Hi,
I had to mount 2 new pulleys and took the opportunity to once again calibrate the axes very accurate. With loose pulley’s, the printhead moved easily, even diagonal. Aligned the belts, gratefully used H60’s alignment helpers to thighten the pulleys. So it couldn’t went wrong… I thought.
My thought is that it was really bad aligned before, and it stressed and worn out the brass gliders? Until at one point it was running “Okay” by wear of the brass gliders. But now you really aligned the axis perfectly and the holes in the brass glider became to big and cause this rattle??? Could that make sense? Idk you asked our opinion and that’s mine
Mine had nearly the same backlash out of the box. Because of the shorter brass bearing in x-axis direction there was more play than in y-axis direction. You can reduce the play by a bad alignment of the carriers with the IGUS bearings :-).
In my opinion the printhead assembly also is to heavy. So i decided to reduce weight and play at once. So I machined Aluminium bushings for small IGUS pressfit linear bearings and bought them together with 2 hardcoatet aluminium shafts. I machined the aluminium bushings a little longer than the brass ones. Even the x-axis bushing could have the same length.
Until now this is a great success. Reduced the weight about 200g and reduced play and sound level.
@jeafke@mcguiver
Thanks for your reply. Ik don’t think the backlash is in the brass bearing, but in the carriage Iglidur bearings, they have the backlash. And I am wondering whether the rods are consistently 8 mm. I am printing for just 2 months now and it would be a fast worn out then… I thought the axes where aligned quit well before.
Maybe someone @Velleman has a suggestion? Do I have to mount new Iglidur bearings?
If I look at the distance between the bearing clamps with the iglidur bearings then I come to the conclusion that there has to be 5 or 10mm of play in the iglidur Bearings to get a 1mm tilting printhead. The IGUS bearings are involved but most of the backlash is caused by the brass bearings
In my opinion the design of the linear guiding system of K8400 has a big advantage: Theoretically you have very low accelerated mass
But because of the vertical distance between the two moving rods there is a strong tilting moment on the printhead during acceleration and deceleration. In addition the brass bearings are relatively short and the printhead assembly together with the two rods is really heavy for its size.
Too heavy in my opinion and that causes noise, vibration, wear and problems if you have a second nozzle. (it scratches surface mainly during acceleration)
@ raby and jeafke: Until now i dont produce or sell these parts. I think I have to test it further.
@ jeafke: 200 gr. diagonally (both rods moving). You can save about 80 gr per rod (120 gr to 40 gr) and about 50 gr for the bearings.
I understand your explanation. The tilting moment you describe must be the noise.
Meanwhile I disassembled the axes and printhead. I found out that the Igus bearings has much backlash on the rods. There is indeed some backlash in the brass bearings, but much less then the Igus bearing.
I am trying to get Igus bearings that closely fit to the rods. But also the rods has to be all over 8 mm and they aren’t, in my opinion. So I ordered new stainless steel rods and new Igus bearings, so called DryLin second generation solid polymer with less tolerance (0,00-0,03 mm). I hope this will fit better.
Also got a bearing with housing to try instead of the brass bearing. If this fits, I’ll have to find out how to mount it. We’ll see.
When I have assembled this new components I will post my experience, about 10-12 days from now…
I dont think you understood completely: 0.1mm bearing play at the short brass bearing (y direction) means about 0.15mm play at the nozzle, same play at the longer brass bearing means 0.13mm at the nozzle and same play at the Iglidur bearings means 0.018mm at the nozzle caused by corresponding level arms and depending on position of printhead.
I dont think you will be happy with the less tolerance bearings because imho you cant adjust the system as accurate as required. In my opinion it is nearly impossible that the rods are strait and parallel enough to run the carriage without bending the rods at some points. The system is statically indetermined without some play. Too much fixed points.
Yes, I understand that the brass bearings are the main reason for the backlash, but the Igus bearings are easier/faster to replace, from thought of all bits of improvement will help
After that I wil try to improve the brass bearings, but I am not able to produce your nice aluminium housing… If the DryLin bearing with housing fits nice to the printhead rods, maybe I can use two bearings per rod (they are 25 mm long). Only the flange in the xy-carriage will be a problem, maybe I have to remove it.
I am wondering how other printers, like the Ultimaker2, deals with this problem.
By the way, my prints were fine, without noise. So maybe the carriages has to be a little less aligned!
I appreciate your interest and opinion a lot, it sure helps, thank you.
Meanwhile I tried something different to reduce backlash in the xy-carriages. With a fine metalsaw I sawed the Iglidur bearings in longitudinal direction to make the diameter a little less. Not alle the plastic parts of the carriage reacted the same with this smaller bearing. One I could finetune with the four bolts, three others I had to stick on a little piece of cellotape on the Iglidur to get the right effect. Now the bearings do slide without any backlash.
The distance between the carriages I finetuned before putting the xy+printhead in the printer, with a piece of solid cardboard to get round the printhead. The distance on this cardboard I measured heart to heart from the ball bearings in the perspex front and side of the printer.
I didn’t use the hammer this time to align the carriages. They move smoothly by hand now but not freely like before by tilting the printer. I think the free movement is only feasible with backlash.
Even though there’s still some backlash (but very little and mainly in the shorter one) in the brass bearings, the rattling noise in the printhead is gone now.
Maybe I once will replace the short brass bearing for a long one.
I did this mainly to get rid of the noise. I have printed some things now and I think, especially with round walls, there is a little improvement. The printstructure seems to be more regular. But not significant. I made rather good prints before this intervention.
The replacement of the brass bearing looks a very good solution. Mcguiver, can you tell me wich linear bearings you pressed in? And keep you the diameter of the axles?
Anoter question:
Is it an option to replace the plastic Iglidur bearings by ball bearings (like the Z axis)? They don’t wear and have no play so in first case it look it’s an improvement (if I can find ones wich will fit in the plastic clamps…)
