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Jack Latragna owns SHM (Gardnerville, NV), a 2500 sq ft mold making business that does turning, milling, sawing, grinding and inspection for compression, transfer and injection molds used in the rubber industry. This guy thinks molds - the one he's currently working on, the one just finished, the one yet to come. These days especially, the ones yet to come.

With remarkable unambiguity, Latragna acknowledges how much of the industry he and other mold makers once supplied routinely has been swept away to places like China, Taiwan, Vietnam and India. "As things change in our industry," he says, "we don't see many high volume production jobs. Hardware stores once carried faucet washers from Brasscraft, Crane, and Fluid Master that came out of SHM molds. But not anymore."

Latragna doesn’t build molds from mold drawings. "I build from part drawings," he emphasizes. Latragna does all the engineering of the mold. When he ships a mold, it's his design, not someone else's. "This gives us a very real sense of the mold as our product. If the mold doesn't work correctly due to some issue, it's our issue," he adds. "There's a very real sense that we build a product, versus being just a job shop."

Dimensional issues are not a problem since the company uses CAD/CAM and CNC. Any quality issues usually arise from a process problem, such as if a part doesn't fill quite right, if the gates aren't quite right, or if the customer wants a handle someplace else on the mold so they can hold it or clamp it.

SHM doesn’t generally work on complex plastic molds. Plastic molds usually require a mold designer to engineer the mold prior to the product/mold being sent to a machine shop. These tend to be more complicated. Rubber molds are different than plastic molds because they can be undercut and don't need slides, so the molds tend to be a bit simpler.

As such, many of Latragna's molds produce synthetic, elastomer products, such as silicone, fluorocarbon, gaskets, seals, bellows and diaphragms. He has also done grease seals used in the landing gear for commercial and military aircraft (a larger version of the Chicago Rawhide seal found on the wheel bearing of a car). In fact, over the past 40 years Latragna has done just about everything: the backsplash on garbage disposals, a gasket for a nuclear weapon, pacifiers, nursing aides that look like breasts, earplugs, and a lot of general industrial bellows, boots or gaskets.

But this shop is not limited to only small molds. "I just finished a mold that weighed 500 lbs," explains Latragna. "The part was 12 in x 8 in x 6 in and looked like a slightly shrunken irrigation box that goes into the lawn where the sprinkler valves hook up. However, this is a military product so I don't know exactly what it is being used for. The print title block called it a boot . . . if the designers haven't thought of a good name for a rubber part, they call it a boot."

Until recently, SHM machined molds with two different vertical machining centers (VMCs). One was an 18 year-old Bridgeport that Latragna decided to sell because the machine had seen its best years and he needed more capacity, tighter accuracy and repeatability, and greater spindle power.

During his search, Latragna came across a GBI/Feeler VM32SA that can take full hp cuts in die steel with ceramic inserts without vibrating or shaking. This VMC uses a mechanically counterbalanced head - ideal for SHM’s operation in the Lake Tahoe area, where the mountains create a great source of deafening thunderstorms and power anomalies that tend to briefly interrupt the plant’s electrical supply.

The Bridgeport VMC Latragna sold also had a counterbalanced head, but his other VMC has no counterbalanced head. Consequently, he would scrap a part every time there was a power interruption. Latragna looked into getting an uninterruptible power supply for the other VMC because they were relying so heavily upon it. "I used it for all my 3D work and a lot of untended overnight machining," he says. "We might get a little blip in our power - not much, just enough for the lights to flicker - and boom! We've scrapped a part and broken tooling. When you only make one part, and it's one heck of an expensive part, that's a 100 percent scrap rate."

If a power outage occurs now, the new VM32SA just stops cutting and the head doesn't drop. No scrapped part. No broken tool.

A large drill uses fairly low speeds. As servo speed goes down, the torque drops off without the use of a gearbox. Though Feeler tremendously improved the torque on drilling without a gearbox, Latragna was concerned about linear guide ways from a dampening point of view. The VM32SA Series uses box ways on the Z-axis with linear guides on X and Y axes, which he feels is a good compromise.

The other VMC has all linear guides and can't hold a candle to the milling performed by the Feeler. For drilling, Latragna feels they might be equivalent. But when milling, the linear guide VMC shakes and rattles. "The Z-axis box way dampens vibration for steel cutting machines, whereas linear guides don't," explains Latragna.

He doesn't feel rigidity is the real issue regarding vibration dampening characteristics. "A number of things can cause chatter. Sometimes it might be similar to positive feedback in an oscillator circuit. It tends to run away and the chattering gets worse. The oil between the box way and the sliding members dampens that out entirely," he says.