By: Paul Colby

Background

Bimetallic cylinders are pressure vessels functioning as a component in a system to melt plastics with abrasive additives such as glass and minerals. These vessels have been manufactured the same way since the 1950‘s. Xaloy has developed and patented a new technology that will improve the useful life of bimetallic cylinders by 300%. This technology will offer the marketplace a product with superior wear resistance properties and, at the same time, reduce manufacturing costs and lead time. This technology applies to new cylinders as well as repairs. There are many companies that can repair external wear parts, but internal repair has, until now, been extremely limited. This will also apply to other industries such as military, transportation, oil & gas, heavy equipment, and aerospace.

Technology

There are several competitive advantages that are gained by Xaloy patent #6486432 “Method & Laser cladding of Plasticating barrels”:

  1. Dramatically increased wear life.
  2. Reduction of manufacturing costs and time.
  3. Repair cost:

Dramatically increased wear life

a. A wider range of cladding materials is available due to not being limited to the melting temperature of the backing material. During conventional centrifugal casting the energy input is external and cladding material must be selected based on the limits of its melting point temperature. Laser cladding delivers the energy internally, thereby making cladding material seemingly limitless.

b. Laser cladding can use a much stronger matrix. The matrix is the mortar holding the bricks on a wall. In the case holding particals together for wear resistance.

c. Laser cladding increases the density of the wear surface.

d. The cladding is more uniform with regard to matrix  and particle distribution

  1. The bond between the wear surface and the base material is far superior.

Reduction of manufacturing costs and time

a. Capping of barrels. With current technology companies have to  weld steel covers on each end of the tube to prevent the unmolten powder from falling into the furnace during the casting. This is eliminated.

b. Preheating and cooling. During conventional casting barrels are exposed to extreme temperatures (2000°F) and stress. To minimize this barrels are slow cooled. Depending on the size of the barrel this could take several days. This is eliminated.

c. Straightening. Because of the temperatures so close to the melting point during casting, barrels can bend significantly (up to .500”). The new patented process makes this straightening process unnecessary.

d. Honing. As stated above, conventional barrels can come out of the furnace bent. To compensate for this manufacturers add extra hard material to give them the flexibility to hone the inside diameter straight. This is greatly reduced with the new process. Xaloy will have to remove approximately .010” compared with up to .400” with conventional casting, saving a significant number of hours.

  1. Lining material cost reduction. With conventional casting, 50%of the liner material is honed out to achieve straightness and surface finish is required if it is a finished part. With the new process less than 10 % of the liner material is removed.

Repair cost Reduction.

With conventional repair techniques, the worn area is completely bored out. A smaller, new centrifugally-cast barrel is manufactured and shrunk-fit into the original for repair.

This is a timely and expensive repair, making it cost prohibitive for many potential customers. With our new technology, the worn area is clad. The area is then honed uniform. That is all that needs to be done. The time required changes from weeks to hours. The costs are reduced 80%. This changes the paradigm of ‘new versus repair’.

Improved Selection for Base Materials.

Currently base materials selection is limited to materials that can maintain strength through the casting process. The barrel is brought to a temperature of 2000°F and then slow cooled to reduce stress. This anneals the material, which makes it soft. For this reason hardened steels do not work, so barrels have to be very thick or have a high-pressure sleeve. This is the only way a barrel can withstand the operating conditions of an injection molding process. With this new technology the backing material is not exposed to this, therefore many heat-treated materials are available. This permits machinery makers to make their barrels thinner and less expensive.This also makes them more responsive to temperature input and changes. This will give the end-user better control of his process.