Problem: An injection mold wasn’t cooling properly, resulting in defective parts.
Solution: An inexpensive vortex tube attached to the exterior of the mold provided additional cooling, resulting in on-spec parts.
Novation Industries, a privately owned injection molding company in McHenry, Ill., was having difficulty with a mold used to manufacture parts for an industrial customer. The 30-year-old mold was originally constructed as a prototype but ramped up into production support use over the years.
The initial design did not include water circuitry cooling, which caused inconsistent molding process control and a growing scrap rate.
Modifying the mold so that water could be used to cool it would have cost thousands of dollars, which the customer and Novation were not willing to pay. Novation manufactured other parts for this customer that were not as problematic and did not want to risk the customer’s continued business satisfaction.
Instead, Novation purchased two vortex tubes from Vortec, a Cincinnati manufacturer of compressed air products. The tubes are mounted outside the mold. Using only a compressed air line, they blast cold air at specific portions of the mold to cool down large core sections when the mold is open. The air is forced through a chamber, which spins it at a high speed — up to 1 million rpm — into a vortex. The air heats up as it spins along the inner walls of the tube toward a control valve, where hot air exits.
The remainder of the now-slower stream of air is forced to counter flow up through the center of the high-speed air stream into a second vortex. This slower-moving air gives off energy and cools as it spins up the tube. The chilled air passes through the center of the chamber and exits the tube at a very low temperature.
Vortex tubes require no electrical connection or water. The tube lengths range in size from 6 inches to 13 inches, making them easy to work with. They have no moveable parts and use no refrigerants or chemicals. They cool quickly and produce up to 6,000 Btus per hour of refrigeration and temperatures as low as minus 40 degrees Fahrenheit, according to Vortec. Cooling is adjusted via an air pressure regulator on the hot end of the vortex tube.
“We have reduced our scrap by 23 percent with the cooling tubes,” said Bill Etten, Novation’s director of manufacturing. “Without the cooling tubes, this molded process did not offer consistent yield or targeted rate. Excessive heat during cycle would sporadically exhibit parts with sinks and deformations, which could negatively impact final assembly and functional end use.”
He said the plant, which operates 34 injection molding machines from several manufacturers and has 100 employees, needs to use the vortex tubes on only three molds, which account for a very small percentage of the plant’s business. But using the tubes solved a challenging production problem, improved cycle times, reduced scrap and kept a valued customer happy.
“We only need to use the tube when we make certain industrial parts that are large and have thick walls,” Etten said. “The geometry of the part does not allow for adequate cooling in the mold. The cold air from the tube helps cure the part in the mold.”
The two Vortec 308-35-H vortex tubes cost $500, the company said. Two magnetic bases used to secure the tubes to the molds cost $150 for a total investment of only $650.
“The alternative was to perform major tool revision and cooling channels inside the mold, which would have cost $7,000 for each mold,” Etten said. “The customer was not willing to pay that level of cost and we didn’t want to push back on the business. We needed to identify an alternate solution.”
The vortex tubes and magnetic bases are simple to use, he said. During job setup, the bases allow technicians the flexibility to position the vortex tubes where cold air is needed. The magnets also saved the cost of fabricating mounting brackets and the difficulty of positioning those brackets on the mold. Further, they allowed Novation to use the tubes on other molds.
In addition to industrial parts, Novation makes parts for the automotive and medical industries.
Bruce Adams, senior staff reporter
Contact:
Novation Industries
McHenry, Ill., 855-279-7508, www.novationindustries.com
