4 Axis Printing - RRF compatibility?

CNCModeller

Hi All,
I like the idea of this latest video from CNC Kitchen which covers the printer design, slicing, and printing with a 4th axis. There are many links to the source information in the description for the above video.

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I'd like to think about this for my Polar printer as being able to print 90 deg overhangs may solve some of my current issues w.r.t. small parts I need however a couple of issues spring to mind.

I'm thinking that for many (non cylindrical) parts you can achieve the same effect by slicing and printing your part at 45 degree to it's "normal" direction thus transforming any 90deg overhangs to 45 deg. So this technology is more focussed at printing >45deg overhang flanges on cylindrical parts. However having the layers conical and print lines staggered might help structural integrity as layers are then 3D.

In terms of technical considerations:-

I assume that I could add an additional 4th rotational axis to a cartesian printer duet build that allows for continuous rotation and since the slicer just generates 4 axis cartesian code there wouldn't be any incompatibilities with Duet and RRF. Is this a correct assumption?
What's much more tricky is that I'd need to add the rotation angle of my polar printer bed to the rotation needed on the 4th axis to make it work on my polar printer. Again I assume that is something that could be done in the real time transformation from cartesian to polar co-ordinates. However I'd have no idea how to achieve that kind of modification to the RRF software for Polar machines. I'm happy to tinker but have no idea where to start...

Any constructive thoughts would be greatly appreciated!

Many Thanks
Barry M

o_lampe

@cncmodeller
I'm not sure, if the printers kinematics are influenced by having a "U" axis in the gcode? They already use a Duet controller
What could be problematic for you, is the fact, that their slicer assumes the part is at bed center...the worst place for a polar printer

Also the design has some issues:
How do they make sure, the nozzle tip is always at the center of rotation?
Tightening the nozzle in just the heater block often causes leaking.
The slip ring to connect thermistor, heater and part fan, might also cause trouble.

CNCModeller

@o_lampe said in 4 Axis Printing - RRF compatibility?:

n has some issues:
How do they make sure, the nozzle tip is always at the center of rotation?
Tightening the nozzle in just the heater block often causes leaking.
The slip ring to connect thermistor, heater and part fan, might a

@o_lampe, thanks for the thoughts , will contemplate some more!!

o_lampe

@cncmodeller
I can see it on a Delta with an effector-PCB that acts as slip ring. But only as second tool.
Of course it would be better with a small geared motor for head rotation. Unless, there is a problem with backlash.
Do we have backlash compensation? (RRF3.5?)

Printing first layer(s) with a 45° angled nozzle must be a nightmare.
There is no 'squish' and because of the conical slicing, it starts with tiny circles. That often ends as a big blob hanging from the nozzle.

o_lampe

Could we use the heatsink as GND? that would make the slip ring much easier and reliable. The heatsink could rotate on brass bearings for better contact and heat-immunity. The way the 'heatbrake' looks, it has full contact to the heaterblock and the heatsink, no real heatbrake unless it's made from utopium