Planetary gearbox: is it worth it?

[littlecatlabs]

Hey guys! Excited to report that I have successfully updated my Rostock MAX v1, which I purchased at a Maker Faire in 2013 before I knew anything about 3D printing, and which never really worked properly, to what is effectively now a Rmax v3 with molded cheapskates, ball joints and an HE280 hot end assembly (for which I'll hopefully soon be posting some pics of a sweet fan shroud + LED lighting assembly I designed the other day). I'm stoked because for the first time in pretty much ever my Rostock is reliably cranking out quality prints and getting better by the day. Makes me glad I kept it - there have been times in the past few years when I've been tempted to write it off as a failed experiment, and now I'm really glad I decided to hold onto it instead.

HOWEVER I am now scratching my head over one of the final outstanding issues, which is that even at moderately low speeds my extruder seems to be skipping steps pretty frequently. This is obviously affecting my part quality, and I would also like to be able to push the limits for how fast the HE280 can melt filament without being limited by inadequate extruder torque. I am considering upgrading to a stepper motor with higher torque, like this one:
http://www.omc-stepperonline.com/gear-r ... -p-40.html

But I am also open to suggestions if there are other things that I can do to try to mitigate this without spending even more money in addition to what I just spent to get the printer up to date. Here are some specs on my system as it currently stands:

Chassis: Rostock Max v1
Delta arms: Latest molded carriages & ball joint assembly from SeeMeCNC
Controller: Rambo v1.1b
Firmware: 0.92.2
PSU: 12v ATX from OCZ rated at 600w
Extruder: New EZR extruder from SeeMeCNC mounted to original direct-drive Nema 17 from Rmax v1, now outfitted with a heatsink
Hot End: HE280 with 0.7mm SS nozzle
Preferred mode of printing: SD card
Preferred materials: PLA, Carbon Fiber HTPLA from ProtoPasta, NinjaFlex
Preferred Slicer: Simplify3D (seems to get a bad rep around here, but I'm happy to defend it - I do product design for a living and in my circumstances, where the cost of troubleshooting gets expensive quickly, $150 is a small price to pay for the quality, consistency and high level of professionalism evident in the engineering behind that software).

Would love to hear your suggestions for how to maximize performance from the extruder. Happy Holidays!

[Xenocrates]

I have a few suggestions.

1. Try increasing the current to the extruder stepper. With a heatsink on the back, it may well make enough difference to help

2. buy the planetary gearbox and drill out the hobbed gear. As a warning, the output diameter of most geared steppers is larger than ungeared ones.

3. buy a planetary gearbox and new hobbed gear from TridPrinting (Not affiliated). You'd need an 8mm bore on the gear. It should work OK.

4. Buy an E3D titan. It has some gearing, and is a complete unit for a reasonable (But more expensive than the previous options). It's also a nice piece of work that should keep the stepper motor temperature from affecting the filament and partially melting it.

5. This is the most expensive option, but also the highest performance. Buy a Bondtech extruder. They are tanks, and I love mine. However, you could almost buy a complete (Cheap) printer for it's cost. I recommend it only if you have plans to work at very high details or with very particular filaments, which the later two of yours are (Another fun few that are hard to work with are glass or carbon filled PETGs, and PVA filaments).



Also, Re: S3D, yeah. Me and Mike aren't fans of it. Me for entirely non-technical reasons. I have no doubt that it's a technically very good slicer, and won't give you any grief for liking it. You've probably read the threads where me or Mike rant a little about it, and don't feel that our concerns are ones you share.

[DeltaCon]

Are you sure it's the motor skipping steps? I never saw that, but I do see the gear grinding the filament a lot. Therefore I can't imagine that the EZR struder has so much more grip on the filament that it indeed can get it to skip steps on the motor. Unless it get's much to little current, or runs much to hot (to high current) indeed.

[littlecatlabs]

Thanks for the suggestions!

Xenocrates, good call on the motor current - a little digging revealed that I've got the Wantai steppers that shipped with the older kits, which require more current than the Kysan motors that apparently have been shipping for a while now.

The Configuration.h setting MOTOR_CURRENT in the firmware was set by default to {140,140,140,130,0} - the recommended settings for the Kysan motor set - and I changed it back to the old spec, {175,175,175,200,0} - about to run a print; I'll confirm later whether it's actually fixed the problem.

According to this github thread, the distinction used to be documented in a comment in the firmware, but got zapped at some point:
https://github.com/seemecnc/Firmware/issues/4

But the commit doesn't seem to have actually made it into the master or current dev branch, so I opened another issue on it.

Also, it would be helpful if this product listing for stepper motors on the SeeMeCNC page were a little more specific:
https://www.seemecnc.com/collections/pa ... pper-motor

It says the motor is a "drop in replacement," when in fact that may not be the case. A note about the Wantai/Kysan distinction, dates when they were respectively shippping, and links to relevant documentation would be right at home there in the listing and would have saved me some time.

Hope the new settings yield good results! Will report back in a bit. Merry Christmas


UPDATE: Made a big difference. Motor skipping much less, still not running very hot. Going to experiment with cranking current even higher; feeling optimistic