|Figure 3 |
When the unibody revolution hit the North American market, so did this repair concept. But dedicated fixture benches soon gave way to other straightening racks and benches that could be used for any vehicle and did not require the installation of specific fixtures for each vehicle. This method of straightening unibody vehicles became the new "fixture" in many repair facilities. In the last few years, the dedicated fixture bench has started to increase in popularity again.
Definition and use
On a dedicated fixture repair bench, the fixtures, or jigs, not only mount the vehicle to the repair bench, but also provide measuring of control points, and hold parts being welded (see Figure 1). This requires a different set of fixtures for each vehicle model that is put on the bench, which means either keeping a large inventory of fixtures or renting them as needed. Often these systems require the removal of suspension and drivetrain parts to mount the vehicle to the fixtures (see Figure 2).
The vehicle is typically raised on a two-post lift, the necessary parts are removed, and the vehicle is lowered onto the fixtures that have been mounted to the bench. Depending on the vehicle and the design of the fixtures, pinchweld clamps may also be recommended for additional anchoring and to help avoid bending the fixtures, or the points that they attach to, during straightening procedures.
The North American collision industry has seen a recent increase in the number of fixture bench structural
| Figure 4|
| Figure 5|
repair systems. This is due to a number of reasons. Many European vehicle makers recommend that structural repair of their vehicles be done using dedicated fixture bench systems. Examples of vehicle makers that recommend the use of fixture benches for structural repair include Audi, BMW, Jaguar, Mercedes-Benz, Porsche, Volkswagen, and Volvo.
The arrival of aluminum-intensive vehicles and the repair networks that are in place for their repair have also helped increase the number of fixture benches in collision facilities. Fixture benches are a part of the required equipment for many of these repair networks (see Figure 3). Aluminum, as with the many types of advanced high-strength steel used in today's vehicle structures, leads to more part replacement. Fixture benches are helpful for part fit-up and installation.
Although it is mostly European companies that are making fixture bench repair systems, the number of companies offering them has grown. Other equipment makers have developed universal holding fixtures for use with their frame repair benches and racks (see Figure 4). While these universal holding fixtures don't provide complete vehicle measuring, they can be used for holding parts in place while welding and to provide extra anchoring during straightening.
Fixture bench innovations
Features added to fixture bench equipment have also been responsible for the increase in popularity in recent years. Benches may now be equipped with built-in lifts to ease vehicle loading. In addition, fixtures have been developed for some applications that don't require complete removal of the drivetrain and suspension. Some fixture sets now have universal bases that work with more than one model when the end or top of the fixture is changed (see Figure 5). This reduces the size of the fixture set that needs to be stored or shipped from a ren-tal bank.
There are other added capabilities being added to new systems. The original dedicated fixture benches typically only had fixtures for measuring the underbody and strut tower position. Modern systems may also have fixtures for measuring certain upperbody points such as door hinge mounting bolts (see Figure 6).
Dedicated fixture benches combine the tasks of anchoring and measuring into a single procedure that can be used throughout the repair process. Once considered the only way to straighten a unibody, fixture benches are being used in more modern collision facilities, thanks in part to on-going innovations.
This Advantage Online article first appeared in the I-CAR e-newsletter, which is published and distributed free of charge. I-CAR, the Inter-Industry Conference on Auto Collision Repair, is a not-for-profit international training organization that researches and develops quality technical education programs related to collision repair. To learn more about I-CAR, and to subscribe to the free e-newsletter, visit http://www.i-car.com or contact I-CAR Marketing Communications Specialist Brandon Eckenrode at Brandon.Eckenrode @i-car.com.