Please advice - steel pipes for water

Hi All,

I am new here, just registered. I am planning to build MPCNC, ordered the steppers, control board, power supply and few other small things today. I will write in the build section later on, for the moment please give your wisdom for the following topics:

I read a couple of articles in the forum and for the moment I am settled on 650 x 650 x 100 - 200 all in mm for the size, most probably I will limit the Z axis to about 100-150 mm. Plan to use it for hobby projects and sometimes for aluminum milling. Maybe also some art projects like wood carved doors for kitchen cabinets. I have already a 3d printer and a laser cutter, so this is out of my scope for the moment.

I have 3D printer, Creality CR-10S PRO, so should be no problem to print the parts. In the same time I am not very experienced printing and I am more in direction to order the plastic parts. This will save me the time printing and will guarantee soft start in the project, so I am quite well spending the money on that. What material is used to print the parts, PLA, ABS, the ones that are offered here I mean? If I decide to print them what material should I order and if possible please give advice about settings? I have printed some volume of PLA so far but it looks to me very fragile …

Have you considered using water pipes, zinkated (galvanized) steel pipes, DIN standard? The 3/4" pipes seems to be very rigid and cheap, but outside diameter is 26,7mm? The good thing is that I have them in my local store, EU, Austria (sorry about that, we are metric and under supplied with raw building commodities ). I have in the store also the 1/2" and the 1" from the same type, datasheet attached.

Alternative will be 25mm stainless pipes, 1.5mm walls. But these are much more expensive. Well … they also look much better but this is not for the look … I have them in 1.5m and 2.5m length so I will need to buy also a special cutter to cut them to size. What is your experience with those pipes, is it worth to spend the money?

If I go to stainless pipes what about welding the frame? A proper weld with angles in the corners may be more rigid, what do you think?

Thanks and have a nice weekend!









Welcome to the forum. I used PLA for my parts and they are working very well. I followed Ryan’s instructions on the web site regarding infill.

European pipe/conduit choices is a big question. One thing I know is that standard steel pipe used for gas and water is much thicker and heavier. That can complicate the build. The lighter steel conduit here that is available really is one of the key components of a less expensive machine. Not having access to that type of pipe does change the calculus.

Welding a frame is a different issue. If you can weld that may make it strong on the corners and side rails, but then you can’t disassemble very well. I also wonder how 3D printed parts manage with the stress of heavier pipes.

Certainly lots of things to think of. Good luck. Tschuss.



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The “STD” DN 20 pipe from the linked table is a full 1kg/m heavier than 3/4" EMT (1.68 vs 0.68). This is not much of a problem for the outer frame, but it adds significant mass to the gantry which will require lower acceleration values (among other challenges) even if the parts could be modified to fit.

Steel 25mm tubing will be very close, in terms of weight, to the EMT but will have a small bit of additional stiffness due to the larger diameter and the stiffer material.




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Thanks for the replay! The 25mm stainless steel is what you mean?

Thanks for the replay! All the time I was focused on the rigidity and totally forgot the weight :slight_smile: I am mostly in electronics and at minimum in mechanics …

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Did you annealed the parts after printing? My experience with PLA is that it becomes much stronger after annealing but it shrinks kind of unpredictable. What brand filament did you used?

I didn’t anneal the parts because it wasn’t part of the assembly specifications. I think Ryan has thought of all the possible improvements and tested everything out. It works as it is designed. So far I have had no issues with the PLA I had from Hatchbox.

One thing to realize is that the center assembly where the axes come together is a masterful design. It fits together perfectly and is very rigid. I don’t see the PLA parts as an issue because the loads and stresses are well distributed. I did use the Imperial dimensioned hardware but I believe that Ryan has it set so you can use corresponding metric without issue.

For example, today I worked on tramming the mill to get the tip of the mills perfectly perpendicular to the bed. I printed out the tramming tool Ryan has on thingiverse after adapting it to my collet nut and then did a sweep around the bed. It was tilted so the that from 5 o’clock to 7 o’clock position the tip of the tramming jig was sweeping the table about .5mm. I had done a dial indicator on the z axis tubes and they were perfect through a 70mm travel. I did the same with the tool mount that spans the z tubes. It was perfect, so I knew that there was a little bit of play with my tool brackets that I printed. I put some shims at the 11:30 position on the bottom clamp and that trued up the router so that it was dead perpendicular to the table.

So what I am saying is that the axes are stiff enough that I can shim up the tool mount and assume that the basic z axis is going to remain trammed as a part once I bolt the router on.

One thing to remember is that this is meant for wood primarily, as a plotter and as a drag knife. It can do light duty aluminum. It is plenty rigid from what I am experiencing to handle what I want to through at it.

