— Reprinted with permission from Metalforming Magazine, June 26, 2003.
The Rockford Company / Custom Metal Products
Die Life Boosted by 16 Fold (& Counting) While Increasing Part Productivity by up to 20%.
When new tooling technologies are used on older stamping equipment, this “fresh breath of life” can make this older equipment work better. This was the case for two sister companies: The Rockford Company and Custom Metal Products (Rockford, IL).
As their Tool Room Supervisor Barry Kasmar explains, the company went from getting 250,000 hits from one of their progressive die sets to over eight million (and still counting) by coating the die set using the Thermal Diffusion process from the TD Center (Columbus, IN). Along with this, they were able to increase part output by up to 20% because the die ran smoother at faster feed rates and was easier to set up.
On the Company / Products Produced
The Rockford Company/Custom Metal Products is a 50-year-old job shop and stamping company that employs 30 people. Primary products of The Rockford Company are leg levelers for the likes of appliances and desks and more. “Whatever needs to be leveled we make levelers for,” states Kasmar. “We ship hundreds of thousands of these parts to dozens of different markets and applications.”
Along with leg leveler production, the contract stamping side of the business—Custom Metal Products—produces custom metal-stamped products and assemblies by using presses as large as 800 tons in capacity. Other services offered from this side of the business include secondary fabricating operations, CNC turning and automated assembly production.
Appliance levelers are comprised of two pieces—a stamped base (cap) and cold-headed screw. (They also make a one-piece leveler made from bar stock.) For the stamped cap, mild steel is blanked out of coil strip stock using a progressive die application designed to punch two caps simultaneously. The cap of the leveler has a flange that is rolled (drawn) upwards. This flange area allows the company who is mounting the leveler to a product to use a socket and drive it down to its proper location. It also allows the worker to use a wrench to make final leveling adjustments when the product is on location. Once the cap is stamped, it's placed in tumblers to deburr or burnish it using corn cob media. Finished caps aren't all the same, some get coated, while others are plastic laminated.
The Rockford Company produces twelve different stock cap styles.
To make the threaded screw that is spot welded to the cap, wire is cold headed and threads are applied. Then the screw and cap are placed into a special machine to spot weld the two together. Some screws are plated and some are also mated to an all-plastic cap. Kasmar says caps can vary tremendously depending on what the customer wants or application demands.
The height of the material from the bottom of the cap to the height of the flange area is critical along with the overall radius and the concentricity of the threaded shaft. Also it has to be an aesthetically-pleasing part design.
Twelve different stock cap styles are available from the company. Caps range anywhere from 15/16" up to 1 3/8" wide with a material thickness from .030 to .090". Cap heights range from 0.190" to 0.375". Threads on the screws vary from ¼"–20 to ½"–13 with screw lengths going from 0.686" to 2.5". The company also produces special levelers.
Kasmar says that with their older press equipment, each job and die set “has its own little quirks. And we've found that certain dies run better in specific presses. So we try to schedule our workload around these problems. We're more efficient by paying close attention to what has worked better in the past.”
Ongoing Productivity and Uptime Challenges
“We're always trying to increase our productivity,” states Kasmar. “We try to speed up our feeds to get the most parts per hour, but certain dies can only go just so fast before they start causing misfeeding and/or part quality problems. If our press lines were a little more modern, we could probably increase the feeds and speeds. But because we are a small job shop, it's hard to get to the next level and make these types of sizable investments. So if we can remain competitive with the capital equipment we are working with, then we're doing our jobs well. And this helps us to keep our manufacturing costs down, of course.”
One of the important challenges for The Rockford Company's increasing productivity was coil stock. “Carbon makeup of the steel material is different between coils or from lot to lot,” says Kasmar. “Sometimes we have to tweak (make minor adjustments to) the die to accommodate the new material. We try out a part and see what changes in the die need to be made to get a quality part. Sometimes it's just changing the radius on the punch to allow the metal to flow better into the die's hole.”
Because The Rockford Company is drawing steel into a hole with a radius, they're creating friction on the tool seat. Anytime friction is present, it creates unwanted heat. Even though they're working with a stamping lubricant, it still generates friction and heat…and this specific tool set continued to break down at anywhere from 250,000 to 300,000 hits. Then the company would have to pull the tool and redress the radiuses on it, a costly and time-consuming exercise.
Press feeding parameters comprise of a combination of several factors such as the speed capabilities of the feeder, the material going through the die, and proper lubrication of the material. Kasmar remarks, “You speed up as much as you can until you feel you're going to have a problem. Then that's where we'll top off how far we push the productivity equation.”
