first of all i would like to say thanks to everyone that is helping others with their problems, you are the best.
I assembled my MPCNC just over 2 months ago and i am really happy with it, with smaller projects i got no problem with squareness of the machine or skipped steps, but when i mill bigger projects the X axis skips steps and i have to stop milling.
i attached a few pictures to give you a better understanding of my built, let me know if you need more information and i will add pictures or a better description of the problem.
Sorry if I seem to ask silly questions but my habit is to look at the simple things first. Is the X position where it starts to skip consistent? Does it vary depending on Y value? I’d just try to eliminate the possibility of any mechanical interference which at times can be difficult to spot.
Do you notice some things like change of sound or the stepper getting (to) hot. Which board and drivers do you use and which current do run the steppers.
Off-topic, which mount do you use?? I need this for my Kress router when upgrade to Primo.
I feel like the error happens more towards the middle of the mpcnc, when i mill smaller things near the opening of my enclosure nothing happens. Thanks for the tipp with the attachment of the Z axis, i will do a testrun without the vacuum and see if anything changes.
I use the ardunio nano with cnc shield v3 and my drivers are at 0,6-0,7V.
Again, what drivers (4988, drv, tmcXXXX) is that with, and also what microstep setting?
I run my purple drivers at 16 microsteps 12V 1.4A… travels 9000mm/sec, plows through aluminum, and has never skipped a step. At first glance, your current seems way too low. However that may be ok if you were like using reds with 4 microsteps. More microsteps requires more current… and mpcnc is spec’d with 80oz motors, which generally run well at 1-2A.
That it happens in a particular location is telling you there is something mechanical going on. Whether it is something that needs to be addressed for reliable operation or not is hard to say. Adding current may be enough to get past whatever minor mechanical issue is there, but there is certainly no harm in investigating and trying to fix it.
Actually it’s spec’d for 50Oz/in + motors. Ryan usually sell ones that are stronger than that though. He also said .6-.7V witch make little sense to me(is that the voltage he’s running because that would be a big issue? Or did he type v and meant A). Assuming he meant A, That is very low current unless he is using TMCs with cool step turned on.
Hehe, maybe I should actually read before clicking links. Sure enough, the BOM lists 50oz motors, but click the link and you are taken to 84oz motors at amazon. I just assumed the link was the recommended hardware; good thing I just clicked links to fill out my orders.
I agree, the V has to be a typo. Pretty sure the stock setup includes a 12VDC laptop adapter. 0.6A may be good enough for most stuff, but when that becomes marginal it is a good thing an 80oz motor can take 2A (so can tmc and purples). I am sure my 1.4A may need to come down a tad when it hits 100F in my garage this summer (got PLA trucks), but for now I’m not skipping any steps.
This also isn’t accurate, not all 80oz/in motors can take 2A it depends on the motor you have chosen. Also not all TMC drivers can handle 2A. I’m assuming you are referring to TMC2209s? But TMC2130s can not. Also I don’t think “purple” is an adequate description of a stepper driver. Are you referring to DRV8825s because they normally have purple pcbs.
Also if you think that your acctualy skipping steps inside the motor, you can always slow down. Steppers loose torque quickly at higher speeds. It would be an easy way to test if that is the issue
I admit my post does leave a lot for wanting. It is definitely true that not all 80oz steppers are equal. I should’ve provided a link to said motor (Ryan’s link is good though). Also wrt tmc handling 2A, it is true not all do. Again if I have a link to the usual 2209 everyone uses on mpcnc, that would have eliminated a need to clarify that. After all there may be someone who reads this thinking their old 2130s from their printer would do 2A for long without shutting down. Wrt referencing drv8825 as purple drivers… depends on the circle you are with. I have discussed tech matters with many folks who are familiar with what “red” and “purple” drivers are. To be honest, one could argue that is wrong since the original polulu boards were all green. However, it is rather safe to say if someone reads purple… they will end up ordering the right one. Idk… this hobby is so filled with traps that resemble the ole who’s on first routine… and I am not helping that out at all.
Not that it has anything to do with skipping step on the x… did you notice your z motor mount is cracked? Depending on the cut, that could slip and bugger up the z positioning. {edit: …of course if that happens then the bit could snag and x motor could skip}
This, my guess, is referring to the vref voltage setting measured between the current trim pot and ground on the drivers. This should equal 1/2 the motor Amp rating, -10%, when using DRV8825 drivers. So if your motors are rated at 2 amps max, then your vref should be set at .9v.
How is the heat on the drivers? If it only happens on long jobs, maybe they are overheating? In my experience, any fan pointed at thw drivers is enough to avoid overheating and overheating turns off the motors until they cool down, like 30s.
As for the perfect amp/ref voltage setting. Too high and the motors and drivers get hot (try to keep the motors at or below 50C). Most steppers will melt a hole through the floor at their “max” rated current.
Just to clarify, when you refer to smaller/bigger projects are you referring to the amount of the work area they cover or the time it takes to complete them?
