Rotomolders seek advanced technology.

"Rotational molders are looking to grow and evolve, and they are looking at evolving technology to help them get there," said one of the record 587 participants at the recent 20th annual fall conference in Dallas of the Association of Rotational Molders (ARM). For example, new sophistication is coming to rotomolding part and tool design through the use of 3-D solid-modeling programs, CNC machining, and rapid-prototyping technologies such as laminated-object manufacturing (LOM), says Terry Zwart, tooling engineer at Lakeland Mold Co., Brainerd, Minn. These tools help designers find problems faster and earlier, while making design changes easier.

Other innovations presently in development or limited use were discussed by Harry Covington, president of Ferry Industries Inc., Stow, Ohio; Glenn Beall, president of Glenn Beall Plastics Ltd., Libertyville, Ill.; and Sandy Scaccia, v.p. of operations at Kelch Corp., Cedarburg, Wis. They see these developments on the horizon:

* Automated mold filling and part ejection.

* Mold heating with infrared, microwave, or induction energy.

* Direct heating/cooling of molds via delivery of heat-transfer fluids through the arm of the machine. (Faster cycle times could result, while eliminating the need for an oven.)

* Internally pressurizing parts in the mold with gas fed through lines in the spider arm. (Benefits would be fewer air bubbles in the resin, less part warpage, and better cooling through improved heat transfer from the mold.)

NEW MACHINES & TOOLING

Several new pieces of hardware introduced at the meeting are available now:

S.T.P. Equipement Inc., Sherbrooke, Que., developed a linear dual-arm shuttle machine that allows the operator to shut down one arm for mold changes while the other arm continues to operate. It's an industry first, says S.T.P. president Jacques St.-Pierre. The ZS series uses PLC controls that can be interfaced with a PC. ZS models with straight or offset arms have 80-120 in. arm swing.

S.T.P. also has a new PC-based control system for its B-series "rock-and-roll" machines, called Mold Reading System (MRS). It reportedly allows for precise programming of rotation, mold angle, speed, time, and temperature - using an infrared sensor focused on the mold surface.

A new retrofittable clamp-release device called the Heads-Up system reportedly takes the guesswork and danger out of mold changing. Wheeler Boyce Co., Stow, Ohio, designed the system with a J-hook and mounted spring that guarantees bolt release and establishes a clearance between bolt and receiver that an operator can see clearly.

Wheeler Boyce and Kelch introduced new mold-venting devices that relieve mold pressure without losing resin powder. Wheeler Boyce uses a baffle, while Kelch offers a pressure-activated rod-in-tube system.

NEW RESINS, PROCESS AIDS

Mobil Polymers, Edison, N.J., introduced HRA-045, an HDPE that has higher melt index (7 g/10 min) and higher density (0.952 g/cc) than the company's previous rotomolding resins. This hexene copolymer is stiffer than Mobil's other grades.

A polyethylene aerosol spray that eliminates pinholes and surface porosity in parts was introduced by Mold In Graphics Systems, Clarksdale, Surface Enhancer is sprayed into the empty mold. Custom pigments or uv stabilizers can be added.

A non-permanent, water-based PTFE mold release for high-temperature use is new from TRA Coatings Corp., Cortland, Ohio. the new coating (#715) is said to be 30% less expensive than standard water- or solvent-based coatings.