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Topic: All bearing Y axis conversion

I have had a pain adjusting the belts to remove backlash on the Y axis. If too tight the motor stalls, if too loose backlash. I think tight is the way to go but have encountered other problems. Motor stalls, rear axial starts squeaking even with grease, rear axial slightly bends down from motor belt tension and forwards from tension from front idlers.

My solution is to go full radial ball bearings. I saw someone already did it on the rear (6x13x5 flanged bearings). I plan on adding qty of 2 (5x8x2.5 flanged) bearings to each of the new idler brackets. and add a printed pillow block with qty 2 (6x13x5 flanged) bearings in the back to help keep the rear axle from flexing under the tension.

I have designed and printed the pillow block and also modded the new idler brackets to accept the bearings. Just waiting on delivery of the bearings to test and work out any kinks.

Smitty

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Re: All bearing Y axis conversion

Sounds like the way to go Smitty.  Looking forward to learning how it goes

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Re: All bearing Y axis conversion

I put some 6x13x5's on the y shaft just for fun http://www.soliforum.com/topic/2069/sol … tear-down/ as it didn't really need it but I had the y carriage off to install linears on it so I figured as long as it's apart wink

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Re: All bearing Y axis conversion

Can you post the pillow block?  I already have the bearings, but I'm reluctant to grind the holes out to 13mm since there is no going back from that.  I would just be concerned about maintaining alignment.  I'm mystified how the holes can be 1/2" while the rod is 6mm.  Maybe the sleeves the bushings are mounted in are actually 13mm, and they just cram them in there.

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Re: All bearing Y axis conversion

Hey Ian, The holes barely took any reaming to make the 13's fit, I think if I had just put a bolt through them and pressed they probably would have gone in straight away. The steel holder that the stock bronze bushing reside in probably enlarged the original hole??? maybe. If I get time in the next couple of weeks I plan on tearing another one down and put the same bearing in it... instead of reaming for a hand fit I will press them in...or at least try wink

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Re: All bearing Y axis conversion

Early on there was some factory photos or something that had someone in the background whacking a printer with a rubber mallet.  I'm guessing they were gently installing those 13mm bushings into a 12.7mm hole.

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Re: All bearing Y axis conversion

Early on there was some factory photos or something that had someone in the background whacking a printer with a rubber mallet.

Haha, I think in the circle alignment video I can hear something like that.

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Re: All bearing Y axis conversion

Can you post the pillow block?  I already have the bearings, but I'm reluctant to grind the holes out to 13mm since there is no going back from that.  I would just be concerned about maintaining alignment.  I'm mystified how the holes can be 1/2" while the rod is 6mm.  Maybe the sleeves the bushings are mounted in are actually 13mm, and they just cram them in there.

The pillow block is designed to fit near the middle of the rod and screw to the back of the case to prevent the rod flex. I am still going to use the existing holes in the sides of the SD3 with bearings. Didn't know I needed to ream them a bit though. smile Not a problem. Don't think the pillow will fit near the ends or if they would even be strong enough to hold the full tension. I can post it if you like but its not quite finished. I need to adjust the model once the bearings get here and I get to test fit the bearings. Its a Pro-e model.

Smitty

9 (edited by Smitty505000 2013-05-18 23:03:21)

Re: All bearing Y axis conversion

Received the bearings and took the printer apart today. what a job to get the rear Y axis shaft out. The grub screws put marks on the shaft that make it very difficult to slide the shaft through the bushings and slide off the pulleys. I got it out with the help of a persuader smile Then had to chuck the shaft up in a drill and use some 320 sand paper to get the marks off the shaft and to be able to even slide on the bearings. Then got one of the bearings stuck on the shaft and destroyed one bearing trying to get it off the "wrong" way. I know the proper way to remove but was in a hurry. Ok so then removed one of the rear bushings. Another job and a half! then had to ream out the hole ever so slightly to be able to persuade the bearing in. Got the one rear bearing in, the pillow block with two bearings and one original bushing is still in until I get a new bearing. The fronts came out good but have to make a couple of tweaks to get them to fit good. Had to put the printer back together to make the new fronts. Printing new fronts now. Probably wait for the new bearing before I do the fronts so I only have to take the machine apart one more time.
I attached a few pics of the pillow block and front untweaked idler brackets, and the pillow and rear bearing installed.

