Bed levelling after CNC or Laser module?

Ho all,
today I’ve used the CNC module and now I’m gonna to re-install the 3D print module… shall I need to redo the bed levelling?
How often do you level your bed?

Im releveling/recalibrating my bed everytime i change the mounting of the Toolhead. Learend that lesson with my SN1. Even when pressing the Head into the lower end of the hole and tightening carefully and you are off by just a tiny bit, the adhesion of the first layer is questionable or the Nozzle is to close to the Printsheet and you get a oversquished layer or two.

I found a way not to do this. Every time I mount the toolhead I leave the screws just barely loose, and push down to seat the tool at the bottom of the hole. Then while pushing down snug all screws then tighten all. I haven’t relevelled in some time now. I do check it every time by going to Z=5 and then slowly nudging down to make sure Z=0 is still correct in the middle. If it’s off then I’ll relevel.

I do it every time I change beds/toolheads.
Just not worth the extra couple minutes it takes to make sure it’s right.

-S

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I’m with @sdj544 I relevel every time I remove the magnetic bed.

Ok I got it, thanks for response!

Just one more thing… the bed levelling has to be done just for 3D Printing and with the magnetic bed installed or shall we do it also before use the CNC with the wood bed installed?

By default there is no bed leveling step for cnc. Although I think it can be enabled through. There have been some posts about this before. And in this one the steps to do a manual levelling for the cnc can be achieved:

Note that this is suitable to cnc flexible things like pcb’s or acrylic that will bend with the bed but that you want to be straight.

If you want to carve something out of a massive piece of wood and need to surface to be flat, you don’t want to do this. In that case you want to completely level the wasteboard by going over it with a flat end mill and just carve it flat.
After which you often shouldn’t need to do the above “leveling dance routine” as the surface should be flat. Except if the material you’re carving isn’t completely flat and you want to follow the curves of it. And yes, most pcb plates don’t have great tolerances or are a little bit bent, which brings us back to step 1 :slight_smile:
In that case you should do the leveling with the pcb clamped on the wasteboard and not on the wasteboard directly.

So I guess in short: it depends :stuck_out_tongue:

Thank you for all the great info!

It will carve it “flat”, which is really to say that it will carve it into a shape that’s flat with respect to nominal machine coordinates. That shape is only as flat as the accuracy of the machine, which includes squareness of the machine elements, stiffness of all the assemblies, and linearity of the linear modules.

These machines are not particularly stiff nor are they particularly square. These deficiencies are inherent to the design of the machine. Stiffness can’t be improved without adding or replacing frame elements. The worst offender in stiffness is the movable base. It’s more than 300 mm long mounted on a base less than 50 mm. Nothing’s going to be stiff with a torque ratio greater than 6:1. The whole issue of torque issue wouldn’t even be there had they put in linear bearings near the edges of the platform like every other machine in this class.

Squareness can be ameliorated to a limited extent with careful assembly. For example, there’s enough play in the bolt holes in the base that it’s pretty easy to get them bolted down significantly out of parallel. Some of the squareness problems can’t be even addressed without machining. One such is the base of the Z-axis, where one surface is rough from casting (the end of the linear module) and not machined flat; this will only accidentally be normal to the machined mounting pocket.

I would be mildly curious to see an actual measurement of how flat a base could be milled in the machine itself, but that would take access to a proper CMM (coordinate measuring machine). I don’t have a spare $10K or so to buy a used one.

Or a surface plate (or any flat reference) and jig to transfer dial indicator measurements. I could use the same jig I made for measuring parallelism of my jointer infeed and outfeed tables.
image

Shim the reference surface so that a 3 point plane is coplanar between the reference plate and milled wasteboard, then take measurements with the dial indicator. The jig slides on 3 sharp points on the base and with careful operation is quite precise.

It’s not precise to microns like a CMM, but it can read precisely to about half a thou.