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Infiltrator goes very large scale for injection press

By: Bill Bregar

July 18, 2014

Infiltrator Systems Inc. has designed and built a mammoth injection press, with 6,000 tons of clamping force, to mold septic tank halves measuring 15 feet long, from 245 pounds of polypropylene.

The machine began turning out parts in March at Infiltrator’s factory in Winchester, Ky. Infiltrator worked with Franchino Mold and Engineering Co. and hot runner supplier Synventive Molding Solutions.

Infiltrator claims the press is the world’s largest low-pressure injection molding machine, with the largest hot runner manifold system in the world. A few other injection presses have higher clamping forces, but Bryan Coppes, Infiltrator’s vice president of engineering, said company officials believe the machine in Kentucky has the largest platen size in the world.

The top and bottom halves of the tank nest together for more economical shipping to distributors, where they can be quickly be assembled into the finished tank after customers purchase the big Infiltrator IM 1530 Septic Tank, Coppes said. The 1,500-gallon tanks are for residential wastewater use, and they come with Infiltrator-molded chambers that connect together to form a leach field.

Coppes said Infiltrator also built another 4,000 press three years ago, to mold smaller septic tanks, each half weighing 150 pounds.

Shipping is the big reason for developing the new low-pressure injection molding press, Coppes said. He confirmed that Infiltrator had been rotational molding septic tanks on an automatic Leonardo machine from Italy-based Persico SpA — making the company one of the early U.S. adopters of that technology. Coppes said the Persico technology is solid — and Infiltrator will keep the Leonardo press at its Winchester plant. But it’s not economical to ship huge tanks to far-flung locations, he said.

“When your freight costs are that high, you have to come up with a solution, either you’re going to build a lot of [rotomolding] plants, all around the country, or you’re going to build something like this, that nests,” Coppes said.

The same principle — trucking giant hollow parts — ruled out extrusion blow molding the septic tanks, which can be done on king-sized Rikutec-brand blow molding machines.

So about a year and a half ago, Infiltrator began to design the injection molding press.

Coppes said Infiltrator used components of two Uniloy structural foam molding machines, repurposing them into a single injection press.

“We had to re-engineer the platens and hydraulics to make this whole thing work,” he said.

He said Infiltrator’s machine, even though it’s “low-pressure,” is a traditional injection molding machine. It is not structural foam or structural web, and does not use gas-assisted molding, he said.

Coppes would not get into technical details, but said a key is the huge mold made by Infiltrator’s long-time tooling supplier Franchino Mold and Engineering in Lansing, Mich., and a big hot runner manifold system from Synventive of Peabody, Mass. The three companies worked closely together.

Both the top and bottom halves of the 15-foot long septic tank are identical. A large six-axis robot does part handling and finishing.

“We have an automation cell that cuts the manhole lids out of every other tank. When you put it together it forms a septic tank,” Coppes said.

The Franchino mold has an aluminum and steel cavity and core. Franchino machined the cavity on a Tarus five-axis mill with a table measuring 9.5 feet by 10 feet. The mold weighs 420,000 pounds.

The injection press took five months to engineer and nine months to build — more than 10,000 man-hours of labor.

“This is the biggest part that we make, and we believe, the largest injection molded part in the world,” Coppes said.

The biggest presses in the world

Infiltrator’s 6,000-ton, low-pressure machine joins the pantheon of the world’s largest injection press.

Here’s a list of some of the others:

• Buckhorn Inc.’s 8,800-ton Husky, used to make material-handling products.

• Cascade Engineering Inc.’s 9,000-ton Battenfeld press (actually two 4,500 presses mounted in tandem, side by side) for molding waste containers.

• In a set-up that’s similar to the Cascade machine, Paris-based Plastic Omnium SA has two 5,500-ton presses linked in tandem,

• An 8,800 MIR injection press at Contenur SA in Spain, molding containers for municipal solid waste and industrial storage products.

• Bemis Manufacturing Co. in Wisconsin coinjection molds eight-foot hoods for John Deere tractors on a 6,600-ton Milacron press.