Display Fixture for a Bumper
There are three types of checking fixtures for large parts:
- (1) Welded-structure display fixture
- (2) Aluminium-profiled-structure display fixture
- (3) Cubing fixture representing all the adjacent elements
The former two have the same function, their difference is in the type of manufacturing material used and production deadlines. Their structures have a similar resistance, but the second one is made from assembled aluminium profiles, and can be produced more quickly. Both are used to position the part on the tridimensional to enable its check.
The third option differs from the first one, because as it is made from an aluminium founding structure, it is more stable and is usually provided with several types of checks to enable the verification of the part thanks to Go/No Go gauges, dial indicators, gap gauges, sensors, and so on, without having to resort to the use of a tridimensional machine.
Another possibility could also be made, a combination between the fixtures described above, that is, a positioner with some checking elements. In order to show you an example of a display fixture of that type, we have made a video that, we hope, will give a clearer vision of how it works.
You will find bellow the translation of the content of this video:
“Hi, I am Xavier Conesa, general manager of Tecnomatrix. I am here to show you the functioning of this display fixture for a bumper.
Basically, a display fixture, more commonly called a positioning fixture, is used to fasten the part according to its isostatism, fixation and screwing points. It also enables to conform it, because as it is a large part, it tends to deform itself easily. That is why the fixations of the part have to be simulated; then, thanks to the references located around the part, the part is aligned according to its vehicle coordinates.
Once we have it aligned and positioned in space, we can place the structure onto the tridimensionnal, measure any point of the part and check its position. Basically, this is what a display fixture is for.
What is more, we have set on this display fixture aluminium blocks representing the gap and flush with the parts surrounding the bumper, so that we can check the gap with a Go/No Go gauge. We have set blocks all around the bumper.
That type of assembly is made from iron tube structures that we welded together and stabilized to avoid any deformation. That kind of checking fixture is multifunctional and is very useful for this application.
Yet, that sort of large part can also be checked through a cubing style checking fixture, and it is also possible to make a similar structure with aluminium profiles. We would only have to acquire the aluminium profiles, and would obtain in the end the same result as this fixture, but with maybe a slightly shorter production deadline.
All the threaded pins have a distinct mark, to avoid any confusion; now, we are going to show you how to dismount the part, and how to take it off the display fixture. We unscrew the threaded pins simulating the fixations of the bumper to its adjacent parts. Now, the bumper can be removed from the display fixture.
The same display fixture enables to check either the assembly of the parts forming the bumper, or each part individually, like this interior lining. Thus, we will fasten the part with the same threaded pins to check that the part is not deformed and can be correctly mounted on the vehicle.
That type of display fixture always comes with a dimensional report, to certify that all the centres and isostatisms are within their tolerances of ±0.05mm, and that the checking areas are at ±0.01mm. Moreover, we prepared an R&R study, to verify that the fixture meets with the repeatability requirements. A user manual is also provided with the display fixture that shows how to mount and fasten the part, in order to use the fixture correctly.
I hope this presentation helped you understand how that type of tool works, see you next time.
Related articles: Cubing-style Checking Fixture for a Bumper.
