Questions, RE: 4'x8' build envelope, spindle's, and stainless?

Mostly Printed CNC - MPCNC Your Builds
#1

Been reading lots and watching lots of videos and have a few questions and thoughts, I can be a little scatterbrain so will try my best here.
I am planning on being able to put a 4x8 sheet of plywood in and have this machine make all my cuts for me. The calculator is great for belt lengths and stuff :slight_smile:

  1. Is there a way to get the right amount of belt in buying the parts bundle for me to make a 4x8 build area?

  2. I plan on using a spindle rather than a router mostly for noise, and hopefully save a little bit of weight, but how does the speed control for them work then?

  3. I plan on using 25mm OD 1/4" wall steel for the non moving tubes to give it some weight and hope it will reduce chatter and flex, will also make threading rod in for supports really easy, will be on a 1"x2" steel frame.
    For the two moving rods will use stainless 25mm od. Now the x and y, one of them will be really long, and the other just long at just over 4’. I have seen others double up on these, but that takes up too much room. Has there been any testing on how the long lengths really matter? And on that note, does it start to get to be a little bit much for the steppers? Would doing double conduit on the narrow axis help enough to make it not needed on the other axis, or would it be pointless to only do one?

  4. how perfect of a straight line and repeatable can I expect? Like if I cut the long way down two boards and then butt them up could I expect them to fit flush?

  5. Why isn’t there more large builds? I see mention of them a fair bit, but other than a mention of plans never any questions or real concerns with making a bigger table even.

  6. Any advice from past attempts?

  7. Would it be possible to use it as a planer for a large surface too? Just not sure how, since this acts more like a 3d printer than a router table, I think? right? no?

Hoping to order the parts here soon.
Thanks in advance.

#2

I’m not sure how well something this big would work. You’re in the beefier cnc router territory now. I don’t think this design was really ever meant to be this big. Just a hobby desktop router. Some of us have gone craze and expanded, but I’ve not seen anything bigger than a 4 foot square cutting area. If all you’re doing is 2D cuts, then the sag won’t be that big of a deal, some of the cuts won’t be perfect 90s through the thickness of the plywood, maybe a couple degrees off. So far I’ve not cut anything that has to butt into other parts, so I can’t tell you how well it will do that. I do know part repeatability is pretty good. I’ve cut out several of the same part and sitting them on top of each other they’re pretty much spot on.

#3

It’s really the 8’ length that’s different, there are a few with 4’ axis. I’m just thinking if I can keep that axis rigid enough then the long axis would really just be a guide, right?

For smaller stuff just keep it into a corner.

The stainless tube is significantly more rigid than emt. By at least a factor of ten.

And if I can figure out this spindle thing that should reduce the weight, and keep it closer in.

#4

I think once you get that long even just the act of moving will flex the long rails. If there was a way to have 2 sets of rails that might work.

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like that if you get what I mean if this was the center assembly…

edit it is not displaying this properly supposed to look like a tic tac toe grid

#5

For the X and y, I have seen that, just requires me to make it almost a foot larger in each direction then. And I don’t have the extra room.

The outside rails will not flex at all even standing on them.

#6

Regarding the 8’ being just a guide: I really hope that’s the case. I’m building one for a 3’ by 6’ work area (mainly so I can fit it onto a single sheet 4’ x 8’ base), but I only ordered the 0.065" thick steel rails. I’m going to try it with the DeWalt, but I have a feeling I wasted money and will need to buy a real spindle. I tried using the DeWalt by hand on some bamboo flooring, and it was nearly impossible to control (and lit the bamboo on fire!!).