February 2010 / Volume 62 / Issue 2|
Bigger, faster, better
By CTE Staff
Daman Products Co., Mishawaka, Ind., designs and builds standard and custom hydraulic manifolds. Typically, the hydraulic manifolds Daman produces include fluid management features, such as threaded and off-axis holes, orifices, cavities, channels and complex valve mounting locations. Tolerances are tight: location and drill depths generally are ±0.005 ", while critical features like those essential to O-ring sealing or valve function can be ±0.001 ".
Until about 5 years ago, the largest custom manifolds Daman produced weighed about 350 to 500 lbs. and measured 10 "×10 "× 30 " or 7 "×7 "×50 ". Then, in response to customer demand for larger manifolds, Daman determined that manifolds of 2 tons and less would comprise 80 percent of the “large” product market, with most in the 1-ton weight range. To enter the market, Daman needed a way to efficiently and reliably produce high-quality large manifolds.
Workholding was a central issue. The largest manifolds Daman made previously utilized the volumetric capacity of the company’s machines. To efficiently use that work envelope, Daman staff had developed a system of compact “feet” that bolted to the machine table and then to the workpiece. The feet acted as risers that “brought the part up off the table so that we were able to machine four sides,” said Neil Henderson, continuous improvement manager. “They permitted machining of a part that was as big as the machine table and saved the space that would have been occupied by a workholding tombstone.”
However, Thom Sibley, custom department production team leader, said using that workholding setup “involved indicating everything in to get it fitting square and somewhat centered on the table. Sometimes, if you got lucky, that might only take 15 minutes. If not, it might take an hour or more to get it located.” Including time spent on programming and part-location issues, an entire shift might go by without any chips being made.
To machine manifolds as large as 4,000 lbs. and about 18 "×20 "×40 ", Daman acquired a 4-axis Mazak FH 10800 horizontal machining center with X-, Y- and Z-axis travels of 66 ", 52 " and 49 ", respectively.
With the new machine, Daman staff continued developing the riser-based workholding concept. The most recent version is constructed of ductile iron and begins with a 20 "×30 "×3 " mounting plate bolted to the HMC’s table. The plate has 54 ¾-10 threaded mounting holes as well as 54 ½ "-dia. holes for pins, spaced 1 " apart. In the exact center of the plate is a tight-tolerance bore.
Courtesy of Daman Products
“When we load it onto the machine, we indicate it in off of that center bore so the center of the plate is directly on the center of the table. Then we torque it down,” Henderson said. Centering the plate exactly is critical, he said, “because once the part is on the center of the fixturing, we are able to machine all four sides with basically the same coordinates.”
Bolted to the mounting plate are two matching feet, each 5.5 " wide × 12 " long at the base, with 12 "-long central riser supports that are 2 " wide × 6 " tall. The 6 " height lifts the workpiece to provide clearance above the machine table for the spindle housing and to facemill the manifold sides without table interference. Each foot has pressed-in pins that match the holes in the base plate. The spacing of the holes for pins in the mounting plate enables the feet to be moved in 1 " increments.
On top of the feet is a 6 "×12 "×2 " top plate, bolted to the feet through screw holes spaced 1⁄8 " apart. The holes permit the plate to move a total of 1 " relative to the feet in 1⁄8 " increments. In the top plate are four rows of holes for bolts that hold the workpiece. When the part is bolted to the top plate, the combination of 1 " positioning of the feet with 1⁄8 " movement of the plate allows the manifold to be quickly and reliably locked into a known position in the machining envelope.
Sibley said the workholding setup has cut average setup time from 2 hours or more to, at most, 30 minutes. Because Daman staff has been using this latest version of the system for about 6 months, the shop is applying it conservatively and confirms the part’s position before each run. “Once we use it more, setup time will probably drop to 10 or 15 minutes,” Sibley said.
Large custom manifolds are usually single-digit, low-volume jobs, so Daman also wanted to create something that would make part design easier and not require a new fixture for every part. Sibley said the goal is to give designers a grid that identifies a range of possible locations for holes used to mount the part to the top plate. “They can put mounting holes in the bottom of the part inside that grid, and it will fit on our fixture,” he said.
Daman Products President Larry Davis said the company’s culture of continuous improvement facilitates homegrown innovations like this workholding system. “The spark for an idea,” he said, “can happen just about anywhere. We let them think through what would be better, and trust that they will come up with an idea, which, in this case, was pretty awesome.”
CUTTING TOOL ENGINEERING Magazine is protected under U.S. and international copyright laws.Before reproducing anything from this Web site, call the Copyright Clearance Center Inc. |
at (978) 750-8400.