Automation & 'ovenless' molding highlight rotomolding expo.

A new automated mold- and material-handling device, a quick-mold-change system, and two "ovenless" machine concepts were just a few attractions of the world's largest exhibition dedicated to rotomolding, held recently in Oak Brook, Ill. As part of the 22nd annual fall meeting of the Association of Rotational Molders (ARM), Rotoplas '97 also displayed new decorating and fastener technologies, new materials, and the first water-based mold release for high-temperature applications.

Seventy-four booths were visited by more than 1500 people during the one-day exhibition, which was 50% larger than the only other Rotoplas show, held in 1994. Other special events at the ARM meeting were the roto-molded parts competition and the naming of the first five inductees to ARM's Hall of Fame.

NEXT GENERATION MOLDS

A new mold-clamping mechanism for quick mold change, and "ovenless" internal mold heating and cooling were two new concepts on display from Kelch Corp., Aluminum Molds Div., Cedarburg, Wis. The new spider-mounted quick-change system eliminates clamps or bolts, which spares worker exposure to repetitive stress injuries ("carpal-tunnel syndrome"). A hand-held hydraulic clamp locks the top mold half onto springs mounted on the bottom mold half. The springs generate the required clamping force, eliminating the need for bolts or other locking devices. A rack-and-pinion system acts as a positive safety lock on the mold.

Kelch has also built an experimental "ovenless" aluminum mold with cast-in stainless-steel heating and cooling channels. The mold is zoned into 10 individually controlled heating/cooling sections. Air temperature is measured inside the mold to permit automatic closed-loop control, says general manager Sandy Scaccia. In a lab test, the small-container mold produced a good part on the first try, Scaccia reports.

Another approach to ovenless, internally heated and cooled molds was unveiled last year by Wytkin Design of Australia (see PT, Dec. '96, p. 24). Its Composite Mold Technology (CMT) is an epoxy, glass, and ceramic composition that is now offered in the U.S. exclusively by Chroma Corp., McHenry, Ill. The technology allows you to charge individual cavities in the mold up to four times during a cycle and provides individual heat/cool control of each cavity. CMT provides 92% heating efficiency versus 5% with a typical oven, says company owner Andrew Wytkin. Chroma has a Wytkin machine in its new 20,000-sq-ft technical center for rotomolding R&D.

TIME & LABOR SAVERS

Canadian rotomolding equipment supplier FSP Machinery Co., which has a new office in Akron, Ohio, introduced the Roboy, an automated material- and mold-handling system for its M-series single-station clamshell machines. Roboy is currently designed with a charge box for slush molding applications but is being adapted for standard rotomolding. It automatically opens, closes, loads, and unloads the mold using a cam-actuated device with an AC variable-frequency drive that is integrated into the rotomolding machine's controls. Roboy adds 25% or more to the cost of the machine.

A 20% reduction in cooling time and increased dimensional stability of parts are claimed for a new two-stage cooling system designed by Ferry Industries Inc., Stow, Ohio. Shown on Ferry's RS1-120 swing-arm machine, the new system has a fan that delivers high-velocity air through tubes positioned on the wall of the cooling station. Water-spray nozzles on the floor and in the air tubes on the wall spray a mist into the chamber, which provides the second stage of cooling.

A new way to record process data for each part for quality-assurance records was unveiled by Ferry. The company linked its Rotocure control with new infrared thermometry (IRT), jointly developed by Ferry and Remcon Plastics Inc., Reading, Pa. (see PT, June '97, p.27). IRT continuously monitors mold temperature and records the time it takes the mold to reach a desired temperature. Ferry's Rotocure system uses the results for subsequent moldings as a benchmark parameter to set the molding cycle. The actual times and temperatures recorded by the IRT for each molding cycle - along with the date, time, machine, mold number, cavity, part number, and part description - are printed on a barcode label that is attached to the part.

In addition, Ferry gained exclusive rights from an undisclosed domestic maker of routers to market a five-axis, moving-table CNC router to rotomolders. The router has a standard eight-station tool changer (16 stations optional) and maximum feed rates of 1000 in./min., which is said to be faster than competitive machines. The 7.5-hp spindle runs at 2000-25,000 rpm. Standard bridge clearance is 30 in. (up to 42 in. optional). The unit is available with one or two 60 x 60 in. tables.

OTHER NEW DEVICES

High output pulverizing with ease of operation are the benefits of the largest pulverizing system to date from Reduction Engineering Inc., Kent, Ohio. The new model 600 grinds 27503250 lb/hr to -20 mesh size and 22002600 lb/hr to -35 mesh.

