Modelling help

Hi there

I am wondering if anyone knows the best way of making a soft touch silicone sleeve for a prototype, like the ones you get for ipods etc. I have workshop facilities at university etc and this would be an integrated cover for a PDA style product which is designed to be robust.

How would I do it making moulds etc?

What to avoid and any tips.

And what product should I buy or avoid.

This is for a model so any alternatives would be useful.

Thanks Chris


At $120 per quart (3 component sample kit) it’s not cheap. But I suspect it would be cheaper than patterns, mold making, and materials for a discrete prototype component.

Even if you are in school, time is money.

i’ve used that softtouch stuff, and it’s avail in a spray can. it’s a one-use can and pre-mixed (but u need to shake it). call them direct and they’ll ship to you.

You can go with a traditional silicone mold with a low durometer urethane. It depends on your wall thickness and how much pressure you can use to inject the urethane. Granted it was a small part, but I have done a 0.020" wall thickness with urethane.

There are videos on that site too.

I think if you do urethane molding, you are going to have trouble making a really clean model, especially if you are doing it on your own and almost surely if you want to stretch the rubber part on on and off the pda. It would be a good learning experience to play with casting though

First off, making the molds can be a little tricky, especially with over-molding another part. You would need to plan all the parting areas and think through the removable insert part. On real iphone cases, the plastic can stretch off a solid insert part once molded… but urethane is not like injection molded plastic and it will tear if you stretch it too much.

Another issue is the pressure that another poster mentioned… usually they let the rubber harden under pressure, squeezing any bubbles to become very very small when it’s hardening.

I had a tech trained by a friendly model shop once to bring urethane casting in-house. It was for low volume urethane rubber overmolding on a boutique product - the product was a lot like what you are doing. The end assessment was to leave the process to the experts… I have pretty detailed pictures of the entire process if you want to PM me. You might want to call a modelshop and ask them about it too, they are the guys doing this work day in a day out and would know the most about it.

All in all, you would spend a ton of time making the molding work, when you could be concentrating on the design. LMO’s suggestion of simulating rubber with softouch paint is a good one, and in a photo shoot it would look a ton better…

more than $.05, but I hope it helps

Cheers Guys for the fast replies.

Some really good info. The paint option sounds really interesting so I will ahve a look into that.

Travisimo I completely agree with what you are saying, as experimentation it would be great to play around with this technique but as you say, my time would be better spent on other areas.