The woes of new machine setup

Finally got a day to get the new Longmill dialed in and maybe get some test cuts going. Not more than 45 minutes into it, just short of preparing to cut anf place my spoil board and all of my stepper motors start stuttering. It really acts like a power issue. The light on the longboard starts pulsating when the steppers start chugging.

Such a drag. I checked all of the wiring. Everything looks good. Sent a message to Sienci to see what they think. I’m thinking power supply. I metered it at ~22v. Couldn’t check amps, but the LED on the LB pulsating tells me that there’s got to be a power problem somewhere.

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well thats a bummer Jim, hope you get it resolved quickly.

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I was have that issue and my backlash bolts were to tight. Check that also.

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I gave it a break and went back out the following morning with the same results. Seems after about 45 minutes of “on time” doesn’t really even mean running as I have yet to turn the spindle on, the symptom returns. I’m pretty convinced I have a bit of bad electronics, I’m betting the power supply but maybe something wonky in the longboard that loses connection when it gets warmed up.

Being a Saturday when I reached out to Sienci I knew I would have to wait until Monday before I heard anything but I’m confident they will assist.

I was able to jog my limits and measure so i can get my spoil board designed. I’ve not spent much time with Fusion 360 so it was good experience. Historically I use Vcarve Desktop but it doesn’t design large enough and I don’t care to pay for the upgrade to Pro.

Still waiting to hear from Sienci but went out to the shop and metered the power supply this morning having not been on and the power supply reads 23.6V. I think this further confirms my suspicions of a faulty power supply… losing connection inside as it warms up. Sent Sienci the update and hope to hear from them today.

Jim I am surprised you have not heard anything, If I were in your position I would be making a call, 1-855-220-1231.

That’s my tomorrow plan. They say that it can take 24 to 48 hours to respond. I figure 2 full business days covers that, 4 calendar days in total. I’m a pretty patient guy but I also have limited time to work with my new machine and losing another weekend of productivity will be disappointing.

Heard from Sienci today.Jason suspects a faulty driver is triggering the overcurrent protection in the longboard. Shipping me a new one. Fingers crossed it solves everything. Won’t be here until Monday though. I can at least get my spoil board cut to size and have the drill code done for the inserts.

That is good news, hopefully be up and running soon.

Finally got the new LB installed and ran some test runs. Same condition popped up. Gonna have to reach back to Sienci and see what they say this time. I still think it’s the power supply. I wish I had a suitable power supply on hand to test this theory with.

Jim, have you checked incoming power to the power supply. I dont think that 23.6V out will cause you an issue but if you have fluctuating voltage under load that could cause issues. I would check incoming voltage and neutral to ground on the supply side which should be zero. It is possible you have a floating neutral which could cause fluctuating incoming voltage to the power supply. Really hope you can get this sorted.

I’ll double check the circuit. It’s a new installation but I certainly could have screwed it up.

As a point of clarity, 23.6v was cold without having been run. After 30-45 minutes it gives me more like 22v but it fluctuates rapidly, again without load. When I check it while connected to the LB its closer to 8v.

8v is too low. Pity you do not have a 12amp power supply laying around. I would be tempted to buy a power supply just to try it out. Hopefully sienci can get you sorted.


I have no idea what happened there. I have hands the size of basket balls so probably meant to hit something else. That should have said 20.8.

I ran it again this afternoon and took careful meter readings. I confirmed the circuit is good. When the machine started acting up the power supply readings were much the same. I really wish I could look at amperage. I have a suspicion that is where the story is. My meter only reads AC amps so I’m out of luck there. Being a brand new machine, I know Sienci will do right by me but, I really just want to be able to use it. I have precious little free time and I would rather spend it making cool stuff and not chasing bugs.

New power supply is on the way. Fingers crossed that the problem will be solved and I can get to making stuff! Thankfully, sugaring season is done so I should be able to get it running this weekend.

Power supply arrived yesterday and, with nothing special planned for today, I got busy. Spoil board drilled for insets, 64 1/4-20 threaded inserts unstalled, board surfaced, router trammed and board resurfaced, risers installed to get my Z height back and checked for square. No issues with the machine at all. Ran solid. Looks like the issue is resolved!


Yahoo Jim, its been a journey, glad your finally up and running.

@CncJim As you have resolved your issue, I am closing the thread. I’m glad that you are back up and running, Jim.