VFD/Spindle not able to maintain speed?

CNC Machines Shapeoko
1

(Shapeoko 4 XL with Carbide VFD)

Last night, I noticed a “cycling” sound while cutting, but didn’t think too much of it. This morning, it got much worse…turned off the VFD/Shapeoko/CarbideCreate/CarbideMotion, re-powered-up and still have the same behavior.

This is a finishing pass with a 1/4" spiral, so barely 0.02" and you can hear the speed rapidly changing. Additionally, this should be at 18000 RPM, but barely gets to 12000, frequently dropping to 5000 and back. Note that you can hear the cycling even when the bit isn’t engaged

Is this indicative of a parts failure?

2

I had the same problem awhile back. Check the solder connections on the aviation plug. One wire may be broke and is barely making connection.

3

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4

Unfortunately, that didn’t do it. Took apart the connection, re-tightened everything down and still the same issue

5

Now it doesn’t spin at all. The connector to the motherboard seems awfully wiggly for an electrical connection.

Does anyone know of a way to test that the VFD/Spindle work, independently of the machine?