LOUISVILLE, Ky.-A new building machine designed to extrude hot cushion gum onto a buffed tire casing-filling any skive holes present-then apply and stitch down the precured tread is scheduled to make its North American debut at the ARA World Tire Conference and Exhibition in Louisville, April 21-23. The AZ CTC Swing Builder, produced by AZ Formen- und Maschinenbau GmbH. of Munich, Germany, eliminates the normally separate production step of filling in skive holes, known as ``buzzouts,'' while automating application of cushion gum and precured tread.
All operations are completed in less than five minutes.
According to Walter M. Seidel, the company's U.S. sales representative, one operator using the unit can process up to as many as 100 truck retreads in eight hours.
By extruding hot cushion stock directly onto the buffed casing, the unit provides substantial cost savings and other advantages over conventional boxed cushion gum, he said, including the elimination of solvent-based cement.
According to Mr. Seidel, the uncured strip rubber used in the unit's ``Mixmatic'' extruder costs about 70 cents a pound less than boxed cushion gum.
This, combined with other savings offered by the process, can translate into a payback period of less than 24 months for shops using the $110,000 machine to turn out 100 or more retreads daily.
Mr. Seidel said that extruding the cushion gum reduces waste by allowing the machine operator to adjust its width and thickness as necessary.
Direct extrusion of the cushion gum onto the buffed casing also allows for correction of minor imperfections in buff contour and the restoration of tire profile and
Extrusion also permits the combining of two otherwise incompatible feed stocks in order to produce a faster-curing cushion gum that is said to increase autoclave efficiency by as much as 20 percent, Mr. Seidel said.
Meanwhile, the AZ CTC's tread builder automatically measures the circumference of the tire for increased accuracy and permits the precured tread to be stretched either manually or under computer control to match tread patterns.
The builder has the ability to stitch down wing treads and can build in pre-vulcanized breaker belts.
It also features an adjustable transport height that eliminates the need for lifting devices.