We are designing a load system that weighs a conical tank held by a concentric ring with four pins normal to TE’s FX-29 compression load cells. These points are at 90 degrees to each other and each sit directly above a load cell, but documentation that came with these load cells say that there should be no lateral forces applied. Our current solution is the pin design seen below:
We have consistently had alignment problems with this design, but do not have the ability to change out the load cells at this point in our design process (we need the FX-29’s I2C, and do not have the budget to shift to a different load cell for now). The pins we printed out of PLA hold up but shift and skate a lot, and even with a small base plate and some tape, the load cells tend to slide around as well. Think trying to balance a table on four tennis balls. I was hoping someone had a creative solution other than mine for this pin design, as I could not find anything online and haven’t been able to adequately explain my problem to TE.
Looking at the included photo the force sensor is placed in concave feature. I would suggest making use of the flat side on the sensor and make a feature where the sensor is fully secured in the printer link the similar sensor below.
For the 3D printed pin, only a single screw is holding it in place, if you can I would suggest using two point to secure to remove the rotation point. For the sensor in the picture above, a metal bolt was used instead of a 3D printed pin.
Fully securing the sensor is something we have definitely considered to better anchor the cell, in retrospect we should have already applied the mounts we had designed to fit them in better. I believe our concern was primarily to avoid ‘pinching’ the load cell by locking it in place as it would be equivalent to a lateral force the load cell’s documentation recommended we avoid.
As for the load cell pin, our primary motion issues were with our inability to anchor our concentric ring with our mounting design (required for other aspects of our design) leading to rotational forces. We did have some slight movement along the single anchoring screw, but based on the shape of the fin coming off of our concentric ring and the design of the body of the pin there is minimal rotation about the screw. With our tank being held up by these four contact points, it is more common for all four pins to come off their respective load cells than for a single pin to slip. We may try a metal pin to see if that reduces our issue.
One option if the tank already has guide rails, would be to extend up the sensor mount to try and minimize the amount of space the pin can float away from the center of the sensor.
