blasting technique or is it photo-etching?

Any of you guys make small plastic injection parts at home?

Thanks.

SGW
09-05-2006, 03:24 PM
Not sure in all cases, but on a new product we're coming out with I think it's being done with texture paint on a positive pattern, which is then used to create a negative mold by covering it with some kind of synthetic rubber goop, which is then used as the mold for the actual part.

Or I may have totally misunderstood the process when it was explained to me....

lathehand
09-05-2006, 03:38 PM
I'm curious as to how the texture is created on mold for plastic. The fine grain structure looks too detailed for CNC to create. Is it done using some sand blasting technique or is it photo-etching?

Any of you guys make small plastic injection parts at home?

Thanks.
It is done by photo etching -Wisconsin engraving is our vender. They have sample plaques that show differant patterns at various depths.

SGW
09-05-2006, 03:43 PM
I just went over and talked to our mechanical design engineer. The process I described previously (the rubber mold business) was what was done for our prototypes. The production (steel) molds will be done either by chemical etching, as lathehand describes, or grit blasting with assorted media.

Peter N
09-05-2006, 03:45 PM
Lathehand beat me to it, it's done by photo-chemical etching. Over here its normally referred to as 'martexing'.
It was very popular back in the 70's-early 80's, but has dropped off in popularity in favour of various grades of spark (EDM) finish. Of course it can also be put on by CNC-ing the form into an EDM electrode and then sparking it, where you get a combination of both finishes.

Peter

HWooldridge
09-05-2006, 03:52 PM
A company called Mold Tech has a standard set of textures that are often employed on finished surfaces. Here is the link: www.mold-tech.com/

I was in the business for almost 20 years and we almost always employed a standard texture provided by a third party vendor like Mold Tech. Only in a few cases was the surface blasted with grit media to generate a texture. The reason behind this decision was primarily for consistent duplication in the event the texture was damaged or worn - it was easier to match the factory standard.

Peter N
09-05-2006, 04:00 PM
I agree with Hwooldridge, grit-blasting is too inconsitent and gives a non-uniform finish. We only ever use it on prototype aluminium moulds to 'replicate' a sparked finish on cavities that have been machined.

Peter

TGTool
09-05-2006, 04:19 PM
I know an auto industry vendor used to make vinyl interior parts like armrest covers by starting with a wax male master which included all the texture including the fake stitching. This was painted with a silver-bearing conductive paint and then electroplated 1/8" thick or so for the actual mold. The wax was melted out, and the electroformed mold used in rotational molding.

Jan

J Tiers
09-05-2006, 04:36 PM
We always had the "RaWal" photo etch done, if the finish was not going to be a plain "EDM" finish.

The photoetch can put all sorts of finishes on that go around corners etc without looking wierd.

All the grit blasted stuff looked like it had been chewed on, we didn't like it. I think it was cheaper for the vendor, which is why they pushed it.

rotate
09-05-2006, 07:22 PM
Thanks, that answer my question.