Monday, July 27, 2015

Lubring (Turcite-B®) – Special Notes on Bonding and Finishing

As a globally reputed manufacturer of Lubring Slideways (Turcite-B®), we are frequently asked to provide technical assistance with regards to the bonding and finishing of the material.
Lubring is a slideway bearing material that is used primarily in machine tool building and reconditioning. As such, the machine builder is usually equipped with enough knowhow on the bonding and subsequent planing of the material, such that it forms the most effective bearing surface. However, we often supply to dealers or first time builders, who need more assistance on the bonding process.

The metal surface to be mounted with Lubring Slideway can be prepared by the normal machining methods such as, grinding, milling, shaping, and planning. The surface roughness of all forms of preparation should be preferably between Ra = 1.6 µm and Ra = 3µm and not more than Ra = 6µm.
Once roughened the surfaces can be cleaned with Trichloroethylene, Perchloroethylene or Acetone. Slideway bearing material should be cleaned similarly.
For bonding of Lubring Slideway the following resin adhesive can be used: Ciba Geigy’s Araldite – Hardener – HV 953U; Araldite AW106. The Araldite should be applied both to metal and slideway and be spread as uniformly as possible by means of a serrated spatula. To obtain the best dispersion of the adhesive, when spreading on the slideway brush in the longitudinal direction; when spreading on the metal, brush in the transverse direction. The total quantity of bonding should be approximately 200gm per sq. mt.
After mounting the slideway a clamping pressure of between 0.1 – 0.3 kp/ is recommended. It is important to keep the pressure constant during the hardening process. Due to the differences in the thermal expansion coefficient of the materials, maximum curing temperature should not exceed 40°C. The hardening time for various temperatures is: 20°C min 15 hours; 25°C min 12 hours; 40°C min 5 hours.
After curing of the adhesive, the Lubring Slideway can be machined by conventional means. The choice depends on the machinery available viz.: grinding; grindstone.
Grinding: For grinding of Lubring Slideway use the same speed as grinding cast iron, taking care that sufficient cooling is used with an ‘open ’stone. The grindstone should be preferably silicon carbide based with rubber or polyurethane binding; grain size 80-30. Alternatively aluminum oxide with rubber bonding may also be used for soft, fine grinding action, pre-polishing and pre-mating treatment.
Oil Grooves: Lubring Slideway can be machined with oil grooves using the same methods and cutting data as used for cast iron. The form and depth of the oil grooves are optional. However, the oil grooves should never pierce through the Lubring Slideway. Oil grooves should be away from the edges by 6mm.
Metal Mating Surface: The metallic mating surface running against the Lubring Slideway should be finished to 16 Ra for optimum performance. The surface finish must never be below 14 Ra or above 20 Ra as applicable to cast iron or steel. This surface finish should be obtained by grinding in the direction of travel. Do not lap or polish to obtain this surface finish.

The above parameters provide an effective guideline not just for Lubring, but for bonding all PTFE-related items to metal.

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