# Inconsistent internal force sensor

**URL:** https://forum.universal-robots.com/t/inconsistent-internal-force-sensor/15222
**Category:** Technical Questions
**Tags:** welding
**Created:** [July 1, 2021, 7:36am UTC](https://forum.universal-robots.com/t/inconsistent-internal-force-sensor/15222 "2021-07-01T07:36:09Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![tor](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.universal-robots.com/tor/32/1876_2.png) [@tor](https://forum.universal-robots.com/u/tor)
#### Post date: [July 1, 2021, 7:36am UTC](https://forum.universal-robots.com/t/inconsistent-internal-force-sensor/15222/1 "2021-07-01T07:36:09Z")

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Hi,

I am integrating a spot weld application with a UR10e. To get to the correct position, I use a Direcation node in the Z-axis “Until expression force()\>40” to make the robot apply a force of 40N before welding. To exit the weld spot I use a Direction node in the opposite direction "Until expression force()\<5 and then go up.

This method works great 99/100 times but sometimes the internal force sensor gets stuck at around 24N when I go up, resulting in the robot moving upwards without ever fulfilling the expression force()\<5N.

Any ideas what causes the internal force sensor to not function properly? No cables seem to be stretched wihen this happens.

Is there a smarter way to get the right amount for force applied?

Cheers,  
Tor

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### Author: ![nik](https://avatars.discourse-cdn.com/v4/letter/n/6de8d8/32.png) [@nik](https://forum.universal-robots.com/u/nik)
#### Post date: [July 1, 2021, 7:49am UTC](https://forum.universal-robots.com/t/inconsistent-internal-force-sensor/15222/2 "2021-07-01T07:49:03Z")

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You could try to specify the force that you’re exerting by saving get\_tcp\_force() into a variable (var) and compare only the force in the Z-Axis by doing var[2] \> 5N.