FolgerTech FT-5 and Duet WiFi issues with Y axis



  • I have an FT-5 where pretty much the only thing stock at this point is the 2020 extrusion because I've been chasing unending problems. Yet while there are a lot of people who have had issues, I know there are a LOT who get amazing results from it even in stock config. By the way, one of the changes I made was switching to 24v.

    Anyway, I eventually determined I had three questionable motors and they were likely the cause for a number of the issues. I've since replaced the four for the Y and Z with essentially the same 1.8 degree NEMA 17s spec as stock but they are a tad taller and are rated at 2 Amp instead of 1.5, have a resistance of 1.4, and are 59g/mm rather than the stock 50g/mm.

    The majority of my issues stem from the fact that the Y and Z axis use two motors. The Z ended up not needing a lot of tweaking. It's the Y that's giving me fits though. Even at 2000mA in config.g I am getting slipping. And the rails are smooth as butter (they aren't locking or sticking), upgraded idlers, now slightly more powerful motor… I am at a loss.

    Now at 2000mA in parallel each motor is only getting 1000mA, right? I certainly don't want to overdrive the driver chip. I don't know how high I can set things in the config.g... 3000mA I assume but probably best not to max it out either and in parallel the motors would only be getting 1500mA. So I stopped at 2000mA since I am concerned about going too high and figured I'd better ask.

    One thing I read was that with the Duet WiFi, the Z motors are in series when using the two connectors on the Duet... the FT-5 stock config is to run them in parallel with both motors turning in the same direction.

    As I said earlier, the Z didn't need a lot of tweaking... the stock setting is 1200mA for the 2 in parallel and in parallel I had to up it to 1500 to 1600 with the new motors they seem to be working OK now. I ended up using both connectors on the Duet Board which I discovered were wired in series and the Z works reliably at 900mA now.

    The Y however still has the motors in parallel but they are wired so they will turn in opposite directions. I'm not exactly sure how I would switch to having them wired in series with the four wires and how they cross over, etc. But my biggest question is why I have to make all these adjustments that differ so greatly from people who have it working stock or even people I've read who are using the Duet. I mean I know the different drivers likely are game changers and any settings are automatically going to vary a bit. But mine for some reason seems to be an edge case even at 24v where I am having to run it at settings far higher than others with similar setups, even with the Duet, and some even at 12v.

    Before making this new thread, I scoured the forums and saw the recommendation to use the 2nd extruder driver and to drive each Y motor separately but unfortunately I'm using the 2nd motor for my Prometheus dual extrusion System. I considered a Duet expansion board but I don't know how this all works for other guys with the stock MKS board so I figure it SHOULD work with just the Duet WiFi alone since others are running it with the Duet successfully.

    So I guess my questions are... how high can I safely go in the config.g for the Y's M906 and what are the up and down sides of running it as it is now (both Y in parallel), vs serial (and how would you wire two Y in series to go in opposite directions) and finally would a Duet Expander be the best way (but I'd have to do something different with my BLTouch then I suppose... not sure what) and if the Expander is the best solution... how are people getting FT-5s to work on Duet hardware alone?

    Ben Lewitt
    Grand Rapids, MI



  • My best bet with 2 Y Motors in series for your usecase would be to connect the first coil of Motor no.1 to the second coil of Motor no.2 and vice versa. I'm not sure IF it would work, but maybe it works?


  • administrators

    The highest current you can use in M906 is 2400mA, however above 2000mA you MUST use a fan to cool the Duet.

    At 24V power I'd definitely recommend connecting the motors in series instead of in parallel. Google for "connect stepper motors in series". To make them turn in opposite directions, swap ONE pair of wires belonging to the same phase on ONE of the motors. Usually one phase uses green and black wires, and the other phase uses red and blue.

    I suggest you eliminate the possibility that you have a partially-blown Y driver on your Duet. To do this, with power off swap the X and Y motor connectors over. Then, in your config.g file insert this command to tell the firmware that the X and Y motors are swapped:

    M584 X1 Y0

    Put it earlier in config.g than the M906 command and any M350 command that you may have. Restart the Duet so that the new config.g takes effect.



  • I have not gone above 2000 on the Y and I have heat sinks on the drivers with a fan blowing on them. And part of my troubleshooting was the put the single X motor on the Y driver and the X motor runs fine on the Y driver so it should be OK. Really good to know though that 2400 is the max you should go though. Just curious, would it let you put in values higher than 2400 in the config.g or will it complain?

    I will look into wiring them in series. Still puzzled how others are running an FT-5 with them in parallel unless they aren't and just never mentioned that as part of switching to the Duet that they also made that wiring change.

    Thanks



  • Oh, one additional question. I had TL smoothers for the MKS board and stock drivers. Do the Duet's TMC drivers benefit from something like that or are they unnecessary?

    Ben


  • administrators

    The TL smoothers were developed to work around an issue with low current microstepping when using DRV8825 drivers. I doubt that they will have any effect if you use them with the TMC2660 drivers on the Duet, except that they may prevent the stall detection working.



  • Thanks. I didn't think they'd be needed. Just wanted to be sure. Wiring the Y axis in series seems to have worked. Finally printing reliably. Now to dial things in.

    Ben


 

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