Materials To Know: Tooling and Modeling Board

I was in a fit of nerd glee the first time I used tooling board. I’d used MDF for similar purposes before, and I doubt I ever will again. Called Renshape, Precision Board Plus, or that green stuff people on another continent buy; it’s all the same extremely useful, unfortunately expensive, stuff. It’s hard to pin down exactly what tooling board is. Most of the blends are proprietary. It is usually a very dense polyurethane foam, sometimes by itself, sometimes with a fine fiber filler.

What makes tooling board so good is its absolute dimensional stability and its general apathy to normal temperature swings. (It even comes in versions that can go through curing ovens.) It is impervious to humidity. It has good surface finish, and it machines perfectly without wearing down tools.

The CNC set-up I coaxed precision molds out of.

This stuff is really tops as far as machining goes. I got super precise molds out of a very basic CNC machine at the LVL1 hackerspace. Renshape cut easily at a high spindle speed, and put practically no load on the machine. Climb and conventional milling were equal load wise with no immediately perceivable difference in finish. In the end I hit the precision range of my cheap digital calipers: +-.005mm, when the temperature is right, the battery is a charged, and the planets align.

I like to do resin casting when I get serious about a part. If you are making a master mold, there’s nothing better than tooling board. I’ve used both Renshape 460 and Precision Board Plus. Both impart a very light matte pattern, equivalent to a light bead blast on an injection mold. There’s no finishing required, though I mistakenly bought Renshape 440 at first and had to sand it a little to get the finish I wanted.

Tooling board is great for masters in metal casting, and is often used in the industry for just that, especially if quick and accurate prototypes are needed. It’s also tough enough to last through a few rounds of metal stamping in the home shop.

If you are doing lay-up for carbon fiber, fiberglass, or leather, this is also a very good choice. It will be unaffected by the chemicals, heat, and vacuum you may use in the process. It is tough enough hold alignment pins for proper set-up without premature ovaling. It is also a very good choice for vacuum forming.

Tooling board is, unsurprisingly, really good for tooling. It’s a great material for soft-jaws, alignment fixtures, and assembly fixtures, especially if you are doing delicate precision assemblies.

If you’re made of money, tooling board can be used for models, signs and props. It sands, shapes, and files extremely well. It bonds well to a lot of substances. It also takes paint very well with none of the absorption properties of wood or MDF. Most professional model shops will use it.
2015-11-05-10.34.01The one big flaw of tooling board is its price — this stuff is expensive. There’s no good DIY version that I’ve scrounged up so far. If you’re making a mold master, a fixture, or anything where you need tooling board’s properties and you are likely to get a few uses out of the board, then it’s probably worth it. Also, be careful of sellers selling plain “Renshape” it is probably going to be the lower grade Renshape 440 and not the more expensive Renshape 460 (or equivalent), where you start to really see the surface finish advantage of the material.

Tooling board is an industrial material. Typically you can call up a supplier and tell them what you’d like to do with it and they will be able to help. If you are making tools for carbon fiber quadcopter frame lay-up, let them know and they’ll have a formulation for that. If you are resin casting, there’s a formulation that gives superior surface finish.

It’s a pretty common material in the industrial scene, but I don’t see it a lot on the hobby scene. This is almost certainly due to its cost, as well as a shortage of small quantity re-sellers. (If someone starts selling assorted sizes on eBay for a reasonable price you have at least one buyer in me.) However, after using it in the niches it is designed for, I really don’t use anything else. I used to hack MDF to fit, but MDF is awful to paint, has no dimensional stability, and dulls tools really fast.

Are you a fan of tooling board? Have a good source? If you have anything to add, let us know in the comments.

33 thoughts on “Materials To Know: Tooling and Modeling Board

    1. I was thinking machinable wax too. There is also a how to guide somewhere on how to make your own from paraffin wax and plastic bags, but I’ve never tried it.

      1. I tried HDPE plastic grocery bags dissolved in molten paraffin, and liked the result – a pink plastic (because of the red printed markings on the bags) that’s easy to carve but a little too flexible for my liking. I had better luck with plastic soft drink bottle caps, which are polypropylene with PE seals. These also dissolved nicely in melted paraffin, and made a harder plastic that was still much easier to carve than the original plastic. I haven’t tried machining either of these, but I think they would both work great for making models .

