Runout of 24V DC spindle?

I originally purchased a Shapeoko 2 and used a Dremel 4000 as the spindle. With it I was very pleased to be able to make 10 mil traces out of the box with 20deg x 0.2mm v-bits. With the X-carve upgrade kit, I purchased the acme lead screw and the 24V spindle. I have only upgraded the z axis to the x-carve components, but the results so far have been lacking.

First, is the DC spindle supposed to vibrate the entire machine? With the dremel the vibration was mainly just in the dermel itself, but with the spindle there is significant vibration passed to the X carriage, the Y axis, the base, and even the table.

Second, trying a test board I couldn’t even do 16 mil traces. I just measured the runout of the v-bit to be over 4 mils, which seems extremely high. The website lists the ER14 collet as 0.6 mil total runout, but is that just the collet or the collet when attached to the motor?

Here is a photo of a test board done before the upgraded spindle.

So you are saying that when the spindle is on and not cutting then the whole machine vibrates? If so, something is wrong. I’ve been lucky enough to not to have a bad 24v spindle and it runs great, and when it isn’t cutting it is pretty quiet, but one thing it definitely doesn’t do is vibrate the whole machine.

I agree with Sketch42. Even under some load mine does not vibrate the whole machine. have you made sure everything is tight and square?

Mine howled wxcessively at first, I reduced the spindle rpm to 7-10000 via easel and found thet the er11 collet wasn’t seated properly into the nut. I had ordered the 1/4" collet in addition to the 1/8" .

Smoothed things out alot.

Yes the whole machine vibrates even when not cutting. The noise of the spindle is comparable to the dremel at 20-25k rpm, probably because everything vibrating is amplifying the sound. The only changes I made changes I’ve made so far were to replace the z lead screw, the z carriage, and z motor mounting plate, so everything else should still be tight and square. I did try tightening the c-clamp holding the motor and the eccentric nuts.

If I measure the runout at various places along the collet adapter and bit it looks like there is angular runout. Near the top of the collet adaptor there is only 0.5mil runout. Lower down on the collet the runout is 3 mil and if I measure on the bit the runout is almost 5mil. Could it be just that collet adapter isn’t aligned with the motor? Maybe the vibration I’m seeing is from the off-axis collet?

jkWestphal, how could you tell the collet wasn’t seated onto the nut? I’m using the 2 wrenches to tighten the nut.

The collet will click into place inside the nut before the bit goes in the collet’s lower face should be almost flush with the lower face of the nut.

See here for some good collet and nut tips:

Thanks for the informative video. The collet in my case was properly “clicked” into the nut before tightening the nut with the wrenches. I taken the bit out several times now and I still get considerable runout that increases the further from the spindle bearing you get.

Is it possible to remove the collet adapter from the spindle? If the off balance collet adapter / collet / nut / bit are what is generating the vibration, removing these should stop the vibration. Otherwise it would be a problem with the spindle motor itself.

It seems likely either the spindle rotor is bent or the collet adaper is not on axis with the rotor.

Have you tried running the motor without the collet and collet nut?

If this produces the same result, on mine the collet adapter is secured with a pair of hex head set screws. I loosened them but the adapter is on there quite securely yet.I’m not sure if it’s pressed on or some sort of adhesive is used.

Within easel under the machine banner you can change the spindle speed. drop it by half and see how it behaves. Being these spindles are not top of the line to keep the price point viable for beginners it may be possible that yours isn’t as balanced as a higher end unit may be.

Probably a bad spindle. I had the same problem. Initially I just thought the spindle was just a ridiculously bad model, but soon after mine self-destructed. Others have had great success with the 24v stock spindle and have had many hours of cutting time. Mine was a wreck from the start and vibrated like crazy. I could grab the spindle and physically move it around like there was no loading within. Did you try it yet without the collet and nut?

I have tried running the motor without the collet and nut, and it seems to run slightly faster and more quietly. I tried removing the set screws you describe, but could not get the collet holder off with gentle prying, which is why I asked. Frankly, when I received the spindle I was surprised how thin the spindle shaft is; it seems like that’s a weak point in the design.

I’m using a power supply I already had and upgrading from the dremel, so I don’t speed control yet (I’m waiting for it to be available on the inventables store).

… after a little tinkering …

And maybe the “weak point” was intentional? Using a dial gauge and some brute force, I was able to bend the collet back to ~1-1.5 mil runout on the tool bit and rerun my test pattern. Here is the result.

From left to right, the vertical traces should be 10, 12, 16, 20, 24 mils. A quick check with some calipers shows that the actual board traces are about 1.5mils wider than nominal, but that is likely because I was cautious with the mill depth. Compare to before fixing the runout, where the 10mil,12mil, and some of the 16 mil traces were completely gone.

P. S. the “thermal vias” should have been exactly centered on the square except for operator error (changing a bit and then “go to zero” requiring an e-stop to prevent the bit crashing, and losing a little bit of registration in the process.)

If you’re having problems with fine traces being obliterated when milling a pcb, your spindle may have large runout. Just using your hands and a dial gauge you can bend the spindle to minimize runout. It also helped to reduce vibration.

If you have a large runout, the forces on bits are much higher than normal and i would imagine they would break often. The whole machine still vibrates for me, so maybe it is a bad spindle.

Can anyone else feel the hum of the spindle on the y rails or in the base of the machine? Fixing runout helped some, but it’s possible the entire spindle is unbalanced leading to most of the vibration. Coming from the dremel which has a rubber coating, I’m not sure how much vibration to expect with the rigid mounting of the DC spindle.

I’ve said it before and I’ll say it again. This is a low cost DC motor that has a ER collet adapter attached to it. It is not a CNC spindle that incorporates the tool holder right into spindle with a minimum of stick out from the housing.
There is no bearing preload and the bearings are low cost bearings that have a lot of slop in them.
A bent motor shaft of just a couple of thou will cause a large run out at the tool.


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Might as well give a full description of the board for reference. The board is 1" x 1.75"

The bottom right has a SOIC-8 and DIP-8 footprint (0.8mm holes). Middle right has QFN-20 and QFP-32 footprints with 0.4mm holes. Both of these devices have 0.5mm pin pitch. The QFN-20 has rectangular pins whereas the QFP-32 has rounded pins. The top right has 10,12, and 16mil traces, along with SOT23-8 and MSOP-8 footprints.

The left side has resistor footprints from bottom to top of 0402, 0603, 0805, 1206, and 2010. Meanwhile the traces increase in size left-to-right from 10, 12, 16, 20, 24mil.

The workflow used is Eagle–>PCB-gcode–>Chilipepper–>Tinyg. I used autoleveling in Chilipepper to probe the board height before milling the traces. Mill speed was 6 in/min. Bit was a 20deg x 0.1mm v-bit (measured to be actually 0.107mm).

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Hi KyleJacobs.

Can you share this neat eagle board (gcode file would be great).

I’m calibrating my new x-Carve and would like to compare the results with your’s.

Here’s the eagle board file. You’re best bet is to generate the gcode yourself with pcb2gcode, so that you can be sure the depth, speeds and other cnc details are correct.

Test board_1.brd (84.3 KB)

Thank you sooo much!
I’ll post my results when I get there.

Thanks again!