Home CNC with Arduino II - Mechanics

Introduction

In this article I will take a brief look at the mechanical side of the Homemade CNC with Arduino Root 3.

Mechanical assembly it's not complicatedalthough it does requires patience to collect the components, as you will probably order most of the parts from China and it will take time for them to arrive.

In this kind of projects it is normal that the time is long because most likely you will have to make several orders, as it is very difficult to know exactly what you need at the first time. There will be things that you will have to wait to order until you 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. Wooden parts
3. Tubes and bearings
4. Hardware

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

3D printed parts

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

Some of the pieces have been improved by other partnersI will give you some alternatives below that I think are better than the original ones.

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

Of course, if you have any questions You can also leave a message here, in commentsand I will try to answer you.

3D printing leads to a long time y a lot of filament.

I think it took me about five dayswith the printer running almost 24 hours a dayand approximately 2Kg of PETG filamentmaybe something else.

About the type of filament, don't hesitate, prints the parts in PETG (unless your printer is one of those that doesn't do well with PETG). PLA is not rigid enough and ABS will probably give you a lot of warping and adhesion problems.The pieces are quite large, as many of them are quite large.

Every cloud has a silver lining, so while you're printing parts, there's time for things to arrive from China.

The rigidity of the parts is very important. I recommend, in general, a infill of a 50%as a minimum, and four perimetersat least.

When it comes to printing, the positioning of the parts on the printer bed is important to ensure that you have as few problems as possible. At this page you can see the orientation.

Many of the pieces that I printed with less infill and less perimeters didn't last long and it's very annoying to have to change pieces after a short time. Also, many of them didn't have the layers well adhered and this later caused problems.

These are the first pieces I printed; at the beginning, as I said, I changed many of them. You can see them bigger by clicking on each one of them:

Keep in mind that the parts to be printed have a lot of plastic and will take several hours to print.

I recommend using a quality printer. I use a Creality CR-10. Here are a couple of the best selling Creality printers, highly recommended.

There is nothing worse than having been printing for hours and having spent almost a kilo of plastic, only to suddenly realise that the print has been ruined by the poor quality of the printer and you have to throw the plastic away and start again.

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

You will see that of some pieces there are variations:

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

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 straps, such as those for 3D printers, or other types of straps.

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

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

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

Lately I've been having a lot of trouble with PETG filament and I'm using it to make parts for the CNC, SUNLU PLA plus filament.

Here are some links to SUNLU PLA plus filament on Amazon:

Wooden parts

There are only four wooden parts. They are the ones that hold the bridge o "gantry (portal), as it is often called in the NCC world.

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

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

Here are some photos of the construction of the first pieces, in MDF (the definitive ones were made in phenolic plywoodwhich is much tougher and has much less flexion).

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 "skates with inexpensive skateboard bearings that slide on square tubes.

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

These tubes can be made of steel or aluminium. What is important is that they are as rigid as possible.

I first used 20x20mm aluminium tubes bought at Leroy Merlin with a 1mm wall. Although the CNC worked, these tubes were not rigid enough and the finish was not good, the machine sometimes jammed and jerked. After a short time I changed them for 20x20mm steel tubes of 1.5 mm wall, also bought at Leroy Merlin.

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

As for the bearings, I have little to say. I bought the cheapest I found on AliExpress and it's working fine. I'm sure that with better quality bearings it would work better, but, as I've never used better bearings, I can't tell you.

Of course, CNCs kick up a lot of dust, a lot of shavings, and a lot of dirt, however they are made. closed bearingsDo not even think of using air ball bearings in a CNC.

Hardware

Nuts, bolts, washers... crazy... You never seem to finish buying screws for the Root 3, you could write a book.

One of the worst things is that there is no shopping list and in conditions with models and quantities of screws. You have to base yourself on the list that comes with the documentation and then go on researching and seeing what is missing (I assure you that you will have to place more than one order for screws, and probably more than two).

Be careful, because not only do you have to buy a lot of measures but many types different.

Don't forget the washersThere are many and of many types...

There is a good budget in hardware stores. I recommend you to buy the screws at RationalstockIt's where I've been buying all my screws for years and it's the cheapest screw place I've found. worldwide (and by far).

Conclusion

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

Building the Root 3 CNC has been a very nice and interesting projectand it's amazing what you can achieve learn.

It is not difficult toIt's simply a matter of going step by step and with patience.

I will soon write the other articleswith more detail on the construction of each of the parts. Don't forget to subscribe to receive a message when they are there so you don't miss anything.
If you enjoyed the article, I would be very grateful if you could spend a minute to leave a comment below.