Appliance Design - August 2008 - (Page 22)

PLASTICS 1. 2. 3. Injection phase 4. Water injection Injection phase 1. Water injection 2. Water holding time 3. Water reverse flow 4. Full-shot water-assist injection 4. molding 3. Injection phase Water holding time Water injection Water reverse flow Water holding time Water reverse flow Water-assist injection molding with the melt push-back method. Engineering Polymers, Wilmington, Del., have developed materials designed specifically for water-assist molding. The resins are made to create a smoother interior surface. Previously, non-modified resins could leave problems such as foaming and voids. Smoothness of the interior wall is an issue when the part is used to move fluids. If it does, these flaws could slow the fluid flow rates, or glass fibers and other materials may break loose and enter the fluid stream, says Rob Palmer, a marketing manager with DuPont. At BASF’s R&D center, which is located in a separate facility in Budd Lake, N.J., researchers use water-assist and gas-assist equipment from Cinpres Gas Injection Ltd, which is based in the U.K. BASF has a joint working relationship with Cinpres to develop applications and implement water-assist technology. At the facility, they have a 400-ton clamp injection molder from Engel as well as Cinpres’ waterand gas-assist pumps equipment. Germany-based PME Fluidtec and Cinpres led the way to develop the equipment and processes for water-assist injection molding. Today, a number of other equipment manufacturers provide capability for this technology including the Austrian supplier Engel, and German companies Battenfeld, Ferromatik Milacron, and Maximator. PME Fluidtec is considered one of the world’s most experienced makers of water-assist molding equipment with more than 50 applications around the world that are producing millions 22 applianceDESIGN August 2008 of parts. Some non-automotive applications from PME Fluidtec include a Bosch refrigerator handle made from 30 percent glass filled nylon 6 at a cycle time of 34 seconds, and a chain-saw handle from Sachs Dolmar that also used a 30-percent glass filled nylon 6 and had a 45-second cycle time. In many ways, WAIM is much like gas-assist technology, and the previous two applications could have been made with that technology, but with slower mold cycle times. In fact, gasassist and water-assist are sometimes used in tandem and equipment suppliers are working 300 290 280 270 260 250 240 230 220 210 200 0 15 30 to combine gas and water capabilities into one machine. WAIM experts say that if a company is going to use the water-assist method, then they should also be able to do gas-assist. In general, they both reduce material costs, cycle times, and the number of parts needed (as different functional features can be molded into a single piece, reducing the number of parts that need to be assembled). Both technologies use a fluid, water in one and nitrogen gas in the other. In either case, the fluid is injected into a resin-filled mold and the oncoming fluid displaces the resin, coring out Gas Injection - 67 sec. Cycle Water Injection - 38 sec. Cycle Gas / Water Hybrid - 38 sec. Cycle Gas / Water Hybrid - 50 sec. Cycle 45 60 Measurement Time (Sec. - Post Ejection) Parts molded with water assist methods do not undergo a post molding temperature increase as do parts made with only gas-assist methods, according to BASF studies. www.applianceDESIGN.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - August 2008

Appliance Design - August 2008 Contents Editorial Shipments/Forecasts News Watch Plastics Switches Noise & Vibration Control Joining New Products Design Marts Association Report: CEA Advertiser’s Index

Appliance Design - August 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.