[munich2007]

Dear forum members
I'm new here and just have started reading through the enormous amount of valuable information at this site. Please allow a question to optimize my search phrase for this forum and google.

I'm wondering, if there is a garage compatible way to produce such control knobs as in the image attached. It would be nice to have Inlay, skirt and body as separate elements, to achieve different color combinations.

The knobs are for rotary encoders of DIY musical instruments, like the midibox sequencer. The material should be soft-touch, the quantity a few dozen to a few hundreds.

It would be nice, if you have any hints for the material and processes one would use.
Thank you, Frank

[anoel]

Frank, the easiest way would be to cast them in a two part slicone mold using the casting material of your choice.

At the low cost that you can buy this type of knob, they are CHEAP and there are a good variety of styles out there. I have no idea why you would want to make your own especially in such small quantities. I'd want to spend my time making the midibox and not having to bother with making knobs.

[munich2007]

Nathan,
thank you for the response. You are right, most of them are low cost, but sometimes you want something special and can't find the knob with the right color or the correct shaft. ..Now I'm sounding like a girl )
There are lots of knobs for potentiometers but little for encoders where you don't need pointer/marks.
Also it would be nice to re-create spare parts of older synths which have knobs and switches which are out-of-stock.
Actually I thought about using silicone mold when I read this nice website about knob repair:
(sorry, this is german)
http://www.jogis-roehrenbude.de/Formteile.htm
What kind of casting material would you recommend to get a rubber-like soft-touch feel?

Frank

[Kyle L.]

Dear Frank,

From your informations, it should be double-injection parts, inside material plus rubber material, it's soft-touching.
another way is rubber painting,

Kyle L.
Eastar Tech
[email protected]

[munich2007]

Kyle, thank you,

can you recommend a supplier for rubber material?
And how would I do rubber painting? Sounds interesting!

Frank

[Kyle L.]

Hi Frank

:rainfro: rubber material: TPE,TPU,TPR from Buyer company,santopere.

Rubber painting is use special rubber oil to spray on the surface.

Thanks
Kyle L.
[email protected]

[tr4252]

Hi,
I've had good results with Devcon products; they have a line called Flexane, which is a flexible room temperature curing urethane. It's black in color. I've used it for resin casting molds, and since it is available in a few different variants (hardness), you could possibly use the 90 durometer for your molds, and a softer version for the knobs. It would probably make useful molds for your inserts, and you could mold them in epoxy resin, which you can color pretty much any way you wish. Molds can of course be made using an existing knob and its components as patterns. I always made 2 piece molds, with pins molded in for alignment.

One thing to be aware of, using these product types, is that air bubbles can be introduced during the mixing process, and you'd probably want to use either a vacuum unit to purge them before you "pour" the uncured material, or else use a closed injection/mixing system as I used to do.

Hope this helps.

Tom

[toolsrul]

Check out www.alumilite.com. I use their products all the time & they have an enormous product offering. If you want a black part you just paint the mold black before you pour the resin & you'll get a very professional looking part or you use get the black resin, many choices.

[munich2007]

Tom,
thank you for the additional info. It seems to be hard to build the product without bubbles. Vacuum seems to be a must. I will look for a small vacuum unit, that can help me in the process.

toolsrul,
thank you for the alumilite link. They have a nice palette of products.

Frank

[toolsrul]

A couple of suggestions, don't stir too agressively which will add air bubbles & also pour into mold holding mold at an angle to let air escape while you gradually
right the mold to the upright position. Good luck.