Smitty

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idler bracket.JPG
idler bracket.JPG 1.93 mb, file has never been downloaded. 

parts.JPG
parts.JPG 1.92 mb, file has never been downloaded. 

pillow installed1.JPG 1.9 mb, 2 downloads since 2013-05-18 

pillow installed2.JPG 1.94 mb, file has never been downloaded. 

pillow.JPG
pillow.JPG 2 mb, file has never been downloaded. 

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Re: All bearing Y axis conversion

Some more pics.

Smitty

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pillow2.JPG
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rear bearing.JPG 1.67 mb, file has never been downloaded. 

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Re: All bearing Y axis conversion

All is running smooth right now but I did notice something else while I had the machine apart. The head has been melting the MK4 a little and it now wobbles. I jammed some tin foil in there for the time being but am going to print another MK4 right after the idler brackets. Also the head was melting the X carriage. I noticed the head really needs to be oriented so the shortest side of the heating block faces the X carriage. This keeps a nice air gap between them.

Smitty

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Re: All bearing Y axis conversion

Looking for my Google+ +1 button! I like that pillow. That is definitely a mod that my machine needs.

SD3 w/ mods:
Glass bed with QU-BD heat pad upgrade, threadless ballscrew w/ 8mm smooth rod, spectra line belt replacement, lawsy MK5 extruder, Lawsy replacement carriage, E3D hotend, Ramps 1.4 w/ reprap discount controller, DRV8825 drivers, 12v 30A PS, Acrylic case, Overkill Y-idlers, Filament alarm, Extruder fan + more.

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Re: All bearing Y axis conversion

Awesome mod. I will put in bearings after my bushings wear out. I think the pillow block is essential because the drive belt is bending it. The primary source of all my y axis elongation issues can be traced back to the backlash in the belt from the motor to the jack shaft. The way to reduce the backlash is to tighten the belt really tight. And this bends the jack shaft.

To check your machine, simply turn the y stepper motor pulley with your fingers going forward and backwards, while looking at your jack shaft pulley. See the slop? If so, I bet your printed holes are not round.

Excellent work smitty, especially with the pillowblock idea.

Btw, did you ream the holes in the frame with a file or reamer? Please tell us how you did it.

14 (edited by Smitty505000 2013-05-19 00:11:02)

Re: All bearing Y axis conversion

Thanks guys. The shaft dosnt bend at all anymore. I reamed the holes with a dowel wrapped in 320 sandpaper. Didn't take much.
Ill attach the .stl for anyone that wants it. Will post on thingverse also. Oh, the pillow takes the same bearings as the other rears. 6x13x5 flanged.

Smitty

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Re: All bearing Y axis conversion

Here are the bearing part numbers from http://www.bocabearings.com/
MF686-ZZ are the 5x8x2.5 flanged bearings for the front idler brackets. 4 total
MF85-ZZ are the 6x13x5 flanged bearings for the pillow and rear shaft. 4 total

Im attaching the new revised front idler brackets that accept the 5x8x2.5 bearings.

Smitty

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left-bearing-block.stl 94.42 kb, 166 downloads since 2013-05-19 

right-bearing-block.stl 94.42 kb, 98 downloads since 2013-05-19 

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Re: All bearing Y axis conversion

Been hearing a funny noise and noticed my Y is kinda skipping. Come to find the belt between the stepper and shaft is ready to break. See photos. I looked up on Stock Drive Products and they have three types of belts for replacement.

A 6Z16-080025 - Neoprene with fiberglass threads = stock
A 6B16-080025 - Polyurethane with Kevlar threads
A 6G16-080025 - Polyurethane with polyester threads

Wonder which would be best??

Smitty

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Re: All bearing Y axis conversion

My guess would be the Kevlar or Fiberglass I think the Polyester may be prone to stretching.

Smitty505000 wrote:

Been hearing a funny noise and noticed my Y is kinda skipping. Come to find the belt between the stepper and shaft is ready to break. See photos. I looked up on Stock Drive Products and they have three types of belts for replacement.

A 6Z16-080025 - Neoprene with fiberglass threads = stock
A 6B16-080025 - Polyurethane with Kevlar threads
A 6G16-080025 - Polyurethane with polyester threads

Wonder which would be best??

Smitty

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Re: All bearing Y axis conversion

I'm wondering if pulleys with more teeth would have helped here. Fiberglass is great to prevent stretch, but it doesn't like to bend around tight radi either. Moreover, I'm wondering if pulleys with more teeth would have helped on the backlash issue. It seems like I have to put an awful lot of tension on this little belt to eliminate the backlash.

