Rim Joining Methods

There are three methods used to join the ends of rims after rolling. The three methods are pinning, sleeving, and welding

PINNING:

This method consists of joining the ends of the rim with a steel pin inserted into a cavity on both sides of the rim extrusion. These steel pins are about four millimeters in diameter, two inches in length, with pointed ends. .The extrusion shape for the rim is made with the pin cavities extruded in place, usually just under the tire bead on each side of the rim. The diameter of these holes is closely controlled to properly press fit over the pin. The rim is assembled by injecting a measured amount of epoxy glue in each rim pin hole, then inserting the pin ends in the holes. The rim is then placed in a machine that constricts the diameter of the rim by means of a band around the outside of the rim and a hydraulic cylinder that pulls the ends of the band together. This force causes the rim ends to be forced over the pins, closing the joint.

SLEEVING:

This method of rim end joining is done in the same way as the pinning process, but uses an extruded aluminum insert matching the inner profile shape of the rim rather than pins. The sleeving method is usually used on rims that are lighter and considered to be of higher quality than pinned rims. The sleeve is typically about three inches in length. After cutting the sleeve blank off the extrusion, it is formed in a die to give it a radius to match the rim. The ends are also tapered to facilitate insertion in the rim voids. The joint is closed with the same constricting machine and glue process as described in the pinning method above.

WELDING:

The welding method is used on all levels of rims from OEM high volume rims to high quality after market rims. The method typically used is called a “flash-butt process”. The process is done in a large welder that grips the ends of the rim in clamps to hold and guide the rim during welding. The rim blank is rolled and cut with extra length circumferentially. The rim is clamped in the welder dies with the ends of the rim protruding about ¼” from the die on each side. The welder then starts the “flash” part of the weld cycle. It passes very high amperage current through the clamp dies while slowly moving one die to bring the ends of the rim together. The current creates an arc between the ends of the rim, burning off the extra metal allowed in the cutting of the rim blank while heating the ends of the rim. After a precisely controlled flash time, the current is turned off and the “butt” part of the weld cycle is initiated. This consists of rapidly forcing the heated ends of the rim together with great force to complete the joint. There is weld flash left around the weld that is removed to smooth the joint and blend it in to the extrusion shape.