A mistake with the z axis

Hello,everyone!

Recently i made a 3D Printer with 4 screw rods for the Z axis.Just like the M3D 3D Printer.I trived the Z axis with two motors and the motherboard is Sanguinololu.Now,i have a mistake with the Z axis.When printing,there are some small waves on the model. As is shown in the picture.


Can anyone give me a hand?
Thanks!

Best wishes to you!
liujinhua

Hi, this looks like banding. This is usually caused when the screw rods are fixed on the opposite end of the motor.

You could use two smooth rods for guidance of the Z-plate and two threaded rods for movement. Important would be to have the threaded rods only fixed on the motor side.

Second of all, is your revolution/mm dividable by the layer height you print on?
You can calculate it here: [www.prusaprinters.org]

Under the option: Optimal layer height for your Z axis


ps. don't open duplicate topics in other subforums.

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http://www.marinusdebeer.nl/

This is a typical Z-Wobble. I had the same problem when I build a Prusa I2.
The threaded Rods where slightly bent, thus the hotend is moving back and force, depending on the actual height.
I recommend to replace the Rods with real Spindles. They are not that expensive and because they are hardened are really strait.
Of course you have to recalibrate the Z-Axis because the pitch is different, but that's a small price to pay for good printing quality.

Hi,Ohmarinus !


Thanks for your reply!Yes,i also think there is something wrong with the four threaded rods when i met this problem.But i don't know why the M3D 3D Printer can make it all right!And i am sure my calculation is correct.

Are there some important points that i ignored for the M3D 3D Printer?I relly don't know why.Could you help me?


Best wishes to you!
liujinhua

Edited 1 time(s). Last edit at 03/06/2015 01:08AM by liujinhua.

Nobody here knows the M3D 3D Printer?

This does not look like z-wobble. The layers to not look like they are shifting. It looks like they are spreading. It's a common over-extruding problem. It is slowly spreading the layers out as the height increases, the layers get thin and no room for them. This can only go on for so long until the extruder gets so close to the surface the next step up is the proper height. Then the whole process starts over again. Measure many different thicknesses of the filament over a long distance and average them. Just because someone tells you it is 1.75mm does not mean it measures 1.75mm. You may also need to change your nozzle diameter. It may think it's using a smaller hole than it is. This makes more paths closer together.

Anything else and you may need to call customer support for your M3D 3D Printer.

Quote
KingRahl
This does not look like z-wobble. The layers to not look like they are shifting. It looks like they are spreading. It's a common over-extruding problem. It is slowly spreading the layers out as the height increases, the layers get thin and no room for them. This can only go on for so long until the extruder gets so close to the surface the next step up is the proper height. Then the whole process starts over again. Measure many different thicknesses of the filament over a long distance and average them. Just because someone tells you it is 1.75mm does not mean it measures 1.75mm. You may also need to change your nozzle diameter. It may think it's using a smaller hole than it is. This makes more paths closer together.

Anything else and you may need to call customer support for your M3D 3D Printer.

Tend to disagree. Z-wobble has this very specific 'rhythm' in the lines, the same kind of pattern you see in the pictures. If it's the filament diameter that's irregular, then the line pattern will not be so rhythmic or precisely reoccurring every *mm

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http://www.marinusdebeer.nl/

Thanks for your reply!

I have changed many kinds of plastic and got the same result.So i don't think that it is the plastic issue.I think there is something wrong with the four threaded rods.They are not straight enough or not concentric.Does anyone know the driving system of the M3D 3D Printer?Or is the material of the spindle special?

Best wishes to you!
liujinhua