Hi...

I want to ask your opinion. With so many advantage of Scara, why is delta printer is more popular than scara?

Is scara too difficult to build ? Too Expensive ? Any disadvantage that make Scara printer not a good choice ?

Regards

it is just tough to get the calibration right.. any error in the printed parts and you are stuck trying to figure out what is wrong!

Correct me if I'm wrong but deltas suffer from calibration issues too? It's hard to calibrate any one axis individually as three motors contribute to that motion. I guess angles are harder to measure accurately in comparison to linear distance moved by carriages along the towers but some Pythagoras makes it easier.

I think the real issue most people have with them is the big cantilever created by the SCARA arm which can cause drop (thus inconsistent nozzle height) across the print bed. That and for manufacturing purposes, SCARA requires a better micro controller since it's inverse kinematics involve trig functions, whereas linear deltas only require squares and square roots which require less computing power. That last point is probably the biggest deal breaker as most (early) control boards were made for Cartesian printers and the trig functions were too processor heavy, while the squares and square roots less so. This wouldn't be an issue if gcode was sliced specifically for the kinematics of the printer and all the controller had to do was command motors to move, but I believe most slicers output standard Cartesian gcode and gcode pre-processors are no fun so the control boards are expected to do the conversion.

I think it's a combination of the cantilevered arm and the strange shape of the build area that discourages users from building SCARA printers.

There is an interesting new SCARA design called the Helios, see [hackaday.io]. He has a couple of video on YouTube too. We've supplied the person behind this project (Nicholas Seward) with a Duet Ethernet and implemented basic SCARA support in RepRapFirmware.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].