Hey there! Looked around both here and on reddit to try and find an answer with no real luck. I’m looking to build the mpcnc with footprint of ~40x40 inches, my goal being to have a workable area of 30x30. I intend to use this primarily for wood, possibly even hardwood milling. Will I have any issues with this size being this big? Has anyone been able to do aluminum milling on a size this big? Any help appreciated. Thank you!
That seems large for aluminum milling but you could get it to work… in my opinion it’s easier to buy larger tubing then cut it down if you need more accuracy/rigidity. Also what are you planning on for your tubing material? Also I recommend a shor z axis 
That was going to be my other question/comment. I wanted to use the galvanized tubing from the big box stores (1 inch, not the smaller stuff) if I can get away with it. I can’t find anyone local who supplies SS tubing, which is what I wanted to use. I can order online if it will offer significant improvements at this design dimension. Shipping costs make it kind of unappealing.
I was going to run a regular recommended height z axis at 3.1inches I think it is. I don’t believe I need any more than that. Max would be 4 inches, but I don’t have any use for anything thicker than 3 inches anyways.
Again, my primary intention is not to mill aluminum. It would just be a bonus. I just need it to handle wood well. If this could handle wood without issue, I might push z axis to 4 inches.
I wanted to use the galvanized tubing from the big box stores (1 inch, not the smaller stuff) if I can get away with it.
That’s a non-starter. Tubing is measured from the outside, pipe is measured from the inside. Conduit has pipe sizes, so 1" galvanized conduit is substantially larger diameter than 1", and will not work with the parts that V1 designed and released. I read one topic on this forum where someone modified all of his STL files to handle 1" conduit, but I got the feeling from reading his post that it was major undertaking with the final STL files being kept private.
I was going to run a regular recommended height z axis at 3.1inches I think it is. I don’t believe I need any more than that. Max would be 4 inches, but I don’t have any use for anything thicker than 3 inches anyways.
Just FYI, Z height must include the height of the bit and clamps as well as the material.
2 Likes
I agree with @robertbu, as far as I know you won’t find anything 1" OD at the big box stores. Most cities have some metle dealer that will sell 1" SS or DOM tubing. I recommend using Google maps and search for stainless steel, then calling each place to see if they stock it and to get quotes. That’s what I had to do before finaly finding a place with reasonable prices.
That said there are all kinds of machines out there. I have heard of at least one person milling aluminum with conduit… its about the amount of care you take with your build and your skill with CAM.
I don’t think you will have any issues with wood, though like others (Ryan the creator of this system included) I would recommend as short of legs as possible, then using a drop table (having the feet higher then the cutting surface) and longer z tubes. You can always have the z tubes stick out the top if they are a little too long. But most of the rigidity issues come from the leg hight.
The one exception to this “rule” might be Menards if you live in a part of the US that has them. In another topic on this forum, someone was able to get 1" SS tubing in stock lengths at his local Menards. I don’t know if that was specific to his Menards or something every Menards carries.
Interesting, I haven’t seen any at my menards but I can never find anything there so maybe.
Awesome, I’ve learned a couple things from starting this thread so that’s good.
I did not know that about the z-height. So let me repeat this back just to make sure I got it all straight. The lack of rigidity comes from the leg height, not the z-height. When I put in my dimensions in the calculator I said I wanted 3.2 inches of z area… I did not realize that this meant with the bit. If I wanted to be able to cut 3 inch material, would I just have to mount the whole machine 3 inches higher than my material floor then? I’m not sure how to calculate my z height if I want to be able to cut 3 inch material. Different bits are going to be different lengths, no? Having longer z tubes will not affect the rigidity?
I do have a Menards in my area, but I’ll have to look into whether they have the stainless stuff. I was initially going to get 1 inch SS tubing, but then when I saw the price I thought I may use the conduit. I forgot that the galvanized parts only go up to 3/4 conduit. I’m willing to use 3/4 if you guys think it would work well at this size. Otherwise I’m just going to figure out how to get stainless for this.
The lack of rigidity comes from the leg height,
Not right, but not totally wrong. The issue is how far the Z axis and end mill hang below the core when cutting. For example, I mount my feet on the base board that is 3/4" below my spoil board, but since the spoil board is above the the base of my feet, this extra leg distance has little impact on my cutting.
would I just have to mount the whole machine 3 inches higher than my material floor then
This depends on how you would would be cutting the material. My formula (not any sort of formal
or recognized calculation) is:
Z working height = Max_Material_Thickness * 2 + 1"
This is for that thickness of material in any situation included double sided milling using clamps. The 1" is to allow for clamps and to be able to drill through the material into the spoil board to put in pegs for double sided milling. Note that you can work with thicker material in certain situations. Say you are using a short v-bit and engraving the surface, you could have thicker material.
My suggestion is to figure out the max thickness you might want, build your Z axis to those specification (lead screw and tubing), but cut your legs to the recommended height for a minimal height machine. That way you get to experience the machine at it “best” in terms of Z height, but if/when you want mill thicker material, you can just swap out the four legs for longer ones…and also get to experience how much impact the taller Z has on your cutting.
I just looked at Menards online site, and found no SS tubing, so it might be only a specific Menards vs. something they all carry.
Good to know about the +1, because I do want to do some two sided milling. This is all very good to know and I appreciate your time in answering. Lastly, will the 3/4 galvanized stuff from the store provide enough rigidity for this size? Or should I try to find the stainless steel tubing?