A new post-molding insert can be installed blind into a drilled hole with a lightweight torque tool. New AR series fastener from AVK Industrial Products, Valencia, Calif., is said to provide exceptional pull-out strength. It has special outside slots that are designed to collapse while the bulb remains intact. Once the fastener is inserted into the hole, the tool rotation is reversed to a counterbore direction, causing the slotted insert body to collapse and fold into symmetrical segments that grip the plastic firmly. Fasteners for different part thicknesses are available.

ECO-FRIENDLY RELEASES

One of the first water-based release coatings for high-temperature or open-flame rotomolding is available from TRA Coatings Corp., Cortland, Ohio. Its new solvent-free TRA #500 release coating withstands processing at 500-700 F. The coating release replaces solvent-based TRA 504HT release and reportedly gives consistent release with no mold build-up. It's made with a fluorochemical agent, which provides lubricity and durability without the use of silicone oils.

Two more new water-based, semipermanent releases come from Chem-Trend Inc., Howell, Mich. Mono-Coat 1026W is for cast aluminum, while Mono-Coat 1001W is for both stainless steel and aluminum. Both grades offer high-temperature stability and multiple releases of LLDPE or XLPE parts with virtually no transfer, the company says.

Meanwhile, Stonekote 6000, a new solvent-based mold release from E.L. Stone Co., Barberton, Ohio, reportedly offers nearly the same fast-release and high-gloss properties as Stonekote 7000 but at lower cost. The new release can be applied to cast aluminum or stainless steel.

RUB-ON GRAPHICS

Preprinted graphics or decals can be simply robbed onto polyolefin parts with the new Mold On Graphics direct-transfer method from Mold In Graphics Systems, Clarkdale, Ariz. A proprietary chemical adhesive is first sprayed on the part, and then the polymer graphic is placed on the part and transferred manually by rubbing the transfer paper with a special pad. Finally, a hot-air gun is used to melt the part surface, which causes the graphic to thermally fuse with the product. The result is a permanent decal that is reportedly impervious to chemicals and light.

Heat-transfer equipment, sprays, or other devices are not needed with a new ink-transfer system from Mark-it Co., Batavia, Ill., that forms a seamless, permanent bond with any substrate, including ABS and XLPE. The new Post-Mold Graphics system has two coating layers, one that fuses with the substrate, and the other which provides resistance to peeling, scratching, uv, salt water, and temperature extremes. The graphic is precut and then applied manually with a squeegee-type applicator. The release paper is peeled back and the transfer fuses to the substrate immediately, leaving no edges.

NEW RESINS DO MORE

Two new grades of hexene-based HDPE rotomolding powders that boast excellent impact strength, ESCR, and stiffness were introduced by Millennium Petrochemicals Inc., Cincinnati. They replace several butene-based HDPEs and have new uv-stabilizer and antioxidant packages. Microthene MP 655-662 (0.945 g/cc, 5 MI) has a 1% secant flexural modulus of 135,000 psi, tensile strength at yield of 3000 psi, and impact strength of 53 if-lb at-40 F (1/8 in., ARM test). Microthene MP 658-662 (0.948 g/cc, 8 MI) shows a flex modulus of 145,000 psi, tensile strength of 3280 psi, and impact of 45 ft-lb at 40 F. The new materials reportedly meet FDA specs for food contact. They are also offered in pellet form as Petrothene GA 655-662 and GA 658-662.

A developmental polyolefin plastomer (POP) from Dow Plastics, Midland, Mich., is said to have the highest modulus on the market without sacrificing impact strength. Low warpage and good processing are also claimed for DSQ 1504, which has a 3.5 MI and 0.949 density. Flex modulus is 167,000 psi and dart impact at -40 F is 52 ft-lb for a 1/8-in. sample.

Dow also has an experimental metallocene LLDPE, XUS 59900.29.L, that is said to have good flow and impact properties. The 0.935-g/cc resin has a 15 MI and 1% secant modulus of 95,265 psi for a rotomolded sample.

Elf Atochem North America Inc., Philadelphia, has replaced its nylon 12 rotomolding powder with a nylon 11 version, which is said to provide improved impact and tensile strengths. New Rilsan BRN P10 Roto 11 Blk Tld is aimed at fuel tanks and containers. Preliminary data show impact strength greater than 125 ft-lb at 1/8 in. and 73 F, which compares with 30 ft-lb for the nylon 12 product. At -40 F, impact strength is 37 ft-lb. Tensile strength is 5800 psi at yield and 7300 psi at break in preliminary tests. Resin modifications reportedly enhance its flow for better insert coverage, and the material can readily produce molded-in threads, unlike the nylon 12 version.

Foama-Spheres, a foamable compound for rotomolders, is now available for making lower densities. Chroma Corp., McHenry, Ill., has added grades for making foam densities of 18, 14, 10, and 7 pcf to its line, which initially had a 30-pcf product.