If you are recycling plastic goods or handling virgin materials, making a product free from metal contaminants is much more important today than in the past. Trends to thinner walls, tinier hot-runner nozzles, and more costly and sophisticated machinery and tooling imply that even the smallest piece of tramp metal can cause expensive problems.
Processors often tend not to recognize the importance of Portable X-Ray Machine. Even virgin material can acquire metal contaminants at various stages of manufacturing and transportation, right until as soon as it enters the throat of the molding or extrusion machine. Contamination can range from tiny particles worn off by equipment abrasion to entire nuts or bolts loosened by vibrations in processing machines. There’s even the human factor: Inevitably, items such as coins, pens, and paper will occasionally fall under the merchandise stream.
For this reason, metal-detection technology is utilized through the entire plastics industry to safeguard processing equipment and to ensure product purity. Metal detectors keep your product under strict surveillance at all times and prevent unnecessary machine downtime and costly maintenance.
Once we talk about “metal detectors,” some processors may think first of magnets. These are generally used effectively prior to the metal detector for capturing ferrous metals. Less familiar to numerous processors are electronic detectors for all sorts of metals. They are active devices that actuate a valve or some other device to reject the contaminated material.
What’s more, electronic metal detectors can be monitored remotely from the personal computer. This capability provides a record of how and where frequently contamination occurs in your plant. Such valuable data may help you compare the purity of different vendors’ resins or diagnose excessive machine wear.
How metal detection works – The two main basic varieties of metal detectors:
Single-coil systems – Each time a metallic particle falls from the high-frequency electromagnetic field, an eddy current is induced within the particle, thereby removing energy from your coil system. As a result the maximum amplitude in the coil’s vibration decreases. More energy is then supplied to improve the amplitude back to maximum level. This disturbance of the coil’s vibration is detected from the electronic circuit as signaling the presence of a metallic particle.
Balanced-coil system – Single-coil systems provide inexpensive solutions for easy, “down-and-dirty” applications. These systems are simpler to setup, however they cannot compensate for products that could be slightly conductive, due to the existence of moisture, acidity, or additives like carbon black.
Balanced-coil systems offer product-effect compensation that suppresses false signals brought on by the merchandise. The advantage is to prevent rejecting perfectly good material. Analog versions require the operator to manually reset the compensation as material moisture content or other variable changes. Newer digital versions can be preset to self-adjust for many different products or a range of moisture content or some other variables in a product.
Making feeling of sensitivity – Electronic metal detectors are high-tech, sensitive devices that must definitely be handled with a certain amount of care. Excessive vibration from motors, chains, as well as other nearby equipment may cause a detector to emit a false signal and reject good material.
You shouldn’t need to sacrifice good material for accurate detection and rejection. In addition to product-effect compensation, state-of-the-art Deep Searching Ground Metal Detector offer adjustable sensitivity and positive speed control to reduce the volume of material lost.
Maximum sensitivity of the detector determines the minimum dimensions of metal particle that it may sense. Smaller particles can slip through, which means this factor is vital to selecting the proper detector for an application. Maximum sensitivity is measured by loading a sample of resin with steel spheres and utilizing the measurement in the midst of the coil, in which the sensitivity is lowest. Steel spheres are used because there is a uniform, defined size, meaning the measurements are repeatable. Also spherical particles would be the hardest to detect due to their relatively low surface.
All metal separators are certainly not equally sensitive. True sensitivity depends on the dimensions of the search coil. The lesser the search coil, the lesser the metallic particle which can be detected with maximum sensitivity. A good rule of thumb to bear in mind is the fact normal sensitivity is all about 1% in the diameter in the coil. Depending upon the sensing aperture, innovative pbgavn are designed for detecting contaminants no more than .4 mm.
Sensitivity is additionally related to the composition and shape of the material. Although electronic all-metal separators will detect ferrous particles, stainless-steel, lead, aluminum, bronze, tin, and much more, they are most understanding of ferrous particles. That is because metallic particles are detected through eddy currents, and the larger the eddy current the larger the sensitivity. Eddy currents on the surface of ferrous particles are higher than those generated on the surfaces of aluminum, bronze, or copper particles, which means that the sensitivity of ferrous particles is greater than the second. What’s more, eddy currents from metallic particles are merely effective on the surface, so the larger the surface, the higher the sensitivity. Because of this flat metallic particles, or particles with irregular shapes, are much better to detect than spheres.
Another feature provided by Portable Walk Through Metal Detector is called positive speed control. Because of differences in bulk density, metal particles may not travel via a pneumatic conveying line at the same speed as the resin itself. Positive speed control senses the particular conveying speed in the metal contaminants and automatically adjusts the open period of the rejection valve to be able to eliminate the metal having a minimum of resin loss.
Junhong Electronic&Technology (Dongguan) Co., Ltd is a professional manufacturer since 2005, specialized in R&D of security detection technology. We have various of products range: Walk through metal detectors, hand held metal detectors, X-ray luggage scanners, X-Ray Body Scanner, Underground Metal Detector, Industrial Metal Detector, Checkweigher, Infrared Body Temperature Detection System; Explosives Detector, Under Vehicle Surveillance Systems; etc.
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