Although dip coating has been around for decades, many OEMs are unaware of the full scope of its capabilities-and possibilities.
Dip coating defines any process where a part is dipped into a polymer, such as Plastisol, for applying a coating directly onto the product. The process is known to deliver non-slip cushioned gripping surfaces to products, protect against abrasion and corrosion, provide electrical insulation and enhance a product’s appearance for sales appeal. The most identifiable application of dip coating is for the grips on many hardware store tools. But it has also been used for products as varied as toys and fitness equipment to outdoor furniture and municipal bike racks.
However, many OEMs may not fully understand the variety of products that can benefit from the process. Dip coating can be used to deliver just about any coating color imaginable and a variety of hardness profiles from relatively soft to hard, along with properties such as temperature resistance, static dissipation and UV protection.
Now comes news that some dip coating manufacturers have expanded their operations to dip coat not just small parts, but products as large as 55 x 55 x 8 inches.
The Dip Coating ProcessIn the dip coating process, parts are typically arranged on a handling rack and then lowered into a tank of Plastisol. After being dipped for a specified time, the coated substrates or parts are then cured in large ovens, dip-quenched and removed from the holding frame.
Plastisol heads the list of dip moldable materials because of its long history of success, ease of processing, affordability and prevalence in the industry. Plastisol is liquid at room temperature and once exposed to a certain elevated temperature, gels and remains a solid. This polymer can range in hardness from 33 (softest) to 96 (hardest) Shore A scale durometer.
Plastisol is also available to match color, hardness, finish and properties including high and low temperature resistance, static dissipation and UV protection. Although Plastisol is the most common dip coating material, latex, neoprene, urethane and other materials can be used instead.
Dip Coating Large Bike RacksDoug Devine, owner and general manager of Sunshine U-LOK Corp., was well acquainted with all the practical advantages of dip coating when he met for the first time with Molded Devices Inc. (MDI). Devine had been searching nearly 20 years for a company that could handle the kind of volume and quality required to service cities and colleges with his company’s 5-foot-long dip coated bicycle racks.
In the summer of 2011, Devine’s son and Sunshine U-LOK manager, Christian, discovered MDI through the Internet. Molded Devices was founded in 1963 and currently offers dip coating and molding, fluidized bed powder coating, and custom injection molding in several facilities throughout the United States. “I told MDI that we were looking for additional capability to build larger inventories,” explains Devine. “They immediately expressed an interest, even though at the time it meant investing in constructing tanks and ovens large enough to do the work.”
As a result of this relationship, MDI expanded its production area and is currently one of the only dip coating manufacturers in the United States that can coat parts as large as 55 x 55 x 8 inches. Size was not the only issue, however. Devine wanted more color choices that might complement municipal, corporate and campus architectural designs. Basic gray or black was not aesthetically pleasing in every environment.
According to Devine, MDI ran a dozen color samples and he ultimately selected six. “In the past, many customers would ask for specific colors, so we anticipate this will bring us more business.”
Once they received their first shipment of dip-coated bike racks in September of 2011, Sunshine U-LOK Corp. quickly increased its inventory, and sales have been brisk. The productivity upgrade is due in part to MDI’s ability to hold to schedule and meet deadlines.
“They bent over backwards to support our vision,” explains Devine. “Their professionalism and quality control has been very impressive. Today, we have ten times the product we had before and the quality and look of our bike racks is so much better.”
Customers are happy, too. Last year the city of Santa Monica, CA, acquired 500 bike racks in a variety of styles-the largest number Sunshine U-LOK ever installed in an American municipality. In the past, city maintenance workers would have to re-paint the traditional steel, powder-coated bike racks three or four times a year. Now, the crew simply wipes down the Sunshine U-LOK dip-coated racks with a cotton cloth and cleaning fluid. Devine is so confident in dip coating that Sunshine U-LOK offers its customers a ten year guarantee on the finish of its bike racks.
Wheelchair PushrimsDip coating is also being used by Spinergy, a company that designs, manufactures and markets aerodynamic wheels for road, triathlon and mountain bikes. The company also makes high performance wheels for wheelchairs. The construction of a wheelchair wheel involves a pushrim, an outer ring used by the operator to turn the wheels without having to put their hands directly on the tire.
According to Henry Mathers, CFO of Spinergy, there are many variations of pushrim design within the industry. Most wheels are offered with an aluminum pushrim, but for those individuals that need a little more grip they offer a vinyl-coated (Plastisol) pushrim. At Spinergy, the pushrim is constructed using an aluminum ring dip that is sent to MDI and dip coated in Plastisol. Spinergy selected Plastisol dip coating because it provided the proper grip for the user without hindering the operation of the wheelchair or irritating the operator’s hands. This was even more critical for those that lack hand strength or have a loss in hand function.
“MDI provides us with a consistent product that does not vary from the original specifications,” says Mathers. “They are able to hold a consistent level of tackiness and durability of material. They also take great care to ensure proper bonding of the vinyl material to the aluminum substrate and have always been very consistent in that regard.” Mathers adds that this was a key requirement because, “if the underlying prep work is not done properly the overall durability of the wheel would be greatly reduced.”
As a full service company, MDI offers more than just dip coating. They also offer support services including assembly, printing and decorating, piercing, slitting, die cutting and packaging. For Spinergy, packaging was important because vinyl-coated pushrims can easily get scuffed or scratched, a factor that doesn’t affect the wheel’s functionality but could affect a customer’s perception of the product.
“When you sell any product to a consumer you want it to look pristine when it comes out of the box, even if five minutes later it won’t look pristine,” explains Mathers. “So MDI developed a method of packaging to ensure there would be no cosmetic damage during transportation or shipping.”
Molded Devices Inc.
West Coast (951) 531-4872
East Coast (203) 755-3741