SCARA single arm

dk

I build a single arm SCARA with Duet wi-fi, but it is not Robotdigg. In my setup moving proximal arm have an effect on the proximal arm.
If there any setting for this version of single scara?
If not, do I need to create .h and .cpp files for new type kinematic?

JoergS5

@dk Hello, nice to see that you try to build a Scara printer.

Where to change firmware was discussed here some time ago:
https://forum.duet3d.com/topic/5651/parallel-scara

There are some source files for single Scara already, so changing this files and adding your required functionality or algorithms would be reasonable.

https://github.com/dc42/RepRapFirmware/tree/dev/src/Movement/Kinematics
in the ScaraKinematics.cpp and .h files.

dc42

I presume you mean that moving the proximal arm has an effect on the distal arm. See https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwareSCARAPrinter in particular the C parameter in the M669 command.

dk

@joergs5 , I very excited someone interested in parallel SCARA kinematic! For my purpose, parallel SCARA will work much better than single Scara.
How did your attempt to create parallel SCARA (Morgan style kinematic) 3D printer with Duet?

@dc42 Is Parallel SCARA kinematics available for Duet?

JoergS5

@dk

My understanding so far is, that single Scara is for robots not requiring too much precision (or it's expensive to get precision). Parallel Scara provides by the overconstraint an added stability and precision, and three arm Scara is used for Delta, and there is a seldom construction in the Reprap forum with three arms also, each arm at a coordinate in the room.

For avoiding the backlashes in the joints, there was an interesting discussion about hylite. You may want to check it, information e. g. at
https://hackaday.com/2018/06/14/folding-robots-with-special-materials/

tjb1

Is it possible for a design like this to draw a square? Or does it need to flip the arms and reposition?

JoergS5

@tjb1

For Scara the nonprintable areas (singularity) are the problem. So you can avoid them or if your square includes such an area, you can try to print while you cross the singularity area.

dc42

@dk said in SCARA single arm:

@dc42 Is Parallel SCARA kinematics available for Duet?

Not yet, but it shouldn't be too hard to add.

dk

@dc42 I understand you are extremely busy with other improvements, but can you give an idea when are you planning to add parallel scara kinematics for Duet?

dc42

@dk said in SCARA single arm:

@dc42 I understand you are extremely busy with other improvements, but can you give an idea when are you planning to add parallel scara kinematics for Duet?

That depends on how many users request it, compared with other improvements and features that are on the wish list.

JoergS5

@dk I have to finish other projects before winter, but Jan/Feb I will implement parallel Scara into Duet and give it David to implement. If he wants to implement it himself, that's fine too, but it is not necessary, if you have a bit of patience.

dc42

@joergs5 said in SCARA single arm:

@dk I have to finish other projects before winter, but Jan/Feb I will implement parallel Scara into Duet and give it David to implement. If he wants to implement it himself, that's fine too, but it is not necessary, if you have a bit of patience.

Sounds great!

dk

I wish I could help speed up the process.
@JoergS5 maybe I can help you with your projects?
@dc42 if I make printed files for test setup it will help?

JoergS5

@dk I don't want to promise something that I can't keep. But what I can promise you is that I will definitely do it. So you can start building a parallel Scara.

My main goals are: precision and expandability for other jobs like grinding/honing/routing/sandblasting.

This is my plan: https://reprap.org/forum/read.php?185,824669
I already bought used Harmonic Drives and will concentrate on them in my construction.
For the plan I will need Duet 3

dk

@joergs5 Great idea! I think even a 2-handed printer (2 hotends) will be a serious challenge in terms of firmware and slicer. Does any slicer support print with 2 hotends in the same time?

I can see a long way of optimization where it is necessary to take into account not only the mutual movement of the heads (so they do not hit each other) but many other details. For example, delay for the second pass through the printed layer, so it has enough time to cool down. Or prevent simultaneous braking of 2 heads moving in one direction to prevent stagger of the printer...

But it is the right way for speed and performance! Especially if you use 2 different hotends, the first 0.3-0.4 mm for detailed perimeter and the second 0.8 - 1 mm for quick infill and supports

JoergS5

@dk Yes, it will be a long way. I've seen some interesting, but failed projects on reprap. The reason was, that to succeed, you need physical and software development, both is important. In those projects one of the two aspects failed. I'll try to make a first working demo with both sides working, then I will publish it.
Duet 3 seems to be ideal for a multiple scara printer, using the CAN bus to expand the number of steppers/extruders.