Homemade CNC with Arduino II - Mechanics

Homemade CNC with Arduino Root 3

Written by Mariete

May 9, 2020

Updated: May 19, 2020 @ 06:51


In this article I am going to do a little review of the mechanical part of the Homemade CNC with Arduino Root 3.

Mechanical mounting it's not complicatedalthough I do requires patience to collect the components since, probably, you order most of the pieces from China and it will take time to arrive.

In this type of project, it is normal that the time lengthens because most likely you will have to make several orders since it is very difficult at first to know exactly what you need. There will be things that you will have to wait to ask them to have others in your hands to see exactly how everything fits together.

We can divide the mechanical assembly into four parts:

  1.  3D printed parts
  2. Wood parts
  3. Tubes and bearings
  4. Hardware store

I will try to give you some advice about each of them as we go along.

3D printed parts

You can download STLs for printed parts in 3D from the Thingiverse project page.

Some of the pieces have been improved by other collaborators, so below I will give you some alternatives that seem better to me than the original ones.

You can find more interesting information in the Root CNC website. I recommend that you take a look to familiarize yourself with the material and information there for you know, when the time comes, what can you count on.

Of course, if you have any doubt additional, you can leave a message here, in comments, and I will try to answer you.

3D printing bears long time and a lot of filament.

I think it takes me a few five days, with the printer working almost 24 hours a day, and approximately 2Kg of PETG filament, maybe something else.

About the type of filament, do not hesitate, print the pieces on PETG (unless your printer is one of those that does not get along well with PETG). The PLA is not stiff enough and the ABS will surely give you a lot of warping and adhesion problems, since many of the pieces are quite large.

There is no harm that for good it does not come, while you are printing pieces, it gives time for things to come from China.

The rigidity of the pieces is very important. I recommend, in general, a infill of a 50%, at least, and four perimeters, at least.

At the time of printing, the placement of the pieces on the printer bed is important to give you the least possible problems. In this page you can see the orientation.

Many of the parts that I printed with less infill and fewer perimeters did not last long and it makes it very angry to have to change parts soon. In addition, many did not have the layers well adhered and this later gave problems.

These are the first pieces I printed; At first, as I tell you, then I changed many of them. You can see them in big by clicking on each one:

You will see that there are some pieces variations:

First variation: On the one hand, you have a first great variation depending on whether you use a tube in a metric measure (in millimeters, as we use it in Spain) and another for imperial measurements (inches). These pieces have to match the tube (the important thing is that if the tube you are going to use is 20mm, the pieces you print are the 20mm metric).

Second variation: Depending on the transmission belts you will have to use one or the other. It basically depends on whether they are for example GT2 belts, such as those of 3D printers or other types of belts.

Third variation: Depending on the spindle, motor, dremel or what you use. There are different pieces depending on why you decide.

Also, of some of the pieces, you will see that there are versions made For other people improving some aspect or providing some variation. I recommend the following:

Root 3 CNC Box Section Linear guide Remix

It has a small elevation where it seats the bearing so that you save putting a washer.

I haven't put these on yet but I will when I have to change them.

It's in this Thingiverse page.

Alternative Belt Clamp for Root 3 CNC

Makes belt tensioning much easier of the X axis. With the original part the tensioning is very complicated.

I haven't put this piece on yet but I will do it when I have to touch this part of the machine.

It's in this Thingiverse page.

A tip: Be careful with the filament you use. There is a lot of difference between filaments.

Lately the PETG filament is giving me a lot of problems and I am using SUNLU PLA plus filament to make parts for the CNC.

I leave you these SUNLU PLA plus filament links on Amazon:

Wood parts

The wooden parts are only four. They are the ones that hold the bridge or Gantry (portal), which is what it is usually called in the CNC world.

Just as they say that the Germans are very good industrialists because they make round holes, these pieces are what make everything "fit". That when the CNC has to make a right angle, it should be 90º and not 89.9º or 90.1º, which makes a circle come out perfectly round and not as an ellipse. In short, that the precision of these parts is very important, not so much its external cut, but rather that the position of the holes is as precise as possible.

Ideally, these pieces should be made for you someone who already has a CNC. If not, as was my case, it is best that you do some paper templates, make the cuts and holes by hand as best as possible and, when the CNC is already working, return to make the final ones.

I leave you some photos of the construction of the first pieces, in MDF (the final ones were in phenolic plywoodwhich is much harder and has much less flex).

Tubes and bearings

The Root CNC is cheap because, among other things, instead of using commercial linear guides (which are very expensive) it uses an ingenious system of "roller skates" with economic bearings, those used in skateboards, which slide on square tubes.

The tubes in the normal version of Root 3 are 20x20mm (there are other versions with larger tubes to give it more rigidity).

These tubes can be made of steel or aluminum. The important thing is that they are as rigid as possible.

I first used some 20x20mm aluminum tubes purchased from Leroy Merlin 1mm wall. Although the CNC worked, these tubes were not stiff enough and the finishes were not good, the machine sometimes clogged and jerked. After a short time I exchanged them for 20x20mm 1.5mm wall steel tubes, also purchased from Leroy Merlin.

My advice: no aluminum tubebuy the stiffest steel tube with the thickest wall you can find. I am something that I have pending in mine, to change the tubes for others of, at least, 3mm of wall. The operation is acceptable with the 1.5mm ones but I am sure that with the 3mm ones it will improve a lot.

As for the bearings, I have little to say. I buy the cheapest ones I found on AliExpress and it is working fine. I am sure that with better quality bearings it would work better but, as I have never used them better, I cannot tell you.

Of course, the CNC raises a lot of dust, a lot of shavings, and a lot of crap, whatever they are closed bearings, do not even think about putting in a CNC bearings that take the balls to the air.

Hardware store

Nuts, screws, washers ... crazy… It seems that you never finish buying screws for root 3, you could write a book.

One of the worst things is that there is no shopping list definitive and in conditions with models and quantities of screws. There is to be based on the list that comes with the documentation and then go investigating and seeing what is missing (I assure you that you will have to make more than one order of screws, and probably more than two).

Be careful because not only do you have to buy many measurements but many types different.

Don't forget the washers, they are many and of many types ...

There is a good budget in hardware. I recommend you buy the screws in RationalstockIt is where I buy all screws for years and it is the cheapest screw site I have found Worldwide (and by far).


Have you already read the introduction to the CNC? If you didn't do it now: Homemade CNC with Arduino Root 3.

Building the CNC Root 3 has been a very nice and interesting project, and it's amazing what you can get to to learn.

Is not difficultIt is simply a matter of going step by step and with patience.

Soon I will write the rest of articles, with more detail of the construction of each of the parts. Don't forget to subscribe to receive a message when they are and not miss anything.
If you liked the article, I will really appreciate it if you spend a minute on leave a comment below.



  1. JuanMa

    Very good initiative Mariete, it seems to me a great informative work.

    • Mariete

      Thank you very much, JuanMa.

      I'm glad you like it and find it useful. I hope that in the future you will continue to find things that you find interesting.


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