        1. And I quote: “[Machinable wax] is not the cheapest or most durable stock, but has two important properties: it machines quickly to a very good finish with excellent dimensional accuracy; and more importantly, because it’s much softer and more fragile than common plastics, even fairly major mistakes won’t immediately result in a broken tool.
          [Here he suggests buying a box of 12 42x42x15mm pieces of wax for $21.] Don’t overdo it – this really isn’t the best or the most cost-efficient material for real work, so get just a single box or two.”
          He obviously likes the modeling board better, but these few sentences don’t really explain why. In fact, they make me even more curious about what exactly is wrong with MW…

          1. Not much is wrong with wax apart from the fragility, which can make small and/or intricate pieces really worrying to deal with.
            On the plus side, if you’re looking to cast you can use the wax to make a rubber mold and then duplicate in wax or plastic or another material, or put the wax directly into investment and cast parts from it, lost wax is a useful process and can be great for making small parts.

          2. Anon: Yes, that’s the point of machinable wax – being able to make a model from which to make a mold, from which many parts can be made. The material is easy to work with, but not strong enough for use as actual parts.

  1. I have used this to machine some really nice molds,fixtures and prototypes. I am surprised so few people know about this stuff, it has been around for quite a while in the prototype and product design world.

  2. I too would be interested to find out more. Does “that green stuff people on another continent buy” refer to an actual product? Which continent? What is it called?

  3. After reading the Guerrilla guide to CNC by Michal Zalewski I got hold of some RenShape and it is excellent. I am about to embark on a new adventure of press-forming some thin aluminium panels with forms made from it and it is nice to see they actually do this in the industry also.

  4. Gerrit, I’m assuming from your name that you are in South Africa :-) Have you found a local supplier for Renshape, or do you have it shipped from non-ZA sellers?
    I was looking for it some years ago, and found a company in Centurion (HT Polymers) that stocked it, but never needed to actually buy some.

    1. Right on the mark! but I live in the US. I’m one of six Coetzees in Amerika, and I’m directly related to all of them, haha. Die inval het begin:P

      I don’t know of a supplier off-hand, but I’ll see if i can find one. I’d also recommend searching for tooling, modeling, or Polyurethane Foam Board (though it’s also used as an industrial insulator, so mixed results with this last search) instead of Renshape. There are a bunch of manufacturers of equivalent materials that may be more prolific in ZA.

  5. Smooth-On sells many different densities of urethane foam. The highest densities can be milled like Renshape. If you have a rigid, sealed container to cast the foam into, the density may be increased.

    Just be sure to coat what you cast the foam into with the proper mold release.

      1. Then tell them thats your way of rewarding yourselves for posting stories that make people want to read more about that particular story. I’m tired of swiping multiple times to get past each story that doesn’t apply to my interests.

        How ’bout this? Going forward I’ll only view HaD from my ad-block enabled browser where I have the luxury of PgUp/PgDn to skip big chunks of article with each keypress. It’s actually part of the reason I view HaD on my phone… I *WANT* you to get paid from advertisements I don’t pay attention to anyway.

  6. Our workshop has always called it ‘plastic wood’, and in Australia at least, many suppliers seem to know it by this name. Here it is a pink colour, comes as “boards” up to several tens of mm thick, is very heavy in the lager sizes, and frightfully expensive. But for SO many things it is absolutely invaluable!

    Knowing the “real” name is ‘renshape’ is good.

  7. My brother uses this to build fishing tackles, we CNC-mill the outer shape of (small) fish and he sands/paints/assembles them. It is a material frequently used by hobbyist fishing DIYers.

  8. I am working on prototype aircraft in Germany.

    Here that stuff we use for tooling is called UREOL.

    Pretty expensive too, so we often just use a totally softer hard foam, xps, thats normally used as a better house insulation. Thats good enough for one-off prototype composite parts.

    1. More hints:

      UREOL could be ordered in different densities. With more than 550kg/m³ you get good finishes after milling and probably sanding. With lower ones you have to paint it with fillers first.

      XPS or styrodur (think its called styrofoam over there, similar to styropor, but it doenst have the tendency to disintigrate into small f**** balls) needs to be painted with 2k Filler and sanded for good finish, but the price is a fraction and it could be tooled very fast.
      It definitely needs some kind of frame to support the whole piece, a mdf plate probably. The moulds for our wings (4 meters each, 4 times) had a frame with 5 inch by 3 inch construction steel covered with one layer of chipboard.

  9. Thanks for sharing, it’s of great help. “Renshape 460 impart a very light matte pattern”. I’m looking for a matte finish. How would you describe the finish on the Renshape 440? Would that be a more intense matte?

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