This is a common concern among processors. We commissioned an ASTM G-77 test procedure to address this issue. In brief, tungsten carbide spinning against a bimetallic (FeB) liner shows no difference in liner wear than standard alloy materials such as Stellite and Colmonoy. Follow this link for more details (Adhesive Wear Test ASTM G77). A hard coated feedscrew contacting a less hard barrel liner is not a source of wear. In extrusion, system alignment, auxiliary die and barrel support, temperature profile, and proper screw design are much more critical to reducing wear.
It can happen. The carbide coating has a mechanical bond to the screw surface. If the screw surface moves or flexes, the bond can be weakened which may lead to a release of coating. What can cause this movement? Excess heat such as a torch or cleaning oven can expand the screw surface. A cold start can result from operating equipment before sufficient heat input (soak) to soften any remaining polymer in the system. Non-compressible tramp material will gouge the screw surface and remove coating at the contact point.
Extreme Coatings has the capability to “strip” the coating from a worn feedscrew. This feature is especially beneficial for large, complex, expensive feedscrews. A screw will eventually wear through the coating at the outside diameter (OD). When that happens simply remove the screw and coordinate with your screw supplier to have Extreme Coatings strip and re-apply a fresh layer of tungsten carbide.
We believe that any injection molding feedscrew that is replaced or rebuilt at 24 months or less will benefit significantly from encapsulation with carbide. Extrusion feedscrew that are rebuilt or replaced within five years will likewise see great benefit from carbide. Obvious gains are longer screw life, however intangible benefits such as consistent quality, through-put, lower energy and maintenance costs, as well as higher capacity utilization offer cost savings and competitive advantage.
Absolutely. Our toll free number is 888-367-2569. Ask for John, Tom or Greg.
This depends on many factors. SPI guidelines suggest .0015” (.04 mm) per inch of screw diameter starting clearance between screw and barrel. For a 50 mm screw this is .003” (.08 mm) clearance per side or .006” (.13 mm) overall. Depending on resin viscosity, output can be reduced 25% with a doubling of this beginning clearance (.012”, .25 mm). The effect screw wear has on production and part quality should be an important consideration. An extrusion system can be especially sensitive to adhesive wear of the feedscrew outside diameter.
Our standard guarantee is double life. In an abrasive process like glass filled nylon, the ASTM G-65 test (Abrasive Wear Test ASTM G65) shows that carbide encapsulation will be three times better than the next best material. From experience we have learned that wear life can improve by three to five times compared to the feedscrew being replaced.
Our quoted lead time is ten business days. We average six to seven days. Depending on feedscrew diameter, we can meet a “rush” delivery if given prior notice.
We provide the Extreme Coatings encapsulation service through your feedscrew manufacturer. Your screw supplier is our direct customer. We do not set the price that you will pay, but experience has shown that a carbide encapsulated feedscrew will cost about twice as much as a screw protected with hardfacing and chrome plate. Compared with tool steels, carbide encapsulation will cost about fifty to sixty percent more. Remember, in all cases, we guarantee at least double the life.
Extreme Coatings does not make new screws or rebuild worn feedscrews. We encapsulate screws to make them last longer. We work with your present feedscrew supplier to provide this service.
Extreme Coatings has a solid reputation as the premier supplier of carbide encapsulation of feedscrews to the plastics and rubber processing industries. Extreme Coatings is a service mark of Surface Engineering & Alloy Company, a wear resistance company with 30 years experience solving wear problems. Since 1997, we have carbide encapsulated over 5500 feedscrews worldwide with great success. We work with all feedscrew and equipment manufacturers. It is likely we have supplied our service through your present feedscrew source. We encourage you to ask about our reputation for quality and aftersales service with your supplier.
Not directly. We supply this coating service through your present feedscrew supplier or original equipment manufacturer. A worn feedscrew should be sent to your screw supplier for any necessary repairs and then prepared for carbide encapsulation. Your supplier will send the coating-ready feedscrew to Extreme Coatings to complete the process.
This is also a common question. After we improve feedscrew life, processors find a downstream component, profile die, calibrator, non-return valve, or other part that wears “quickly”. We have tried to solve a lot of these issues with thermal spray coatings and have learned that some respond well, others not. For inside diameter surfaces we offer our NiBoride nickel boride material. Click here for more details. . For non-return valves – tip assemblies, we have developed the Cushion Master. This is a solid tungsten carbide check ring and rear seat that provides from six to eight times the life of standard tip assemblies. Click here for more details.
We get asked this question a lot. The answer is no. Our process is line-of-sight and we cannot fit the spray apparatus inside a barrel. Spin cast barrel liners of tungsten carbide are available from all the major barrel suppliers.