To rework a die, it has to be pulled from the press because the die only has about 1.5" of clearance. Kasmar says they don't pull the die out that much, but enough that it creates a problem with downtime. Reconditioning a die set is not an every day occasion, but is happening enough that it was giving Kasmar concerns with overall throughput and downtime on specific critical jobs.
Solution to Stamping Productivity – Thermal Diffusion Tool Coatings & The TD Center
Kasmar says they decided to try a tool coating to improve tool life. “Our production manager had past experience with the TD Center tool coatings when he was with a previous stamping company employer. He suggested that we try TD's coating on one particular tool and see how it works. I talked to the people at TD Center and explained our specific issues. They made suggestions toward design and functionality preparations for the die's form block and the punches. We did what they recommended and then sent them the tool. They performed their coating process and quickly sent it back to us.”
The end result? Kasmar states, “Before the coating process, this press application could only run 120 SPM . . . now it typically can run up to 20 percent faster. Also, the cap die form tool needed maintenance after 300,000 hits to restore the radiuses prior to tool coating . . . now it is performing at 8 million hits and counting without a redress.”
The Rockford Company is planning to use the TD Center coating on all of their cap tool sets and tooling for other long run stamped parts. Custom Metal Products have also used Thermal Diffusion coatings on critical or “trouble” stampings or other types of pressworking applications.
What took them four hours to get a first part set up without the coating now only takes them one and a half hours, because the material is much easier to get through the die set.
“We have less friction with the coating and it seems to keep the material from dragging . . . important in starting a job as well as in continuous operation.”
“The tools run so trouble free that we aren't being squeezed by our production people to get the tool back out to the production floor in a hurried fashion,” mentions Kasmar.
Kasmar adds, “Now we don't have to touch the radiuses because of the coating. All we have to do is sharpen the first section of the punches that cut the material. Before the coating, we had to spend about 40 hours a month reworking the tool at about $60 per hour. So it cost us $2400 a month just in shop costs when we were forced to rework the tool. We probably don't average 10 hours a month on the tool now. We just go through the sharpening process. So we recouped the cost of the new tool in about six months. Plus, we have less downtime by not having the tool in the repair shop.”
Lot Size, Lubrication, Anxiety and Cost Considerations
Kasmar also found that their first part is much easier to produce using the TD Center process. What took them four hours to get a first part set up without the coating now only takes them one and a half hours, because the material is much easier to get through the die set.
Their typical lot sizes for the caps range from 30,000 to 400,000 pieces, depending on the customer and how often they order. One customer might order 60,000 caps four times a year. Five of Rockford's presses run the caps, and they typically go through one setup per day per press on each of the five presses.
Kasmar says, “We have less friction with the coating and it seems to keep the material from dragging . . . important in starting a job as well as in continuous operation. We're finding it offers a specific lubricity benefit and that's an added bonus. We are using less lubrication too, which is a cost savings for us. It's just a much smoother running tool now with the coating.”
Anxiety levels have also been reduced. “The tools run so trouble free that we aren't being squeezed by our production people to get the tool back out to the production floor in a hurried fashion,” mentions Kasmar. “If production is down, we're down. Without downtime now, it's much easier for all of us to do our jobs.
“We did think the coating was a little pricey at first, but because of our production manager's past experience with this coating and specifically with the TD Center, he was insistent that it would be worth every penny. So based on our results with the first die, we were very, very pleased.”
Any future applications with Thermal Diffusion? “We'd like to take every applicable leveler die set and have it TD coated to help us remove problems and continually increase our productivity and uptime,” states Kasmar. “And our goal is to send die components periodically as we fit them into our production schedule. The TD Center does a good job working with us on turnaround time in just a few days, and this is important because we need to get our die sets back into production as soon as possible. We need them back in days, not weeks . . . and they deliver, period. And their technical service and understanding of our business goes a long way to keep us impressed with what they do for us.”
On Thermal Diffusion
The TD Center's thermal diffusion process is a hot process (1800°F) that combines carbon from the tool surface with the element Vanadium to grow a Vanadium Carbide layer that is ‘welded’ to the substrate metallurgically. This method of thermally diffusing a vanadium carbide layer into the surface creates an incredible adhesive bond far stronger than any deposited coating and better adhesion means longer life. Because of the high temperature TD process, the coating will not chip, peel or spall off the substrate, and it's extremely durable, providing excellent protection from both adhesive and abrasive wear. TD is a layer of super pure, ultra-dense carbide that completely covers the part, and is bonded below the surface. The carbide is 0.0002–0.0003" thick with a hardness of 3500 to 3800 HvU (Vickers Hardness), well above 90 Rockwell C.