Speed control issues with cheap CNC machine. - Page 1
Forum section: electronics / general

author: brummettm58
author_rank: Newbie
timestamp: February 03, 2017, 10:24:05 pm
content: Ok, so I purchased an SX CNC 6040Z, 3 axis machine. Put everything together without documentations. Got it running using the CNC Controller Software. Using VCarve 8.5, created a simple circle to test the operation. Starts off at 12:00 (position), moving at say speed X. By the time it gets to 3:00 its only running speed (1/4X), if not slower. Then at about 5:00 it starts speeding up to about 3X speed till about 7:00. At which point because it's running so fast, it bangs to a stop, shifts the X-axis about 5/8" sideways, and then takes off again. At 9:00 position, again slowing to about a fourth of the starting speed, but again, at about 10:00 starts to speed up again. I've tried several setting, have SPP set so it move the exactly distance in both the X-axis and Y-axis.It operates the exact same way making a square except the X directions runs at 4X the speed, while the Y runs at a normal speed. I think if I use tooling, I'd just break bits.I emailed Planet-CNC. Got the response the JP-3136B is a counterfeit of a obsolete boards that has software issues and isn't supported. I've lessened the Y-axis ball screw coupling which makes it easier to push back and forth, but still requires a lot of effort.Any help pointing me where to look to fix this? I don't mind buying a new MK3/4 board if that fixes the issue, but since it's not a direct replacement, several changes are required. So if that's the case, maybe a Gecko 540 would be better option. PLEASE HELP??

author: metrologist
author_rank: Super Contributor
timestamp: February 04, 2017, 12:18:55 am
content: I do not know about your specific machine, but gather it is a small cookie cutter type from ebay. I also do not know vcarve software.These problems can originate in the hardware, software, electronics, machine configuration, or even bad part design and practice resulting in bad machine code.I use a variety of tools to create machine code and read this code directly. I could tell you what the code is telling the machine to do, but it sounds like one of the axis is not configured properly or has a mechanical issue.When setting up a machine, it is easier to start with just one axis and get it set properly, then move to the next. Movements should be smooth, accurate, and repeatable. I would set 0 in table center, and then methodically make moves to one edge, measure the distance moved is correct, back to center, verify return to center, move opposite side, measure distance moved is correct, back to center...repeat other axis...move diagonal to table corner, verify, center, verify, corner, verify..... If at any time here there is a mismovements, they need to be corrected before moving on.The G540 is convenient, but make sure you can interface via a parallel port. I personally would avoid that driver system as it wraps everything up in one device (like a TV, radio, DVD, player all in one). I use a PC to C10 parallel breakout board that controls separate Gecko motor drivers. That way if anything fries, I just have to replace the one device.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: February 04, 2017, 03:09:45 am
content: Big thumbs up to planetcncSave yourself a lot of grief and wasted time...just rewire the thing to suit one of their controllers and get on with making stuff.