An automotive company was able to reduce job setup time by 75 percent by making a shop-wide workholding change. Contributed by Kurt
High-end automotive aftermarket manufacturer MGW provides custom designed shifting devices called short throw shifters for sports cars including Corvette, Mustang, Viper, Camaro and others.
With a history in CNC machining dating back to 1984, the company operates numerous Okuma and YCM horizontal and vertical machining centres. The company initially handled contract machining for several industries such as the aerospace and microwave sectors, and has certifications in these areas. But the short and repeated part runs for the shifter products mandated more efficient setups, moving the company to a new workholding jaw system by Kurt.
“One of our biggest challenges was to find an efficient way to switch from one shifter setup to another quickly to save on costly machine downtime,” said George Ciamillo, vice president of MGW. “We needed accurate workholding that did not need to be indicated every time we setup for a repeat job.”
Mr Ciamillo said that prior to the new system, they were using custom machined blank jaws which required time-consuming levelling, indicating and locating every time a job was set up.
Making It Work
The company knew that no matter how fast a CNC machine operates, if setup time was not minimised, the overall machining production time and cost would be too much. It boiled down to what jaws are used in the setup. The new system, called Dovelock, consisted of a master jaw with built-in dovetail quick-clamps designed to hold and lock the quick-change machinable jaws into position.
In the initial setup, each master jaw had two bolts that were fastened to the stationary movable jaw of a 15.2 cm tower. Once the master jaws were in place, the machinable jaws, located with the master jaw, were then locked up using the master jaw’s three quick-clamp bolts.
The system’s machinable jaws were able to be swapped out for future jobs by loosening the three quick-clamp bolts at the top of the master jaw and sliding it forward at an angle or sideways out of the master jaw.
Another feature is that the machinable jaws could be rotated 180 degrees and machined on both sides for holding two different parts. The workstop located on the master jaw enabled for repeatable location accurate to ±0.0025 cm. Interchangeable jaws also allow for the handling of different part sizes.
The company produces hundreds of shifter parts including shifter bodies, brackets, linkage arms and other components mostly machined from aluminium, operating an eight-hour, five-day workweek. Using the previous jaw setups, the company would go through two to three runs per setup to get its first acceptable part.
With the new system, Mr Camillio said that the jaws usually yield an acceptable part on the first operation. He added that the company reduced job setup time by 75 percent.
With thousands of these parts machined a week, the company reported that “it realised an improved spindle time of at least 10 percent. That is operating both horizontal and vertical machining centres at between 5,000 and 12,000 rpm feeding between 50 to 200 inches (127 to 508 cm) per minute.”
Additionally, the system allowed milling into the changeable jaw plates using the full volume of jaw material. With previous jaw setups, it was necessary to avoid the two cap screws when machining a feature or pocket into the jaw plate. Utilising that extra area of metal, the system allowed for new workholding setups.
The system also enabled the machining of multiple steps on the same pair of jaw plates. By rotating the jaw plates and machining different steps on both sides, fewer jaw plates were required for those jobs requiring different steps. Operators could also accurately clamp wider parts into two side-by-side sets of jaws.
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