That doesn’t work so well. You’ll have a hard time finding a bit that long. If you want to cut 1/2" into a 3" block, you would need a 1/2"+ long bit, 3" for the stock, and the bottom of the collet would need to be at least 3.5" from the spoil board, add a half inch for margin, so 4". Cutting 3" into a 3" block is more than 6", but unless it is foam, your bit will just break or you’ll otherwise just have a bad time.
If your xy work area is larger than 24", then you really should get 1" tubing (DOM is cheaper than SS). If you want to cut aluminum, then make it smaller unless you have a ton of patience and budget for scrap.
The 3/4" conduit is measured by the inside diameter and the outside is 23.5mm. 1" conduit is common, but the 1" describes how much wire you can fit in it, not the outside diameter. The outside diameter of 1" is 32mm, IIRC.
Make sure you pick your tubing before you buy or print your parts.
Is two inch material being used a little more common? I’m going to have to watch a video of it being built again to understand the limitations of the z axis. @jeffeb3
this doesn’t make sense to me from what i have read elsewhere here on the forum. i haven’t run any tests myself but it was my understanding that short legs works best. however i could be wrong. i would say the end goal for the most rigid machine would be as short of legs as possible and the material your milling as close to the core as possible.
he is correct about the fact that both the leg height and the Z axis (of the core) both have large effects on the rigidity of the machine. however the legs are sandwiched between the leg caps and the table, so to adjust that height after the machine is built requires complete disassembly of the machine and new leg tubes. while the height of the core Z axis tubes can be longer then what you use. so for example you can have core Z axis tubes that are 12" long but only use 5" of them and the other 7" will just hang out above the core with no real detriment to the machine (other then looks of course). also to change out core tubes you only need to disassemble the core, witch is the last step of assembling the machine.
it is always best to build it to the stock dimensions first! after putting it together and using it a couple of times you will have a much better understanding of where you need to make adjustments to customize the machine to your specific needs.
This is not always true, get pricing for both. In my case the SS was almost $50 less then DOM.
1 Like
Where did you order/get yours from?
Yeah, the problem is if I build it smaller and then want to go bigger later I’ll have to re-buy tubing altogether, and I want to avoid that.
I guess I’m going to have to do a little more research!
my understanding that short legs works best. however i could be wrong.
Most people mount their legs at the same height as the spoil board and make a Z axis to match, so increasing leg length is the same as increasing the Z axis height. But imagine I built a minimal machine, then I swapped out the legs for one 6" taller and at the same time put 6" of spoil board on top of the existing machine. The amount of Z working space and the amount of the Z axis that extends below the core would be identical to a minimal machine. The longer legs would introduce some minor stability issues, but if so, there are corner brackets for the MPCNC out of Thingiverse to address this very issue.
For most builds, this distinction is not needed, but sometimes it is important. I wanted a machine that would cut a bit thicker material but would still preform reasonably on thinner material. So I mounted my legs to a base board and built a machine that would handle 2 1/4" materials. I then made two spoil boards to mount on the base board…one thicker spoil board that would bring the stock up towards the core for thin materials and one thinner spoil board for more working height for thick materials.
adjust that height after the machine is built requires complete disassembly of the machine
As someone who has changed the height of my Burly 3 times, all I had to do was loosen the belts and the screws holding the legs, swap the legs, and then tighten everything back up.
1 Like
i got mine from a small, local, metal supplier and scrapping company. if you live in the west Michigan area i would be happy to give you the name. they explained to me that they have a higher volume of SS tubing so they get bulk prices witch lowered the cost vs the DOM. the SS came out to $75 after taxes for just under 20ft. (my build is a little smaller with a 2ft x 2ft work area).
i understand that, and the 1" tubing is probably one of the most expensive parts of this machine. that is why i think it is better to buy larger tubing and cut it down if you need to. i believe the entire machine can be assembled with tubing that is longer then needed except for the legs. the extra tubing length just hangs out. so getting larger tubing (except for the legs) still lets you build the MPCNC in a smaller size without cutting. so you can test the smaller sizes and see if it works for you before cutting off the extra length. does that make sense? kind of hard to explain. 
That makes perfect sense!
If I wanted to do the same, what is the z height that I would use on the calculator for this? Or should I just use your formula and go to z height of 6"? [(2.5*2)+1 =6 ]
ahh, ok that makes some sense now. but would it not be just as good to have mounted your legs on say 6" risers, then added 6" to your Z tubes, then have 2 spoil boards like you do now, one that is 6" taller then the other. so when you are cutting thin material you have very short legs and uses very little of your Z axis length. and when you are cutting larger material you use the thinner spoil board and more of your Z axis length. or does the Z axis length introduce more instability then leg length?
this is a very good thread, i’m learning a lot too, thanks for asking the question @pab-l0
I’m not an engineer, so my thoughts are just from how I think things work based on my reading on the forum. As for 6" legs and a 6" taller Z axis, the other thing to consider is mass. I did the calculation based on tables on the internet, and each inch of additional Z axis adds around 2.5 to 3 oz. to the weight to the Z axis. So adding an extra inch or two, especially if using the DW660, is not much of an issue, but 6" would add over a pound. That mass has to be accelerated by the steppers.
that is a very good point!