Can only go one pass

I can only go one pass before it veers off course. I just built this machine but I had already used the grbl boards and they worked before. Any ideas?

You really need to provide more information while seeking advice. Several of us here have built CNC machines of our own design and almost everyone has built a machine from a kit.
If you’re “veering off course”, you’re most likely losing steps. You lose steps when your machine can’t overcome the force required to move as planned. Why? Can’t say without some details.

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Pictures of your controller / GRBL board please :slight_smile:
What steppers you got?
What PSU voltage?
What are your $100-102, $110-112 and $120-122 values?

Right now we have a “the car dont work” scenario but know nothing about the car :slight_smile:

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I am using nema 17 stepper motors. I don’t have a power supply box as I plug the board directly into the wall.

Nema17 with A4899 / DRV8825 drivers are marginal at best.
You do have a power supply, its inside your box, what kind of voltage do it supply your stepper drivers with? 12V? 24V?

Bottom line - this arrangement is weak and very prone to stalling. (I´ve been there)
With a very rigid and very smooth machine it can do wonderful stuff, but the envelope is very small and limited.

Kudos for making your own, its very rewarding, and frustrating… :wink:

I let it go this time and it seemed like it enlarged the carving every time it went around

Enlarged or offset to the one side?

My advice to you is to take a video of your machine, where you jog it around and show us with sound how it work. Post that video to a youtube account.
It will tell us a lot.

Will do

I can’t, it is pretty much not working at all right now so I will send some pictures

The first problem is in this photo. The yellow side gets left behind causing the machine to stall.

That is the front and back of the y-axis
This is what it did. Near the blue line you can see what it did the first time around and next to it is what it did the second time around. It did not get to the other side before stalling where the yellow is. Also the z-axis moves around a lot when the x axis is spinning bumping up and down.

I know there are a lot of problems and I am pretty close to just giving up.
Thanks for the help.

The biggest problem right now is the y axis pulling one side more. When I built it I made sure it was directly in the middle.

Your primary two problems are:

  • 1 - Weak build (not rigid or smooth mechanically)
  • 2 - Insufficient power (steppers too small and underpowered)


  • You can improve the build by adding a 2nd Y-stepper/screw so each side of the gantry have its own mechanics. This will improve axis rigidity by a large amount.
  • Change the drawer slides to SBR16 supported rails.


  • Exchange the Nema17´s to Nema23´s, even the 140oz/in size will offer significant potensial.
    But I´d recommend getting the 270oz/in kind
  • Get a 36V PSU and use TB6600 stepper drivers.
    This will allow the Nema23´s to utilize all their strength.

I commend you for building your own DIY CNC machine, most dont do that :slight_smile:
If you think CNC is a cool thing, keep at it - but I would advice you to consider a rebuild, smaller in size (easier to get rigid) learning from your first iteration.

My first iteration CNC was similarily weak, and I have walked the upgrade path suggested.
Its frustrating, but also very rewarding. CNC isnt easy, there are a lot of things to learn - and it do take time :slight_smile:

I have looked at the rails and the other motors but my budget was basically 200 dollars. :slightly_smiling_face:
Thanks for all the help and advice!

$200 get you what you got unfortunately. One can simply not expect much else with such a restricted budget, assuming you need to purchase everything new.

Having said that, I had some success with Nema17´s myself but it was still prone to loosing steps.
If you use the same hardware you got now, build a smaller but more rigid machine/sturcture you may have better success. However Nema17 with A4899/DRV8825 drivers and unknown supply voltage can only do so much.

$200 would get you 4x Nema23, 4x TB6600 (or 2nd hand TB6560), Ardunio UNO and a 36V PSU.
It would be a significant power upgrade. Get them 2nd hand if need be.

Do you guys know a way I could wire two stepper motors together for the y-axis? the grbl board only has three axis spots.

Yes, that can be very easy.

If your GRBL gshield have four drivers slots, typically named X/Y/Z/A.
A can be slaved to any of the three, typically Y.

if you have individual drivers (like TB6600) then simply split the signal to the two Y-drivers.

It only has 3

What board? Be specific. Give us a link.

That is the grbl board