Rear Idler - Bearing Upgrade

[prisma zinc]

I found the stock rear bearings would bind and generally not rotate particularly well. I therefore produced a bearing caddy for some more substantial 608ZZ bearings that I had in stock. like these on Amazon:https://www.amazon.co.uk/gp/product/B09PVDDBWF/ref=ox_sc_act_title_1?smid=A2X2IS1I8BHRL9&th=1&psc=1
In addition to being much more articulate the elevated position appears to shift the centre of gravity of the spool forcing the spool forward on to the drive wheels. I think IMHO having the rear idler lower than the drive wheels has the adverse effect. Whatever the hypothesis, the respooling was like night & day after this quick & dirty retro mod, more so than my rubber tyre install. Anyway if you have some spare 608 bearings in stock, well worth a test for the time it takes to print a sample. The assembly uses the same 3D printed to secure the 2 halves of the idler. The larger bearings act as spool end stops so there is very little loss in width (approximately 1mm max).

[fierce light]

Genuinely curious as to what part was binding? as I have not experienced this at all.

[cinder aspen]

As am I, and I have multiple units

[prisma zinc]

They were quite tight in the trays and did not move well, may just crappy bearings from Ali. There is much less material to interface with a smaller bearing so it might just be also my parts. Having said that my Bambus tend to be dimensionally very accurate. Aliexpress but they were really did not like revolving. Upgrading the bearings in my case made a massive difference to the respooling. Again, may be just my bearings. Absolutely no critism of the design intended, Still think having the rear idlers lower will not max the drive retention though and a better quality bearing will always work better.

[fierce light]

My trays came out of a P1S so I dont think that has anything to do with it.

Prob the bearings then

[prisma zinc]

They were generally very tight

[cinder aspen]

Maybe last set came from a very over extruding hotend and looked like shit.. still work fine

[prisma zinc]

Yes could be

[fierce light]

I have the best luck with them in the rearmost notch, the only downside is eventually some cardboard spools deform enouigh that they start dragging the tray bottom, so I moved to the 2nd farthest back notches.

[prisma zinc]

I found them problematic with full spools of filament which ever position. I still think there a little bit under specked but only my personal opinion.
The trouble with bearings is guaranteeing quality as in my case, usually the only full proof way is to slightly over engineer in such cases. I many a time purchased expensive stuff only to find they the same cheap crap just marked up more.

[fierce light]

Yeah we have seen a ton of variance on people's MR148's throughout the beta. I had 2 in one pack that were like 8.4mm in the center LOL

[cinder aspen]

I have a bunch that are like 8.2

[prisma zinc]

A difficult issue when specifying. I sometimes use a specialised supplier but these days the source cannot be qualified.

Anyway, no offense intended with this mod, happy to remove if uncertain

[fierce light]

I know xbst found a decent source, and the ones in the undisclosed beta kits seem to be consistent.

[fierce light]

No no, was genuinely curious as I've not seen that as a complaint until now

[cinder aspen]

Isik is getting ABEC 5 bearings for his kits

And misumi shafts

[prisma zinc]

The bearing do not need to be 608s or anything near, but something that will allow a little more wriggle room, tolerance wise on the interfacing walls would reduce the likely hood of my experience being repeated.

[next bluff]

I've never seen binding of my bearings but i do agree that the lower idler was a step backwards, the older style of rear idler (which used 608's) was much better at pushing the spool towards the rollers and i got alot less slip on smoother lighter spools than i do now.

[charred geyser]

I too have the bearing binding issue, my rear idlers are a bit toight, i actually prefer to run them with no bearing at all and they spin just fine, just sit a little lower.

[opaque sage]

Check your print isn't binding on the outer of the bearing goes to far through and binds on the shell of the tray?

They should run smooth otherwise (unless your bearings are bad.

[charred geyser]

Ohhhh I didn't even think of that. That is probably happening

[magic cairn]

The Tray is holding the outer part of the bearing but it is rubbing on the outer part of the idler slightly. The idler is holding the inner bearing but the Tray wall is rubbing on the inner part of the bearing.
The ABS part warps slightly so that gap in the CAD does not really exist in real life.
Stock vs. my proposed fix. Make chamfer larger to avoid outer part of bearing on idler. Cut away a section of the tray so it can not rub on inner part of bearing.

[static charm]

I too have crappy bearings, none of the ones I got would spin very well. I ended up taking the sides off the bearings and cleaning the grease/oil out and just leaving them open so that they spin super easy now.

[errant willow]

i'd recommend putting the sides back on to prevent dust/debris being able to get into the bearings causing them to bind up

[desert wind]

This is exactly the problem I’m having. You are truly the GOATed one. TY.

[severe ocean]

I had the same problems!
But I went for the lath instead of thinking like an adult like you have😅

[spark garden]

Looking really smooth

[scarlet scarab]

Waaant. Made out of steel? My hackerspace just got a new lathe....i should tinker

[severe ocean]

Aluminum yes, make sure you change the model cause the tolerances are different for the bearing to fit properly.

[scarlet scarab]

I'm too much of a novice to make them. The dual taper would confuse me. Looks like you cnc lathed them. Well except for the surface finish on one.

[severe ocean]

I did cnc them, the surface finished is from the spool/TPU tires rubbing off