Think3DPrint3D Kossel Mini Carriage Adaptor Smoothness?

Greetings All,

I'm building the Think3DPrint3D Kossel Mini R3. This is my third printer kit, second delta style, but first with Delrin V-rollers on extrusion. I'm concerned that the movement up and down the extrusion isn't smooth.

To build the carriage adapters, I followed the instructions to "tighten the nyloc nut until you just begin to sense a slight resistance to rotation, or roughness, from the bearings, and then back it off slightly so the V-roller turns smoothly." Each wheel spins freely.

Later, when I put the carriage adaptors onto the 2020 extrusions, they seem to fit correctly, but when I move them up and down the extrusion, I feel some resistance every 10mm or so. The resistance is less when the tensioner bolt is loose, but when I tighten it to the recommended amount "...Tighten the tensioner bolt to apply a small amount of preload to the rollers, while ensuring the adaptor can run smoothly and easily up and down the tower extrusion and is just able to fall to the bottom of the extrusion under its own weight," the resistance every 10mm or so is noticeable.

Is this normal? Should I just continue on, or is there something I should be doing to make the movement more smooth? Is this a matter of the bearings needing to be broken in?

I'd rather solve things at this step rather than wait until I see I have bad artifacts when I start printing.

Thanks for any advice,

John

Not sure what the problem could be. I'd proceed and see if it works
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Replacing the roller carriages with linear rails was probably the best upgrade I did to my Kossel Mini R3. It reduced effector tilt dramatically. Replacing the extruder was probably #2. Those printed gears wore out quickly.

Thanks for your thoughts, tomasf. I do expect to do some upgrades in the future, but I'd like to start with the stock configuration first, as much as I can.

I'm starting to think I have the tightened the 3 nyloc nuts on the rollers too tightly. I'd guess the rollers are not perfectly aligned with the extrusion gap. I loosened the three nuts on one carriage, and that problem went away (only to be replaced by being too loose). Maybe I just need to find the best happy medium, relying on the tensioning bolt to set the correct tension against the extrusion as opposed to the three v-roller wheels.



John

Rollers worked fine when I built mine you probably need to adjust the tension on the nuts as you already said you have done. I saw very little problems with the rollers and i saw large improvements without them so this might make one believe that the rollers could have been causing some of my print problems, such as effector tilt or un-level beds or layer shifts in the middle of prints.

I will echo Tomas, I have recently upgraded to rails in place of rollers and I have seen improvements. I also upgraded to magnetic arms and aluminum belt carriage adapter that can be tensioned with a screw driver which helps get the belt tension just right. Upgrading the extruder sounds like a fairly good idea and will most likely be looking into that and also some machined aluminum corners for my next upgrades to add even more rigidity to the build.

I have seen large improvements in my auto calibration already but i still need to do some more commissioning to get start test printing. That being said the printer kit from T3DP3D is VERY well designed in my opinion and i am certain that R3 of the kit has many improvements from my original R1 i purchased and i am more than certain the kit if put together correctly and with care will work just fine with the rollers.

A flat spot on a bearing ball will not get better over time. It's pretty easy to replace the bearings in the Delrin rollers, so I'd try this first.

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Ace67aod
Rollers worked fine when I built mine you probably need to adjust the tension on the nuts as you already said you have done.

Thanks!

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Ace67aod
I will echo Tomas, I have recently upgraded to rails in place of rollers and I have seen improvements. I also upgraded to magnetic arms and aluminum belt carriage adapter that can be tensioned with a screw driver which helps get the belt tension just right. Upgrading the extruder sounds like a fairly good idea and will most likely be looking into that and also some machined aluminum corners for my next upgrades to add even more rigidity to the build.

My R3 + kit was a special order with basically the R3 components, but swapping in the DuetWiFi and Titan extruder. I already own a set of Haydn's magnetic rods (from when I thought I'd be upgrading my first kit) and have my eye on some of the work dc42 has been doing with carriage and spider, and will swap them in at some point. When I was looking at other kits, the rails were appealing too, but I'll start down this path first and see how it goes. One comment that concerned me about the rails was some noting they were much noisier than the rollers. As this is to be the "family room" printer, it needs to be pretty quiet.

John

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o_lampe
A flat spot on a bearing ball will not get better over time. It's pretty easy to replace the bearings in the Delrin rollers, so I'd try this first.

Do my symptoms sound like a flat spot on a bearing? I have the same issue on all three carriages, so it would surprise me if I had equally bad bearings all around.

My understanding is this type of bearing (623ZZ) doesn't need lubrication. Is that a correct assumption?

Again, maybe I'm just being overly sensitive to this movement, as I've not used this type of mechanism before. If I have things adjusted to where the wheels have a slight grip on the 2020 extrusion, I can raise it to the top, release it, and it will slide in a continuous movement to the bottom. The concern is that if I am lightly holding the carriage as I raise it or lower it, I will feel a slight change in movement approximately every 10 mm or so.

Thank you.

John

I felt that the bearings were running roughly on my kossel xl. The two bearings are 4mm apart, so I filled this gap with a 3x3x7 bearing (which I had to hand - a 4mm wide bearing would probably be better) with a 0.5mm washer on each side. You can then tighten the nylon nut quite firmly, and the bearings run smoothly. A couple still have flat spots so I will replace them. Seems to be less play on the carriage
Adrian

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AdrianR52
I felt that the bearings were running roughly on my kossel xl. The two bearings are 4mm apart, so I filled this gap with a 3x3x7 bearing (which I had to hand - a 4mm wide bearing would probably be better) with a 0.5mm washer on each side. You can then tighten the nylon nut quite firmly, and the bearings run smoothly. A couple still have flat spots so I will replace them. Seems to be less play on the carriage
Adrian

Interesting! Thanks for the information. I'll look into that.

Just replaced my lumpy 3x10x4 bearings and used a 3x8x4 bearing between. Seems to work well - the 3x8x4 just fits snugly in the centre of the delrin ring. You can tighten the outer nyloc nut really firmly, and the bearings run smoothly and freely. Seems to be very little play on the carriage now.
Adrian

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AdrianR52
Just replaced my lumpy 3x10x4 bearings and used a 3x8x4 bearing between. Seems to work well - the 3x8x4 just fits snugly in the centre of the delrin ring. You can tighten the outer nyloc nut really firmly, and the bearings run smoothly and freely. Seems to be very little play on the carriage now.
Adrian

Thanks for the update! My printer is complete, and on initial testing, I didn't notice any strange artifacts, so perhaps I was being overly concerned. I'll keep this in mind for if/when I update the mechanics.

John