Faster Inspection Feedback Improves Part Quality

Let the Good Times Roll: At the Maryville plant of Kawasaki, Renishaw 5-axis scanning probes now collect data and reduce feedback to machining cells from hours to minutes and may ultimately eliminate the inspection systems for gears and cam lifts.

Kawasaki (Maryville, MO) encourages motorcycle enthusiasts to “let the good times roll,” but good times of another sort are rolling at the company’s Maryville small engine plant, where two 5-axis scanning probe systems are slashing CMM inspection and probe calibration times, and speeding up quality control feedback for machining of small engine components.

The 5-axis REVO systems from Renishaw Inc. (Hoffman Estates, IL) are installed on Crysta-Apex 121210 coordinate measuring machines (CMMs) from Mitutoyo (Aurora, IL) that replaced two PH10 articulating heads using SP25 scanning probes on traditional 3-axis CMMs. The REVO-equipped CMMs have cut inspection times by half or more on scanning intensive applications. They have also eliminated the need for custom probe configurations, cut probe calibration times from six-seven hours down to about 45 minutes, and improved part quality by adding new capabilities to collect large amounts of form measurement data.

Of primary importance is how the REVO systems have greatly increased inspection throughput, data quality and flexibility of the QC department, enhancing its value as a strategic support asset to both manufacturing and R&D.

THE KAWASAKI PRODUCTION SYSTEM
Opened in 1989, the 800,000 sq ft Maryville plant produces single and twin-cylinder air-cooled or water-cooled engines that are 1000 cc or smaller for commercial and consumer lawnmower OEMs, as well as for a sister plant that manufactures ATVs and Mule™ utility vehicles. Operations at Maryville include aluminum die-casting, plastic injection molding and extensive amounts of machining, painting and assembly. All of the approximately 500,000 engines produced per year are run-off before shipping.

“We use the Kawasaki Production System (KPS),” says J.C. Watts, the quality control technical group supervisor at the Maryville plant. “Our quality and engineering requirements are comparable to the best in the automotive industry, though our manufacturing is focused on lower volumes of many different kinds of products.”

The plant has 50 machining lines that are typically arranged in a U-cell pattern, with start and end machines across from each other. “Primarily this is one-piece production, with machining lines running a part through multiple processes at a high rate,” explains Watts. Kawasaki utilizes automation in many die cast and some machining operations, accomplished through the integration of Kawasaki robots. On one of the crankcase lines, robots load raw materials and unload finished parts that are placed into inventory for assembly to draw upon. Machined parts include aluminum, cast iron and steel.

“We’re running similar tolerances that an automotive powertrain uses for high-end products. There are probably four or five critical processes for our aluminum parts and 15 for the steel parts,” adds Watts. It is not uncommon to find tolerances “in single digits in microns” for form, and 0.05 mm true position.

The QC lab is responsible for inspecting 125 different mass-produced parts, as well as vendor parts and those produced for engineering development. The environmentally-controlled lab is located adjacent to the machining lines and parts intended for routine inspection are delivered on carts or via train (an electric vehicle towing several trolley carts). Critical components may be hand delivered for priority inspection during a line changeover or if an operator suspects a problem.

5-AXIS SCANNING ADVANTAGE
“When I started here we had a couple of 3-axis CMMs with PH10 articulating heads and SP25 probes, and another CMM with a fixed probe head,” recalls Watts. “We were frustrated with having to make probe configurations and being limited to what we could do even with the articulated heads. We had so many different probe configurations that calibration times of six to seven hours took a bite out of our inspection throughput, too. We wanted to do better than what the industry considered the norm, so we looked at several options and this 5-axis REVO system appeared to be the fastest and most flexible available. It was the best fit for our requirements.”

Kawasaki bought a new Crysta-Apex 121210 in 2009 with the REVO system installed from the factory, then retrofitted an identical machine in 2010 after the first machine was up and running with all the part programs. The REVO 5-axis scanning probe head can collect up to 6000 data points/sec. It is engineered for high-speed precision measurement of contoured surfaces and complex geometries requiring high-volume data collection to validate fit and form with high accuracy.

The system uses two rotary axes, one in the vertical plane and one in the horizontal, for infinite rotation and positioning. Five-axis software drives the measuring head and synchronizes its motion with the linear axes of the CMM. Look-ahead algorithms drive the probe path and CMM in coordinated continuous motion. The head adapts position while measuring on the move, maintaining stylus tip contact with changing contours at scanning speeds of up to 500 mm/sec.