and is easily reconfigured to accommodate changes in the part over time. In-machine gages also are standard products with predefined specifications, interfaces, software and mounting options, which can substantially reduce engineering time and simplify purchasing and spare parts inventories. On the other hand, the in-machine option requires a gage for each machine. The cost can rise quickly for a multima- chine system. It also requires space in the toolchanger and adds time to the manufacturing cycle. In extreme cases, the added time could make the difference between a system that needs X number of machines to meet demand and a system that needs X+1 machines to achieve the same production. Balanced against this is the fact that each machine is au- tonomous. Among other things, this means that one machine in a multimachine system can be reconfigured for a modified part—or even a completely different part—at relatively low cost without impacting the overall production process.
The distinction between the capabilities of gages and those of touch probes is narrowing.
Today’s in-machine WRG gages are robust and include spring-loaded recoil to help protect the gage in a collision. To assure the best performance, they also include provision for air blow to remove chips from the gaging area. The gage can check dimensional as well as form measure- ments in a single operation. And, using wide-range contact systems, a Wide Range gage plug yields a practical diametrical measurement range of up to 20 mm with no manual intervention. In-machine solutions are a viable alternative to end-of-line gaging in many of today’s manufacturing systems. But they are not the only one available.
Don’t Use a Gage at All
In the rapidly evolving world of metrology, the distinction between the capabilities of gages and those of touch probes is narrowing. At the moment, the border lies at a tolerance of about 20 µm. Above that the touch probe offers some advan- tages; below it, a gage is the only choice today. The touch probe’s big advantage is cost. Even ultrapreci-
sion probes like the recently introduced Mida Diamond line cost much less than a gage. And, since any CNC machine
almost certainly uses touch probes for tool setting/checking/ etc. already, the technology is familiar and easy to implement. Cycle time and machine positioning accuracy have been the traditional disadvantages of precision touch probe solu- tions; but that, too, is rapidly changing. A modern probe like the Mida VOP40P optical transmission probe, which incorpo- rates piezoelectric technology, begins measuring the instant contact is made with the workpiece. As a result, a multipoint inspection that may have required 15 seconds with a tradi- tional touch probe can be accomplished in five seconds or less with this highly accurate piezoelectric probe. Alternatively, the new Mida WRSP60 radio transmission
probe offers the ability to scan a surface as well as measure discrete points. Or, both modes can be combined to inspect size and shape in a single operation.
Let Each Technology Do What It Does Best Touch probes probably will never completely replace gag- es, but as the capabilities of the two technologies continue to converge, hybrid solutions will become increasingly common. As the symbiotic relationship between precision manufactur- ing and precision metrology continues to evolve, system de- signers will have a growing number of viable process control options to choose from.
Using an engine block as an example, one could: 1. Inspect the cylinder bores and crankshaft bore simultaneously using an end-of-line gage.
2. Inspect the cylinder bores and crankshaft bore sequentially using two in-machine gages.
3. Inspect the cylinder bores with an in-machine gage, and the crankshaft bore with a precision touch probe, both in-the-machine.
Selecting the best solution will depend entirely on the details of each individual manufacturing system. In that environment, an open mind and a careful evaluation of the strengths of each solution individually, and in combination, will inevitably lead to innovative applications of all the avail- able technologies. Common among all is the capability to control the quality and in particular, the process, by signal- ing the cutting machine the time and the amplitude of the compensation. And that’s not all; another important feature is to control the parts after the tool change to assure the opera- tion has been performed successfully and that the machine is again running good production quality.
45 — Motorized Vehicle Manufacturing 2016
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