Fast Set-Ups for High-Volume Machining of Transmission Parts

Sept. 29, 2011
Kurt Mfg. clamping system effective for producer of diverse coupling components
Kurt Manufacturing’s Leader Chuck clamping system provides fast machine set-ups and precise concentric clamping for Leyden Transmissions.
The clamping system offers a simple, top-face operation so more chucks and therefore workpieces can be “banked” closely together.
Leyden Transmissions’ Doosan V850 five-axis, twin spindle vertical turning center with spindle speed up to 1,800 rpm. It has a maximum turning diameter and turning length of 33.46 in., so it will handle the wide variety of couplings and similar components produce at Leyden Transmissions.
Leyden Transmissions’ coupling components vary widely in size, bearing configuration, and insert designs.
Kurt’s Leader Chuck workholding system is sufficiently flexible to handle a wide variation in component size in high-volume operations, because it achieves quick set-ups from part to part.

Workholding is a big challenge for machine shops and operations when orders range between a few dozen or thousands of parts, and when the part sizes and weight vary considerably. At Leyden Transmissions in Liversedge, England, coming up with the right workholding methods using Kurt Manufacturing Co.’s Leader Chuck clamping system impacts everything in the manufacturing process. Efficiencies are improved for the operators as well as the machines, part output is faster, and deliveries and customer satisfaction are increased. Importantly, the operating revenues are increasingly attractive.

Leyden Transmissions is an ISO 9001-certified precision manufacturer of power couplings and braking systems for cranes and hoists. Its products are used in a range of applications that demand precisely machined solid or semi-rigid couplings that join motors and gearboxes. In addition to these coupling products, Leyden Transmissions performs contract machining for automotive, fluid and hydraulic, railway and structural industry applications.

When Mike Robinson became the managing director of Leyden Transmissions in January 2010 he brought with him a wealth of lean manufacturing principles and experience from the automotive industry. One of those principles called for initiating a quick-change philosophy for Leyden’s extensive machining operations. This change, according to Robinson, was critical if Leyden was to achieve its ambitious plan to double sales volume in three to five years, and implementing Kurt’s Leader Chuck system was instrumental to the change.

“Our vision is a 20- minute maximum set-up time for any part, from stopping one job and machining on the next,” Robinson explained. “That includes loading any tools and workholding required and downloading the NC program. It’s an aggressive target, but it is achievable once everything is in place.

“We started along that route by purchasing a new Doosan V850 five-axis turning center,” he continued. “It has a part size-capacity of 500×1,350 mm with a 60-tool carousel so that tools can be changed while the machine is operating.”

For workholding on the turning center, Leyden chose the Leader MMY MultiChuck system because it was the best option for addressing the quick-change requirements, Robinson indicated. “The machining center and everything that went with it was a significant capital investment, but we had a solid customer base, steady sales volume of a million and half dollars a year,and minimal debt. We were in a strong position to make a strategic capital investment that would provide an immediate high return.”

Kurt’s Leader MultiChuck provided what he called “a proven stock solution” that covers the majority of the shop’s workholding requirements for its families of parts. That, coupled with the Doosan’s probing capability, allows automatic measurement of offsets. The Leader Chuck’s low profile and top-operated loading design make it ideal for Leyden’s part configurations. This is particularly true for larger parts that weigh over 50 lb. and require an overhead hoist for loading and unloading into the machine workholding.

“For most of our coupling products we have to locate on the bore of the parts,” reported Robinson. “The Leader Chuck system allows us to do that quickly. Starting with round bar stock, we bore a hole in the middle and then mill it square before any cross feedholes are drilled into it. That gives us a good size bore to locate and work from. It acts as an accurate datum with everything subsequently measured from it.”

Part of the Leyden’s new machining philosophy is to “hit five sides in one set-up, which is where the 5-axis Doosan comes in,” he said. “The six sequential machining operations are replaced and it can be done in just two, with just the back face being accessed after the cycle is completed on the 5-axis machine. This is a radical departure for our customers’ projects but the parts tested have proven that the process is successful.”

With this process, Leyden will conduct runs or one part or up to 400, and numbers in between, too. The majority of the part-runs are of on to 30 parts, so the need for quick change-over is acute. One of Leyden’s longtime customers has over 65,000 different part numbers in its product line, and often this calls for machining spares one component at a time. Materials for this work range from EN8 and cast iron for couplings, to phosphor bronze and super-duplex stainless steel for pump bodies used in harsh environments.

Leader Chuck workholding “is well-suited for handling these part requirements,” according to Robinson. “A full change takes just three to four minutes,” he said. “It’s great for fast set-ups of our multiple size workpieces. That, plus Leader Chuck’s ability to clamp both inside and outside diameters, make it very flexible by holding parts with 16- to 125-mm diameter bores and with just five mandrel cores.”

New processes often bring the challenge of worker acceptance. At Leyden Transmissions, engineers have accepted the new working practices without any residual issues of the former methods. If Leyden’s engineers encounter a workholding problem, rather than waste time struggling with it, the Leader Chuck system allows them to remove the job from the machine and insert a new one quickly, so the spindle keeps turning. This gives the engineer time to evaluate why the previous job was not proceeding properly, and correct it while the machine continues to produce good parts.

“One of the concerns early on was that components’ overhang from the bore to the face being machined might be too heavy for the Leader Chuck system,” reported Robinson. “One component, for example, has a 38-mm diameter bore and a 200-mm flat area. The weight of the part together with the cutting force of the tool contacting the workpiece appeared to be too much for the workholding to handle.

“On a trial run working with Leader Chuck’s sales engineer, Will Hare, we gradually increased feeds and speeds until we reached the tooling manufacturer’s recommended rates,” he continued. “We were pleasantly surprised that the Leader Chuck’s rigidity far surpassed what we thought it would do.”

Now, Leyden Transmissions is targeting for future growth with prototype part machining, using the Leader Chuck system. “With the quick set-up and changeover time advantages we get, it will allow us to go after new customers who can use our coupling expertise,” Robinson explained. “There are several valve manufacturers in our area who serve the hydraulics and oil-and-gas industries. We believe we can win business from them because of the reduced set-up times we can achieve.”

Latest from Cutting Tools