Ghost in the machine.. wanders off when profile cutting

Yeah they are the strongest and by far the most rigid.


as stated… does everything you need. :star_struck: :star_struck:

edit… I’ve ordered a 2 flute up cut end mill 4.5mm

Hope someone can fill me in regarding wiring up a 12V fan to an SKR Prov1.2

on a side note: GO Australia ( gold medals in the swimming )

you mentioned earlier wiring up a fan to 12V so it constantly runs while machine is on.

Is there a particular outlet I can use for a SKR Pro V1.2 as there are three dedicated fan outlets FAn 0,1 & 2. but am thinking there’s an easier way yes… to avoid having to change settings in Marlin

Just hook your fan to the power input for the board. Jam the wires under the screws that hold the 12v+ and 12v- from your power supply.


With a 2 flute, start with your router’s RPM as low as it goes. a two flute has a cutting edge twice as often as a single flute…twice the load. So if you spin it half as fast it would be equal.

I had this problem too with the same board. Even the shaking in the belt sounds familiar. The connectors of my steppers and board were different types so the connection was never rock solid. Yours are probably the same way.

If this isn’t something you’ve tried yet give this a shot: Make sure your stepper wiring is making good contact with the SKR and then hot glue them in place at the connector. Not a lot of glue but just enough to keep any wiggling from happening at the connection point. Not too hot either, use the lowest temp setting on the glue gun. The glue isn’t permanent and can be removed by hand or with a light bath of isopropyl alcohol and tweezers.

This fixed the issue for me. No problems after 50+ hours of run time.

Hope this helps and good luck.

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This is what I do. To be clear, it is +12V and ground, not -12V.

I’m a mech Eng so I should at least get credit for close enough?

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SO I’m looking at the fan wires… all three are black but one has a grey dashed line. One must be the signal… the smaller one I believe. just have to plug her in I guess.

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Welp, I’m in over my head @jeffeb3 you’re up. My fan just had a red and black wire

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Yes try the two larger wires. Make sure the fan blows in the right direction. The case should have an arrow on it. If it does not have an arrow it will either not spin in reverse polarity, or the center will get really hot after 30 seconds or so.

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Those fans should have a keyed connector, where there’s a tab on the port that normally only allows the fan to connect one way.


OH NO … I am somewhat concerned as I can smell burnt electrical odour when I sniff the fan closely.

I’ve swapped it for another fan I have laying around. This one is very tight as in the blades seem to be slightly under friction (not spinning freely) I hooked the fan up it lit up and fan rotated slightly.

Hhmm… let’s try another one. (process of elimination here) I’ll pull one from the water cooler CPU fan

Make sure the fan days 12V on it. 5V fans driven at 12V will get too exciting. Same with 12V fans driven at 24V. You can drive 24V fans at 12V.

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yup it states 12V on the fan… just not sure which are positive as there’s 4 wires & all are black but one has a dashed white line denoting POS. but the company states that it’s NEG. Hhmm ??

EDIT - I went back to the seized fan and applied a drop of oil to the shaft rotated it for approx. a minute and hey the fan glides easily again… back in action as this fan has power + some sexy blue leds
I bet Jane will like these sexy LEDS :wink:
BUT I bet after all that… the driver temp. is prob. not the problem.
Process of elimination right - next up check the wiring connection to the X axis driver, might need a little glue to hold it in place.

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4 pin connector means that it’s a PWM fan.

If you hold the connector so that the wires are towards you and the key tabs are down, number the wires from left to right as 1 to 4.

  1. Ground. Or negative DC voltage anyway.
  2. +12VDC relative to ground.
  3. Tach signal
  4. PWM input for speed control

There are diagrams for the 3 pin as well as 4 pin in that Coolermaster link above. The brand of the fan doesn’t matter, since they’re all made to plug into PC motherboards, so they all share the same pinout. Pretty sure they’re made so that if the PWM pin isn’t connected, they run at full speed, I’ve never used a 4 pin fan on anything but a 4 pin connector myself.

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I’ve used a couple of PWM fans without the PWM signal and they have all defaulted to max speed.

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All good now on the fan… I went & purchased a 9cm fan with red/ black wires. (easy install)

Regarding the machne’s performance. I also just received 3 new bits in the mail, one being a 4mm up bit 2F. I’m running it now & all is smooth… BUT I’m a bit paranoid as the shaft length on this bit is 40mm it’s so long !! I’ve decided to slow things down and pray all is OK

So far it looks to be cutting cleanly @ 6mmSec. 2mm depth passes. All the stringy wood shavings have stopped.
As Ryan mentioned earlier… probably the main culprit was the badly worn bit.


Here’s the final result… next up I’ll mount them to the kids B-Room wall

Just glad I can finally get my little factory cherning out a few projects taht have been on the backburner, starting to feel like forever ago.
Now the main issue is Covid and wood supply here in Australia is dwindling at the local Bunnings (aka Home Depot )

Thanks all for your much appreciated input.
Such and awesome community here.