For one Connecticut manufacturer of close-tolerance, precision-stamped and coiled metal parts, an eight-year journey to provide its customers with higher precision parts from progressive tools has reached a happy ending. In-house CNC machining has allowed it to stamp parts at a very low cost, and then machine crucial features into them.

In just a few short years, the company jumped from one used machining center to 12 new centers, including some highly automated centers with the potential to reduce cut times by nearly one-third, while maintaining tolerance and finish requirements.

What differentiates the Farmington, Connecticut-based Connecticut Spring & Stamping (CSS)’s approach from traditional machining suppliers is that stamping and then machining results in a much lower-cost part than a fully machined part. Also noteworthy is that, by doing all of the processing in house, CSS controls all aspects of the part, from prototyping and development to final production. Designing and building both the progressive tooling for the stamping and the fixtures required for the machining process helps CSS meet the quality requirements of its customers, especially those in the medical device industry.

It all began in 2004, when CSS began to see more customers looking to get higher precision parts off a progressive tool. CSS had decided that CNC machining was the way to go, and began researching and learning all it could about the process. It jumped into the CNC world by purchasing a used Fadal machining center. After engineering and designing its own fixtures, it was off and running.

Fadal machining center

According to Mike Vanadestine, a CSS self-directed work team leader, “The initial customer for this process, a major firearms manufacturer that needed a machined safety, was very happy with the quality of the parts and remains so to this day.”

He explains that the “one-stop shop” process CSS uses differentiates it from traditional CNC machining suppliers. “We have the in-house engineering personnel who can aid in any redesign or alterations needed to achieve the functional requirements directed by our customers.”

This gives CSS an advantage because the customer needs to partner with only one vendor. “We are able to take a stamped part and then machine critical features, and this can be done at a considerably lower cost than having to machine the complete component,” says Vanadestine.

As the word spread that CSS could machine stamped parts, the company began to get requests from other customers looking for the same accuracy and finish that the CNC machines were producing, so it started looking at additional machines to keep up with the demand.

In 2009, the stakes were raised higher, as CSS found its new medical customers were looking for even tighter tolerances than had been achieved before.

Robert Allen, CSS director of engineering for tooling and metal form, notes that the company was no longer looking at holding ±0.003 tolerances, but instead was asked to hold tolerances of ±0.0005. To achieve these close tolerances would require a very accurate CNC machine, and after doing a great deal of research, CSS settled on the Hyundai Kia VX400.

Hyundai Kia VX400

“These machines are significantly more accurate than our first machines and are able to hold tight tolerances all day, every day,” says Allen. “We have also taken on a five-axis machining job using a rotary table and all the machine’s capabilities.”

For example, CSS recently worked with a medical device company that had been purchasing one of its parts as a completely machined tube, but wanted to explore the possibility of moving to a stamped part with machined features. The project is tricky, since the tube has important features that had to be duplicated in a stamped part. A pin has to smoothly ride on a surface to create the torque necessary to grab flesh. Also, there could be no bumps or ridges that might cause the tube to skip or the surgeon to feel tension. Finally, a coined feature was needed where wires could be attached that made the instrument head articulate.

CSS engineers successfully moved toward changing to a stamped part, finishing the critical features using the CNC machining process. The result is a savings of about $6 per part, a great result for the customer, which manufactures about 100,000 of the parts per year.

After CSS gained experience in CNC machining, it realized it was extremely time-consuming to load parts in the fixtures, and the loading process was increasing cycle times. So in 2011, the company kicked its machining abilities up another notch by purchasing two Hyundai Kia VX380TD machines, which use a rotary-type table to shuttle parts in and out of the work zone.

Hyundai Kia VX380TD

The operator will no longer be taking fixtures in and out; instead, everything is mounted directly to the machine base and is shuttled in. These new machines have the potential of cutting 25 to 30 percent off the company’s current cut times, all the while maintaining tolerance and finish requirements.

But CSS isn’t stopping there. “We are currently expanding our CNC department and capabilities with the addition of the Hyundai Kia VX380TD machines,” says Allen. “We will have 12 vertical machining centers and are also making room for additional machines as we continue to grow this very technical aspect of our business.”