Comparison: Faro ScanArm vs. Standard Checking Fixtures

I have found this video in YouTube and I would like to add a few nuances which, I think, are important when estimating the return on investment. There are data that cannot be given so coldly without being sure that they are true. Most of our readers know how things really are in this sector, and their first reaction when being confronted to uncorrect data may be the exact contrary of what this article wants: finding potential customers.

As far as standard checking fixtures are concerned:

• It is not true that they can only be used for one single part. In many occasions the same checking fixture can be used to check similar families of parts by moving or modifying a few elements.
• They only need a minimal maintenance depending on the way they are used and on the material used for their manufacturing; if the materials are the correct ones we should not have problems of wear-and-tear, broken parts, or short useful life.
• Due to the requirements of the market, manufacturing deadlines are getting shorter and shorter, since suppliers do not have other option but to adapt themselves. In all cases the deadlines range from a few days to a few weeks, with a general tendency to a decrease of about 10 to 15% per year of the design or manufacturing deadline.
• Prices for standard checking fixtures can range from 500€ to 50,000€ – for checking fixtures for large assemblies of parts, which are very complex -. As for the example of the checking fixture displayed in this video, I do not think that it cost more than 4,000€. The crisis the automotive sector has been going through over the past few years has made the prices plummet. The requirements and the complexity of the checking fixtures are still the same, but prices are reduced of about 15% from one year to another.
• Most of the parts or assemblies are not rigid enough to be measured completely free. Generally, parts have to be conformed in order to be measured in the same conditions as the vehicle environment. Some parts even need a simulation of their outlines or of fitting areas, to fulfill their function and be checked correctly.
• No car manufacturer will accept to work without cubing fixtures – simulating the part environment – to carry out a visual check of the gaps and flushes of the outline of most of the parts. In the end, they are the ones assuming the investment in checking fixtures and they set the requirements for these checking fixtures.
• The part fixations and RPS must be correctly reproduced. All the clamps or element applying a pressure must be only used if there is a solid holding point bellow. In that case the part should not be more deformed than when mounted on the real vehicle. Conforming the part with its RPS is a symbol of safety for measurement and repeatability.
• It is totally wrong that checking fixtures can only provide us with qualitative data (checks by attributes). Depending on how the design is made they can integrate variable measurement elements such as dial indicators or other means giving a precise information.
• The data provided by checking fixtures can also be stored automatically through electronic systems. There is an infinity of sensors available to extract the data and store them easily.

As far as CMM fixtures are concerned:

• They must be calibrated every time they are mounted, and once they have been adjusted it will not be easy to dismount them again, as it means to have to calibrate them again. Mounting and adjusting requires a long time which will make us let the CMM fixtures mounted for some time.
• Standard elements cannot be used to simulate the whole range of RPS we can usually find on parts. Many centring elements are positioned with inclinations, special shapes, threaded pins, etc., and they cannot be represented by standard elements.

With all this I do not want to say that Faro system is not interesting, but it is NOT as interesting as this presentation wants us to believe. Collecting data for a further process, and having a traceability is something that will go mainstream in all production systems, but we have to study very well the return on investment.