If you want a more rigid setup, especially for milling metals, that is an entirely different realm of a tool.

There is a balance between the steppers, the drivers, the boards, the power supply, the conduit, the bearings, the pla, the size of the build, and the v-belts. Change the parameter of one of those things, and the other things have to change with it.

Another thing to consider is that the standard bit is 1/8". The routers and spindles that use these effectively can be small and light weight. Start adding bigger bits and that requires a different spindle, which adds weight and then this factor is going to affect everything else.

At least this is my thinking. I’m pretty new here. Just have been thinking about a hobby CNC for a long time.


I like the concept of water pipes, because it doesn’t require a specialty store, but more options also produce more opportunities for mistakes. Tube size is already a place where enough people make mistakes, and those mistakes are costly.

So even though I would like it, I think the existing options are a better balance overall, and it’s not that hard to source 25 or 25.4 mm tube.

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You need to choose. The machine can do it all but it will not do it all well, you need to decide. You can not mill a door and aluminum on the same machine and expect good results on both, you will be able to do the door and if you can do any metal it will be extremely slow and always crossing your fingers. One or the other. You can either build a big one and a small one, or learn on a tiny one and decide what to do from there. 100-200mm is gigantic in the CNC world, not tiny.

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Hi Ryan, thanks a lot for your replay! I read here on the forum that the machine dimensions work like x/y vs. z , so if x/y are longer than z has to be shorter and vice versa. It’s like longer x/y is twisting the z axes, therefore I have to keep it short to keep that twist at minimum. Is that all correct? I have measured one typical door yesterday and it seems that i need bigger x or y, something like 900mm x 800mm, so that means my z has to be 100mm or smaller if I want to work also aluminum? It’s a bit difficult to decide as I have no fixed application for the machine for the now and I guess the first version will be used to get more experience before more mature decision. One other question that I have is what is the maximum length of x/y axes for which I can go without additional supports? And respectively what is the optimum distance between leg and support?

Hi jamie, thanks a lot for your replay! Yes, you are right, after some thinking on the topic I came to the idea to check steel vendors and suppliers in Austria and Germany. Most probably I will manage to order standard pipes from somewhere. Using standard sizes have only benefits, so I agree this is the way to go.

I have a Lidl, Parkside pgs 500 a1, 500w grinder (geradschleifer). it comes with 3.2 and 6mm collet M14. up to 30k rpm with knob regulator. Is it suitable as a router? the neck is 40mm. It’s a bit heavy for it’s 500w.


Hi Marion, thanks a lot for your replay!

That’s my thinking too. Once the balance is not there don’t expect something good. In the same time the machine is very much configurable and this is why I came to it. The question is how to configure. I was thinking I can use this machine to jump start another one using it to produce the parts. In this case the time required to do the aluminum milling is not a problem, or hard wood milling and drilling. I think it will not require big z movement to do that. At the moment my 3D printer is printing parts for another printer, I have z=400mm but I am using no more than 100mm …

Last week I am printing with cheap ABS, had some troubles in the beginning until I set the printer, but now it’s working good. The key combo where extrusion temperature and extrusion speed. I am totally blown how neat and strong are the parts coming out of the machine. Using infil only 25% - 30% I have very light and strong parts. Infil is in honeycomb shape. Parts oriented x/y in length seems to be stronger.

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[attachment file=“115163”]

Which wall thickness should i take? What is the electric conduit equivalent and if I can should I take thicker?

I can also use different wall thickness for the stand and for the moving axes (gantry), is that a good idea?

How tolerant are the plastic parts to diameter variation, as example if I paint the pipes are they going to fit during assembly?

Not really. They’re not really made for tolerances, so can have quite a bit of runout at the cutter. Also, like you said, heavy.

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Yep … unfortunately you are right …

There are adapters already designed for it.

I was really hoping for some more comments and help here … I found cheap stainless steel pipes with delivery to my address but can’t decide for the size. I am not much experienced so I really need some help.

Size depends on your projects. Carving foam surfboard blanks, go huge. Making aluminum brackets, go small. You can not do both though.


You can get long rails and make the machine smaller and just leave the pipes hanging out, it will have to be run a little slower but will be more rigid (easier to use). Unfortunately you have entered the land of no best answers (engineering) just explanations of the trade offs you will be making.

All parts ordered. Finally I decided to go for stainless pipes 25mm x 2mm. Plastics ordered from Germany from eBay ( user optimus_prime97 ). All electronics and the remaining of the HW also ordered.

Plastics? The 3d printed parts?

oh he’s actually an approved seller. my bad.