Spindle tilted


is there a way how to adjust it?

Primo with 25.0 stainless steel. Problem visualized with 25.4mm 3 flute “wasteboard” bit.

Easyest would be to shim the pipe on mounting points.

Uploading: 16229750757792383416083444039244.jpg…


problem no 2. I was milling 24000 rpm. it left burning marks on the mdf. Should I cut less material with 1 pass or reduce speed?

Assuming your ruler is perpendicular to the work surface, you are off by a lot. I would explore a manufacturing or assembly problem before I took the shimming step. I’m not sure if this applies to the Primo, but there was a squaring step in the Z assembly for the Burly,

Ryan: At this point hang the assembly off the edge of a table. Make sure the rails are sitting flat on the table, if it is not loosen, push down on the rails, and tighten the toolmount screws. If the rails are twisted it will rock back and forth…that is bad.

On the Primo, there is also this note about adjusting the core:

Ryan: You want each bearing to be in equal tension. This flexes the Core properly and keeps the Z axis perpendicular to the work surface.

And you want to make absolutely sure your legs are adjusted to the same height, and indicated in the the “Leveling” step on this page.

If you are confident that your assembly is correct, then you can resort to tramming and shimming. Shimming inside the mount will give you more flexibility than trying to shim at the attachment points. For determining where and how much to shim, a tramming arm is used. There are a couple of simple tramming arms on Thingiverse, plus they are easy to construct out of scrap wood. By rotating the tramming arm and measuring how far it is off the surface, you can accurately determine where and how much to shim.

As for the burning, with a sharp bit, it is usually caused by either 1) the RPM being too high, or 2) not moving the router fast enough. Each turn of the bit needs to shave off material, moving too slow or at a too high RPM means you grind the material creating heat.

In addition to the router being off square, scalloping like I see in the photo can also be caused by deflection. And you can have both squaring and deflection issues. Deflection can be caused by pushing the limits of the machine, but can also be caused by looseness in Z the axis. Check your Z axis for play. If it is okay, then reauthor your surfacing pass with a smaller DOC plus a smaller stepover. I think I use 1/4 of the cutting width (6mm) for my stepover when I surfaced my spoil board. I’d practice on some scrap to make sure the problems are worked out before I resurfaced the spoil board.

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My core is off by a little in the Y axis, and when going positive Y, the 1" surfacing bit will often scorch the material a little, because the lower part of the bit rubs instead of cuts the material.

If I surface with the bit moving in X, I get ridges in the material, but no scorching.

I think mine is a matter of a small imperfection in the router mount print, and I could probably fix it with a better print. I just haven’t actually done that yet.

I’d check if your Z tubes are perpendicular to the table, using a square. If they are, then it’s the router mount, or shimming the router will do the job well enough. If not, then some tramming work on your core is going to be needed to solve the problem.

I think it might be the part, but I don’t fully
understand what to tighten to pull it straight

This might also be, but I think this makes X and Y square.

I found that the gantry clamps also keep the core stable relative to the X and Y gantries. They might allow a little bit of flex too with the top and bottom bolts. A small adjustment there will allow the core to adjust a little relative to its axis.

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Dan and Robert have you covered, all great advice.

I have one thing to add. Your test with a 1" surfacing bit is a brutal one. Should you fix that lean, absolutely, would you notice it very much with a 1/8" bit…probably not.

I highly suggest using the CNC for a while, get it dirty, break it in, learn some things, and make some mistakes. Then come back and try to figure out why you have a lean. After some use you will want to see if things are still square anyway.


I have the same problem. I have a minor tilt which I can only see with a 16mm surfacing bit and only barely. Still it pisses me off. :smiley:

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I have still few issues to fix. Ordered by mistake a 2mm lead leadscrew. Decided not to mess with Marlin, and am waiting for the proper leadscrew with 8mm lead. I can use the machine, but have to calculate a lot Inserting instead of 22mm cut depth 88mm in Estlcam :sweat_smile:

I started testing with MDF, but after cutting plywood, I will probably avoid MDF in the near future. What creates the burning marks with MDF? Spindle too fast, X and Y too slow?
No broken bits so far. Cut into a bolt head once, but was surprised the single flute bit was still ok. Found nice curly iron from the wasteboard later. Probably the 4 times slower z speed saved the bit and machine. I use 3,175mm (1/8?) single flute and 3,175 ball nose mainly for now.

Have reprinted all 4 top covers on the legs, used too much force tightening them down, all cracked. Broke several stop blocks for switches (dual endstop). Had connected left switch to right motor, the stop blocks were the first to give up. 1 top leg mount has also few cracks, but decided not to rush changing it.

Have bundled the z motor cable and 1,5kw spindle cables together. Decided to take the risk.

Need a real project for the MPCNC now. I am testing with the dxf files that I have created in the past to order stainless steel parts from a laser cutting company.

Need to finish the electrical cabinet, and make a case for the Ramps display and Jamie`s analog joystic.

As mentioned in my previous post, both of these play a role in whether your endmill is cutting or burning. The number of flutes on your endmill and the diameter of the endmill also play a role. The first place I really got this concept was this video.

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Sorry, I focused on the tilt when reading it the last time…

Thanks for the video, got few things more clear now!