The bagging Machine weigher control unit uses micro-computer technology to provide comprehensive and flexible control of a weighing machine. This controller can handle any load cell based weigher, including net Weighers, Gross Weighers, and Weigh Platforms. For high speed bagging, we must use this controller with a direct load cell bagging machine.
Net Weigher – In the net weigher system, the material is fed into a weighing pan before being discharged (into a bag or to downstream material handling equipment).
Gross Weigher – In the Gross Weigher system, material is fed directly into a bag (which forms part of the weighted assembly).
Basis details of functions in the Main menu of the Bagging Machine Controller
Before starting the bagging process controller checks the Plant Inputs parameter and Plant Output parameters.
If all parameters sequence found ok then go ahead for bagging otherwise check faulty parameters and then repeat the same process until the fault is rectified.
To get the fastest material (Urea) filling with consistency and good accuracy, a two-speed feed arrangement is used to deliver material from the top buffer hopper into the weigh pan. Initially, a fast main feed flow fills the weigh pan, then the flow is reduced to a dribble feed rate in order to achieve an accurate feed cut-off.
The weigh pan is supported by a Load cell assembly which accurately converts weight into an electrical signal, allowing the Bagging machine Controller to monitor the weight of material as it is fed into the weigh pan.
Upon reaching the required weight, feed is stopped and input is provided to the controller so that the downstream equipment can accept the weighment, the weigh pan doors are opened and the weighment is discharged.
The few most important steps are listed below –
This weight is user required weight and a combo of nominal weight plus overfill weight value.
The weighing cycle is started by pushing the “RUN” Button when all plant inputs and outputs parameters check result is ok. On discharge of the first weighment, the next and subsequent weighing and discharge cycles in the batch are started automatically, provided that no faults occur or no holds are applied in the cycle.
If mains Power is lost while batching is in progress and is subsequently restored, the operator must reselect the material originally being bagged and the number of bags to be made up before the system can be run again.
On initialization of the weighing cycle, the feed mechanism is commanded to feed material into the weigh pan at the main feed rate. At the same time main feed Blanking timer is started which prevents monitoring of the load cell signal during the timer period.
Also, this timer ensures that variations in the load cell weight signal that are due to both the initial impact of material in the weigh pan, and shock-loads introduced by opening of the feed gates are ignored.
At the main feed (fast Feed) cut-off point, the feed rate into the weighing pan is changed from main feed to dribble feed (Slow feed). At the same time, a Dribble feed Blanking Timer is started which prevents monitoring of the load cell signal during the timer period. This timer functions identically to the Main Feed Blanking Timer.
Also, the period of dribble feed must be long enough to ensure the settling of the weighing pan after the main feed cut-off, but must not be so long as to slow down the overall machine Cycle.
Due to the filtering of the load cell weight signal, there is a slight delay in the true weight value being seen. This happens due to in-flight material and can cause problems with stop feed command during the cycle.
Also, the above effects would produce an overweight if the feed cut-off point was made equal to the Target weight value. Therefore to resolve this problem we use In-flight compensation.
This is the most important factor for the accuracy of a bagging machine bagged Urea Bags. In This process to maintain maximum weigher throughput, the controller did not check all weighments. The controller checks occasional weighment according to a predefined sample rate. For example, if the sample rate is given 10/3 then the controller will do sampling 3 bags out of 10 Bags, and this process will continue.
In the bagging process, every sampled weighment is checked for Underweight and Overweight tolerance values.
If the weighment is outside the limits, automatic discharge is stopped and the operator must accept the out-of-tolerance option. And after checking the machine if the again limit found ok then the process will continue.
The bagging machine controller plays a crucial role in bagging plants, ensuring efficient and accurate packaging of products which high speed.
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