Wescast Industries Inc. calls itself "the world's largest producer of exhaust manifolds for passenger cars and light trucks," so producing high-quality castings consistently is critical to its business plan. At its operation in Wingham, ON, Wescast designs, casts, machines, and assembles, high-quality engineered iron products for automotive and light truck OEMs and their Tier 1 suppliers in North America and Europe. One way of maintaining product quality is to continually evaluate customers' needs, as well as its own operation.
Recently, Wescast undertook a renovation of its sand-handling systems at Wingham, specifically the area of the plant that's responsible for metering recycled sand, fines, and a bentonite-clay premix for casting sand.
The existing system had been comprised of two production lines using three screw conveyors for each line. These conveyors transferred the recycled sand, fines, and premix into two mullers, and from there the materials were conveyed to a molding area.
The equipment operators of had various problems with inaccurate measurements and materials plugging the conveyors. Also, the system did not have any alarms or alert mechanisms to warn the operators of system failures, which delayed their response time. Ryan Pletch, an electrical projects coordinator for Wescast, commented, "we were seeing accuracies of ±40% using the system with the screw conveyors, and it was forcing us to scrap parts and increase maintenance and production time." Due to these issues the company chose to replace the metering system as one component of its renovation project.
Wescast began evaluating its options for the improvements, starting with a review of feeding equipment manufacturers and suppliers. AccuRate (www.accuratefeeders.com), a product line for Schenk Weighing Systems, sent its local representative, Firing Industries, to meet with the Wescast engineering staff and get an understanding of their needs. Based on conversations with the engineers, Firing brought in a Mechatron loss-in-weight feeder and demonstrated its features.
The Wescast engineers were impressed with the Mechatron feeder's ability to clean, disassemble, and reconfigure from the non-process side. They also recognized how easy it would be to operate and perform routine maintenance on it. Feeling they were getting close to resolving their material metering problem, Wescast scheduled a visit to the AccuRate test lab to confirm the feeder's accuracies using their materials.
The results of the testing proved the Mechatron to be the optimal feeding solution for this application. Because the feeder was able to meet the necessary accuracy and maintenance requirements Wescast chose AccuRate to supply four Mechatron feeders and four DisoCont loss-in-weight controls.
AccuRate aided the installation effort assigning a service technician. According to Pletch, "having the technician onsite gave us the training we needed for operating, maintaining, and troubleshooting our new equipment".
He added, "start-up was simplified by the Easy Serve software of the DisoCont control package, which made control set-up, calibration, and customization a straightforward process."
The four Mechatron feeders and four DisoCont controls were installed near existing sand-supply hoppers as part of two production lines in the renovated sand mixing area. Each production line called for two Mechatron feeders and one sand-supply hopper. One feeder metered the fines and the other a bentonite-clay premix. With accuracies of ±0.25-0.75%, the feeders meter the materials on to a belt conveyor, with sand coming from the sand supply hopper. The feeders are monitored by the DisoCont controls and a Wescast-supplied HMI package that displays alarms, feed rates, material usage, and operating status. All of the materials from the feeders and sand-supply hopper are conveyed to a muller, where water is added through a separate control loop based on the conductivity of the sand. Then, the sand and clay mix is conveyed to the molding area.
Wescast's renovated sand-handling area, including the two process lines with the Mechatron feeders, exceeded the company's "return on investment" goal. According to reports, the cost of the project was recovered in a little over a year.
John Cove, mechanical projects engineer at Wescast, reports that "the accuracies of the Mechatron feeders were critical in exceeding our ROI goal." By replacing equipment that had accuracies of ±40% with the feeding systems supplied by AccuRate, Wescast has been able to reduce maintenance, work stoppages, and production errors, and maintain its production totals of more than 14 million cast exhaust manifolds.
Investment Caster Finds Water Blasting Effective, Productive
Rely Precision Castings, an investment casting operation in South Africa has begun using a water water-blasting technology to remove the shell and clean its castings, a technique that reportedly improves the castings' surface quality and increases the process efficiency.
The company has been in operation over 50 years, using the lost-wax process to produce castings in various commercial alloys.
Gordon Baker, Rely Precision Casting's new business development manager, reports that ceramic shells had been removed from the castings using a pneumatic hammer or shot-blasting process. But, for softer alloys this may not be the best process. "The water-blasting machine runs at about 9,000 psi and the more delicate the job, the less pressure is applied," according to Baker. Also, the newer system is capable of varying the amount of pressure being used on a particular casting. "Water blasting allows cleaning on a localized area much more efficiently," Baker says, "as the jet of water can be directed very accurately to the area where it is needed."
By controlling the water pressure, Rely Precision Castings can apply sufficient pressure to break the chamotte and colloidal silica shell, without damaging the casting. Technical director Carlos Palinhos reports that using water blasting on a line of pump impellers has increased productivity for the foundry.
"Previously, because of the constraints around the shot-blast system, we could only supply 30 impellers a week," Palinhos says. "But, by using the water-blast system, we are now able to supply 100 impellers a week." Cast in a hard chrome-iron alloy, the impellers could not be shot-blast in groups, because the hardness of the castings increased the possibility of them damaging each other. Also, the castings are produced with impeller threading in place, so part definition is important and water blasting preserves the parts' details.
"Investment casting offers a far better surface finish when compared to conventional sand casting, and now, with the water-blasting system, the quality of the finish has been enhanced even further," says Baker.