My stock MXL pulleys are 18teeth, and have a flange diameter of .63" Given how close the jack shaft is located to the rear frame, I'm thinking I could safely increase the diameter of my pulleys to 28 or 30 teeth.

Does anybody think this would actually help with backlash and to reduce the stress on the belt, and resultant breakage that Smitty already encountered?

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Re: All bearing Y axis conversion

The breakage is more indicative of over-stressed belts, as a result of being over-tightened, rather than anything to do with belt type etc - you can see from how its failed.

I would replace with the kevlar, because they stretch less, and then readjust so that it wasn't so incredibly tight (which it would have been to fail how its shown).

If it was so tight for calibration reasons, then its the y-axis carraige belts that need attention rather than the y-motor belts..

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Re: All bearing Y axis conversion

Adrian, thanks for your insights. In my experience the stepper to jack shaft connection is the source of nearly all my y-axis elongation (out of round small circles), and it's because of backlash. I was surprised the other day when I turned the y axis stepper motor and notices the back and forth play, and my belt was quite tight! When it's tight enough to prevent this backlash, I'm sure it's also overstressed, as you mentioned. It's like a catch 22, tighten the belt to get rid of backlash and then you need Smitty's pillowblock bearing to prevent the shaft from bending, not to mention the belt breaks prematurely.

Do you know of any strategies to help eliminate this backlash without resorting to the scenario above? Perhaps kevlar will help, as you mentioned. Do you think pulleys with more teeth would help too?

21 (edited by adrian 2013-05-19 12:46:46)

Re: All bearing Y axis conversion

Briggs wrote:

Do you know of any strategies to help eliminate this backlash without resorting to the scenario above? Perhaps kevlar will help, as you mentioned. Do you think pulleys with more teeth would help too?

Potentially more teeth will help, GT2 in the variety normally used for upgrades is 20.

Re the out of circle circles - I found it was my y-axis carriage belts being uneven that caused more issues than the Y-rod-to-stepper interface... I have that 'snug' but using IanJohnsons belt tension gauge I make sure both sides of the Y-Axis are identical in tension. Since doing that, my circles have not even been something I consider to check that often actually.

So I'd probably go Kevlar, check Y-Axis Carriage Belts, then think about GT2 upgrades.

Its also worth noting that its a bit catch-22 on the y-rod belt - because the more you tighten the interface to the motor, the more tension on that part of the rod there will be, leading to potentially worse circles than before... is your y-rod straight and not bent noticeably ?

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Re: All bearing Y axis conversion

Thanks for the advice Adrian. My jack wobble is barely perceptible, but there. So perhaps I've got the sweet spot. My circles are almost perfect, so I think I've got the long belts dialed in, but will keep an eye out for them, and look up Ian's gauge. When my belt breaks I will certainly try kevlar.

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Re: All bearing Y axis conversion

Some very interesting conversation. I think larger diameter pulleys is a good idea that will reduce backlash by increasing surface area and more teeth in contact. I would prefer Kevlar but it only comes with a polyurethane outer material and its temperature rating is like half of neoprene. Neoprene is rated around 200 deg F. I ordered up a couple replacement belts "neoprene fiberglass" from amazon to fix for now. Also want to see how well it works once I complete the bearing mod. Contemplating putting the stepper outside the frame with a flexible shaft coupling and getting rid of the drive belt.

Smitty

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Re: All bearing Y axis conversion

Smitty, at this point why not just use two steppers? It'll be cute seeing two motors stick out on either side of the frame. Makes me think of Princess Leia.

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Re: All bearing Y axis conversion

Briggs wrote:

Smitty, at this point why not just use two steppers? It'll be cute seeing two motors stick out on either side of the frame. Makes me think of Princess Leia.

I am going to try this, just ordered another y step motor. Do I just halve the steps per mm in eeprom to use 2 motors at once? I.E. from 88 steps per mm to 44 since with two motors I'll have twice the power?

Also can I just splice the wires from the New motor into the current one?

My SD3:  Clear plexiglass case, case heater, X axis stabilizer, Z axis stabilizer, thumb screws, filament guide, heatsinks on all motors, extruder fan, controller fan, heatsinks on motherboard, Y rod pillow block, USB and Power on/off switch, fully calibrated including trimpot tuning. Am I missing anything?