FAQ
What is the difference between a checking fixture, a gauge and a jig?
There is absolutely no difference between these three terms. They all have the same meaning, and their use depend only of the customers’ preferences. They can be used to refer to simple “Go/No Go” control elements, or to complex fastening systems with all types of controls. Some customers also call them “control devices”.
What is a positionner or a CMM fixture?
As its name suggests, a positionner is an element of fixation enabling to position a part by aligning it by its RPS on a CMM machine. Contrary to a checking fixture, which also positions the part in the same way, a positioner does not have any type of control element giving information about the part, and enable the CMM probe to access easily to the areas to measure.
This picture displays a positionner fastening a puffed plastic tank in vehicle coordinates for its measurement by CMM machine. As it also represents the part fixation points, it can also be used as a checking fixture for these areas.
What is a dimensional checking fixture?
Mechanical assembly for the dimensional verification of mass-produced parts,which function is doing the same repetitive controls on parts assemblies that have been aligned in exactly the same way, independently of the person doing the measurement. Checking fixtures are frequently used by parts and components manufacturers in industrial sectors such as automotive, household appliances, railway, aircraft, pharmaceutical, etc.
They are also called jigs or gauges and are designed for the verification of a determined part.
The checking fixture displayed on this picture has been designed to check a hood air bonnet, a plastic part located in front of the windscreen. We have represented all the vehicle fixations of the part by simulating the screws with clamps. We have also represented the part outline to check its gap and flush with Go/No Go pins. This checking fixture even enables to mount the real windscreen to analyse its fitting with the hood air bonnet. Since it is a gauge for a large part (1,200mm long), it is very heavy (200kg), and has had to be produced on an aluminium founding base plate, and provided with a transport trolley.
The fixture displayed on this second picture is a cubing simulating the area of the car door where the rear-view mirror is mounted. The foldable arms with bushings located on their extremities enable to measure points by dial indicator, in order to get data to analyse the part flush with the car bodyside. In this type of checking fixtures, the fixation areas of the vehicle bodyside have to be simulated, with their real thickness. Moreover, the fixture must be provided with a torque wrench, or the tools necessary to mount the rear-view mirror in the same conditions as in the production chain. In some occasions, it is necessary to mount the real rubber gaskets, or a prototype with performances identical to the vehicle gaskets.
