|Optimizing tooling on Northeast Tire’s new 4-axis Alzmetall machine reduced time to machine nine 2-in. pockets on the mold container from six hours to 34 minutes. |
Northeast Tire Mold in Akron, Ohio produces tire molds and, as a supplier to a number of OEM tire manufacturers, produces about 500 different tire molds a year with 20 of any part being a large run.
Northeast Tire Mold owner Chris Sipe recognized that the only way to stay ahead in his industry is through technology, and he decided to invest in equipment that would enable the shop to directmachine a tread mold versus the typical casting process.
Direct-machined molds are more precise than cast molds and need a minimal amount of clean-up and deburring.
Additionally, directmachined molds are made in anywhere from eight to 12-tread segments with separate sidewalls, so if one segment has a problem, that portion can be quickly remachined instead of having to recast the entire mold.
Achieving these goals meant significant investment in new equipment.
Sipe selected an Alzmetall machine that was suitable for the application he had in mind. But, before investing in the equipment, Sipe assembled a team consisting of Northeast Tire Mold employees and outside suppliers to consult on the purchase to help optimize everything involved in the operation of the new equipment.
A member of this team was Dave Ivory, Seco Tools Inc. (www.secotools.com) technical specialist. Northeast’s faith in Seco was based on a long-standing 12-year relationship. “We started working with Seco when we got our first turning center. Then, we stayed with them because they offered the best service,” Mike Christie, vice president of the company, said.
“We showed Dave the parts we wanted to make and had him analyze the machine — the horsepower, the spindle speed and the coolant pressure — so that we could put together a tooling package that optimized the machine’s capability,” Sipe said.
Because of the various pieces involved with a directmachined segmented mold, they have to be assembled within a special container that fits within the press and holds all the pieces together for the curing process.
Northeast Tire Mold invested in a 5-axis Alzmetall for the machining of the tread and a 4-axis Alzmetall for the machining of the containers.
Machining the mold container
The container material arrives on Northeast Tire Mold’s shop as a flamecut sheet of 1020 steel resembling a giant flat donut or washer that can have an outside diameter of 60 in.
These giant washers are run first on a Defum 3-axis turning center where they get rough machined with a Seco indexable turning carbide DNMG 432 TP200.
“The flame-cut area is tough and leaves a jagged edge, so we have to turn the O.D. to a specific diameter. It’s really tough on the tool, but we machine within 0.001 in. of finish dimensions,” Christie said.
Next, it goes to the Alzmetall 4-axis for the holes.
“The top of the container looks like a piece of Swiss cheese. There are so many different holes and notches in it.”
The most time-consuming part of the container machining process had been the creation around the diameter of the piece of nine 2-in.-deep pockets that are 3-in. wide.
On the previous machine, this was a six-hour operation. With a switch to the new machine that could handle the Seco R217.20 high feed milling cutter used in a plunging operation, this time was cut to a mere 34 minutes.
“We were doing it the same way on the old machine with a 2-in. plunge mill, but we didn’t have near the horsepower on that machine. With the new equipment, we took the tool to its maximum capability within an hour, running at 42 hp and 7,200 rpm,” Ivory said.
Drilling, drilling, drilling
After the plunging process, the container goes into the drilling operations. First, 72 holes with a diameter of 0.257 in. are drilled with Seco’s feedMAX solid carbide drill using the 7 times diameter size to accomplish the depth required.
Then, each hole is thread milled with Seco’s solid carbide Threadmaster. Next, 46 holes as large as 0.875-in. in diameter are drilled with Seco’s CrownLoc drills. The exchangeable crowns on the drill allow for high cutting speeds to reduce machining costs. This provides a precise hole to finish with thread milling.
Finally, four large holes are made with Seco’s indexable Perfomax drills that can handle heavy metal removal.
“Overall we went from producing one part a day to four parts a day. The biggest time saver was in the plunging operation where we became almost 19 times faster. Our goal is to optimize the difficult, extremely technical molds. “We want the best machine tool and everything that goes with it — the foundation, the holders, the collets and the tooling,” Sipe said.