A Familiar Ring of Success
If the Jostens name isn’t familiar to you, it should be! Jostens is one of the nations largest ring manufacturers, famous for graduation class rings. Headquartered in Burnsville, MN, the company has been making rings for more than 100 years.
A class ring is a symbol of accomplishment and a source of pride that lasts a lifetime. Therefore, the highest standard of manufacturing quality is absolutely essential to Jostens. In order to produce the highest quality rings at a reasonable cost to the consumer, the company uses the a combination of craftsmanship and the latest computer-aided manufacturing (CAM) techniques available. One of these advanced techniques is computer-aided numerical control (NC) simulation and verification. This process enables programmers at Jostens to visualize the entire machining process before their design is brought to the shop in the form of an NC program and transformed into a ring casting.
For conceptual design, Jostens uses Alias Studio computer-aided design (CAD) software on SGI Indigo 2 workstations. CAD gives the designer the freedom to quickly design, visualize, and redesign without putting a pencil to paper. In addition, the rendering qualities are invaluable in getting an accurate picture of the concept at any point in the process. If changes are needed, they can be made very quickly and redisplayed for approval. After approval of a concept, the designer exports the ring design as an IGES file. That IGES file is then given to Master Tooling and Process Support to begin prepping the design for production.
The Master Tooling and Process Support departments use CAM software to generate tool paths to machine all the tools needed for a particular ring design. SDRC’s CAMAND gives Jostens the flexibility and control for programming a variety of machine tools on the production floor. The CAM software’s 3-5 axis programming capabilities enable Jostens to achieve it’s goal to provide the best quality product to it’s customers. CNC programmers at Jostens have developed an integrated process which utilizes many machine tools to provide significant time savings along the road to the final production part. By combining the use of multiple axis mills, wire EDM, and plunge EDM, Jostens saves a great deal of time. This helps the company to provide the customer with a high quality product at a lowest possible cost.
Simulation and Verification: A Key to Efficient Manufacturing
One of the most important steps to minimizing expenses and ensuring a quality part in the entire production process is verifying that the NC tool path is correct before attempting to machine the part. The traditional test, re-program, and test again cycle is much too inefficient for Jostens’ operation. Therefore, after the toolpath has been generated, the G/M code is verified using VERICUT simulation and verification software from CGTech.
VERICUT provides simulation capabilities for the all the 3-5 axis and wire EDM parts, with focused control over the orientation of our 5-axis machine tool including the cutters used on that machine. “VERICUT simulates the motions of our 5-axis mill accurately enough to nearly eliminate the need to mill test parts. VERICUT also prevents any crashes with the mill since any abnormal movement in the G/M code will show up in the simulation,” says Eric Smith, Master Tooling Engineer.
For example, with the cutter, shank, and holder geometry displayed, VERICUT detects transitions and spindle moves that would have caused a collision between the part or fixture on the shop floor. Catching that glitch before the part is cut has saved costly spindles, fixturing, and mill time. These capabilities of VERICUT enables Jostens to run both critical and non-critical tools. Critical tools are those cut from production tools at very low tolerances (.0005) while non-critical tools are generally plastic prototypes cut at higher tolerances (.001 to .002) with minimal operator intervention. The operator only needs to put the proper cutters in the machine at the beginning of a job, replace any tools during OPSTOPS and inspect the finished tool upon completion of the program. That in and of itself gives the operator the freedom he needs to more efficiently schedule the work for the shift.
Perfect Tool Paths and Finishing the Process
After the NC program has been proven on VERICUT, it is brought to the shop floor and machined. “After running the tooling programs are run through VERICUT, we know they will be machined correctly the first time,” says Smith.
The resulting customized tools are combined to create a wax model of the desired ring. The model is sent to the casting facility where it is investment cast, polished, packaged, and distributed to the customer. Investment casting, or “lost wax,” has been used in various industries for decades. This precision process successfully casts the detail required to meet the customers’ expectations as well as Jostens’ standard of quality.
Jostens uses a three part molding process for investment parts. The customized mold halves (each designed specifically for the individual customer, a particular high school, for example) are assembled with the corresponding bezel top and the whole assembly is injected with investment wax. The “wax” (individual wax ring) is then placed on a wax “tree” (a collection of different rings in an arrangement that resembles a Christmas tree). The tree is then placed in a slurry of investment plaster. When the slurry has solidified, it is placed in a furnace where the wax is melted, decantered, and the residue is burned out. The precious metal for the rings in that tree is then poured into the solidified mold cavity. After the metal has cooled, the plaster mold is broken to reveal the new rings. The cast rings are then separated, cleaned, polished, and shipped to the customer.
Old verification process
Before Jostens invested in VERICUT, proving out the toolpath was a time and material consuming process. Programmers developed the toolpath then simulated the toolpath using another verification software program. They then brought the part program to the shop and cut the part on the mill using an acrylic prove-out material. Afterwards they looked at the part under a microscope to detect any gouges.
After identifying the gouges, they went back to the part program and corrected the errors. Depending on the part, this iteration process could occur upwards of five to six times before the part program was perfect and ready for production. “At this stage of development,” says Smith, “the main concern was not the material cost, but the significant amount of mill time and programmer time spent on the prove-out cycle.”
Verification and the Bottom Line
Since implementing VERICUT into the process, Jostens has dramatically reduced the amount of test parts needed before going to production: for complex parts, no more than two test parts are required, and for fairly simple parts, no test parts are required. The superior graphics and zooming capabilities of VERICUT enable the programmers to see, with excellent detail, the problem areas of the part. Reduced programmer and mill time, along with a regimented operating protocol for the mills, has increased the percentage of quality, market-ready parts per run to more than 95%.
“VERICUT has saved Jostens significant time and money since its implementation into our process,” says Smith. “The program completely eliminates cutting multiple iterations of a part to reveal any flaws in the toolpath. We save a great deal of programmer and mill time because of VERICUT.”
onsidering that gouging a steel master tool costs the company between $2,000 and $3,000, the amount of money Jostens saves by detecting mistakes hidden in the tool path quickly adds up. Not to mention, colliding with a fixture could cost between $1,000 and $3,000. Preventing a spindle crash saves $10,000 in damage.
Many people take for granted the intricate and elegant designs with which they decorate their fingers. And most are completely unaware of the role computer technology plays in bringing those designs from a concept to the tools used to create the casting that made their ring. People are concerned with aesthetics, quality, and cost. For more than 100 years, Jostens has striven to provide consumers with quality rings at the best value possible. Today’s simulation/verification technology helps the company to continue its rich tradition in style.