CNC Machinable Rubber


(Patricio Suarez) #1

I need to make two light seals for a camera. They need to be black and somewhat flexible. Thought of some type of rubber. Is there a type of rubber that is machinable?. Anyone tried with yoga mat material?.


(William Adams) #2

Folks have machined rubber — one trick for it is to freeze it to make it less flexible and easier to cut:

https://www.shapeoko.com/wiki/index.php/Materials#Rubber


(Phil Thien) #3

I have no idea if this would work, but could you use your machine to make a mold to cast a seal? Machine a groove in a piece of some plastic, fill with some sort of black caulk, allow time to cure, and then carefully remove?


#4

Ya. Rubber can be interesting. But, you do need to keep in mind the properties you are looking for.

I am going to go on the presumption that you don’t mean rubber in the literal sense (one of the few materials that are actual rubbers, natural of synthetic) but in the broad sense of an elastomer, or even a non-elastomeric, but compliant, polymer. For a light seal, with not major environmental seal requirement (watertight at pressure, gas tight, etc) there are a lot of options that may be easier to work with than a rubber.

Freezing is an option, but isn’t a great choice if it can be avoided. You need to maintain good heat sinking during the machining process, which will involve liquid N2, dry ice, or pretty significant electric cooling in most cases.

A lot of the higher durometer urethanes machine OK with sharp tools, and are available off the shelf in sheets. Holding can be a challenge. You can sometimes get better results if you squeeze the sheet between two pieces of stiff material (I have done this between aluminum plates on a manual mill). Tie it together with screws in the waste area.

You can cut the profile you need in a material like formica and use that as a guide for a knife cut by hand.

You might also consider materials such as ABS and machine ridges into the mating surface (like “record grooving” a pipe flange face) or have the seal extend out and around the corner a little.

If you need the compliance, and have the room, you could machine a groove in ABS or Delrin for an O-ring (circular or square profile). They can be made to length to fit.

You can also, as mentioned, cast the seal.

There are a ton of other options. These are off the top of my head. When I need something like this, I usually knife cut or have it burnt with a laser.


#5

Addenda: A quick search found a number of sources for machinable elastomers.

For example (first google hit): http://waminco.com.au/materials

Another thing I wasn’t clear about: Holding the material during machining can be a challenge. When I talk about clamping the material between two plates, the plates may be premachined with the profile you are going to cut, plus a smidgen, so you are not contaminating the elastomer with aluminum chips.


(Patricio Suarez) #6

Thank you much everybody. It is more work than expected. I think I will redesign the body to use a rubber gasket that I will embed in the body. Like this:

It is good to know all this though. I love this community!!!


(Jesse Glessner) #7

You don’t state what shape (round, rectangular, odd shape), however, if it is round the BigBox hardware stores carry “O” Rings at reasonable prices.