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6/1/1999 | 4 MINUTE READ

Rotating & Shuttling Molds Speed EPS Molding With Inserts

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Expandable polystyrene bead molding equipment has taken on a new look in order to keep up with the need for faster insert molding. Machine builders say insulated concrete forms (ICFs) are one of the fastest growing EPS applications in North America. EPS shapes act as the forms into which concrete building foundations are poured. Plastic inserts act as spacers to hold apart the two sides of the form. After the concrete sets, the wall is now thermally insulated by the EPS, which is held in place by the inserts.

To keep pace with burgeoning demand in this application, molders need some way to load the plastic inserts into the machine and steam parts at the same time. For safety's sake molders want to load inserts outside the press area. One novel approach to meeting this challenge is a rotary steam chamber. Another approach uses a horizontal shuttle.

In a handful of other recent EPS machinery developments, increasing sophistication is evident in the prominence of computer controls on new pre-expanders, block molders, and foam cutters.

New spin on insert molding

The most novel solution to the insert-molding challenge is a rotary-style molding machine--the first of its kind for EPS--from Kurtz GmbH of Germany. The K138R machine was developed specifically for the concrete-form market, says Ron Watkins, eastern region sales manager for Kurtz North America, Plymouth, Wis. The first unit has been in production since late February at PSC Moulding in Ajax, Ont.

As shown in the schematic above, the K138R has a three-position turntable that rotates 90° in either direction. The operator (or a robot) places a set of inserts on the loading device (in the 6:00 position as seen from above) while parts are being molded in the 3:00 position. Next, the turntable rotates the loader into the molding station. The loader indexes up and down in order to deposit the inserts onto the male mold mounted on the normal moving platen. At the same time, parts are unloaded from the female mold half in the demold station (12:00 position). The turntable rotates 90° back to the starting position, and the mold closes to begin the next cycle.

The 138R molds two standard 9- to 11-in.-wide forms per 95-sec cycle. A larger model, 1410R, molds three standard forms on the same cycle, reportedly making it the most productive machine for this application. Kurtz expects rotary machines to be used also for EPP.

Another way of loading inserts without delaying the cycle is an adaptation of the shuttle system introduced a few years ago by Hirsch Maschinenbau of Austria. The Vacutrans HS 1300 AV1-B machine has a transfer plate onto which inserts are placed outside the machine. When the mold opens, the female mold half with the finished parts shuttles to one side of the press for demolding while the transfer plate moves into the press to deposit the inserts onto the male mold half. Then the shuttle reverses direction to start the next cycle. Concrete forms containing up to 24 inserts have been molded in a total cycle of 70-90 sec. With a conventional press, loading inserts, molding, and demolding parts would take 4-5 min, says Mark Clark, president of the new Hirsch USA division in Peachtree City, Ga. He notes that Hirsch has over a dozen North American users of shuttle machines for ICF molding.

The Hirsch shuttle machine is also suitable for a different sort of insert molding--i.e., with "skin" films. Kurtz's Watkins says skin molding of fabric onto EPP will see big growth in the U.S. during the next two years, particularly for molding automotive headliners and other interior trim. Kurtz offers both standard and shuttle machines for skin molding, but Watkins urges molders to consider the new rotary models for this use, too.

Lots new in pre-expanders

Increasing sophistication in pre-expanders is evident in the new Windows-based computer control from Hirsch. This Visual Control option for the company's Preex 6000 central pre-expander is a PC that graphically displays a process diagram with parameters like temperature, pressure, and valve status shown at the appropriate location. Other displays include set-up recipes, production data, and process trends for variables like steam time, pressure, and density (minimum and maximum specification limits, actual values, and averages). These data can be downloaded to standard spreadsheet packages for quality analysis and troubleshooting. The Visual Control PC can also be used for remote process control.

PC control is also featured on the first pre-expander introduced by Nuova Idropress of Italy, represented here by V&L Engineering Co., Portland, Ind. This batch-type unit is said to be unique in having a truncated cone bottom. It is said to give shorter cycle, more uniform beads, and very low densities (0.6-0.7 pcf in one pass). Cycles are speeded by better and faster emptying (in 10 sec) so that cleanout is said to be unnecessary. More uniform expansion reportedly results from the conical shape, which directs less steam to the bottom than to the top of the unit.

What's new in block molders

Hirsch has expanded from shape molding into block molding with two acquisitions in 1998--Moldex-Wieser of Austria (now Hirsch Wieser) and Berndorf of Italy (now Hirsch Italia). New developments in block molds from Hirsch include a horizontal machine that opens from the bottom rather than the side or end. This allows the block to drop down onto rollers for easier unloading.

Also new are the Monolith V and Powerblock vertical machines from Hirsch Italia. New Windows-based Visual Control system with Quality Management software is standard.

Computers aid foam cutting

The new multi-axis contour cutter from Hirsch Wieser (formerly Moldex-Wieser) has a Windows-based PC for graphical set-up of programs for cutting very complex shapes. Animated displays let you preview the hot-wire cutting movements. The computer can import AutoCAD files or graphic files in standard formats.

Designed for cutting foundry forms with draft angles, the new machine has up to 20 wires manipulated by two independently movable posts. With two to four axes of motion, it can skew, taper, and rotate all at once. It can make a transition from a square block into a seven-sided polygon, for example, and it can perform in one cut what would require four cuts from a conventional profiler. Depending on the number of axes, price runs from $40,000 to $160,000 with software.