[pilotarix]

Hello all

I used the MicroMark Mini Mill for a couple of years without any issues. But over time this machine became too small, thus I decided to get the next bigger one. This is basically the G0704 from Grizzly or also known as the BF20 from Optimum. There are many other clones out there but these two ones are the ones most people refer to.
Anyhow, I did the brake-in procedure like recommended in the Grizzly manual and milled two small brackets for the DRO I would like to install. Total operation time so far is the brake-in time plus approx. 45 min to make the two brackets. When I started the machine today to drill one more hole in one of the brackets I realized that the engine was not running evenly, instead it was like a stop and go in slow rpm's and had no power.
I would assume that this is not really a new problem and other people have experienced that as well.

I did a short video so it might become more clear

https://youtu.be/us3qB90e9Cs

I appreciate every help.

Thanks
Chris

[109jb]

You obviously have something binding and tied to rotation. I'm not near my machine, but I think if you place the gear selector mid-range it will be in neutral. I would first put the gearbox into neutral and turn the spindle by hand to see if the binding is in the spindle side. When in neutral you could also turn the motor on to see if the rhythmic wow-wow-wow is present on the motor side. this would isolate it a bit. In my experience, Grizzly is very good in terms or warranty period support. Once isolated get hold of them and they will get you sorted out.

[pilotarix]

thanks for your answer,

I put the gear box in neutral and now you can see that this is clearly related to the motor, no binding and the spindle turns easy by hand.


https://youtu.be/13Tjtn8QwE8

[xjdubber]

do those have dc drives controlling the motor? (its a motor not an engine). It sounds like it goes into over current, slows down or stops then because current drops tries to be speed up. Could be setting issue on the drive, or most likely wiring issue.

[COMachineist]

Yep sounds like motor surging, your motor controller card needs to be adjusted. My G0704 did that also when I first got it. Search Hoss's thread he has something on adjusting the motor controller card with the pots(variable resistors) to control motor current, voltage and I think acceleration. IF you can't figure it out call Grizzly tech support, they will most likely send you a new card. It could also be a bad card. I just put a KBIC 125 controller in mine and it was a much better controller. Chinese electronics and QC suck badly.
CH

[pilotarix]

@CoMachineist

Thanks for the info.
There are five potentiometers on the motor controller card. Vmax, Vmin, Accel, IR? and CL.
Unfortunately I could not find the information in Hoss's thread but there is information out there to adjust the Optimum
BF20 motor controller. Other than Vmav and Vmin I adjusted every controller separately in both directions to see what the effect is.
Finally I had to adjust both "IR" and "CL" slightly more positive and the problem was gone. I did some test runs with hight and low rpm's
and drilled a 3/8 hole into 1" tool steel with no problems.
However I think I lost confidence in that machine already. .Well, I hope for the best but I will be prepared for the worst.

Thanks,
Chris

Attachment 272724

[COMachineist]

Yes that is the one. You can get directions from a Kb control manual. These are chines knock off copies of the KB controls and act some what like them. You can use the manual though.
Why would you say you have lost confidents in the G0704? If you are under any illusion that this little mill is anything better than a 1100.00 Chinese mill which by the way is a good value for a hobby machinist of a once in while small business shop mill then you should have went with a Tormach 1100 or even a Hass Machine. These mill can do some nice things and they surprise me every day.You can get a copy of the manual here .http://www.kbelectronics.com/manuals/kbic_manual.pdf
Just give it time these are always a work in progress
CH