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How to achieve more precise mixing by


source:[Gravimetric blender]   release time:2021-01-22 13:56:52




The weighing type mixing machine is suitable for the occasions where a variety of raw materials need to be accurately mixed in proportion by weight in plastic injection, extrusion or hollow molding. This series of products adopts German Siemens PLC control system, adopts advanced batching algorithm, can be automatically calibrated according to the actual feeding volume to ensure accuracy, and the operation screen is simple, easy to learn and convenient. This series of products uses high-precision weight sensors to control the batch mixing ratio difference within ±0.1% to ±0.3%. Customers choose the appropriate model according to the hourly usage and the number of types to be processed.
If you think all blenders are similar, then it's time to change your opinion. For any injection molding, extrusion or compounding process, the accuracy and consistency of the blend is very critical. It has an important impact on the stability of the process and the repeatability of part quality. The benefits are higher finished product quality and better cost advantages. Sometimes, just in case, plastic products processors will add excessive colorants or other expensive additives, which will bring changes in mixing, and such changes in the injection or extrusion process can lead to excessive waste and parts. Inconsistent quality/composition or reduced processing speed, all of which is a waste of money.
However, there are now technologies that can eliminate the uncertainty in the mixing process and accurately measure the material to a single particle, such as the weighing batch mixer of a well-known auxiliary equipment manufacturer. This equipment series combines precise electromechanical design with an adaptive Smart Blend (SB) control system to ensure that the mixing accuracy of each component reaches 0.5%, even if the bulk density of the material changes.

How to achieve more accurate mixing by gravimetric blender;

The working principle of the gravimetric blender

For gravimetric blenders that control the amount of materials by weighing, the accuracy of the load cell is very important, but it is just a part of the mixing system. The real uniqueness of the mixer lies in the design aspect—— This series of equipment weighs materials in a sequential manner. For example, to mix 3 materials, including the first main resin, the second resin and an additive, add one material at a time, with the smallest component first and the largest component behind. In this case, the additive as the smallest component is first sent to the weighing bin, then the second resin, and finally the main resin. After completion, the pneumatic cylinder puts the batch of materials into the mixing chamber.
How to achieve more accurate mixing by gravimetric blender 2
The blender measures and mixes free-flowing pellets, including recycled materials and additives. According to the model and configuration, the equipment can mix 4~12 kinds of materials
The mixer uses a precise distribution system and extremely sensitive load sensors to measure materials. Its proprietary control system makes the measurement accuracy further optimized. It can adaptively determine the subsequent materials based on the true weight of the first component. Feed amount. Assuming that the first additive component added in the above example deviates from the set value by a certain percentage, the control system will record the difference, and then automatically adjust the subsequent resin dosage set value to maintain the second resin and additive. When adding the last main resin, the process will be repeated.
In addition to correctly processing the first batch of materials, the system can also automatically adapt to any changes in the form of materials, such as pellets of different sizes or recycled materials (which will affect the flow of materials), to ensure that the mixture in a single or multiple processes accuracy. In this way, more stable and higher-quality products can be produced without excessive use of expensive additives.
How to achieve more accurate mixing by gravimetric blender
Most mixers use horizontal sliding gate valves, which are equipped with U-shaped pins for dosing. This is an easy-to-wear part, which will reduce the accuracy of feeding over time. And the equipment adopts a unique vertical metering valve, no need to use U-shaped pin, thus reducing maintenance and ensuring the consistency of accuracy, even if used for several years
Continuous process control
There are many material-related factors in the processing process. Over time, these factors may affect the consistency of the injection or extrusion process. The control and monitoring system of the TrueBlend blender can help detect and diagnose these Problems, the most important of which is to provide immediate feedback to the operator when a problem occurs.
In actual production, the control system continuously monitors the feeding and mixing process, and can issue alarms for the following situations:
1. Component valve failure: monitor the weight of the batch at the end of each batch to ensure stability, and automatically detect valve leakage;
2. Material flow error: monitor the flow of component materials to ensure their consistency, if there is an error, an alarm will be issued;
3. Discharge outlet failure of the hopper: monitor the weight of the hopper to ensure that it is completely poured out at the end of each batch.
Not only that, the control system can also inform the operator some other information, such as when the material is insufficient, when the bulk density of the material changes, and even when the pressure of the compressed air changes. When a discrepancy with the standard process is detected, the controller will provide an explanation and suggestions on the inspection content. It can also be networked for remote monitoring and diagnosis.
It is worth mentioning that another important factor to ensure process integrity is the control of humidity. Applications with high temperature and humidity sensitivity require special attention. When the material is in the standard temperature range (below 150°F, 150°F=65.56°C), the TrueBlend mixer weighs a batch of materials, mixes them, and prepares for the next feeding of the hopper. However, if the material is heated to a higher temperature (375℉, 375℉=190.56℃) to maintain the heat of the material and prevent moisture from entering, the mixer will not prepare a new batch of material unless the molding equipment has feed demand.
The mixer provides a dry air blanket option, which can introduce hot dry air into the silo and mixing chamber to prevent the material from re-wetting during processing.
How to achieve more accurate mixing by gravimetric blender
The easy-to-use touch screen can realize the quick setting of the mixer, and automatically weigh the materials in the formula according to the order of the system to maintain the precise mixing relationship between the different components.
How to achieve more accurate mixing by gravimetric blender
A dry air blanket is optional to introduce dry hot air to fill the material mixing chamber. The system prevents the material in the mixer from rewetting
Data collection and reporting
A significant advantage of the gravimetric blender is the ability to collect detailed information about the actual situation of the injection and extrusion process. Because each material component is measured in the process, the processor can obtain exact data on "which equipment and which task is consuming which material". But how to collect this data and make good use of it?
This problem is solved by many standard reports generated at the machine level or collected on a factory scale. The standard report covers:
1. Current equipment status;
2. Active and recorded alarms;
3. Shifts and total inventory;
4. The amount of resin;
5. Orders and work reports.
The report can be generated according to the schedule or according to the specified time span, and the results can be displayed on the hybrid controller, and can also be shared through a U disk or Ethernet connection.
What is really interesting about this data collection function is that when you compile it into a separate database, it can perform a deeper analysis of plastic processing operations. In order to make this operation easier, the control output of all mixers can be compatible with standard Microsoft SQL databases, which facilitates enterprise-level analysis, and brings better consistency and higher performance to workshop operations effectiveness. For example, formulas can be recorded and stored centrally, and yield reports can be automatically generated; the use of resins can also be analyzed through formulas, shifts or totals to help manage inventory; for the purpose of ensuring quality, statistical analysis can be performed. Having so much data in one place opens the door to achieving higher efficiency and better process control, which was not possible with the previous generation of plastic processing technology.
[Gravimetric blender]