Upgraded to metric rods

Do your couplings still flex ok as it sounds like an alignment issue as I am assuming the nuts ran up and down the threaded rods ok prior to fitment

 

Either way, you should change the pulses per mm. This is a "precision" instrument and all of the cards must be in alignment for things to work correctly.

Regarding jamming, try some lithium grease. It will likely solve your problem.

 

I tried silicone grease but that seemed to make things worse. The couplings are ok and I can move the whole assembly up & down.
Strange thing : it moves up without issues, but jams on its way down.

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Did you put grease on the threaded rod and nuts? Are your smooth rods parallel? Both of those have bitten me in the past. Outside of that, I've got nothing constructive.

 

Maybe it's the grease. I'll get lithium grease tomorrow. Which should I go for? Spray (only found a wd40 lithium ) or tube? I guess the spray is easier to distribute.

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pleasure don't use WD40. I don't trust any of their products :/

The tube is actually easier. Spray tends to go everywhere while a tube (or drops) can be applied to specifically where you want it.

 

WD40 works great for what it was designed for, and one of those things is not a lubricant, but most people thinks it is. It will actually remove grease.

I used bearing grease on my rods, and it did take a little while for the noise to go away, it wasn't instant.

 

WD40 wont last long. Even car oil will last longer. Use synthetic grease from automotive shop , it needs to be somewhat thick so motor oil will not work and wd40 will almost fail..

 

While waiting for the Lithium grease(damn holidays ) I checked the rods again and figured that the left coupler was wobbling. It's excentric for about 1mm. This worked before as the imperial rod nuts were a little smaller than 8mm and therefore provided some "wobbling" space. But now, the 8mm nuts fit perfectly and there's no more room for wobbling, resulting in jams/lockups. I ordered 2 new couplers...

 

One thing about WD40 that I've found, is that once applied, it tends to flow like a river to all nooks and crannies. Before you know it, everything will be covered in it including parts you did not intend to cover.

 

Preliminary results with my new M8x1mm pitch rods are very encouraging. Dramatically reduced Z ripple and more consistent external measurements. I don't have enough time on the machine yet do declare this a definitive fix but it is a relatively cheap and easy one to accomplish.

 

Mine are "normal" M8x1.25. I think you'll need to do some more calibration, but good to hear it's working for you as well.

I just realized that with 8x1, you're down to 50 microns layer height with a Nema 17 (200 steps/revolution) Quite an improvement...

 

I already did the calibration. With 8x1, the steps/mm are 3200.

 

Back in business. The new coupler did the trick.

 

Question -- would it be better to use the Zn plated nuts with SS threaded rod?
Stainless-Stainless seems to gall under loads (not that the extruder is much of a load) -- I was hoping for brass or some other dissimilar metal...

 

@Tor, definitely worth to think about. I used stainless rods + stainless nuts. Didn't really work for me. Even after changing the coupler. I just installed brass nuts to see if that's any better. Doing some testing now...

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This happens when I use 300mm/s



This is with brass nuts, lubricated, clueless....

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Oh, that's easy. You're trying to move Z too fast. That buzzing is because your feedrate is so high that the stepper motor can't move before the next pulse. With 1mm rods, the fastest speed is somewhere under 4mm/sec. With the stock rods, 5mm/sec is probably the fastest you should move.

 

Huh... The default homing speed in the firmware was 600mm/min (sorry min, not seconds). I already patched it down to 200 which works at least sometimes. But when starting a print, it almost always locks up the same way.

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Set the "Max Speed" down to 3mm/sec or so. Unless you've reflashed for EEPROM mode, you'll have to reflash the board.