Reducing setup, machining time

G&Z Industries, a precision parts manufacturer for the aerospace industry, recently implemented Kurt Manufacturing’s new PinLock system in a newly acquired Mazak HCN 4000 horizontal machining center.

The first job processed using the system was a cylindrically shaped aerospace housing. Twelve of these components were set up and relief milled with ±0.002" accuracy on the machine’s two PinLock equipped pallets. Previously, only two parts were machined per setup. Machine cycle time was reduced by half over the previous method while setup time was reduced from 7 hours to under 60 minutes. More importantly, the improvement laid the foundation for similar workholding improvements throughout the company’s machining operations.

“We wanted to develop a process that would maximize the output potential on that new machine,” reports Gene Kline, director of G&Z operations. “But we also wanted a process that would be easily adaptable to existing machining centers and new ones as they are added. Because we are a longtime user of Kurt workholding products, we brought in David Zaval, our Kurt manufacturer’s representative, to see what new modular workholding ideas he had that could improve our productivity with the new Mazak.

“Initially, David helped us target a repeat job for improvement that is run throughout the year. Previously, it was run on a vertical machining center, two parts at a time, with 6 to 8 hours needed for setup plus quality control verification time.”

The setup Zaval recommended on the Mazak HCN 4000 included a new 10" x 10" x 24" Kurt tombstone on each of the machine’s two pallets. The Kurt PinLock system was installed in both tombstones enabling the processing of 12 parts at a time – three for each fixture plate. This reduced cycle time by half over the previous method.

The new process improved quality, cycle time, and setup time while reducing scrap. But the most important aspect of the new process is it paved the way for company-wide productivity improvements, a focus of the company since it began operations more than 60 years ago. 
 

Modular workholding

Kurt’s PinLock allows for creative design of the fixture plates. A window cut through the plate, adjacent to the mounted PinLock, allows machining from the backside of the fixture plate without having to reposition and re-clamp the part. This saves even more setup time and speeds up the machining process.

G&Z now has approximately 20 custom aluminum fixture plates dedicated to the system with more being generated as their use is expanded. Each of the plates has a machined PinLock mounting hole in the upper left and lower right corner, giving it accurate and rigid alignment on the tombstone face. Pointing to the PinLock mounting hole, Kline says that each fixture plate is identified with a serial number, the company name, and logo to show ownership and for coordinated use, particularly when plates are moved in the future to multiple machining centers.

The PinLock system can be applied to setting up and interchanging multiple pallets for a series of machining centers.

This was G&Z’s ultimate goal when it instituted the system, according to Kline. “We wanted to make the new Mazak maximally productive from the outset and become the foundation for a new modular workholding system that we could adapt to all of our machining centers. We liked PinLock’s helical extraction design over other locating systems. It’s fast and adds to setup accuracy by overcoming binding in side load conditions and enhances the setup for every application when changing parts.”

That’s because the PinLock system uses a pin assembly to engage and create a locking force with line contact, as opposed to other locking systems that use point contact. The PinLock system consists of high precision pins, bushings, and liners that provide locating repeatability up to ±0.0005". The system can be used with Kurt tombstones, grid plates, and vise adaptor plates for a shop-wide, modular workholding setup. That was the long-range goal for Kline in redesigning G&Z’s machining processes around the PinLock workholding system. 
 

Scrap reduction a plus

While the overall setup time with the PinLock system after the initial setup was just 12% of the first setup process, quality control requirements were also much less. First-part quality with each initial setup in the PinLock system was consistently within tolerance requirements so no re-work, adjustments of the workholding, or extra inspections were needed.

“We were really impressed with the first-part precision coming out of the PinLock setup,” Kline says. “All of the parts are machined from 6061 aluminum in various size configurations and all are for demanding aerospace applications. Milling of these parts is at top machine speeds up to 18,000rpm. Some of the required tolerances are as tight as 0.0002" and we get that easily because the setups with PinLock are very rigid. That ensures first part accuracy and repeatability. With acceptable work on each of the first parts run and everything after that, we’ve seen our scrap rates go down dramatically.”

G&Z’s first PinLock system is dedicated to the new Mazak HCN 4000. With the company operating two 8-hour shifts, the system is in constant use. 
 

Future plans

“Dave Zaval has been a great source of support to ensure we get the latest workholding information we need and the products that make sense for our applications,” Kline notes. “Once our machine operators saw the repeatability and the ease with which the PinLock system has achieved, they began looking at other ways we can use it throughout our machining operations. We’ve already planned on implementing the system into our 5-axis machine and will follow that with several existing horizontal machining centers. Any new multi-pallet machines that we add in the future will definitely include a PinLock system because it makes our setups so much faster while it improves part repeatability.”

Kurt Mfg. Co. 
www.kurtworkholding.com

G&Z Industries Inc. 
www.gzind.com

Eric Brothers is senior editor of AM&D and can be contacted at 330.523.5341 or ebrothers@gie.net.

Watch a video on “How to Use the PinLock System” at http://bit.ly/r2p2NM.