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Z Wobble
#1
Just curious - has anyone started any hardware projects to address the Z wobble?

Kieth
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#2
are you meaning the Z screw being "factory bent" and bed moving on X and Y axis because of this?
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#3
Yes, almost every print I have seen, including those posted here, have some z wobble... And yes, my own prints have it - and although it is an acceptable level, I feel there is a lot of room for improvement. I'm considering trying a "hose" coupling instead of the solid metal, just as an experiment.

Kieth
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#4
I have it too, and in fact am starting to wonder if it's not the cause for my prints to be offset, there is no play on x and Y and still I'm getting not round circles and rectangular shapes are off as well.
Since the Z skew is bent, I believe it could offset the bed to some extend while turning...
So far, Da Vinci is printing very well with Repetier, this is my only concern with parts never being accurate :-(
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#5
On many prints I have a xy shift part way up it, I attributed this to the fact that the glass is also somewhat loosely held and can slide.
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#6
Take the four corner screws out. Lift up on the metal, and bend the tab that contacts the glass down. *slightly*. Do this for all four tabs. When you put the screws back it will flatten the metal back but it will maintain a spring tension that stops the glass from moving. Alternatively, you could put a very small drop of jb weld in each corner, just enough to hold but little enough that it could be removed if needed.

Kieth
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#7
For z wobble I found that the two bearings on the right on the z axis were loose. What they should have is some type of glue on them to take up the play and stop the wobble. What I use is loctite 638 to fill the gap and hold the bearings in place. This is best done with the machine assembled so the bearings are in the right place when you put one drop on each side of the two bearings on the right side. Do not get any loctite on the shaft, just on the bearings and plastic housing. Loctite 638 can fill gaps up 1/64th of an inch. I also noticed that one of the white mounts for my z axis 8mm rods was loose where it held the 8mm rod. So I used a little there to. Now I no longer have z wobble.

The same was true for the bearings on the left side of the y axis and the bearings on the back side of the x axis behind the head. All these are made to float in place when the machine is assembled. Then a drop of loctite or some kind of glue is used to lock them in place. I know this because I have two da vinci printers and have seen the loctite or glue on one machine and it was missing on the other machine. Someone is forgetting to glue these parts in place on the production line.

Another thing I have found is that the rods for the x axis can be loose in their pockets. These are the rods that the head rides on. I removed them and wrapped 1/2" wide masking tape around these rods about an inch or so from the end so it is just visible with the rod inserted to take up the play. About one wrap of tape is enough. Sometimes it only takes just a small strip 1/4" long.
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#8
I thought of doing that the first day I gotr it, but figured Id rather have it shift a bit than pop off the print due to hitting a curled edge.
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#9
why not use hot glue instead of the loctite? Or is the build chamber hot enough to melt the glue?
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#10
I think the loctite is more like what was used at the factory. It also would flow around the bearing a little better than hot melt glue. Hot melt glue may work good too but I know loctite works and I'd rather not do the job twice if something else doesn't work.

I don't the build chamber would get hot enough to melt hot glue. But that is something else to worry about.
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#11
Could you post pictures of your models now that you have done these mods please?
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#12
Does it need to be loctite 638? That specific compound is pretty expensive on amazon. Would a different sleeve retainer, like loctite 640 work? or even super glue? I'm just uncertain about what will and won't work in this situation.

Thanks!
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#13
In the end I think I'll either have to glue the plastic bracket that hold the two upper tray or print else that sets better.
My tray always oscillates
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#14
Def don't use super glue.

You could try some thin plastic, like the lid from a tub of "butter" ( margarine) - cut a thin strip to wrap around the bearing and reassemble. You might need to smash the strip a little with a hammer or something similar to make the strip thin enough so there isn't to much pressure going back together. The plastic used on those tubs is, imo, rather malleable.

There are a few other parts concerning this z issue. My suggestion is not intended to be permanent. Rather it will let you are how much of a problem it is -or is not- before opting for a permanent fix.

Kieth
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#15
I will give this plastic tub idea a shot later this week and let you know how it goes. Thanks for the tip! I like avoiding permanent changes if I don't know how they're going to work out
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#16
A word of warning to anyone who wants to try the loctite method:

I got a hold of some loctite 609 and thought I would try using it on the z-axis bearings. Even though I used a syringe to apply the loctite and was being very careful, I managed to get a small amount between the rail and the bearing. Ended up having to take practically the whole machine apart to get the slide bearings out and clean out the one that got loctite in it. No permanent damage was done, but it was a huge pain!
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#17
I just printed out a circular part like a tube on my DV2.0. It came out rather oblong.
Checking the bed bearings I can see some wiggle between the right side bushings
and the vertical rod. It seems like the bearing is too big or worn.
The printer is brand new with less than 2 hours of use.

Has anyone else seen this ??
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#18
2.0 is mechanically similar from what i have heard, and if so then the answer iss the bushings as above.

Kieth
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#19
Quote:2.0 is mechanically similar from what i have heard, and if so then the answer iss the bushings as above.

Kieth

Thanks for the quick reply Kieth.
I took the right side of my Davinci 2.0 off yesterday as well as the right side waste tray holder
and laid it on its side with the opening facing up. It made it easy to really see the problem.
Laying the printer on its side allows you to precisely put the thread locker between the bushing
and plastic bed mount without getting it on the shafts or dripping.

The issue was as stated above the bronze bushings were spinning loose on the vertical shafts
and installed loose on the plastic bed. I used HobbyKing #608 ($0.99) thread locker and it now
holds the bearings to the bed removing the mechanical slop.
BTW. it needs a good 24 hours to cure just like the Loctite #638 ($28.00) which I didn't have.

This was a good time to check for play in the X and Y axis shafts as well. (no slop found)

I did find another problem though.... https://forum.voltivo.com/showthread.php?tid=8397

Jerry
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