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Why are there no simple industrial robots (mainly for simpler tasks like pick and place) that are:

  1. Cheap (<=3000$),
  2. Lightweight (<=10kg),
  3. Fast (600mm/s at end effector),

Most of the robots I have looked at cost more than 10K$. Many of cheap ones use 3D printed (plastic) components. I'm not sure whether these robots can survive the continuous and long operating hours in factories.

What's the bottleneck developing such a system? Why haven't established companies not entered this market?

Could someone give some insight on this?

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High quality, low backlash gear reducers cost almost \$1,000 a piece. You need one on all 6 joints. High powered servo motors cost $500+ each. High quality bearings that allow for high pre-loading are a few hundred each. Add the electronics, aluminum body, labor, etc. and it adds up quickly.

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  • $\begingroup$ 1) Does low backlash gear refer to harmonic drives?, For a accuracy of +/-0.5mm, repeatability of the same range, do we need really high quality low backlash gear like harmonic drv?, 3)Couldn't we compensate for the gear backlash in the control? $\endgroup$ – vinjk Jul 9 '17 at 1:16
  • $\begingroup$ 1. Yes, harmonic drives are probably the most commonly used in robotics. 2. If your arm is 1 meter, 1 arcmin backlash in the shoulder joint translates to 1.74mm in lost accuracy at the end effector. Also, expect your backlash to increase as the robot wears. 3. Typically your sensors are attached to the motor, and increase in accuracy by the same amount as the speed is reduced. So it is blind to what is happening outside of the motor. If you attach the sensor outside the gearbox, you'll either have low accuracy or a high cost sensor. $\endgroup$ – James Jul 9 '17 at 3:00
  • $\begingroup$ Hi James, just a question on how you got that figure 1.74mm. How I try to calculate the offset due backlash is, offset = arm_length*sin(backlash_rad) When I calculate for 1arcmin and 1 metre arm length, I get 0.29mm. How did you calculate? $\endgroup$ – vinjk Jul 9 '17 at 11:16
  • $\begingroup$ Oops, you're right. For some reason I was thinking an arcmin was 1/3,600 of a circle instead of 1/21,600. High precision gear reducers will have 1-3 arcmins of backlash, cheaper planetary gear reducers might have 14+. $\endgroup$ – James Jul 9 '17 at 19:09

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