CNC For topo foam work

[texasjeff]

I am looking to build a CNC for cutting topography surfaces in foam. Specifically I need the foam surface to look like stone, brick, riverbed, and a variety or other surface textures. I also need to cut wood frames out of hardwoods, such as teak.

The main key in the router is to speed up production and repeatability. Hand carving just takes too long and it's too hard to repeat a surface.

So I know I will need a table that is capable of at bare minimum 3' X 6' cutting. Accuracy isn't that great of a concern however the less sanding I have to do the better off I am. Speed is really the main key here.

Cutting aluminum and stainless sheets would be great in the future, but for now that isn't too important. When I get to that level I will probably buy a commercial machine (ShopBot, V-Max, or something similar).

I know I will need a Z axis of at least 6". I want a moving gantry and I want to use a non proprietary controller. (The downside to the ShopBot)

Now with all that said, I have limited tooling. I have a table router, drill press, table saw and hand tools. I don't have a metal shop or anything like that at my immediate disposal. I don't have a welder, and I haven't welded since high school. Although I do think I want a heavy steel frame for greater accuracy and machine life.

So with all of that said I am looking for some suggestions and some help. Especially if you are in the Houston area (I am in Tomball) and can spend sometime showing me how one of these thing goes together. I don't need schooling in cad or anything like that. I pick up software very fast and I have already starting using Rhino3D and WinTopo to get a jump start. Perhaps I can find a suitable plan and have someone local cut the parts for me on their CNC to give me a greater understanding. I would of course provide materials, pizza, and Beer or Root beer as needed.

BTW. - I was considering the CadCut machine, but I just can’t spend that kind of money right now. My ballpark figure is around $2000 at max for this first machine.

All help and suggestion will be much appreciated.

Thanks,
Jeff Lutz

[Chagrin]

If your main goal is to cut topography from foam, you should focus on that and drop the idea of cutting stainless or aluminum. A machine sturdy enough to cut metals is uneconomical for cutting foam. Similarly, I think that you'll find it easier to make hardwood frames using traditional techniques (table saw/router table) rather than a CNC router since the setup cost is so high doing it CNC and you won't get as good of a finished product without increasing the cost of your router table considerably.

[High Seas]

texasjeff - Greetings and welcome!
You might consider an aluminium extrusion setup. No Welding, relative ease in "errector set-style" assembly - and you're only limited by your ability to source the bits and pieces cheaply.
You could develp a machine that would be "reconfigurable" for future use as a metal machine. I haven't tried metal milling myself - but expect milling Aly won't be too difficult. The extrusion frames can be quite rigid - and if you back them with a bit of ply - "she ain't goin' nowhere." The trick will be setting on your design - yes moving gantry - has some advantages - look for all the ways to keep it and the router/spindle as rigid as you can.
Some recent designs on the 'zone have shown the Y Axis being wider than the working "bed." This is good - you give up a little floor space in the shop - to get the full width of the work surface. You'll quickly note there are heaps of trade-off here.

Sorry cant take ya up on the pizza-n-beer , maybe later! Jim

[Cold Fusion]

Texasjeff, I might take you up on that pizza deal. My cnc router is almost done and I live in Missouri City, Texas. If you want to you can give me a ring at 281-403-1893 and we can talk details.

[texasjeff]

Chagrin - I agree with focusing on the foam aspect. That is the main goal. But I should elaborate on the wood aspect. I want to be able to cut 2D/3D images into my frames, while I will still make the actual frame with a good ole skill saw and router table.

The matals that I would need to cut are 20 guage stainless and aluminum. So my thought was that it was so light weight that the same machine would be able to do the job. I might be wrong and if I am please elaborate.

High Seas - Thank you for the greeting. I have considered the aluminum extrusions, and luckily I have a company just a few miles from me that deals in nothing but aluminum and stainless products. I was under the impression that the cost of extrusions was double that of cold steel, but I may be wrong. I haven't checked into it yet.

I have been reading posts on "The Zone" for the last 4 days, getting very little sleep I might add. I am totally confused as to which way I want to go with this. Stepper or servo, mdf or metal, build my own controller or buy one, etc., etc. I really am at a loss on where to start. I know that it all starts with a good design, but I am not an engineer.

Regardless of materials for the table, I know I will need a controller and probably steppers instead of servos. Any thought on what I should go with considering the applications I will be using it for? I would also like input on whether to go with a linear slide setup or a ballscrew setup? I don't like what I have read about all thread so I think thats out.

Cold Fusion - I will give you a shout in the AM. Thanks for the offer!

[chuckknigh]

How big are the metal pieces you need to cut? It might be more economical for you to build 2 tables, than to build a super big one with the level of rigidity you'd need for metalworking. Cheap X-Y tables can be fashioned from "cross slide vises" that are commonly available at Harbor Freight, for not much money.

As to the allthread, it actually has several benefits, not the least of which is easy access to parts. You can use easily available taps to make the nuts, too...and if something breaks, a fix is available at Home Depot or Lowes, instead of waiting for a mail order delivery. The thread can "wander" a little bit, but it's not too bad -- the other choices are simply better.

Since you said accuracy is not that high a priority, allthread might be a good choice.

However, if you have a McMaster-Carr, Fastenal, or something similar in your area, ACME is a better choice...and the cost is not much more.

Low cost ballscrews can often be found on surplus medical equipment, including hospital beds. If you have a salvage place in your area, take a look for linear motion components.

The stepper/servo debate is an easy one to solve. How's your budget? Considering that you want to primarily cut foam, small-ish steppers should be sufficient. You can scavenge those from printers or copy machines, at extremely low cost. Servos, and the related electronics, typically cost a lot more.

-- Chuck Knight

[Chagrin]

I think the thing to watch out for with this project is your top speed. If you're going to be cutting 6'x3'x6" stacks of foam you've got a lot of volume to cover. This means you're going to want to gear up your system and once you do that the machine will become impractical for hard materials.

An inexpensive servo implementation will run around $700 for just the motors and controllers. The xylotex 3-axis board at $125 and surplus steppers would run around $250.

If you really want to get an idea of what you're doing, make yourself a small 18"x18" MDF or pine frame testbed router with wooden slides running on drill rod and allthread with homemade acetal nuts controlling the motion. This can be done for around $50 and you'll be surprised at the accuracy you get. What you'll learn will save you a lot of money before you start dumping it into a production-type router like you're planning.

[texasjeff]

That sounds like a good plan Chagrin. I think I will start with a mini and use it for learning. Any suggestions on which plan to use?

Chuck - The metal pieces could be as large as 3'X6', but most of the time they would be small 1'X1' at most. I would need to nest parts on the sheet and cut as many out in one run as possible. I want to keep some inventory of what ever I create. Again repeatability, efficiency, and speed is key. It is likely I would build 2 machines. One really fast for cutting the foam and one really accurate for cutting wood and metals. Besides it will take 1 machine a long time to cut a 3'X6' topo even if it is fast. I am assuming it would take it about 2-3 hours. If it cutt as fast as the PRTAlpha Bot it may take less time.

Chuck you have a nice looking machine. How is it working for you?