4 z axis 3D printer
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@gtj0 this looks what i am looking for ,I will have a look!
Thanks! -
Unless you have a very large bed that is flexible enough to twist under the forces applied by the leadscrews, it is better to use just 3 motors to lift the Z axis. Three points define a plane, and a sufficiently rigid bed is a plane.
Duet WiFi hardware designer and firmware engineer
Please do not ask me for Duet support via PM or email, use the forum
http://www.escher3d.com, https://miscsolutions.wordpress.com -
@dc42 Yes I have a large bed 1300 x1300 but I did stiffeners as support so I would say it is rigid enough for this size.
can i do the same you just said with 4 motors as I already did the mechanics and everything is great so far? -
With the 4 screw setup it's the rigidity that's the issue. Let's say you have 4 motors at the 4 corners: X0 Y0, X1300 Y0, X1300 Y1300, and X0 Y1300. Now let's say the X0 Y0 motor moves its corner down but the others don't move at all. With a perfectly rigid bed, the line between the X1300 Y0 and X0 Y1300 corners are going to make a pivot point forcing the X1300 Y1300 corner UP. Something is going to break.
Could you can make the 2 "back" motors a virtual motor?
Maybe support the bed directly between them instead of at the corners then use the 2 Z motor connectors on the Duet to drive both motors together? Then you'd have a 3 point mount without having to actually move the motors or leadscrews. -
@gtj0 Thanks! it is clear now
I think I have some flexibility on my bed and no issue with that.
I want to be able to home them to Z-MAX and sync the motors using limit-switches and use Bed levelling using multiple independent Z motors after that ? -
If you set up some hard stops at Zmax at each screw, that force the bed perpendicular to the Z axis, you can just run the bed slightly beyond Z max. The motors will stall when the bed hits the stops and that will force it into the level state and synchronize the motors - no switches needed. Prusa does this in the i3 printers to align the X axis perpendicular to the Z axis and synchronize the Z motors. It seems to work pretty well/reliably.
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@mrehorstdmd that is great
how can i configure this , or just i enable motor stall detect ? -
@marine85 In your homing macro you can reduce the motor current at the start to make it easier for the motors to stall and then increase it again after.
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@phaedrux many thanks , but is there more details to do this
I am beginner with G code
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Well there were the two guides posted above. Did you read through those yet?
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@phaedrux Yes I did but nothing has been mentioned regarding Macros
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The homing files are macros. So is config.g really. A macro is a file containing a sequence of gcode commands.
How far along are you in the commissioning of your printer? It may be best to start with a simple endstop for homing to ensure everything is working before moving on to a more complex arrangement like auto bed leveling.
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@marine85 You really don't need stall detect. If the Z axis is 300 mm long, send the bed to Z=305. It's going to stall when it gets to Z=300 because you've set up physical stops that prevent it from going any further.
Reducing the current when you get close to Z=300 is probably a good idea, especially if you have a lot of torque available in the Z axis.
