Choosing the Best Load Cell for Side Load Protection in Automated Feeder Systems

[JMorris]

I am looking to make an automated feeder system using hoppers. The first design used 50lb single ended load cells. However, a side load was accidently applied to the system and the load cell was rendered inoperable. i am not worried about the accuracy of the system when a side load is applied, i am worried about the load cell not being damaged.

I am about to make the next and larger version of the machine, this time with 200lb load cells. Which type of load cell would be the best to produce no worst accuracy than the single ended load cells, but will perform better negating a side load.

I have called up suppliers and have been informed of multiple things. Such as:
1. nothing will because the weight of the load cell is too small.
2. S beam would, but most others say this is the worst choice.
3. a few say sheer beam would be best.

Any comments on a course of action would be greatly appreciated.

 

[Danger]

I don't really know anything about load cells. My approach would be to modify the feed system so that side loads can't occur. Maybe some extra guide rails? Sorry, but that's the best that I can come up with.

 

[JMorris]

appreciate your help. under normal conditions the side loads are not present. they are though, when something such as an operator bumps into one, or the machine is being moved.

under ideal conditions neither should be an issue, however...

 

[Danger]

In that case, it's simple... eliminate the humans.
Fred Garvin and Brewnog both have extensive knowledge of sensing devices; they should be able to help you out.

 

[TVP45]

Load it with a ball; no side loads.

 

[JMorris]

Load it with a ball?

 

[TVP45]

Load it with a ball?

Yes. It only works in compression, but a hardened load button (if you want to save $) or a captive ball (more $) pretty well eliminates side loads. Pretty standard fare from most sources; have you talked to a load cell sales rep?

 

[JMorris]

ive talked to about 7 sales reps and nobody mentioned a captive ball or a hardened load button. most have pointed me to a sheer beam, but these don't start out till about the 500lb level, and my hopper will only hold a max of 187lb, so the tradeoff for some side load protection is less accuracy.

i shall research the two things you mentioned.

 

[TVP45]

I don't know what you're doing, but have you looked at the MB series from Interfaceforce?

 

[JMorris]

just looked at, and it looks like the majority of the others i am finding.

i am trying to measure a hopper and the contents of it. this will send a singal to the PLC, and the PLC will determine whether or not to increase the speed of the vibratory feeder that is located just under the hopper that is moving the material to its destination. the weight measurement has to stay on track like 60lb/hr, equates to 1lb/min, and many times every second the PLC is determining whether or not the vibratory feeder is moving at the correct rate, and this is all based on the output of the load cell.

 

[Ivan Seeking]

Normally the load cell mounts are designed to prevent side-loading. This is a common issue.

Just use a piston and sleeve assembly.

 

[FredGarvin]

Another method is to constrain the motion of the hopper to only the vertical direction, i.e. mount it on vertical rails.

Or, like Ivan mentioned, set up a piston with a pressure transducer. The pressure in the piston will be directly proportional to the load.