Failure Mode Of/Upgrading Z-Stepper?

[Rara]

The past few days I've been getting some weird behavior from the Z-axis and have been thinking maybe the motor is starting to give up - I've been getting some false 'homing' where I'll be printing parts sequentially, it will finish one and when it re-homes to start the next, it will hit the limit switch, but it will drop 1-2" down or so rather than stay at the home position and start air printing. I've also noticed it will do this at times when homing Z while using manual controls - it will on occasion hit the limit switch, and then fall a couple inches before catching itself (but does not return to the switch).

Today as I was running a part, I just happened to be sitting right next to it as it was about 3/4 done; I heard a 'bang' as the nozzle hit the part, caused Y-axis to skip some steps and started printing the layer about 1/4" off from where it should have been.

In all my years with my printer it has never done any of this, odd behavior or skipped steps, so I am thinking something is awry here. Does this sound consistent with a motor problem, or something else?

This brings me to my next point: I'm working on a yet-to-be-revealed project in an effort to create the ultimate, "last word" of sorts in build platforms; but it's going to add a fair amount of weight to the platform and I am starting to question if the little Z-motor will be up to the task of moving all that around reliably. (more to come on the platform, but details of that not relevant to the current topic beyond that I think I'll need some extra muscle for it)

Anyway, to my primary question: what would be involved in upgrading the motor to the same size as the X/Y motors? Is it a plug and play sort of thing, or would I need to make some firmware changes or something as well? I know I will lose a little Z-height since the motor seems to be the end stop, but that is ok for now (I've got a fix in mind, but that will come after the platform proof of concept).

Thanks!!

[ednisley]

Does this sound consistent with a motor problem

Stepper motors have one moving part and tend not to "go bad" under the light duty we ask of them in 3D printers, so I'd suspect external factors that increase the torque required from the motor: crud on the leadscrew or guide rods, forgetting to lube those things for the last year, or perhaps the consequences of a good hard whack that misaligned the rods.

That said, if you have an old-old M2 with the original Z-axis motor, then you need a new one. The easiest way to tell is with an ohmmeter: turn the power off, disconnect the motor, and measure the resistance of one winding. If it's more than 25-ish ohms, then it's the old motor. If it's just a few ohms, then you have a good-enough motor and should look for external problems. Remember to subtract the resistance of the test leads!

http://www.makergear.com/collections/pa ... ts/z-motor

That's not a drop-in replacement for old-old printers, so kibitzing with MG's tech support will be in order.

You can DIY it with a motor obtained directly from halfway around the planet, but you must be very comfortable with hardware & firmware tinkering:

https://softsolder.com/2013/06/28/maker ... ransplant/

[jimc]

I agree with ed here. The question you need to find an answer to is, is your platform actually contacting something. If your nozzle whacks something then yes the platform can fall. If your limit switch is going bad and the bed keeps rising and hits that hard then it will fall. If you z gap is set really tight and your homing and the nozzle is hitting the bed then it will certainly fall. Old motor must be change out if thats what you have. Old ones get really hot and if you converted to 24v then you absolutely must change it out. When you get a z motor from makergear it has the leadscrew already pressed into it so its ready to go.

[Rara]

No physical contact, that I could tell at least. Limit switch is old and a possible culprit.

That said, I've have a pretty old one - shipped to me in late 2012. It is the original motor, and it gets VERY hot while working. I recall reading it was normal, that it could be helped with a firmware adjustment to reduce current but it wasn't really necessary, so didn't think much of it; but this was within the first few months of having it more or less; did this change? I've definitely burnt a finger a time or three brushing against it as I tend to keep my tools sitting on the bottom, hah. Not as bad as an extruder burn, but it definitely hurt! Over the past year-ish I did do the 24v upgrade, and the Rambo is also new after I fried it (long story short, it was my fault and nothing to do with the printer). I've got an order in the works now so I suppose I'll add a Z-motor to it...what about my X/Y motors though? They are also original.

[jimc]

The xy motors are fine but good god change the z motor. Given that you did the 24v upgrade i cant believe it lasted this long. It got smokin hot in 12v let alone 24. The new motor will run cold.

[Tim]

The xy motors are fine but good god change the z motor. Given that you did the 24v upgrade i cant believe it lasted this long. It got smokin hot in 12v let alone 24. The new motor will run cold.

Agreed; you're lucky to have it last as long as it did. Mine gave up the ghost within a few weeks of doing the 24V upgrade.

[Rara]

Just curious, for those of you who have had failures after going 24v - how did your motors fail?

I'll consider myself lucky then...when I was forking over the cash for the 24v/V4 and a few other odds and ends I was considering selling it to a relative who didn't have the cash for a new M2, and just buying a whole new one to get all the upgrades on a fresh chassis (my 12/19v was working fine, just felt like upgrading). If the Z-motor had gone out immediately I may have regretted not going that way.

[jimc]

mine actually didnt go. my red machine had the old style motor when i was refurbing it. i automatically asked rick about the motor. he sent me a new one and i swapped it out right when i converted to 24. i kinda had a feeling about it so i got it before it failed.

[Tim]

Just curious, for those of you who have had failures after going 24v - how did your motors fail?

From your description, I'd say it failed exactly like yours did. I started getting incidents where it would home in Z then act like it just hit something and fall back a few inches. But then it would go through a whole print with no problem. Later, though, it started doing that more often, and then it would happen in the middle of a print. That was when I realized that the motor had to go.

In the electronics industry, where I work, we test chips by running them hot for a period, because it's exactly equivalent to running at a normal temperature for years. Running hot shortens the life of anything electronic. The hotter it runs, the shorter the lifespan.