[CarlosNalvarte]

Hello everyone,

We started building Thor exactly a month ago for an industrial application project as part of our Capstone project at Camosun College. We already received all the 3D printed parts plus all the electronics and motors. Little by little we achieved the assembly of this robotic arm; however we are having some issues regarding articulation 2 (the piece that looks like an 8). There’s always some misalignment at the bottom of this articulation that leads the two motors(articulation 2) to not grab the internal indentations and therefore to not be able to move.

Regarding to articulation 3 (the open belt), we got a motor that has a 6mm shaft and since the pulley we ordered has an internal diameter of 5mm, we drilled the pulley so it makes contact with the motor’s shaft. This way it could fit with the shaft. So far with this adjustment we are partially able to control the movement of this open belt articulation. On the other half of this pulley we have attached a 5mm rod so it makes contact with the bearing that goes at the bottom of the articulation and also with the motor’s shaft.

I have one more question and it’s about Asgard usage . So far I tested all of the articulations and even checked each STEP output with the oscilloscope and everything seems alright. In order to test Art 2 or Art 3, do these two need to be combined (as in the case of Art 5 and Art 6) or they should be able to work by separate? I did some testing a week ago and it seemed that to make the 8-shaped piece to move, I had to move both Art 2 (2 motors) and Art 3(open belt) altogether but I’m just wondering if that was just a coincidence.

And just to double check, Art 2 slider (in Asgard) controls both motors at the bottom of the 8-shaped piece (rotates the 8-shaped piece from one side to another) and Art 3 slider controls the movement of the open belt which moves the combined Art 4+Art56+Claw altogether.

So far I haven’t run into some other issues. As per my calculations it seems that Thor will consume at most 15A due to the current of each motor plus any extra current the additional parts (sensors, drivers, fans, claw servo).

I hope I can submit some images soon, will keep in contact. My email is carlosnj95@gmail.com if anyone would like to directly contact me. I could also rewrite this in spanish if my english writings skills are not good enough. I just need some guidance.

[CarlosNalvarte]

I would also like to add that our robotic arm was completely printed using resin. We still have problems using articulation 2-3. We found out that the bottom section of this articulation is not aligning properly with the motor gears, so we lifted a bit the gears that go on top of motors of articulation 2 making a better fit with the internal indentations of the 3d printed piece.

I’m just wondering if the use of resin might have been an error as the robotic arm feels heavy. With help (using both my hands to grab art56 and 4) the motors can do the work but as soon as I leave it on its own, the whole ‘head’ falls. I’m 3d printing the head of the robotic arm with PLA to see if that makes a difference.

[Angel LM]

Hi Carlos!

First of all, sorry for the delay in answering!
Secondly, I think you are the first person to print Thor in resin! You must have a huge resin printer! Hahahaha

As you say, usually a resin printed piece is heavier than a plastic one (especially if the resin one is completely solid). This can be a problem, since the motors are sized for the weights of the plastic printed parts and it can happen what you say, that the motors do not give enough power to move the arm.

There is a user who had a similar problem to the one you mention about the second articulation and he designed some supports for the lower part that I think solved his problem. I link the post here in case it helps you.

Regarding Asgard’s doubts. In principle the Art2 slider should move the two motors with printed gears that are located at the bottom. The Art3 slider should move the motor of the pulley that has the open belt.
Both movements are independent, so it must have been a coincidence what you say.

As the “stable” Asgard version has no direct kinematics implemented all the movements you make of the joints are independent. The only exception are Art5 and Art6, which as you say are related, since each of the sliders moves a motor that is connected to the semidifferential.

I hope this clears up your doubts and let us know if you have managed to solve the problem with the second articulation!

[Author]

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