Welding Systems

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Welding Systems Special Machines

Precise Welding Produces Accurate Fuel Gage Reading

Headliner Adhesive The accuracy of the fuel gage in many products depends heavily on a projection welding operation used to assemble fuel tank sender units. This is being done on two similar eight-station dial index machines.

The welding operation is simple enough. It projection welds at four points to join a bracket to a plate. However, there's more here than meets the eye.

Three holes in each of these two parts must be properly aligned to ensure correct positioning of three steel tubes that are subsequently welded into each sender unit. A machine vision system and precise fixturing were designed to achieve the correct alignment. The fixture design facilitates easy modification to accommodate any future changes in part configuration.

Each machine has a 6-ft. diameter index table with eight stations. There are two fixtures at each station to handle two different size sender units. The largest round plate is 5.4 in. (138 mm) in diameter, whereas the smaller one is 4.6 in. (113 mm). Both sizes of units are run at the same time on these machines. (There are numerous combinations of each family (113 mm & 138 mm) of parts that run in the fixtures.)

Here's a "bird's eye" description of the indexing table:

Station 1: Load (manual). First operator loads the plate and bracket for the large assembly

Station 2: Idle

Station 3: Load (manual). Second operator loads the plate and bracket for the small assembly

Station 4: Projection weld four spots on the large assembly

Station 5: Idle

Station 6: Projection weld four spots on the small assembly

Station 7: Idle

Station 8: Unload automatically

As noted, the location of the bracket on the plate is critical for proper alignment of three holes in each of the two parts. One of the tubes ultimately mounted in one pair of holes is designed to carry a float for determining the fuel level in the tank. If the two hole centers are off just several thousandths of an inch, the fuel gage reading could be significantly in error.

Locating pins and ceramic tabs in the 16 Peak fixtures ensures that the two parts are lined up properly prior to welding. This is confirmed with the use of two cameras mounted overhead at the second loading station. Should the parts be misaligned in either of the two fixtures, the vision system signals the machine to stop.

Projection welders were used on both machines. Welding can be done on both stainless steel and terne-plated steel. This is an advance over previous welding systems used for these operations. The earlier systems could only weld terne plate, and the accuracy of the welded assembly was a problem.

A small pick-and-place device is utilized for automatic unloading at station eight on both machines. The entire 8-station welding system is sequenced utilizing Controllers. The production rate per machine is 1500 assemblies per hour.

Examples of other precision welding equipment delivered by the company include linear vibration and ultrasonic welding systems.

Peak Industries has been a supplier of custom automation and assembly components and special machines and systems for the automotive and other manufacturing industries since 1966.