Making hydroforming tools with a copy mill
Globe Engineering Co, a specialized metalforming and welding company in Wichita, KS, combines conventional and unconventional metalworking methods and equipment to an unusual degree. This combination of high-technology and long-accepted methods gives Globe a broad range of capabilities.
On the unconventional side of daily production, machinists there might precisely trim excess metal from workpieces with a computer-controlled laser that was designed and built in-house. Or, if surface forming is required, one of Globe’s five hydroforming units might be used.
More conventional methods are important at Globe, too. These could include tube bending, metal spinning, welding, and copy milling. There are four copy-milling machines in the shop. One of them is a Hosoi 1610, available in the US from the OKK/O-M Div of MMTS, Melville, NY.
According to Albert Nelson, Globe Engineering president, it is inadequate to classify the sophisticated Hosoi mill as “conventional.’ Trace milling is not new, but Nelson points out, “We would have a hard time making the tooling for our hydroform operations without the Hosoi.’
Tooling traced from plaster splashes
The primary use of the Hosoi 1610 is fabricating the hydroforming tools. Tool production starts with a highly precise plaster pattern called a “splash.’ This can be supplied by the customer or made by Globe technicians following customer’s blueprints.
Patternmaking is a highly exacting process with dimensional tolerances of 0.0003 or finer. The splash is installed in the Hosoi to duplicate its contours in steel.
Once on the copy mill, the contour of the pattern is followed closely by the machine’s electronic tracer at speeds up to 88 ipm. Little or no hand finishing is required because finishing accuracy is within 0.012, comparable to the precision available from electrical discharge machining.
Dary Murphy, machine operator, points out that there is unusually close correlation between the contour delivered by the electronic tracer and the metal removed by the mill cutters. “We can actually machine to closer tolerances than 0.0003 if we slow down the machining rate,’ says Murphy. “Sometimes it seems to take longer to set up than to machine.’
Traces in three dimensions
The accuracy, speed, and tool life of copy-milling machines depend essentially on two developments. The first is that of high-speed, carbide-tipped ball-end-mill cutters. The second is that of an extremely sensitive trace mechanism coupled to a transistorized servodrive motor. The combination is necessary to provide a high-speed, accurate copy trace.
The trace mechanism itself consists of a feeler connected by a trace spindle to a mask plate that controls light-reading photodiodes. Diode output controls the displacement–and hence the output– of a differential transformer.
Transformer signals control the pilot stepping motor of the milling machine. The tracer can trace workpiece contours in all three dimensions.
Sophisticated aerospace work is Globe’s forte
Globe Engineering Co was founded in 1948. The company now has an annual income of over $6.5 million and about 100 employees.
While specializing in the fields of metalforming and welding, largely for the aerospace programs, the company offers a very diversified product line, working more in stainless steel than aluminum.
Products range from a variety of aerospace parts and spinners for jet and turbo propellers, to light reflectors installed in factories in the US, Mexico, and Canada.
Nelson points out that in production operations with today’s sophisticated CNC machines, it is possible to improve efficiency by doubling up one operator to two machines, or by using a less skilled operator to replace a highly skilled machinist.
“Not so at Globe, though,’ says Nelson. “The Hosoi is not a production machine. Almost every tool that Dary Murphy makes is unique.
“We need more sophisticated machines like this to keep up with the operators’ skills.
For information on Hosoi copy mills, circle E36.
Photo: Hosoi 1610 copy-milling machine in use at Globe Engineering to produce hydroforming tools.
Photo: The electronic tracer follows contours of the plaster (splash) pattern, rear. Traveling at speeds to 88 ipm, the tracer guides the tool that is making a duplicate in metal, as shown at left. Machining tolerances are 0.0003 or finer.
Photo: Globe Engineering uses the Hosoi 1610 to manufacture a variety of close-tolerance metal shapes.
Making hydroforming tools with a copy mill