I have an issue where my CNC is splaying out when stepping down. Checked for anything loose, but you can see it’s actually splaying/twisting from the horizonal (X) arm (I can’t upload a video as I’m a ‘new user’ but hopefully this link works - Splaying.mp4 - Google Drive ):
This is resulting in very innacurate cuts, as it splays more with more pressure put on it. No matter how slow a work speed or plunge speed I put, it it does this. It also seems to create a bit of an arc in its cut.
Before I get asked - it’s not a blunt bit. I’ve tried several, new and old. The plunge depth doesn’t seem to matter either - 0.1mm will splay as much after a few cuts as 0.4mm on the first.
Anyone else seen this or anyone else know why it would be having this issue? And more importantly - anyone have a fix?
What kind of bit is it? And what kind of wood?
Admittedly, it looks to me that the bit has not cutting-down ability. The twisting of the head is unfortunately a problem of the Snapmaker - its rigidity in the linear module has limits. But I’ve not seen it that pronounced before, so I assume your linaer module needs tightening. If you’re still within warranty, I’d contact Snapmaker support first, if not, try this: https://support.snapmaker.com/hc/en-us/articles/1500000110341-What-should-I-do-when-the-slider-of-the-Linear-Module-comes-loose- And there are more sources (videos etc.) here in the forum that might help you adjusting the linear modules.
I had the same with some pine wood, where I could see the shifting of the head on harder parts of the wood. I reduced cutting depth from 1 mm to 0.5 mm and that solved it for me. I used the Snapmaker provided 2-flute end mill.
Here’s a video that shows how SM2 mills aluminium, and there also the rigidity of the linear module turns out to be a bit of a problem: Snapmaker 2.0 milling Aluminum - YouTube - but again, your case looks extreme.
A Facebook user solved it with an additional linear module - see here: Snapmaker Enthusiasts & Users Group | First test video of the SnapMaker CNC ultra ^^
And there are others that added linear guide rails to increase rigidity.
Thanks for such a quick reply. I’ll get in touch with SM and check on the tightening vid for my own edification, as it didn’t used to do this, so I assume it’s loosened along the way.
My first clue was similar to you - having issue with the harder parts of pine, which is why I then tried the MDF. Even a V bit does this, but not as pronounced (for obvious reasons of physics).
It looks like you’re using a Dremel bit, not a milling bit. I would recommend using a proper CNC bit. You should also get the backlash tightened. I think between the two, you’ll be back up and running.
@Doogs75 I am finishing up a design which should help reduce the problem of the toolhead splaying out as I have had the same issues. It seems that more than half of the resulting movement is from the entire X-axis linear rail rocking from it’s connection to the two Z-axis linear modules. So rather than adding an entire new external linear guide rail to each Z column I am making a brace that will use a roller wheel to secure its position using the outside surface of the Z-axis extrusions (Pictured Below). The other main issue with the SM2.0 is that the whole bed surface has a lot of movement in it from the same exact issue so I upgraded my unit with rails to support the build surface as you can see from others in My new Snapmaker 2.0 A351 - Snapmaker Showcase - Snapmaker: where creation happens
or
Finally got a version of the bracing system that should be easy and cheap enough for anyone to do! There are still some other mods I’m working on but this should make a noticeable difference in reducing the “Splaying Out” effect while machining. Hope this helps you!
Thanks @Elliot. I’m (very slowly - real life keeps interfering) working on putting “proper” ways underneath the bed, as I’m also one of the lucky ones that seems to have 1-3mm of height difference from corner to corner (when I do that, I’ll get a shop to properly machine the bed frame to flat/parallel). This should force the bed to stay completely level, and it’ll become even more important to stop the splay. If/when I ever get there, I’ll let you know how I go.
- Snapmaker Showcase - Snapmaker: where creation happens 
