Suggested build height for CNC'ing aluminum, wood, laser?

Mostly Printed CNC - MPCNC Advice
#1

Hey, so I’ve been lurking around the forums and just started printing out the 3d parts. I went to my local hardware store and thankfully they have 3/4 inch EMT conduit so I know that I can make this build a reality.

Before moving ahead, I was wonder what might the “best” build size would be if I was only going to be cnc milling. I already have a smallish 3d printer but plan on building a d-bot some time in the near future, so I would rather specialize building the mpcnc for one function. Although the 1m square build size seems appealing, I want to avoid stability issues and having set up struts in between. Right now, I’m leaning towards the maximum recommendation of 30" x 30"; however, I was wondering what the best height should be? Also how stable should I expect it to be if I’m already pushing 30" x 30"? Should I dip to 25"?

Thanks!

#2

Build it small, 18x18. Learn CAM, Learn what good cuts look and sound like. You can have the belts, conduit, and table cut and built for as big as you want. Then when you feel confident enough to go bigger move the 3 corners out further. Extremely easy to transition.

I promise it is worth it to learn on a machine that is as rigid as possible.

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#3

Awesome, thanks for the reply Ryan. So then would you say that 18" x 18" is by far the most stable, and greater than 18" x 18" your cuts may get a little loose? Also what would you suggest for height? I’m guessing it needs to be higher than the drill bit and the material that is being cut into, but I’m not sure on the limits on thickness or size of specific bits.

#4

Nope 1"x1" would be the most stable, but 18" Outside dimensions should be rock steady.

I would say 3" Z is very useful.

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#5

Haha, well I guess that would be true. How modifiable would the Z-axis be if I ever decided to increase the height?

#6

Two new pipes and a longer lead-screw.

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#7

Good to know! Thanks all

#8

Actually, sorry one more question that came up. I’ve purchased my EMT conduit, but I’ve noticed that after I lay them all flat, some of them are slightly bent. Is there a good way of straightening it?

#9

It should be pretty straight. When cut to length is the bend still visible? If it is I would just say put the arch up so the weight will pull it into place.

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#10

The bearings might actually straighten it with some use. Not sure but they have a lot of force.

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#11

I haven’t cut them yet, but I notice a slight bend in 1 of the 3, 10 foot conduits. I wanted to see if this was a big problem and if I needed to return them for straighter ones instead of cutting. I’ll go ahead and see how they look afterwards.

#12

If it is a long bend through the length of the pipe you can try to straighten it some by standing on it and rolling it on a hard surface. If the bend is more localized you could attempt to straighten it a bit and then use that area to cut out the legs and possibly the z axis. The bend would have less effect on the short run pieces versus over the long runs of x and y. But you are correct in assuming you want them as straight as possible for accuracy.

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#13

I only noticed that they weren’t quite flat when I put them onto the floor of the garage, and I don’t think there is enough of an angle when on the ground to be able to effectively flatten them by standing on them. Might try and prop them on a table then hold them down in a vice grip and see I can try and straighten them a little while they still have the length.