5th crash in 12 months

I got the 48 x 30 February 2023 in the past year I have had issues with the machine racking/jamming, Up until yesterday I had 4 crashes always on the right y rail. The x rail would jam on the right y rail. When it occured I would always check/replace wheels and delrin nuts and couplers on y rails. But could really not find an issue, even unbolting machine from table then remounting, last time I checked for square using the gsender tool 300mm on X 400mm on Y gave me 500,5mm give or take on the hypotenuse. I had been fairly convinced that I was having a motor stall issue. so I swapped y motors and cable and went as far as swapping the cables on the yi and y2 drivers.
So yesterday I had a particularly dramatic crash the resulted when the when the x rail was traveling from the front to back. When this occured I was at the table saw about 30ft from the mill when I heard a loud crack. when I got to the mill and prior to hitting the e stop the left y motor was running but I am not sure if the right motor was. To free the x rail I had to unmount the machine at which point the x rail fell free of the y.
I have completely dismantled the machine at this point and have found the right side top v wheels shattered, the bottom v wheels gouged. Gouges on the right y rail from the gantry being forced into it. The right y leadscrew severely bent. Delrin nut damaged. On the left side the v wheels damaged. The delrin nut destroyed. Removing the motors I find evidence of shorting/burning of the red wire at the cable to motor plug (right side). There no evidence of the coupling slipping either on the motor shaft or leadscrew. when I had everything apart I connected both y motors and they ran but had no load on them.
My concern is do I have a driver issue and how could it be tested for an intermittent failure?

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Hi Mickus,

It might be that the shorting of those exposed wiring could happen due to fibrations running the machine, stalling one motor and leaving the other running as it should. This would explain the problems you have had and have now.

I think that if you get the wires sorted and the damaged parts renewed, your problems might be gone for good. Connecting issues can have you scratch like that untill they escalate.

I had issues with my touch plate, having it to not detect my bit. After some nasty crashes I found out the connector was badly wired. Fixed the issue, never to have any problems again.

Your crash sound terrible and I am sorry you have such bad luck. Any chance you can contact sienci about it?

Thanks Eddie, I should have been more specific. The issue was in the cable to motor connection plug, with the pin for the red wire being burnt. But what you say still stands. I did ohm out the cable then connected the motor and it ran OK. So I question if the short was the root cause or the result of the jam as the motor would pull a higher amperage due to the resistance to movement. I looked at the board and visually it looks OK. But I do question if it really is, and I still cannot make up my mind if I should just replace the board also.

@Mickus You should definitely open a support ticket with Sienci. I have never read of a Long Mill structurally destroying itself like yours has done. I am sure that Sienci will want to look into this and help you out.

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Yes I intend to call and email this morning. I wish I would have taken the time to look at everything before hitting the estop because at that point the damage was done. I am confident the left y motor was still running but not sure about the right side. If as I suspect the right side was running surely the machine should have stopped as if it was running and stalled there would have been no feedback to the controller from right y motor. I need to power up the longboard an look at diagnostics.

I had a similar issue on my z-axis motor. I kept getting random z plunges into my work. Closer inspection of the wiring and motor reviled a scorched wire at the motor plug. I replaced the motor and wiring and have had no further


Looks very similar to mine Jim, I have decided to swap the motor and cable and ordered a longboard for good measure. Hopefully that covers all bases.

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This is an update and the issue is likely solved. I completely dismantled the machine:
Had damage on Y rails due to the X rail racking so bad, feathered damage up with emery cloth.
On disassembly found stripped bolt X rail to gantry right side, re-tapped hole.
Right y motor burnt connection, replaced motor and cable.
All V wheels replaced, total of 4 completely broke and 2 with gouges.
Replaced all the bearings.
Replaced bent right leadscrew.
Replaced all delrin nuts, left side nut stripped right side not too bad but damaged.
Replaced all motor couplers, used a similar coupler but with the addition of set screws that screw down onto shaft.
When I had it back assembled found the IOT not getting power, ended up replacing IOT.
Also took the time to replaced the spoilboard.
I was concerned if I had an intermittent issue with a driver on the longboard so I have a longboard on backorder and I think that would complete the repairs and solve the issue.