If you are recycling plastic goods or processing virgin materials, making a product free from metal contaminants is a lot more important today than in the past. Trends to thinner walls, tinier hot-runner nozzles, and more expensive and complicated machinery and tooling imply that even the smallest piece of tramp metal may cause expensive problems.
Processors often usually do not recognize the importance of High Depth Ground Gold Metal Detector. Even virgin material can acquire metal contaminants at various stages of manufacturing and transportation, right up to the moment it enters the throat of your own molding or extrusion machine. Contamination may 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 including coins, pens, and paper will occasionally fall into the merchandise stream.
For that reason, metal-detection technology is used through the plastics industry to guard processing equipment and to ensure product purity. Metal detectors keep the product under strict surveillance all the time and stop unnecessary machine downtime and costly maintenance.
Whenever we speak of “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. These are generally active devices that actuate a valve or any other device to reject the contaminated material.
What’s more, electronic metal detectors can be monitored remotely coming from a computer. This capability offers a record of where and how frequently contamination takes place in your plant. Such valuable data can help you compare the purity of various vendors’ resins or diagnose excessive machine wear.
How metal detection works – The two main basic varieties of metal detectors:
Single-coil systems – Whenever a metallic particle falls with the high-frequency electromagnetic field, an eddy current is induced in the particle, thereby removing energy from the coil system. Consequently the maximum amplitude of the coil’s vibration decreases. More energy is then supplied to improve the amplitude to maximum level. This disturbance from the coil’s vibration is detected by the electronic circuit as signaling the existence of a metallic particle.
Balanced-coil system – Single-coil systems provide cost-effective solutions for simple, “down-and-dirty” applications. These systems are easier to setup, nevertheless they cannot compensate for products which may be slightly conductive, owing to the existence of moisture, acidity, or additives like carbon black.
Balanced-coil systems offer product-effect compensation that suppresses false signals caused by the product. The main benefit is always to prevent rejecting perfectly good material. Analog versions require the operator to manually reset the compensation as material moisture content or some other variable changes. Newer digital versions can be preset to self-adjust for many different products or an array of moisture content or some other variables inside a product.
Making sense of sensitivity – Electronic metal detectors are high-tech, sensitive devices that really must be handled with a certain amount of care. Excessive vibration from motors, chains, as well as other nearby equipment could 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 Welding Apparel Needle Detector offer adjustable sensitivity and positive speed control to lower the volume of material lost.
Maximum sensitivity of a detector determines the minimum size of metal particle that it can sense. Smaller particles can slip through, so this factor is vital to choosing the proper detector for the application. Maximum sensitivity is measured by loading a sample of resin with steel spheres and utilizing the measurement in the middle of the coil, where the sensitivity is lowest. Steel spheres are used because there is a uniform, defined size, meaning the measurements are repeatable. Also spherical particles are the most difficult to detect due to their relatively low surface area.
All metal separators usually are not equally sensitive. True sensitivity depends on the dimensions of the search coil. The smaller the search coil, the smaller the metallic particle that can be detected with maximum sensitivity. A good rule of thumb to keep in mind is the fact normal sensitivity is about 1% from the diameter in the coil. Based on the sensing aperture, innovative pbgavn are designed for detecting contaminants no more than .4 mm.
Sensitivity is also associated with the composition and shape of the content. Although electronic all-metal separators will detect ferrous particles, stainless-steel, lead, aluminum, bronze, tin, and more, they are most responsive to ferrous particles. That is because metallic particles are detected by means of eddy currents, and the greater the eddy current the greater the sensitivity. Eddy currents on the surface of ferrous particles are more than those generated on the surfaces of aluminum, bronze, or copper particles, meaning that the sensitivity of ferrous particles is more than the latter. What’s more, eddy currents from metallic particles are merely effective on the surface, so the larger the surface, the greater the sensitivity. Because of this flat metallic particles, or particles with irregular shapes, are quicker to detect than spheres.
Another feature provided by Needle Detector Conveyor Belt is called positive speed control. Due to variations in bulk density, metal particles may well not travel via a pneumatic conveying line in the same speed because the resin itself. Positive speed control senses the particular conveying speed in the metal contaminants and automatically adjusts the open time of the rejection valve so as to get rid of the metal with 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.
Office: +86-769-22688609, 22688610, 22688612
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Email: [email protected]
Address: No.23, Xintian street, Baizhoubian, Dongcheng district, Dongguan city, China