View Full Version : Weight default

October 2nd, 2010, 05:05 PM
Hello to all
We have a machine that deal with milk conditionning on sachets of 250g, but the proportioning is not constant; sometime it's more than 250g or sometimes it's more than this.I dont know if it's on the programm or? The machine is equiped with a Siemens plc CPU 222
Can some one help me.Hope to read you soon
Best regards

October 2nd, 2010, 05:52 PM
We did a weigh in system several years ago, and it was for much larger weights,. However, we had a similar problem. What we found was that the load cell mounts weren't solid and that threw the whole system off. We didn't find that until we checked the mountings and found that the concrete they were mounted on was crumbling. So, my question is: Are the weight cell mountings solid ? PS, we had to pull off the "clean" tile to discover this.

October 2nd, 2010, 09:01 PM
Is it a new machine that you're commissioning? Or is it an existing machine that has been working for some time?

If it's a new machine, it could still be a config or install problem.

If it's a machine that has been running, something has changed... not necessarily intentionally, but something has changed. You just have to figure out what it is.

October 3rd, 2010, 12:16 PM
Yes you're right ozee,it's a machine we've bought from Morocco recently.You told about configuration;precisely on what parts do you think it is; for example hardware, or instructions,,,?

October 3rd, 2010, 12:19 PM
It's a certain quantity of milk that is injected in a sachet and this is done by a valve

Paul B
October 3rd, 2010, 09:53 PM
I think we really need more info. I have done a lot of work with weighing fiber in pans where there is vibration issues and update times. It's hard to tell you what to look for without more information. Do you have a stable load cell signal? 250g is not much weight, obviously it is easier to weigh 2kg on average over long time. Does your system sample for a period of time? What is the speed of weighing - do you need to weigh this 250g every five seconds or every 60 seconds?

Clay B.
October 4th, 2010, 03:57 PM
First question. Is the actual weight off. When you take this to another scale is the weight different from what you are weighing on the filler.

Second question. What are you using to stop the fill cycle. Is it a valve?

Third question. Did you calibrate this machine before you started running.

More detail about the system is needed.

The most important question is what the error is. Is it weighing wrong or is your repeatablity off.

October 5th, 2010, 04:40 AM
did you take off the cap on top of the filling tank?
is the valve timer operated?
are the restrictions open?
is the valve greased and running smooth.
is enough air pressure.

October 5th, 2010, 06:32 AM
Are you asking about a carton filler?.
Ones I have seen use a time valved to fill the carton and a scale to checkweigh after the filling position.
Carton fillers need a steady level in the filler bowl that feed the filling position.

October 5th, 2010, 07:19 AM
Do you have a copy of the program running in teh machine, could you possibly post it to the forum ?

There could be any number of reasons for this happening, but start with the basics, like load cell as previously mentioned


October 8th, 2010, 08:12 PM
i think it's more on the load cells because a timed valve for this kind of machine is not applicable, the dose is based on the weight and it's very difficult to maintain the quantity if you're only using timers for valves because the flow rate is not stable. it's just like using mass flow meter wherein the sensor disregards the flow rate and instead calculate the mass of the media. be sure to calibrate it first.

October 10th, 2010, 06:33 PM
Hell to all.Thank you for your diffrent reponses.
I think Mr jgonssison is more near to the response.Unfortunately I haven't got a copy of the programm, but I'll try to get it as soon as possible.
As I said it previously; there's no cell for the dosage: the valve open for a certain time and close after
Hope to read you soon