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Large CoreXY Z Lift

Posted by Mathew96 
Large CoreXY Z Lift
February 13, 2018 12:51PM
Hey Guys,
I'm planning to get my old ABS-Prusa a new companion, a 1000mm³ CoreXY (well 1000mm frame building volume will be a bit smaller)
Currently I'm struggling with how to handle the "Z-Lift" when crossing outer perimeters, I know not everybody is a fan of Z-Lift on travel but that's not the topic.
My idea was that with that build volume and the bed's weight it might cause trouble to do a quick z-lift.
The solution might be to realy lift the head with maybe a solenoid when a travel z-lift ocurrs but I don't really know of a way to implement this in a firmware/slicer.

Has anybody had similar troubles with their CoreXY designs?
Or do you just don't use the Z-Lift function?

Thanks for your answers!
Mathew96
Re: Large CoreXY Z Lift
February 13, 2018 01:16PM
Use 3 ballscrews, with independent motors. Not only will small "Z-lifts" be fast enough, you could use a Duet board and get the auto-level function for FREE !
If you're concerned about the weight, larger motors or a belt ratio will work well as the Z speed doesn't need to be as fast as the XY.
Z lifts are typically very small, around 0.2mm. For a 1605 ballscrew that would be around 15 degrees rotation, which probably would happen pretty quick even at 60 RPM that would be less than half of a tenth of a second.

A solenoid is an interesting solution, though it will add weight to the carriage. Don't know if there's a firmware that currently supports it as a separate function.
Re: Large CoreXY Z Lift
February 13, 2018 02:13PM
I didn't read all your message; skipped the solenoid section :-)

An idea came to my mind, I don't know if anyone has tried!

Instead of moving the build plate down and up during the z-lift you can move the printhead up and down.
Only a small stepper is required for moving the small mass of the printhead.

When I have finished building my new Hypercube300 I will make some experiments.

/Niels

Edited 1 time(s). Last edit at 02/13/2018 02:16PM by oz9ny.
Re: Large CoreXY Z Lift
February 13, 2018 07:48PM
That sounds like a great idea. It only needs to move up and down a little. so it might be easiest to do using a solenoid and lever. A simple gcode post-processing script could be used to insert lift/drop commands into the gcode file to drive a solenoid. Just add lift after every retraction and drop just before extrusion restarts


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Large CoreXY Z Lift
February 14, 2018 01:05AM
Hey,
thanks for the answers so far!

First: I took a look at the Duet board as prot0typ1cal suggested looks nice to me, maybe not the cheapest but I might consider it. I have not chosen any electronics yet. (Maybe build my own...)
Second: A servo might be a good step in the right direction, I have some RacingServos collecting dust, these might be ideal, they are quite light and powerful enough to lift the head. But the board needs to support it.
Re: Large CoreXY Z Lift
February 14, 2018 04:45AM
The thing about the duet boards is that the developers are pretty good at taking good ideas, and making them work with their boards. They constant work on the software for the hardware and have new updates about once a month.
Re: Large CoreXY Z Lift
February 14, 2018 05:14AM
Well that is surely something I personally can't do when designing my own hardware...
But it's great that the community and developers are so active!
Personally I like the challenge of designing the electronics, but maybe I will go with the DuetBoard (or similar) and create my own later on.
Re: Large CoreXY Z Lift
February 14, 2018 10:41AM
Quote
the_digital_dentist
That sounds like a great idea. It only needs to move up and down a little. so it might be easiest to do using a solenoid and lever. A simple gcode post-processing script could be used to insert lift/drop commands into the gcode file to drive a solenoid. Just add lift after every retraction and drop just before extrusion restarts

Problem with a selenoid is that you may be very dependant of gravity. Stepper and small screw will be better and more precise in my opinion.
Re: Large CoreXY Z Lift
February 14, 2018 01:44PM
Quote
oz9ny
Quote
the_digital_dentist
That sounds like a great idea. It only needs to move up and down a little. so it might be easiest to do using a solenoid and lever. A simple gcode post-processing script could be used to insert lift/drop commands into the gcode file to drive a solenoid. Just add lift after every retraction and drop just before extrusion restarts

Problem with a selenoid is that you may be very dependant of gravity. Stepper and small screw will be better and more precise in my opinion.

It doesn't need to be precise, it only needs to return to the same position each time. Think ball and cup, or a seating mechanism.

I think a stepper motor would be overkill
Re: Large CoreXY Z Lift
February 14, 2018 01:44PM
Quote
oz9ny
Quote
the_digital_dentist
That sounds like a great idea. It only needs to move up and down a little. so it might be easiest to do using a solenoid and lever. A simple gcode post-processing script could be used to insert lift/drop commands into the gcode file to drive a solenoid. Just add lift after every retraction and drop just before extrusion restarts

Problem with a selenoid is that you may be very dependant of gravity. Stepper and small screw will be better and more precise in my opinion.

Solenoid and a spring perhaps?


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: Large CoreXY Z Lift
February 14, 2018 02:01PM
I would probably mount the extruder on a lever with with a spring pushing it downward. Use a bearing from a HDD for the pivot. The solenoid would work against the spring to lift the extruder up 0.5 mm. I don't know how anything can be more precise than moving it up and down between two hard stops.

You're right, a motor, driver, more wires to run the motor, screw, nut, some sort of short linear guide, and firmware mods could do the job, too.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Large CoreXY Z Lift
February 14, 2018 07:25PM
Quote
Origamib
It doesn't need to be precise, it only needs to return to the same position each time. ...

I think you mean it doesn't need to be accurate. It really doesn't matter if it lifts 0.5 or 0.513 or 0.6 mm. The nozzle does have to return to the exact same position when it comes back down, which is the definition of precision.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Large CoreXY Z Lift
February 16, 2018 03:08AM
Okey, well as soon as I have built the frame I will try to take a look at the Duet board and then later on try to integrate a solution with a servo/solenoid.
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