Scara Arm 3D Printer that works

A recommend of SCARA 3D Printer that plug and play from RobotDigg.
[www.robotdigg.com]

I've recently published a blog entry about my initial experience with this printer at [miscsolutions.wordpress.com].

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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].

I've made some more improvements to this printer including getting rid of the backlash and adding a Z probe.



This will be one of 3 printers on the Duet3D stand at the forthcoming TCT exhibition in Birmingham, UK.

Edited 1 time(s). Last edit at 09/24/2017 07:53AM by dc42.

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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].

Should be fun for you to program the firmware but frankly from a mechanical point of view this machine is a piece of junk. Just looking at it makes my eyes sore. Anyway, an other attempt to cash on a different design.

Edited 1 time(s). Last edit at 09/27/2017 12:45PM by MKSA.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Although the mechanics has its limitations, I don't know of any other low-cost mechanical system that is capable of producing 400mm long prints such as this one, especially from such a compact mechanism.



Not bad for a "piece of junk". Click on the image for larger version.

Edited 1 time(s). Last edit at 09/29/2017 05:17PM by dc42.

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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].

Is the whole arm hanging via the leadscrew from the motor with a FLEXIBLE coupler or is the leadscrew supported by a lower bearing ? The print quality is rather poor print.
Note that I don't criticize the kinematic of the machine (to lay bricks, pour concrete to 3D print a house, it would be the way to go), but the way it is built here.
This kind of machine must be well made not "cheap".

Edited 3 time(s). Last edit at 10/06/2017 12:16AM by MKSA.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

The leadscrew is supported by a lower bearing.

One of the reasons for the less-than-perfect print quality of that print is that the circular parts of the model have evidently been constructed using a small number of relatively large segments.

That aside, I think one of the main issues is that the resolution (angle per 1/16 microstep) on this printer is too low - about 71 microsteps/degree on the proximal arm and 100 on the distal arm (it was 80 before I replaced a pulley). I think this is what gives rise to the vertical banding that I see on vertical flat surfaces, and the angled banding on inclined flat surfaces. Switching to 0.9deg steppers would double the resolution, but I suspect that still wouldn't be quite enough, bearing in mind that microsteps are not all exactly the same size. Some of the banding may be due to segmentation, but as the predominant banding is at an angle to the vertical on inclined surfaces, I don't think this is a major factor at present.

Another issue is that the combination of linear rail and leadscrew doesn't prevent the proximal arm rocking a little, which means that the head sags by an amount that varies greatly with the Y position of the print head. The sag is 0.86mm at its worst point. Fortunately, mesh bed compensation (which is really mesh head sag compensation in this case) takes care of that very well. I think the sag would be less if the design used two leadscrews, one one either side of the linear rail.

Earlier this week I changed the position of the proximal homing switch, which allowed more proximal arm movement in one direction and increased the printable length by 50mm to 450mm. If I reroute and extend a cable, I should be able get 500mm or more. Not bad for a small printer!

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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].