urethane casting resin for pattern making

[forhire]

I need to make some new patterns. I am planning on cutting them on a cnc mill. In the past I have made wood patterns and had a pattern maker cast them in plastic for long life. I'm thinking I can skip that step if I machine them from plastic. I've looked at tooling plates from freeman supply. Then I came across some videos showing a guy cutting urethane casting resin. Looked slick. I don't know what type of resin it is. freeman has so many varieties. Anyone have a recommendation? Thanks.

YouTube - ‪Homemade CNC Router 2009‬‏

[slowlearner]

The only urethane casting resin I know of that is a 1 to 1 mix and that color is Dynacast. It is a Kindt-Collins product. Freeman Supply recently purchased Kindt-Collins.

[rocketflier]

Why not machine the original from aluminum?

Many of the task products at Smooth On are listed as 'machinable'. I would just contact the customer support at either and describe your application.

You could also do the same thing you did before, only you'd make the mold and cast the patterns!

[forhire]

Originally Posted by rocketflier Why not machine the original from aluminum? Many of the task products at Smooth On are listed as 'machinable'. I would just contact the customer support at either and describe your application. You could also do the same thing you did before, only you'd make the mold and cast the patterns!

Thanks for the link. I'll call them in the morning.

I think the plastic is about a 1/3 of the weight of aluminum and these are large patterns. The plastic appears to be a cheaper than aluminum. But your correct... milling time will likely be similar... and aluminum would hold up forever. I guess I want to save some weight and cost.

We've discussed casting the patterns from aluminum in the past but the plastic patterns have held up very well. I'm making patterns for a new part, thankfully not replacing my existing ones.

[forhire]

I got this answer from the author of the video

"The green plastic I use in a lot of my videos I use for making master models and plastic rigid molds or inserts. It's made by www.alumilite.com Replicator 400 I love this particular urethane because it has no solvents so it's easy to cast inside without all the bad vapors off it. Another thing I love is that you can polish this material to a high gloss finish. So if you machine an insert or master model you want to cast other parts off of, it's a great choice.

For actual pattern making (sand casting), short run patterns you would want to use a glass filled casting resin like BCC quick cast. For making core boxes you can use surface coat epoxies and hard urethane rubbers that hold up very well."

[microcnc]

Hello forhire, thanks for visiting my site www.fendleyautomaion.com

I didn't see your post here on the zone till today which was a little clearer what you wanted to do. If you want to make your patterns out of plastic you can always use freeman Ren Shape 5179 Foundry Pattern and Tooling Board. It's abrasive on cutters but it machines quicker then aluminum. Another is McCausey Lumber Company: Model & Pattern Materials: Tooling Boards 1200 tooling board. I think the 1200 board is similar to the 5179 tooling board you can call them and they will help you with your selection. I believe it's green in color.

Another cheaper route if you are making multiple patterns or you want to replace your tooling when it wears out is to machine a negative from
Modulan Tooling Board 652 from Mccausey lumber. There are a few ways to do this.

Machine a negative in the tooling board which is easy on cutters and cuts like butter. Then you can machine lighteners (smaller versions of the pattern). You can cut these from tooling board or if you are making a bunch of the same pattern you can cut a negative in tooling board for the lightener.

Then you can use a cheap casting resin or some sort of back fill material to cast the lightener. For smaller patterns you could even use a rigid foam from SmoothON to make the lighteners and then you place the lighteners into the negative of the pattern.

Typically you want to have about 3/16 to 1/4" space between your pattern and lightener. If you are going to machine the lightener from tooling board for a single pattern I typically just cut it like I was cutting the pattern from the board and program it to leave -.150" stock instead of cutting to zero stock. This way your clearance is machined in automatically.

There are other ways of doing this too. I wouldn't use wood for a lightener though. Even when the lightener is encased in the outer plastic heat and humidity can make the wood expand and contract to crack the pattern. So it's not really worth going that cheap.

Again if you need more help with this feel free to contact me though my website.

[jetski]

A company called BCC in Franklin, IN. has all the Silicon, polyurethane, in different duometers, you could ever want in sizes from several ounces to 55 gal drums. Roger Burnett is the owner and knows his business. I do not have his number but if you go bccproducts.com it will give you all you need.