Simplified stack mold centering

Engineered to simplify the design, production, and maintenance of stack molds?and to help you help your customers speed their products to market?a standardized helical gear (HG) centering device is now available from stock from D-M-E (Madison Heights, MI). Designed to ensure that a stack mold?s parting lines open at the same time and space, shot after shot, D-M-E?s Frank Eigler, senior liaison engineer, and Chuck Azzopardi, product manager of mold components, say their lightweight, compact HG systems offer several advantages over many types of rack-and-gear and harmonic arm centering devices, not the least of which are easier adjustability and zero robot interference.

Built from components originally developed a few years back by D-M-E?s Germany-based operation, the company can supply complete, off-the-shelf systems or, off the same shelf, field-proven system components, which include the following:

? A nylon insert nut.
? Double-sided HG shafts?with lengths cut to size.
? Blank nut housings?lengths cut to size; mounting holes machined.
? Nut housing cap.
? Bearing housing.
? Taper roller bearing.

?D-M-E Normalien marketed these components in Europe for decades. Mainly they were used in unscrewing molds. We saw in them perfect pieces to put together to eliminate extraneous work on the part of our stack mold customers, so they could concentrate more on the molds themselves,? Eigler says.

Off-the-shelf productivity

Azzopardi gives all the credit to the development of the HG centering device to his colleague, Eigler.

?The main components, like the shaft and the gear shaft nuts, have been used for decades. Anyone who built stack molds could buy them off the shelf, but they had to design and assemble all the other components.

?Frank worked around stack tools for decades at Tradesco, now StackTeck, before joining D-M-E a decade ago. He has the design expertise and he talked to stack moldbuilders to get their input on how best to put these well-known design elements together?all off-the-shelf-components?and to make a line of standardized products that make moldmakers? lives a whole lot easier. It?s as easy as buying ejector pins.?

The HG centering device is strong, but it?s lightweight. It?s also designed to be robust. However, humidity, temperature, and contamination can adversely affect the performance of the nylon nuts. Regular greasing can increase their service lives, though the nuts are designed to work in clean environments without external lubrication. You should keep your PM eye on them, though.

?Nylon is weaker than steel and aluminum, but if it breaks, it can easily be replaced, so nothing is lost,? Eigler says. ?It?s like a built-in safety.? The taper rolling bearings do have to be greased regularly, but Eigler and Azzopardi say no other maintenance is required.

An easy entry

In addition to its brochures and manuals, D-M-E also can provide an informative DVD demonstrating the ease of installation, ease of alignment, and operational capabilities of its HG centering systems. Currently, sizes with gear shaft ODs of 28 mm (1000- and 1200-mm-long sizes) and 38 mm (1500 mm long) are available off the shelf. However, at one customer?s request, a unit with a 48-mm spline (2000 mm long) was produced. It reportedly will be made available to the marketplace soon.

Eigler says D-M-E can work with you to package the proper components to accommodate your specific shut height and parting line opening requirements. Azzopardi emphasizes the fact that the systems are built from off-the-shelf components. ?The moldbuilder doesn?t have to spend time reinventing the wheel,? he says.

?We can design the centering systems in-house, if the customer is new to stack molds. We even have similar concept designs we?ll be fine-tuning over the next year or two for rack-and-pinion centering devices. We believe in letting our customers chose what works best in their application.??CK