Let Me Customize That

Custom-built gaging solutions take into account when, why and how measurement must be done to come up with the right system for the job.

Gage users frequently ask about custom-designed and custom-built solutions for their measuring problems. After hours of searching big catalogs or looking through endless Web pages without finding just the right gage for their job, they are often pleased to discover that some manufacturers do specialize in “specials” and make them an important part of their business.

Most builders of custom gages are happy to ask questions, listen to your needs and make recommendations for a solution to best fit those needs. Sometimes, however, part manufacturers are not really sure what their gaging needs are. Over the years, we’ve fielded many requests for gaging that would measure irrelevant dimensions. One manufacturer wanted to gage the overall thickness of a gear to ±0.005 inch, but that dimension, in fact, was meaningless in the assembly. Conversely and even more importantly, a manufacturer may fail to recognize a critical dimension and allow it to go through the process unmeasured. One benefit of using a gage 
builder is that such a provider tends to do more than design and build gages; it also helps manufacturers determine how, when and why to do their gaging.

There are three levels of custom gage building to consider:

1. Customize the standard. Customizing a standard gage is the most common way to get that special solution to a measurement problem. Usually this is not a major chore to the gage builder, but it still requires design know-how and manufacturing capabilities. Most modifications involve making the gage bigger (though sometimes smaller) to meet part measurement requirements or making special contacts/anvils to access the desired point of measurement. Many of these designs are fairly straightforward, but with extremes of size and difficult locations, only a gage maker experienced in part fixturing, gage design and performance will do.

2. Build the solution from standard components. Most custom fixture gage builders have learned that a lot of gaging applications are very similar to each other. Over time, they have come up with solutions that use common fixturing and probe-holding components that can be used in similar applications. After all, a shaft is a shaft, and a pulley is a pulley. Sure, some are bigger than others, but in general, the applications, dimensions and tolerances tend to be similar. Thus, it’s not uncommon for a builder to have a family of standard components that can be pulled together to create a customized gaging solution. And in such situations, the cost of gaging and delivery can often be significantly reduced.

3. Design from a blank sheet (or monitor). There are challenges, however, where existing designs just won’t fit. Whether it’s the size, shape, speed or tolerances required, a modified or standard solution just won’t work, so a custom gage design can easily be justified. But there are many other reasons that can support a custom design as well.

Many people would recommend putting the part on a coordinate measuring machine, understanding that, with a CMM’s capability, any part can be measured. That may be true if there are unlimited resources and time is not an issue. But in most cases, production can’t wait for the part to be taken offline and put in a queue to get measured on a CMM. A custom-designed gage is likely to be faster to use and in many cases will perform better.

Semi-automated or automated gaging is usually cost-justified in applications in which a part must be inspected every 45 seconds or less. This figure includes not just gage operation, but the entire gaging cycle. While the part measurement itself may take only three seconds, the complete cycle includes, at minimum, placing the part in the gage, operating and reading the gage, and removing the part from the gage. Other required actions may include recording the measurement, sorting parts into appropriate categories by size and removing rejects from the lot. In such cases, a CMM is simply not an option.

The ability to combine several measurements in one custom gage is another important means of speeding up a gaging operation. There are limits, however, to such combinations. It might be possible within a single fixture gage to check several diameters on a large diesel engine piston, but making the same number of checks on a refrigeration compressor piston might require two or three gages, because the contacts will not fit closely enough together. By having the knowledge and the tools available, the best, most reliable solution can be selected.

Many other factors can be used to justify the need for a custom automated gage solution: 
the quantity of parts to be measured; the fact that a part is a critical component and every one of them has to be inspected and the results recorded; or maybe the skill or manpower is 
just not available to measure the number of 
parts reliably.

With so many variables in play, it is hardly surprising that semi-automatic or automatic gages can rarely, if ever, be bought “off the shelf.” But in the case of the part supplier who has to meet his production requirements for speed and reliability, a custom gage may fit the bill.