View Full Version : mold cavity surface finish

09-24-2010, 02:02 PM
I have built a few molds out aluminum for my company. We were buying them from another place and the ones we were buying are made of tool steel. They also have some kind of finish that looks almost like an orange peel, but with a smaller, "softer" look to it. It gives the mold a matte looking finish and you can't really see the orange peel look in the overmold either. I was wondering if anyone could tell me how they do this to the cavity and if it can be done to aluminum.

09-24-2010, 02:19 PM

It sounds like they are cutting the cavity, with a EDM, first they make an electrode out of graphite or copper, & then burnt it into the steel, yes it can be done on aluminum

09-24-2010, 02:23 PM
there is no chemical that can be used to achieve this or something like it? or a secondary process?

09-24-2010, 03:10 PM

Yes it can be chemical eched,& done by laser , there are lots of ways to do it, but it is all a special process to get the texture even

09-24-2010, 07:55 PM
Sounds like a "electro-less nickle" plating to prevent corrosion and gas burning added to the cavity.

09-24-2010, 08:54 PM
What are the finished molds used for? ( the processing of material)
Aluminum can be used for a multiple of processers with the proper surface coating.

09-24-2010, 09:06 PM
To obtain a pebble grain finish on an alum mold all you need is a pressurized sand blaster and some steel shot.This is cheaper than acid etching and works quite well.

09-25-2010, 05:45 AM
Just so I'm sure- you are actually looking for an "orange peel" effect? just asking because I spend hours getting rid of this effect on aluminium mirrors.

09-25-2010, 07:28 AM
the finish on the molds is like a micro orange peel finish, it almost looks like a bunch of tiny tiny cracks?...and i was wondering also how to get an orange peel finish. What I am looking for is to get a matte finish on the final molded product. They are for cable connector overmolds. Currently the ones I have done are coming out with a slight gloss because all of the walls on the mold cavity are smooth.
I am wondering in general how certain finishes are achieved. I was sitting in a chair with a plastic seat and saw the finish that was even different from an orange peel look. It was a stackable chair like the one in this link:
and i was wondering how they got this finish. Many car interior parts have a similar looking finish.
Where do people go to have this process done on their molds?

The sandblasting does sound interesting. Is steel shot the only medium that would work? And would it work on a 7075?

09-25-2010, 04:04 PM

The chairs are a straight EDM finish, which you could do with etching,or Glass bead blasting, don't even try the steel shot blasting unless you have had experence doing it, or you will destroy your mold

09-26-2010, 04:39 AM
We use bead blasting here and it gives a beautifuly uniform grey surface. You could also use "passivation" to get a grey surface.

09-30-2010, 09:03 AM
i use sand blasting all the time on aluminum moulds for blow moulding,it gives a very nice result depending on the grain you use.i usually use the finest as it gives a matte surface and also gives good air venting properties.
I also sandblasted hardened parts,it takes a bit longer but it also gives an even smoother matte finish.

03-09-2011, 01:10 AM
Any chance somebody have a photo of a part from an Aluminum mould where the mould has been sandblasted. I'd like to see the result. We're just about to machine a mould which requires a matte surface and I just want to eyeball the result before I commit.

3D Accuracy
04-10-2011, 08:40 PM
Any chance somebody have a photo of a part from an Aluminum mould where the mould has been sandblasted. I'd like to see the result. We're just about to machine a mould which requires a matte surface and I just want to eyeball the result before I commit.

Hello frogger:

I'd be careful trying to sandblast an aluminum mold. Look into bead blasting with a softer medium than sand or you may end up with a finish that resembles a corn cob instead of a nice matte finish!

Do a little testing on sample pieces before blasting your mold.

Have a terrific weekend!
3D Accuracy

04-17-2011, 10:16 AM

I do the exact molds DWAS you are talking about for overmolding.

I use a coarse glass bead at low pressure to blast the mold and get a great matt finish . Forget about sand etc it just not give you as good a finish. Using fine shot I have not tried yet?

I usually cut the mold up to .25mm deeper so I can surface the mold after blasting as it rounds of the edge of the mold around the parting line . I use Alumec 89 which is similar to 7075 but harden all the way through

DWAS are you using low or high pressure molding? and what connectors are you overmolding ?

I am also looking in the future to basically engrave different finishes with a cutter and use 5axis . It is great to have a high speed spindle :-)

I'll try and throw up a photo when i get a chance



04-17-2011, 01:37 PM
Hi Rob,

I am going to make an EDM attachment for the SX3 within the next few months. Will only work on machines with a movable quill. Not the (s)X4 etc. 4 axis EDM. Should be interesting.

Did you find a relay?