[LazyH]

Hello, I've been wanting a milling machine for a while and was ready to use my metal casting skills to construct a small milling machine in my old shop. Due to unexpected family troubles, however, I have had to give up my old shop and need to find a way to fit all of my tools and equipment into a 4x5 storage room at our new apartment. Considering the space and inability to perform any metal casting until I find another shop I will be trying a cnc machine now.

I have been doing a bit of research on this topic here on cnczone for a couple weeks and figured I should make an account to start documenting any building I do and ask questions to those more experienced than I.

Ok, with all that out of the way here's my idea. I was considering a 3 axis machine with between 1-2.5 feet travel in each direction, just about right for making the tools I'll be working on while allowing a little extra room for expansion in the future. Since it's also going to be difficult to get much rigidity with the equipment I have, I was considering a fixed gantry design made from thick walled square steel tubing in a space frame design. Once the frame is welded together I was going to try setting the whole thing in concrete or cement for that extra bit of rigidity. I'll have to double check the measurements but I know the width will be limited by what I can fit through the doors to the storage room, since even if I build it in the room I doubt the landlord would like a huge mill left behind when we eventually move out. I was hoping for at least 2 feet travel in x axis (sliding table), and 1-1.5 feet travel in the z axis. I'm hoping for the ability to add a 5 axis adapter to the table too, so that extra half foot would be good for clearances there. I have a few sketches of the space frame design, once I find them in the boxes we packed I'll upload them to see what everyone thinks. Considering my design ideas, with 20mm box ways (searched "ssr linear" on ebay) would this be able to do any milling in steel or stainless or will I be limited to aluminum and wood/plastic for my materials?

I got the concrete idea from a concrete lathe design on makezine, I don't know how successful the build was or if anyone even finished one, but the idea looked good as a concept and when I saw the epoxy-granite area here in cnczone I felt it may be a practical idea.

If anyone has any ideas or suggestions I'd love to hear them.

[LazyH]

I forgot to mention, unlike in the concrete lathe design the ways will be bolted directly to bars welded to the "space frame" on my machine, I'm hoping that this will improve rigidity and allow easier changing of parts if any wear occurs.

[ebrewste]

Tough to say without more details, but I don't think the 20 mm SSRs will keep you from machining steel. Also, consider making the design that you can make the concrete portion optional. You might not need it and not dealing with the concrete would be nice... If you could try it without the concrete before committing to it, it would be a very interesting option.

[awerby]

Most machine designs are based on epoxy-granite rather than regular concrete. It's less likely to shrink and crack, for one thing, and it holds onto steel pretty well. See if you can break up the design into individual blocks that can bolt together so the thing can be disassembled when you want to move. THK is just one brand of linear rails and the SSR blocks are just one option. You should do a little research to figure out which linear bearing system is recommended for stainless steel milling; they're not all the same.

[rocketflier]

Checkout http://www.cnczone.com/forums/vertic...77804-cnc.html

[LazyH]

Most machine designs are based on epoxy-granite rather than regular concrete. It's less likely to shrink and crack, for one thing, and it holds onto steel pretty well. See if you can break up the design into individual blocks that can bolt together so the thing can be disassembled when you want to move. THK is just one brand of linear rails and the SSR blocks are just one option. You should do a little research to figure out which linear bearing system is recommended for stainless steel milling; they're not all the same.

OK, I think I'll be going with ebrewste's idea of trying the design out without any concrete/cement or epoxy. I was comparing the benefits of a couple different mixes of cement and found that in other applications the addition of paper in the cement mixture helped alleviate most of the problems you listed on top of the benefit of helping to dampen some of the vibrations a mill would experience. The good thing about concrete is that its very budget friendly which is what I need right now. Also it would seem easy enough to break the concrete out from the frame to try again with epoxy if it does fail. On the other hand there was an engine block filler based on epoxy I was just looking at from moroso for ~26 dollars per gallon, for a budget build would that prove adequate when mixed with sand or would it prove inadequate for my designs? I should say that the ability to cut carbon steel or cast iron is optional for my applications, even though I would like that added benefit if possible.

[LazyH]

here are some sketches of my machine, not 100% accurate/proportional but should be enough to give you an idea what my goal is. Steel is cheap so I'm happy with over designing the frame. I'm wondering if i align everything right, if i can get away with rebar instead of tubular steel for some of it.

[LazyH]

Checkout http://www.cnczone.com/forums/vertic...77804-cnc.html

WOW, that thing looks SOLID!!! I don't know if mine will be as rigid, I always wondered how a gantry system works in comparison to a turret design, it would seem like a gantry is like two turrets supporting each other with one axis moved to another part of the machine but most of my search results here on cnczone I've seen are of a comparison of two individual machine models (often from different manufacturers too), not just the design itself and how each compares with similar budgets or materials. (for example, are a lot of budget routers made with a gantry because of budget and simplicity or because it has higher rigidity for the materials expense?) I know travel in the axes is another consideration but how does that affect rigidity in a given design for a given weight and materials budget? All questions I would love to explore and answer myself IF I had the time and money to do so. Then again with my space frame design, it's possible to compare two different setups by making a model with copper wire and solder. Once I get my tools unpacked I might make a few designs, both turret and gantry style, with the same "quantity" of materials (the copper wire) and see which is easier to make rigid for a given work area, and again for a given machine size (total footprint and height).

[Hezz]

Nice triangulation space frame concept. I think it would be hard to get it all aligned straight if it was a tear down kind of frame. But if you to put a frame like this inside of an EG mold it seems like it would make an exceptionally stiff and massive frame. Perhaps it would be better just to make it small so that you could move it around.

[LazyH]

Sorry for the long delay, I haven't forgotten about this thread yet. I've been slightly altering my design and even coming up with a few new ones in case my first doesn't work, I also managed to get a hold of some tapered roller bearings that should work well for the spindle bearings once I get to that point, though I can reuse them for other projects if I decide on something else for the mill. Haven't yet had a chance to compare paper concrete with epoxy aggregates yet though, hopefully I'll get a chance in the near future and I'll post my results as soon as I can.