ShipShape rotomolded containers withstand the tender mercies of fork lift operators. They are sized to maximize use of space in boxcars to meet bulk shipping needs. This container is from Meese Orbitron Dunne Co. (Ashtabula, OH).
Rotational molding, or rotomolding as it is commonly known, draws businessmen into the fold with its relative lack of complexity as compared to some other plastics processes. Neither the equipment nor the parts it produces are typically held to the same degree of precision as in injection molding, for example. Yet the market for rotomolded parts is very competitive and it takes both good technical and business skills to thrive in the current environment. Several examples illustrate how rotomolders go about meeting today?s competitive challenges.
Enviro Plastics (Fort Worth, TX) is a privately held company operating under the leadership of Ed Washburn, president. Its primary products are construction components such as sewer lines, and cabinets for air purifiers. Washburn has been in the business for 14 years, and was previously with Essex Environmental (Hirst, TX). Following his time at Essex, Washburn intended to retire, but was persuaded by prospective customers to set up another operation.
He formerly produced a hazardous-waste drum and a portable toilet, but no longer makes those particular products. Enviro is a 100% custom molder, which is to say that they maintain no proprietary products in their portfolio. The customer builds and pays for the molds and Enviro runs them. As is also typical, the molds are of cast aluminum or fabricated sheet metal. His products mostly use 35 mesh PE powder.
Washburn is trying to diversify the markets he serves. One specialty is gas tanks for classic cars. The customer is usually a supplier or distributor of the spare parts rather than the car collectors themselves. Quantities are normally in the range of about 20, which works well for rotomolding, but would not be economically feasible for blowmolding, for example.
Enviro has one machine now, with a second machine on the way for a relatively high-quantity tote-bin order. Gas heat is used to boost oven temperature to 575°F, which Washburn says he can maintain to within about ±5 deg F by controlling the burner.
Half of one arm?s capacity on the new machine will be dedicated to tote bins. Many 100-parts/month orders have been picked up in the last six months. The new machine will be almost fully utilized when it gets on the floor. There is no mold shop maintained at Enviro, yet it has over 100 active customer molds and adds a new mold about every three weeks.
Savvy Custom Moldmaker Aids Rotomolder
Behlen Mfg. (Columbus, NE) exemplifies the proprietary approach to rotomolding. It has not excluded custom work entirely, but is largely devoted to making products for its own line of agricultural equipment.
Dave Slusarski, manager, points out that the business is very price competitive. Various factors are involved. ?The machine runs at a fixed pace, and you are stuck with that.? Raw material prices are going up. Customer education is an ongoing need, especially to reinforce the necessity to compare apples with apples when evaluating prices.
Slusarski says, ?The mold manufacturer works with us to get the advantage of technology that has evolved over the last five or six years.?
Behlen has three plants, two of them devoted to rotomolding. Those two plants are primarily used for making water tanks for use with horses and cattle. The tanks vary from 9-ft diameter and 3-ft deep to a smaller 2- by 1-ft length and width with a depth of 1 ft. Notwithstanding the size of these products, Behlen maintains some inventory. The product is shipped all over the country.
It is important that these tanks not leak, and that is within Behlen?s control. It is the ranchers? problem to get the livestock and horses to the tank and get them to drink.
Behlen uses powdered PE material, and has two rotomolding machines?standard Ferry Industries (Stow, OH) Model 330s. About 50 employees are devoted to rotomolding out of a total employee count of about 1500. The plants run three shifts, five days a week.
Material Prices Pose a Challenge
Rotational Molding Technologies Inc. (Romotech), which operates out of New Paris, IN, does both custom and proprietary work, and is privately held. It serves marine, automotive, agricultural, truck/bus, security, construction, and dunnage markets. It uses cross-linked PE and also LDPE. Machine capability is provided by three standard Ferry independent arm versions, Models 280, 330, and 400. Sixty employees keep the operation going 24 hours a day, five days a week, plus two Saturdays per month.
The business is not without its frustrations. Dave Smith, president, identifies as a technical challenge the fact that the materials available are not always suitable to the needs and/or expectations of the product.
On the business side, he says that the ?extreme runup of resin pricing has dampened the recovery from the 2002 slow-down.? In addition, he says that ?resin pricing is a crime, the vendors know we have no options and are clearly gouging: they just might kill this industry, but clearly do not care as we represent 1% of capacity in monomers."
Inhouse Mold Service Appeals to Customers
Rhino Inc. (Maple Lake, MN) is privately held and does both custom and proprietary rotomolding under the supervision of Joel D. Carson, general manager. The operation distinguishes itself by having a custom fabrication and repair shop that provides a full-service function for the manufacture, maintenance, and repair of steel and aluminum molds.
A significant challenge is to handle the recent fluctuations/upward trend in PE pricing while servicing a market sector that mandates firm fixed-price contracts for a year at a time to cover an annual catalog season.
Carson says that roughly 50% of Rhino?s rotomolding is for its proprietary product line of outdoor equipment, including sleds, portable ice houses, trailers, ATV and travel boxes, duck boats, kayaks, dock wheels and bumpers, dock locker boxes, and water rafts.
Primary custom molding markets include industrial floor cleaners; fuel, chemical, and water holding tanks; kayaks, floating docks, playground equipment, storage containers, and numerous other industrial and commercial products.
Rhino primarily uses powdered noncross-linkable PE, but also some cross-linked PE, vinyl, and ECTFE. It also does two-shot foaming. Rhino?s stable of machinery includes six standard carousel machines from Ferry Industries and a shuttle machine from STP. The Ferry?s are Models 330, 370, 400, 430, and 550. The STP is a Model 100.
Rhino has 80 employees, including office, assembly, sales, and management personnel, as well as rotomolding machine operators. The first shift runs Monday through Friday, 7 a.m. to 3 p.m., and the second shift runs Monday through Thursday, 3 p.m. to 1 a.m.
Additives Provide Antistatic Properties
In a recent development on the materials side for rotomolding, Teknor Color Co. (Lodi, OH) has introduced two advances in its proprietary H2Stat antistatic technology for rotational molding. The H2Stat additive imparts permanent antistatic properties in rotationally molded parts and ends pigment swirl in granite colors.
Typical antistats for rotational molding work by migrating to the surface of the part and attracting moisture, which serves as a conductor. This migration eventually results in a decrease in the level of antistat in the part. But H2Stat is inherently conductive and does not migrate from the part.
The H2Stat product is added at the rate of around 30g per 45 kg of resin, or less than .01% loadings; but for end-product antistatic use, loadings can range up to 450g per 45 lb, or 1%, with the loading dependent on the specific nature of the application.
Several examples illustrate applications of the product. H2Stat prevents sparking that can occur in routine handling of molded parts, and discharges that can disrupt or damage electronics. One molder is using H2Stat in the rotationally molded body of carts used in hospital operating rooms where oxygen is administered.
Another molder is studying the potential of the additive for use in products involving the handling of gasoline.
In addition, a molder is using H2Stat to prevent the buildup of particles on statically charged white rotomolded boats during prolonged warehousing or storage in retail outlets.
Assn. of Rotational Molders International
Rotational Molding Div., Society of Plastics Engineers