Weigh conveyor

Hi guys:

I got a HI 1769-WS connected to a compactlogix 1769-L32E CPU. Rslogix V13, four load cells HI HLPB110-43 and a junction box from hardy.

The four load cell are underneath a small conveyor which is mechanically isolated from the rest of the line, the fastest production is a box every 2.4 seg, lenght of weight converyor is 1 meter, speed of conveyor is such that the box is on top of the weight conveyor for 1.68 seg, my question is:

- What is the best approach to get every box weight, as you know the weight begins from zero goes to high value and then down to zero as a box passes on top of the weight conveyor?

Can I try to use a photo cell to catch the weight as the box travels on top of the weight conveyor or you have a differrent approach



Regards,



William

widelto said:

Hi guys:

I got a HI 1769-WS connected to a compactlogix 1769-L32E CPU. Rslogix V13, four load cells HI HLPB110-43 and a junction box from hardy.

The four load cell are underneath a small conveyor which is mechanically isolated from the rest of the line, the fastest production is a box every 2.4 seg, lenght of weight converyor is 1 meter, speed of conveyor is such that the box is on top of the weight conveyor for 1.68 seg, my question is:

- What is the best approach to get every box weight, as you know the weight begins from zero goes to high value and then down to zero as a box passes on top of the weight conveyor?

Can I try to use a photo cell to catch the weight as the box travels on top of the weight conveyor or you have a differrent approach



Regards,



William

Click to expand...

If you can, have a photocell detect the leading edge of the box approaching the scale. Then a timer can start, which has be field adjustable, to ensure the box is completely on the conveyor to be sampled at a stable weight.

Also, the feed in conveyors need to be set up as to provide an adaquate gap between boxes, to ensure that there is a time period when no boxes are on the scale

Ian

Widelto

We recently commisioned a similar system where we had multiple weighing units on a single conveyer, we used 2 photo-cells to not only trigger the weighing process but also check the position of the various boxes on the conveyer, this worked very well..

If i look at similar complete supplier packages they all have the same type of setup with a photo cell to trigger when it has to sample the weight.

Reagrds

You will also be better suited to set your sampling rate by taking 3 to 4 weight readings then averaging the results the two methods is to use 1 photoeye to start the weighing application then either a timer to control the number of samples or a second photoeye to end the sampling and initiating average mass. When you set your photoeye position you will need to have the first photoeye posisioned to a spot where the load cells have stabilized usually after the first 1/2 of the length of the conveyer though I have seen a lot of inmotion weighing systems where it was needed at the 2/3 mark and your average weighing completed before you start getting tansitiion false readings from leaving the conveyer. Most manufactures I've seen use a programmable type of scale head the 920I indicator from Rice Lake is about the most flexible almost as good as having a PLC and scale in one package. IN these cases the scale head is programmed with the sample rates and triggers then performs the calculation in the Macro set up then transmits the weight in standard Ascii.

The use of the scale head makes it much easier to deal with the various requirements of weights and measures act for example being only allowed to zero 2% full scale capacity, without calibrating however the act prevents calibration without having somoene qualified to recertify after it is done ( PS you only need to worry about the act if its a Final weight for sale scale.

Hi all:

Tks for the replies, basically i´m going to use the weigh conveyor to verify that boxes are complete, boxes contain 12, 24 or 48 bottles depending on size. So i can not average weigh, but thanks anyway for your time and effort in answering me.
My biggest concern is to have a steady measurement not depending from conveyor motion,now i´m leveling conveyors and as soon as i finish i´ll let you know.

regards,

Just to clarify the average weigh its referring to average weight on the same box. If done correctly it can be just as accurate as weighing the box statically

Mordred, sorry I misunderstood you.

In my proyect I can change the number of readings in order to get an average, so you are right.

regards,