AthenaII (2019) Drive Gears not staying put

[brhub...@gmail.com]

Hey all,

This is a post related to print quality and contains a question at the end.

After my belt failure, I noticed that my belts were riding against one end of the drive gear (tension was trying to walk the belt off the gear away from the motor). I suspected the friction caused by this could have led to my belt failure, so I went ahead and moved the drive gears out toward the end of the shaft on the motors. After carefully setting those and ensuring both set screws were tight, with one of them sitting square on the flat of the motor shaft, I started printing. Lo and behold, most of my print issues are gone. However, I noticed about 5 hours of printing later that two drive gears had waltzed right back down tight with the motor (I had set them to be flush with the end of the drive shaft, that was no longer the case). I was able to hear some clicking as the motors changed directions, presumably due to the set screw flipping from side to side on the flat of the motor shaft. This manifested itself in some wobble at the top of my print, similar to issues I've had in the past. After the print completed (successfully!), I went and re-adjusted the drive gears back to where I wanted them. I made sure to tighten down real good on both set screws for each drive gear. I set another 7 hour print in motion. About 4 hours in - all good, no motion in the drive gears, and a near flawless surface finish on my print. Now, 6 hours into the print, the drive gears have shifted again, the clicking is back, and I have the slightest inkling of wobble (still great compared to previous prints though!). I think this is good evidence that a loose drive gear could be the cause of some of my previous print quality issues.

My question: does anyone have any tips to keep these suckers in place? I'd rather not have to readjust and re-tighten those gears every couple hours of printing. I've contemplated loc-tite but it seems weird to put that on a set screw.

Thanks.

[Michael James]

So, here’s my experience with that issue. My brother-in-law, who is still in high school, built an Athena II with my help… We had tried to hand cut the frame out of wood (normally these are CNC routered) and we noticed, after shifting in his prints, that one of the rods was off by a fairly small amount, less than a quarter inch. But that drive gear and belt were, in fact, rubbing, even after moving them back and tightening. Getting sick of this issue, I went ahead and built 3d files for the frame and had one of my manufacturing plants at work machine it out of aluminum 6061. After replacing the frame and measuring every distance from each rod, his printer works without flaw.

 

So what does this tell me? That spacer in the beginning that we used to screw the 3d printed motor housings into the frame allow for some user error. If you’re off just by a little bit, it can cause unnecessary forces that will slide that belt toward/away from center, effectively trying to fix itself. Once I had a highly machined part, with pre-drilled holes, it solved the issues. So, wherever you drove screws into the wood may have been slightly off.

 

Check it over again, measuring the distance between each of the rods. If something is off, take the frames off, flip them over, and try re-assembling, being extremely critical about the distances between the rods, and making sure that spacer is absolutely perfect.

 

If anyone is interested in these metal machined frames, let me know. Now that the program is made, I can see about what it would cost to make/ship these things.

 

Hope this helps!

 

Sent from Mail for Windows 10

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