Ok, I see the problem in this picture. Now we need more details. How often does it happen, 25%, 50% of the time. Any chance of seeing a video? You don’t have to cut material to run the program, leave the bit out with the router off and get a video of the action happening.
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A couple of initial thoughts without seeing a video:
- if it was the software and you have run the same program before with a good result, you should get the same result next time. G-code hasn’t changed and software doesn’t behave randomly.
- If it was a power supply problem you should see this type of cut happen in a higher power load area, (which in your case hasn’t happened) although it be related to a duty cycle issue but we don’t know if anything is getting hot.
- An electrical connection might be most likely. How dusty is it where the maslow board plugs into the arduino board or look at the connection to the motor. Electrical connection issues are common problems with controls on all sorts of equipment and lead to very random behavior that is often very hard to track down. This item is where I would start my search with the limited info shown.
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Hi Robert, thanks for your helpful answer. I go and test everything you mentioned. <And i also will test the different things, driving the GCode with routing and without routing, clockwise and counterclockwise. And i also can prepare a video. I hope i can post the results this afternoon. Thank you, Axel
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When I have cuts that have gone wonky like that, it’s because my sled has snagged on the edge of something that’s been cut (like that cutout that dips down toward your issue area). Is it possible that this has happened? Also, was that cut done counterclockwise or clockwise?
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As I think about this more… I have to change my mind on a couple of things
- Movement of the motors is kept track of by using the pulses from the encoders. The path is out of control randomly suggesting a loss or gain in pulses (electrical connection) however if that were true then the machine would lose it’s home position.
- It’s not a sled sticking issue because of the motor movement you noted.
- So if it Isn’t an electrical connection or sled sticking then…
- Power supply could still be it if it is the left motor with the random movement and the board is overheating. Meaning problem never happens when control boards are cool.
- It could be computer specific. You computer may have decided to make a longer disk access for a while and stops paying attention to the maslow. This one would be easy to rule out.
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Hi, i checked this, the sled din`t snagged on the edge of other cuts. What i have to try, thats right, is, if it makes a difference between counterclockwise or clockwise. This problem here happens when the router works clockwise.
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Hi Robert, thanks, i will check also these things. I give you an update tomorrow.
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Another thing that it could be is the USB connection. I have not seen behavior exactly like this before, but we have seen issues where if the USB connection is not good the cut will work sometimes, and sometimes something will go wrong.
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This drove me nuts as well…
The tiny heat sinks aren’t good enough to drive the motors for any length of time especially at the edges. Stick a couple CPU coolers with fans on each driver chip. I stuck a bent sheet of copper on mine with fans blowing on it until I get around to making a proper Mod to share with everyone. 
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Hi Tim, thanks for your response. I will check this heating thing and install a fan. Yesterday i have tested routing this path in many different ways. The result, it happens only on the right side, and the problem is bigger when routing clockwise. Then the problem is on the topline of the path (you can see it in the videos). It makes no difference if i am routing with a 3 mm or 5 mm routerbit. When routing counterclockwise it happens a bit, but on the bottomline of the path. And it doesn`t happen when the maslow is driving the path without routing. With these results i think its more a construction problem of my circular sled which is not working completely smooth. However, could it also be an electronic caused problem?
- video is first round
- video is the same path second round
- video is same path without routing
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How are you powering your heatsink fans?
around the 14 second mark on the second video, there’s a lot of jerky movement on the left chain… initially I thought it had gone slack momentarily, but it looks more like the assembly was moving.
One thing I noticed is that while the bearings are not moving, the chain doesn’t “pivot” about the ring but rather pivots about the point where it passes through the mount holding your bearing (about an inch away from the ring). I think this would cause an issue. How does your chain mount to your bearing brackets?
From the videos, the problem looks mechanical to me. Instead of rolling, the chain mounts jump in steps.
Do the rollers have bearings?
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Hi, thats exactly the moment where my problem is. The left chain gets loose, the right chain get stronger. And here is a picture of where the chain is fixed to the mount of the bearings. It is fixed that it cannot turn around. Do you mean this?
Hi Gero, no, the rollers don`t have bearings, thats a point i want to improve soon as possible.
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Spring clamps, bent copper, electrical tape? Point off for no duct tape, otherwise just about a perfect mod!
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Here’s a crude diagram of what I see is potentially a problem. I’m not a ring specialist, so maybe @bar could chime in…
Ideally, I believe, the chain is always pointing to the center of the router bit (red line). The software calculates how much chain to spool out based upon the red line. Because the carriage doesn’t move smoothly, in reality, the chain is along the blue line. The effect is that, I believe, not enough chain will be spooled out and therefore the cut will start to ride up and when the carriage gives, it drops back down to where it needs to be… With both sides doing it, you might have some weird cut pattern. Maybe its more prevalent at the edges?
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Are the rollers running on a threaded part of the screw?
I’m sure you have washers on the inside of the mount to stop the rollers touching the sides.
If you have them on the thread, you could check the inner diameter of the roller, if they allow for a thin sleeve/pipe to get thing smoother as a quick fix.
Grease for the rollers and @Bee 's wax for the sled and you should be running as smooth as on ice.
I have piles of left over power supplies from dead equipment. For those I’m using a 12v 3a brick going into a Chinese step-up board. The fans are 24v recovered from scraped medical equipment.