Delta Robot

This is a description of the assembly of the Delta Robot by marginall clever. I find the mechnica attartive but unfortunately, there is no assembly instruction for the robot and a picture is only available in the blog. I have copied the pictures here in case they vanish from the blog:

 


The parts are:

  • 3 Servos Futaba S3003
  • 12 threaded rods M3 x 150 mm
  • 15 screws M3 x 15mm, 3 nuts M3
  • 6 screws M3 x 25 mm
  • plastic parts (see picture)
  • two wooden base plates (3mm)

Assembling the baseplate

The base plates are made of plywood and the cutting is done using laser-cut technology. One plate is cut ok, but the second plate is badly cut and required a lot of work to open all wholes. I expected a better work for the price of this kit. The second plate also shows heavy signs of burn and smells like an old fireplace.

The servos do not fit the base plate as the servos have little noses at the screw mounts which have not been taken into account for the laser cuts. I removed the noses and the servos require a lot of force to got into the openings.

Assemble all servos in a cyclic order so that all shafts are on the same side:

Servotest

I tested all servos using the default sweep scipt and an iteduino (as this has the pins nicesly on board to connect the servos). I use pins 9,6 and 5. All servos run fine, except for one servo, where the mechnics seemed to have problems to go to the zero position. I then use the program to position the servos at 90 degrees (horizontal).

Assembling the robot arms

The plastic parts are 3D printed with VERY POOR quality. None of the wholes are circular adn I had to drill all holes again. All parts look like the 3D printer has a jitter of at least half a millimeter.

The assmebly turned out to be a nightmare. I had to fix every single part. If I have a housing for a nut, I expect this to fit the nut. In most cases, I had to cut the housing to remove debris and print errors. It took about an hour to fix all errors. The interim step is shown here:

Finally the screw connecting the mount with the ring are in the way of the screws connecting the rods. When assembling all parts, the lack of accuarcy and quality made me think about throwing the whole junk away.

As the scews cut their way into the plastic, I do not expect this to last long. I will then have to replace them with screws, nuts and washers ...

Finally, I got the robot assembled:

Unfortunately, the platic of the printed parts is far too weak to hold the mechnical focres and the servo connections loosens after a vew seconds. The mechanical design also introduces a torque on the servo mounts which propper joints would have compensated.

Interim Summary

This delta robot is a very badly build kit. 90 USD is a bit much for the cheap plastic parts that are not accurate and that can not stand the mechnical requirements. I will have to replace the platic parts and especially the joints with correct mechanics to make this robot work. I also had to replace the cheak Futaba analog servos by metal digital servos.

This kit needs to be completely re-designed.

Repairing ...

After some discussion with other makers, I readdressed this robot again and changed the following:

Correcting the surfaces

The printed parts have a rough surface as shown in the picture here:

This creates a tremendeous friction. I polished all surfaces to be a flat and even surface.

Adding Washers

Even after polishing the surfaces, the plastic still remained somewhat sticky. I therefore introduced at all joints washers so that the platics glides on a flat metal surface:

I also drilled all holes that are not used as nuts with a 3mm drill so that the screws can move freely.

Use some Grease

Finally I added silicon gel to all joints. Silicon gel is free of acids and therefore not attacking the plastic.

Summary

With all the fixes applied, the robot now somehow moves as expected. However, the moves are still not precise which is due to the poor design. But as we say in Germany: Nothing is worthless - it can always serve as a bad example.

This kit needs to be completely re-designed.