I need some help with calibrating my Prusa I2. I am starting with the X axis, I position my carriage to a specific spot (limit switches not installed yet) and tell pronterface that it is zero. I’ll have the carriage move 100 mm positive and then 100 mm negative but it doesn’t go back to exactly the same spot it started from and if I do that same sequence a number of times, the number keeps increasing in the negative direction. I noticed this when I was trying to calibrate, every time I measured the “100 mm” it was supposed to move and did my calculations and entered the new number into the configuration it kept bouncing back and forth a little higher and a little lower than 100 mm it was supposed to be. I have tried increasing the power to the stepper as someone told me it might be skipping steps but that didn’t affect it at all. I’m new to the 3D printing community so any help would be very much appreciated. TIA
I would have said power as well but as you have tried that maybe check connectoins are making good contact and the drive wheel is not slipping on the stepper spindle. You could also try a different firmware and see if that gives the same affect.
which firmware would you recommend…Marlin?
How much off is it? Also how much slack is there in your belts? I agree with @John_Cooper_choffee that you need to verify your pulley isn’t slipping as well.
Another test to do, is repeatedlu test your move 100mm in one direction. If the movement isn’t consistent, you have drive issues to work out before you calibrate.
Might also want to check speed. Maybe your hardware isn’t able to move that fast.
It usually starts out being off by around 1.6 mm and then just keeps going up every time I move + 100 then -100. The belts are pretty tight and I am using aluminum pulleys and they are tightened down really good as well. I haven’t tried moving in the same direction multiple times yet so I’ll give that a try next…I would only be able to move 100 mm twice so I’ll try it a bunch of times at 10 mm and see if its consistent there.
Draw a line with a marker on the shaft and the pulley to ensure that they are not slipping. You can also draw a line on the belt and the pulley to ensure that it is not slipping.
It could also be that the current to your stepper needs to be adjusted.
I’ve tried adjusting the current both up and down and neither way helps. I’ll draw the line to make sure there’s no slippage.
I’ve been helping @Mike_Smith with this, and I’m pretty much at a loss too. He’s using the DRV8825 stepper motors from Pololu. I figured maybe the 1/32 microstep might have been too low of a current but that would just make things jittery, not constantly lose steps like it’s doing.
@Mike_Smith , try setting the stepper driver to 1/16 stepping by taking off jumpers 1 & 2…and then halving the steps/mm in your firmware. See if that makes any difference once you’ve made sure the pulleys/belt aren’t slipping. There’s a table here http://www.pololu.com/catalog/product/2132 that gives the settings for microstepping.
OK I’ll give everyone’s suggestions a try tonight when I get home. Hopefully I can get this worked out before my hotend gets here so I can get this thing printing. I’ll post my results tonight. Many Thanks!!
@Mike_Smith I was suggesting any different firmware really just to rule that out. Marlin is good.
OK Thanks. If it comes to that I’ll try Marlin.
@ThantiK mentioned trying to reduce the micro stepping to 1/16 instead of the 1/32 of the DRV8825. Looking at the Pololu website indicates that to get 1/16 micro stepping Mode0 needs to be low Mode1 needs to be low and Mode2 needs to be high. In looking at the RAMPS 1.4 specs the jumpers under the stepper drivers are labeled as jumpers 1, 2 and 3. Can I assume that Mode0 is Jumper 1, Mode1 is jumper 2 and Mode2 is jumper 3? If I do it backwards then I will be at 1/2 step.
Yep, that’s the case typically. 1,2,3 are 0,1,2.
OK so after some trouble shooting I think I have it narrowed down to a possible 2 things. Please let me know which you think it might be. I went from 1/32 micro-stepping to 1/16 and no change. Up to this point I had only been checking my x axis. So before I tried a different firmware I decided to check my y axis and when I did I noticed that the y axis sounded much smoother while the x axis sounds like it has sand in the motor. When I set home on the y axis and then moved 100 mm positive and then 100 mm negative it came back to the exact same spot. So now I’m thinking maybe it’s the motor so I put the y axis motor in the x axis spot on the RAMPS 1.4 board and now it sounds like the x axis motor did, like it had sand in it plus it would not return to the same position it started from so its not the motor. Next I switched the stepper drivers and there was no change there either. So now I’m left with 2 possible culprit’s: 1 the RAMPS 1.4 board could have a bad solder joint or something to that nature, 2: the firmware has some sort of a problem with the x axis. I’m guess the more likely is that the RAMPS board is bad but I’m hoping I’m wrong. Something else to note is that I have the same calibration values for both the x and y axis yet when I tell x to move 100 mm it does (approximately) but y moves almost 200 mm.
@Mike_Smith that’s because your Y/X microstepping values are different. Once they’re both 1/32 or 1/16 they will move the same. I merely mentioned changing microstepping values to make sure the motors were able to handle it (apparently they can) just swap the X axis back to 1/32 (put all the jumpers back on) - I have a RAMPS 1.4 being delivered sometime next week; we’ll swap them out and see if that fixes your problem. Nobody else at the lab has a RAMPS 1.4 so I don’t have anything to test until then.
The 1/16th microstep will also make the motors sound a little different. I’ll give you some help next week but this week I’m stuck at work (worked for 18 days straight so far, no breaks)
That’s whats weird, when I changed the micro stepping I did it for all the axis’ not just x, and y was moving double the distance of x. That’s what got me to thinking it was something with the RAMPS board…maybe something to do with the micro stepping circuit. Thanks for helping me on this. Just let me know when you could meet after you get the board.
I sent an email to the guy I bought the board from to see if he would do an exchange, hoping he will but I am expecting him to say it was something I did or that there is no warranty on electronics. If he won’t exchange it who at the lab do you think would be able to possible help diagnose the board and maybe fix it?
@Mike_Smith the people I know at the lab who know this kind of thing are Chorca and Kyle, Kyle isn’t a member anymore, and Chorca hasn’t been around in forever. – I’ll ask around and see if anyone else has good PCB tracing experience. Hopefully it’ll get replaced if it is faulty. If not, worst-case scenario is borrowing my old RAMPS 1.2 board to at least get you going until you can get another.
I also have a Sanguinololu you could borrow - that’s actually off of one of my machines right now, and free to use (no waiting for my delivery) but it lacks a fan mosfet.