Rigid Yet Flexible Workholding Solution is Key to Short-Run Productivity

The best workholding devices combine two seemingly contradictory attributes: rigidity and flexibility. Rigidity to hold parts during machining, maximizing accuracy and productivity. Flexibility to quickly handle a variety of workpiece configurations.

JBJ Manufacturing Co. (Faribault, MN) uses a Kurt MoveLock two-piece vise mounted on a custom made base to achieve the rigidity and flexibility it needs for short-run machining of steel and cast iron components. The five-year-old, 38-person company machines a large variety of precision parts in runs of just four or five parts up to 500 pieces. To be efficient and profitable with this kind of work required a creative approach to workholding.

Wide Variety of Part Configurations
JBJ machines mostly heavy iron and steel parts used in drive trains and other systems for construction and agricultural equipment manufactured by nearby companies. The components cover a wide range of size and configuration, from an inch square to parts longer than two feet.

JBJ founding partner Bill Vos explains the problems created by such a wide variety of part sizes and geometries: "There are a lot of good multiple clamping systems on the market, but most of them are designed to hold parts made of softer materials such as die castings or small, rectangular parts that clamp rigidly and easily," he says. "Our work machining iron and steel requires aggressive milling cuts, so we looked for a part-holding system which was precise, quick to operate and had the extra rigidity we needed."

Vos and his partners Jerry Vold, Jim Krueger, and John Mickelson are the JBJs in the company's name equation. During the ‘80s, the four acquired good shop backgrounds with other companies. With a strong manufacturing economy in the ‘90s, they saw a good opportunity to start their own machining business to help supply nearby heavy equipment manufacturers.

Using Daewoo vertical machining centers designed for tough work, the four set out to build an innovative, customer-driven shop capability. That meant running 24 hr/day, five days/week. Early on, the partners saw some limitations in standard, single-station, screw-type vises. The devices were rugged enough, but couldn't provide the size versatility needed for certain short run work that had to be produced and delivered quickly. Even multi-station vises weren't quite what JBJ wanted.

Rigid, Multi-part Solution
Enter the Kurt MoveLock, a two-piece vise that employs the company's AngleLock concept for part clamping. The MoveLock's two components are the moveable jaw and the base which covers the clamping mechanism. The vise has exceptional rigidity, can handle a very wide range of part sizes in multiples, and clamps quickly with a single hex nut.

The cast iron vise uses Kurt's AngleLock concept for precision clamping. When the vise screw is tightened, the vise piston is driven forward and locates on an internal segment. The lateral force clamps the part, while downward pressure is applied to the movable jaw. The downward pressure minimizes or prevents part lift. For every pound of clamping force on the part, there is a half pound of force exerted down on the moveable jaw. The piston produces a repeatable 5/16-in. stroke at up to 4000 lb clamping pressure, and affords quick and easy exchange of parts.

JBJ customized its setup by designing mounting plates to fit two Daewoo DMV 400 pallet changer tables. Each plate (24 in. wide x 22 in. deep) has 12 machined mounting slots, which allow for infinite adjustment within the range of the machine table. Two of the vises are used on each vise table for holding two small parts or a single large part.

The setup can handle two parts of different sizes or different sides of similar parts. The two-pallet setup allows for load-unload operations on one pallet while the machine is finishing the second pallet.

Part clamping is straightforward and manually operated, so there are no pneumatic or other hookups. It also has a low profile with no swivel handles to protrude or cause clearance problems when pallets rotate. The arrangement can handle parts in the 500- to 1000-lb class, with the 180° rotating pallets indexing in 5 sec.

Vos says JBJ gets the heavy cuts it needs with tenths accuracy and mirror finishes when necessary. The complete setup, with four vises, cost under $1500 not including the time needed to machine the mounting plates.

Kurt Manufacturing Co., 1325 Quincy Street Northeast, Minneapolis, Minnesota 55413. Phone (612) 572-4424.