Premier Manufacturing Company (Tualatin, Oregon) designs and manufactures heavy duty coupling components used for tractor-trailers and construction equipment. In business since 1924, the company produces parts that link trailers to dump trucks and off road construction equipment as well connectors used between double and triple trailers hauled by over the highway trucks. The products include couplings, drawbar eyes, hinge assemblies, dolly jacks and accessories.
The products play a critical role in safety, so strength and reliability are overriding considerations. Accordingly, many of Premier Manufacturing’s products are cast in Permalloy, proprietary alloy steel developed by the company to handle rough, abrasive applications. The alloy’s unique properties cause it to work-harden at contact surfaces and create a tough, wear-resistant outer shell.
Presently, most of the coupling components are sand cast at foundries. Premier sends the foundry actual-size physical models of the parts called patterns. After sand is packed around a pattern to make a mold, the pattern is removed and molten steel is poured into the void to make each part. The cast material is so tough to machine that finish dimensions of the cast components are near net shape, with hand-grinding performed to final finish dimensions.
Many of Premier’s components are being retooled, some of this is due to wear but more often it’s to yield a better part for customer’s needs or more accurate dimensions to improve secondary processing efficiency. Zach McCurter, the company’s mechanical engineer, reverse-engineer’s older parts and creates CAD files for them. During the reverse-engineered process the components are then reviewed and optimized to yield a better modern-day component via FEA analysis and other proprietary processes. Ultimately the new CAD files are passed over to William Gillin the machine shop supervisor for the tool path generation, verification and machining of the tooling. . “This whole retooling process is a very interesting way to spend time. I enjoy it,” Gillin said.
The new patterns are machined from cast iron or a machinable polymer. Many of Premier’s connecting components have free-flowing, 3-D contours, and the patterns must reproduce them exactly. To efficiently machine the complex shapes, Premier recently acquired a five-axis vertical machining center with a dual-axis trunnion table that gives it simultaneous five-axis machining capability.
Before joining Premier, Gillin had experience manufacturing complicated plastic injection molds but hadn’t worked with five-axis machines. “When we bought the new machine I was tasked with learning how to program it and run it,” Gillin said, “working with five-axis programming, post processors and CAD software was a new experience. There were a lot of variables.”
The multiple variables made it “very difficult to zero in on where the problems were coming from,” Gillin said. Some of the difficulties involved a machining simulation program that didn’t work well with Premier’s CAM system and post processor.
“The simulation software set up was not very intuitive,” Gillin said. The complex 3D machining programs for the patterns were large files that required extended verification time. “I’d set the software up to verify the CAM program and that sometimes would take a night and a day to complete. Then I would find out that something wasn’t set quite right, for example a fixture was not in the right zero.” However, the simulation software would not enable modification of the CAM program, so Gillin had to go back to the CAM package, make changes, and again output the program into the verification software.
To resolve the issues, Premier acquired NCSIMUL Machining simulation software, part of the NCSIMUL SOLUTIONS offering of software solutions and services from Spring Technologies (Boston, Mass.). NCSIMUL Machine enables users to simulate, verify, optimize and review machine programs based on the characteristics of the specific parts, tooling, and machine tool involved. Three-dimensional graphics help users avoid machining crashes while complex algorithms and embedded process-based knowledge enable optimization of cutting conditions. Use of the software reduces the time spent on debugging programs, eliminates risk of spindle collision, tool breakage and scrap, and improves cycle times and process efficiencies.
According to Gillin, “NCSIMUL allowed me to really start zeroing in on the issues that I was facing with the simulation software and the post processor. Once you have everything output into NCSIMUL, you can change things around. You can put in a different fixture if you want, you can move your clamps. That’s really valuable.” Because he could manipulate the machining program inside NCSIMUL, Gillin said, “I was able to trust that portion of the process.” The software, he said, “was kind of a pillar of sanity when I was learning how to do all this with the new five-axis machine.”
NCSIMUL software detects the particular difficulties that can arise in simultaneous five-axis machining. For example, Gillin said, “Issues are likely to occur when using five-axis motion and trying to squeeze a tool into a very tight area on a part. In the CAM program it looks good, but I will send it to NCSIMUL and see a gouge. I’ll look back at that area in the CAM program and more often than not it was an area where the toolpath already looked kind of choppy because it was having a hard time fitting the tool in there.”
Reliable machining verification also permits Gillin to make best use of his time. “Premier runs it lean and all of us wear a lot of hats. Right now I’m the machine shop supervisor and I’m also the CNC programmer for the three, four and five-axis mills for tooling/fixture work and the CNC milling setup guy for any production needs. NCSIMUL allows me to set up a complex job with a lot of simultaneous motion, take it out to the machine, hit go and walk away, and not lose any sleep at night over it.”
The free-flowing 3D surface areas of Premier’s components require application of small ball end mills in long-running programs to generate good surface finishes. “Some of our cut times are 12 or 15 hours and we can’t possibly stand there and monitor it the entire time,” Gillin said. The shop operates on one shift, so the lengthy cutting processes are run lights-out. “I have confidence that when I come in the next day that I’m not going to have my day ruined when I go see what the machine’s been doing all night,” Gillin said. Without reliable G-code simulation, he added, “I would really have to stick around that area at the very least, if not with my hand on the big red button, verifying everything.”
Premier anticipates that the redesigned patterns will produce more precise castings that can be accurately and repeatedly loaded into a CNC machining center, thereby providing a way to finish components more quickly and accurately than via hand grinding. To maximize productivity, Gillin envisions use of a horizontal machining center and pallet system with tombstone workholding to nest multiple parts and machine them lights-out. “So while using NCSIMUL for machining Premalloy parts is in our future, we are using it heavily now to help us get there,” he said.