Both X-axis bearings on my TAZ6 have about 0.30-0.35 mm play. Translating that down to the nozzle, it easily ends up being a millimeter, which is significant when the nozzle is half of that… You can easily see vibration traces in the prints when the print head makes a sharp acceleration. Is this really normal, or do I have a set of extra-sloppy bearings? It seems excessive given that it’s a $2.5k printer, not a $500 one…
You have extra sloppiness. Try loosening the bearing holder mount and then moving it onboard or outboard for better contact then re secure
Not sure what you’re suggesting. You mean moving the polymer bearing in the mount or moving the mounts themselves on the carrier?
I was suggesting moving the mounts. You can also wrap some tape around the barrel of the bearing itself and re-insert it for a tighter fit.
I think he’s referring to the bearings being loose on the rods. In my case I ended up going to a bearing from PBC linear that fit the smooth rod to a point that I took the rod out and set it vertical and slid the bearing over it and let go and it was about 2 full seconds for it to slide down the rod. They are pricey at about $13ea but it was well worth it.
Yeah, the play is between the rod and the bearing, not between the bearing and the mount.
Yes. But if you move the bearing to one side or the other of the rod inside said bearing mount, then you are theoretically in contact with the bearing and the rod with no gap at that point of contact (and a bigger gap on the side not in contact with the rod)
Those particular igus bearings are designed for preload press fit applications. In the holder like they are without that preload, that’s your contact pattern. You options are to move the bearings to get some better contact, wrap tape around it to force better contact, swap them out for different bearings such as the oilite bronze ones that some people are using, or find and or machine a bearing housing out of aluminum that allows preload and retrofit. Or go openbuilds.
Ah I see. I have a CNC mill so maybe I’ll see if I can make a sleeve. Do you know where I can find specs on what the sleeve diameter should be?
According to the igus website they fit an “h7” size socket but I haven’t been able to find that dimension. It might be easiest to buy one of their socket mounts, then get the dimensions from that. I suspect that with a 19mm barrel diameter the socket should be around 18.750mm . Maybe 18.5, but too much squish will lock the bearing to the rod
Ah, it says “Recommended housing bore H7”. Apparently “H7” is an ISO tolerance. For a nominal 12mm, it is a hole that is between 12.000 - 12.018. That should really be done with a reamer, and I don’t have a 12mm one. A twist drill won’t hold those tolerances, but maybe it will still be better than the printed housings. It’s worth a try.
The bearing itself is about 19mm OD, so 12mm seems too small for a diameter and too big for a radius.
Oh my bad, I looked at the ID. For 19mm, H7 is 0.000 - +0.021mm. (I used http://theoreticalmachinist.com/IsoTolZoneCalc. The tolerance designations are intervals depending on the nominal diameter.
Although http://www.igus.com/wpck/3665/drylin_r_rjm_01 indicates that the 12mm shaft bearing has an OD of 22mm. not 19mm. Apparently the X-axis shafts are 12mm but the YZ ones 10mm. It’s the X-axis I’m most worried about. There is similar play in the Y-axis but since it’s preloaded by the weight of the table I don’t think it wobbles as much.
McMaster wants $65 for a 22mm reamer so I think I’ll try interpolating a hole first. That probably won’t be better than 0.1mm so we’ll see how that works.
The X axis is indeed 12mm. Usually the ones people are concerned about first is Z, because of banding offset.
The Y axis openbuilds project will fit a stock Taz 5 with minimal modification. there is an X axis one as well, but it’s to my knowledge so far untested. It looks right, it prints, I juat don’t have a 6 to put it on for certain.