New lathe is possessed

C

cannibal

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Hello! First post but I feel like I'm going to spend a *lot* of time here.
I picked up a new direct from Vevor 7x16 800w lathe. It's listed as a direct drive lathe and sure enough the brushless motor is mounted directly on the spindle, no belts or gears connecting the motor to anything.
I've contacted the company and it sounds like the techs that normally work on this machine are all on vacation or something, but basically they don't have any parts in stock to send me for replacements or any troubleshooting help, they can't even send me a service guide or a wiring diagram for the controller board.

Here are the problems
  1. Speed control knob: it's maxing out at 2500 RPM at about 1/4 turn of the knob and the whole rest of the swing of the knob does nothing.
  2. E-stop electromechanical switch: The machine also takes a long time to turn off once the e-stop has been pressed or the chuck guard is lifted and the safety switch engages. I'm not sure if that's normal on these machines because of the huge capacitors on the board or if they're supposed to shut off right away.
  3. Forward Reverse switch: Lastly when the switch is on the "0" setting between Forward and Reverse the machine will not turn on. Not sure if this is supposed to be an "idle" kind of thing or if the machine is actually supposed to turn off here, again no familiarity with these mini-lathes.

Tested so far:
The potentiometer for the speed controller- It is listed as a 4K7 pot, and testing it with a multimeter accurately shows 4.7K Ohms at the full swing of the dial and the resistance is smooth through the range when the knob is turned.

I checked the electromagnetic on/off switch with built in e-stop, I'm getting 120v at the mains and at the send once the switch is closed. The switch seems to be working fine as far as I can tell with the meter but it's 30 bucks to replace it and from what I've been reading they are notorious for going bad. I might bypass the switch and wire the machine directly from the main just to rule this component out.

I know nothing about this board other than I don't want to accidentally touch those caps. I've checked it front and back for bad solder joints or any obvious signs of bad components but other than swapping the board out I am not sure what else to check for. I don't see any adjustments anywhere on this board and am guessing it's all in firmware/software.

I'm at a loss and I really would love to get this machine working properly to start producing some parts. I have included some attachments in the event that it might help and hopefully the video works, but I am at a loss here and really hope someone might be able to shed some light on what I might do to get it going. Thank you in advance for any help and honestly if you've read this far I feel like I already owe you a beer.
 

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I'm no help with your problems, (old as dirt, don't understand most electronics) but Welcome to the Group. Someone will be along with exactly the right ansers, once they get up.
 
What might be helpful to post is a model number or url to the purchase page. Quite often these lathes have a common manufacturer. Sometimes we can find documentation under a different Brand name.

There's bound to be someone here that can offer help, even if it's not model specific. It's tough getting a new machine starting out when it's not working correctly.
 
You probably won't get much help from the factory-we recommend folks stay away from Vevor stuff.
It looks from the video that there are more problems than just the pot range- motor behavior doesn't look normal.
You would need to do some reverse-engineering to fix the range issue, but you need special soldering equipment
for surface mount components like that- and you would need a schematic diagram
To me it looks like the speed controller is faulty- and there may be other problems you haven't found yet

Frankly if Vevor won't provide any service I would return the machine- get your CC company involved if necessary
You should not have to re-engineer a new machine
 
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After reading through the manual I see that 2500 is the max RPM. So, you are getting the full speed out of it you just don't have the fine adjustment you would get with a different value pot installed.

As far as the E-stop goes, without some modification to the machine my guess is that's how it is going to work.


Little machine shop has lots of info on mini lathes. At first glance I didn't see anything that matched your lathe but I didn't spend much time searching either.
 
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I am not familiar with the Vevor lathes. I have a Grizzly G0602. I have replaced the OEM motor with a brushed DC motor. I use the E Stop only for initial startup and ending shutdown. The E Stop is intended to cut all power to the machine so if there is a fault with the controller, the motor will go dead. I use the Forward/ Off/Reverse switch for normal operation. While you may be able to switch from forward to reverse instantly, it is not a good idea as it puts undue stress on the electrical and mechanical components. I always bring the lathe to a full stop before reversing. Your lathe may have circuitry in the controller that prevents reversing until the lathe speed drops below a set speed to preclude instant reversal.

As to the behavior of the speed control pot,it sounds like there is a maladjusted limit switch. When I built my speed control, I built in additional pots on the circuit board which set the upper and lower speeds of the pot. Mine is set so that a full counterclockwise rotation is zero rpm and full clockwise is 80% of maximum available rpm. (I set it this way as my controller is capable of overdriving the motor so Iimit the maximum to stay within the ratings.) Mid range is at approximately 50% rotation on the pot. More than likely, your controller has a similar system.
 
No adjustments on the board, which is a big red flag. It either works or it doesn't
And this brand is known for problems throughout
 
Thinking about your symptoms and your diagnosis,, it is looking like a faulty controller. Do you have variable speed between zero and 25% rotation?

Do you know what type of motor you have? If a brushed d.c., you most likely have a PWM controller where the speed is controlled by varying the duty cycle of the pulses. A brushless motor varies the frequency of the voltage applied to the motor.

Speed control pots are typically voltage dividers where the output voltage is determined by rotation of the pot. As such, they are relatively independent of actual value. However, if there is an external resistance for setting range, a mismatch there could cause a problem such as you describe.
 
T Bredehoft said:
I'm no help with your problems, (old as dirt, don't understand most electronics) but Welcome to the Group. Someone will be along with exactly the right ansers, once they get up.
Click to expand...
Thanks! Appreciate the warm welcome :)
I dig the Studebaker in your avatar.
 
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