AIE - 3649
Weighbatch Extruder Controller
Madhu Marketing & Services - India, Weighbatch
Weighbatch make two types of gravimetric extruder controllers.
1) Gravex Controller:
The Gravex range are typical "loss-in-weight" controllers which sit on the inlet to the extruder and measure the mass rate of material going into the extruder throat.
The Gravex throughput controller sits between the material storage hopper and the extruder throat. It monitors the loss in weight of the material in its weigh chamber and from this calculates the mass throughput rate of the extruder. In Auto Control mode Gravex can control the extruder or the process line speed to achieve a set kgs/hr or a set grams/meter
When the weight of material in the weigh chamber falls below a preset value a slide valve opens and refills the chamber from the material storage hopper.
To prevent damage to the load cells the Gravex has a protective outer hopper made from powder coated zinc plated steel. The inner weigh chamber and the inlet slide valve are made from 304 grade stainless steel. The control electronics are mounted in a cabinet attached to the outer hopper.
In order to operate the Gravex controller needs input from the process: The extruder RPM and the process line speed. In order to control it needs to be able to change the extruder speed. There are many ways this can be done depending on the control wiring for the main system.
Rather than run potentially hazardous signals from the main electrical cabinet to the Gravex controller, a set of interface modules are installed in the main electrical cabinet and a low voltage communications cable run to the Gravex controller.
All control signals are optically isolated. Speed input modules can use digital pulses or analog voltage input. Extruder and line control can be by motorized potentiometer, digital output, relay output or analog output.
Fundamental to the design of Gravex is the idea that when not in Auto Control mode, the extruder or line speed control should revert to the normal operator control. To best achieve this Gravex uses control signals to increase or decrease the speed rather than setting an absolute speed using an analog reference output. The preferred control outputs are motorized potentiometer (for older lines) or direct ramp up/down digital inputs to the line PLC (for newer lines). Analog control output is the least desirable option because it almost impossible to avoid a step changes of speed when changing from Auto to Manual control mode.
2) Monex Controller:
Then Weighbatch Monex product is a range of extruder throughput monitors used on the output of palletizing extruders. Typically compounding lines or recycling lines.
The Monex is similar to the Gravex controller but operates on a "gain-in-weight" basis. While the Monex can control the extruder in the same way as the Gravex it is more normally used to simply monitor the extruder output.
The monitored output can be used as feedback to control additive dosing.
The Monex controller operates by accumulating material in the weigh chamber and monitoring the rate of increase in the weight. Periodically the weigh chamber is emptied and material released to storage. By specifying the release weight the Monex can also act as a simple batching system.
3) The Weighbatch ExtruBlend is a combined blender and throughput controller in one compact device. It combines the features of a MiniBlend blender and a Gravex throughput controller.
The ExtruBlend is ideal for lines where the alternative blender mounting options of mezzanine or floor mount are not practical.
Being based on the MiniBlend blender, all material is fully mixed prior to being released into the throughput control weigh hopper. This eliminates the weighing errors which occur in systems with mixers in the weigh hopper.
The ExtruBlend range is available in capacities of 150, 300 and 600 kg/hr, with up to 8 components.
(For images, please see next pages)
For More Details Contact:
Madhu Marketing & Services, Vadodara
Mr. Sabu Philip