Faster Inspection Feedback Improves Part Quality

“Though our SP25s were scanning probes, we were doing 95 percent touch probing because scanning was too slow with a 3-axis CMM,” recalls Watts. “Our cylinder and crank bores are probably the best examples of where we believed touch probing was inadequate. To accurately collect enough data points to measure the geometry of a bore 80 mm to 100 mm in diameter and 150 mm in length, the SP25 probe took so long we limited those inspections to machine set up or special requests from our design department.

“Now, on every crank case we measure, the REVO does a spiral scan of bores and the system outputs the values to software,” continues Watts. “We also send a graph of the data points to our network that can be used by anyone in QC, engineering or production, and it really helps troubleshoot problems. You can VISUALIZE the problem. What would take three to four minutes to touch probe with an SP25 is now being measured in ten seconds with the REVO.”

The REVO scanning heads have all but eliminated the need for touch probing. Now 95 percent of inspections utilize scanning, with no “time penalty” as before. This allows Kawasaki to collect so much data that it challenges the speed of computers doing the analysis. The REVO probe can also do “head touch” probing or be used for traditional machine-touch probing when the situation calls for touches.

“With scanning inspections, our production and engineering people have a lot more confidence that the data is valid,” adds Watts. “With touch probing it is easy to get one speck of dirt that causes an out-of-round condition if you’re only sampling seven or eight points. It can throw off the location of that circle. We have specific documented examples of flatness errors that existed that we would not have caught with touch probing, and cylinder bore geometries that would not have been caught with touch probing because of the amount of data sampled with the touch probe. We still caught these problems before they left the plant, but the parts were scrap. The scanning capability allows us to catch form errors much more quickly, without a time penalty on our inspections. It has definitely made us more proactive in catching quality problems early in the game.”

FEWER PROBE CONFIGURATIONS, MORE FLEXIBILITY
Using scanning inspection, the Maryville operation now has two probe configurations that measure all of its mass production parts, reserving custom probes in a changing rack for a few special applications. Special configurations for vendor parts have also been eliminated because the infinite positioning angles of the REVO system allow measuring of a part without special fixturing or consideration of which probe to use.

With so few probes, calibration time has dropped to around 46 minutes. Quality technicians now monitor the calibration instead of calibrating every shift. “We are now able to measure all of our mass production parts with just two probe configurations,” explains Watts. “We were able to eliminate the large ball stylus configurations because of the large approach angle that the REVO creates between the stylus and the work piece. During scanning the REVO maintains the approach angle, which allows a large cylindrical feature such as a cylinder bore to be measured with the same stylus used for measuring a 5 mm bore, with no chance of shanking the stylus.”

Flexibility of the scanning system has also proven to be a time-saver for the shop. “We can measure any part on either machine with a limited amount of fixturing and no special calibrations,” states Watts. “We measure all of our parts on three types of fixturing. The REVO probe orients itself to the part after it’s initially aligned. The utilization of special fixtures has almost been eliminated, without concerns of measurement error due to part alignment.”

Kawasaki programs all of its inspection routines in-house using Mitutoyo Mcosmos 3.1 software. The upgrade to REVO instigated a shift to parametric and modular programming of inspection routines through in-house development of coding that allows a program to be used for a part family. “We might have 30 different crankshafts, for example, but because every one of them has the same features, only in a different size or location, we can use the same inspection program to measure all of the parts,” explains Watts. “That’s one of the big advantages we gained.”

Infinite angles of the REVO system make it simple to create parametric programs because there is no concern about the stylus interfering with a part feature due to size or orientation of the feature. The probe automatically aligns normal to the feature being measured, simplifying programming.

FASTER INSPECTION, BETTER DATA FROM QC TO R&D
Watts says the transition from 3-axis to 5-axis programming is not difficult and that a programmer with limited ability can still program REVO inspections the same as 3-axis. However, when it comes to optimizing the speed of inspection, it is critical to use head motion as much as possible. “This allows you to scan parts the quickest, without inducing measurement error,” states Watts. “REVO opens up a lot of possibilities, with few limitations, so speed gains are obtainable for both the higher and lower skilled programmers.”

Inspection results may be relayed to the machining lines manually or they can be accessed locally by line operators over a computer network. “Some of our inspection reports supply offsets directly back to the machining centers’ coordinate system. This allows the CNC operator to read the offset adjustment right off the report, allowing no misinterpretation of what offsets the operator needs to input,” says Watts. “We take advantage of some of the ‘best fit’ algorithms and work with our production engineers, especially on parts that require more complex algorithms to get the adjustment right, to utilize multiple process adjustments simultaneously. We had limited ability to do this before the REVO, but the REVO allows us to utilize parametric programming which, in turn, enables us to expand our capability across the board more easily.”

According to Watts, 5-axis CMM scanning has been a game-changer for QC at the Maryville plant in terms of speed, data quality, and inspection capacity. “We’ve enjoyed big gains from having two machines that are completely redundant. If one machine breaks or is down for calibration, there is no problem to measure critical parts on the other machine. That’s a big advantage in the quality lab, because we were the ones who, in a pinch, had to get the large part on the small CMM, or the part requiring the odd angle probe on the machine that didn’t have it. We used to get requests from R&D to measure certain geometries, and it was next to impossible to achieve that in the time allotted. But now we can provide the data much quicker and, being scanned data, our people have greater confidence in it. This new flexibility, the reduced fixturing, form measurement, the parametric programming – these are all collateral advantages in addition to the raw inspection speed.”

The Maryville facility has run more than 50,000 parts through the two REVO equipped CMMs. Watts indicates there are plans to expand the use of the REVO system to gear inspection and cam lift if it proves feasible. “We’ve developed our own algorithm and sub-routine in our software for cam lift, and that’s something that would have been more difficult to do without the REVO system due to the angle the probe requires to measure the lift on the lobes.”