Tool design capabilities, skillful pre-production work, and a problem-solving focus are key attributes of a company that holds close tolerances on high-volume eyelets and rivets
Deep drawing of eyelets, rivet bodies, and other tiny parts is a metal forming specialty that relatively few companies in the U.S. perform. Deep drawn eyelet metal stamping originated in the Naugatuck Valley region, near Waterbury, Connecticut, during the Civil War. Interestingly, even today, many of these stamping specialists still operate out of this south central Connecticut area.
An example is Howard Engineering Company, a custom stamper in Naugatuck, Connecticut. Howard has been manufacturing deep drawn stampings and eyelets since 1956, and is said to be one of the leading manufacturers of eyelet parts in the United States.
The privately owned, ISO 9002-certified company started in a garage with a few small, rebuilt machines salvaged from the "Great Flood," which struck Waterbury and surrounding towns of the Naugatuck Valley in 1955. Currently, the firm has 34 employees and more than 40,000 square feet of workspace that encompasses 29 eyelet transfer machines, eight punch presses, and other supporting pieces of equipment.
"We specialize in making very small eyelet parts with very close tolerances out of stainless steel," says Nelson Keefe, General Manager of Operations. "At one time we were the leading manufacturer of pop rivet bodies in the world, at least before the Asians got involved. These are the little rivets that are used to hold on license plate frames.
"We were one of the first people anywhere to make these little parts. They went from aluminum to steel, and then we perfected a way to do them with stainless steel, which is very hard and not very malleable. Today, about 90% of our entire output are parts made with stainless steel, since we are now very expert at it," said Keefe.
Growth of Eyelet Manufacturing
Eyelet machinery was first used to make brass buttons for Yankee uniforms, and then to deep draw brass shell cartridges when rifles left the ball and powder era. And because of the vast amount of water in the central Connecticut area, brass manufacturing mills sprang up all over the region to meet the needs of the new metal forming industry.
In the early days, it was one die, one punch, and one hit at a time. Then, after the turn of century, multiple dies and punches came into being. A supporting industry of equipment manufacturers gradually took off; it included makers of milling and turning machinery, such as Bridgeport Milling Machines, and producers of eyelet transfer presses, such as U.S. Baird.
In contrast to regular punch presses used for deep drawing, transfer machines stamp mostly smaller parts at extremely high volumes. Deep drawn parts are commonly formed on single stage hydraulic presses that fabricate low volumes of parts at a slow rate. Parts manufactured on eyelet transfer machines tend to be thinner, but tolerances are usually much tighter. Tolerances on transfer machines range from 0.002 inch on diameter to 0.005 inch on length.
Eyelet volumes can range from 100,000 parts up to several million. Transfer machines use carbide steel dies and often make use of 12 to 13 workstations, but they transfer an individual blank instead of parts on a metal carrier strip. This allows for cost savings on excess material discarded at the end of the forming cycle.
Eyelet transfer machines fabricate parts with multiple or progressive dies, but the part goes through the press as a separate part using a specifically shaped blank, not on a strip of metal. Also unique to a transfer machine is the use of slide and transfer fingers that pick up the part and move it from station to station. The rigid fingers enable the machine to keep the part in very tight registration from station to station, permitting the machine to hold very close tolerances.
Handling Difficult Jobs
Howard Engineering is proud of its ability to produce parts from difficult slugs of stainless steel. Mr. Keefe attributes this ability to the company's prep work that it performs before starting production, its tool design capabilities, and the quality of the metal used.
"I can't say what processes we use to work with stainless, since they are trade secrets, but it has to do with punch and die clearances, the speed of press production, and the percentage of reduction from one station to the other, among other things," Keefe said.
After production, the prominent stamper provides a multitude of finishing operations as value-added services. Although the company does not offer welding or assembly applications, it provides parts cleaning, polishing, passivating, plating, and heat treating. The company has two rooms for tool and die making. One builds multiple and progressive dies and tooling for the eyelet transfer machines, and the other, progressive dies for the regular punch presses.
Both tool rooms are capable of handling carbide steel tooling with jig boring and grinding. The company has an enormous complement of presses: 29 U.S. Baird and Platarg transfer presses in sizes from 6 tons to 75 tons. It also operates eight regular hydraulic punch presses from several different manufacturers, in sizes from 30 to 100 tons.
Even though 50% of its business involves rivets, the firm can still handle parts from virtually any industry except chemical refining. Howard routinely cranks out products in brass, ordinary steels, and aluminum, but the bulk of its work is in stainless steel. Although the predominance of projects are in eyelet sizes and configurations, the firm also makes large and small deep drawn parts for water faucets, auto bearing seals, BB guns, bicycles, and TV filters.
Howard Engineering's main markets remain in automotive parts, consumer products, electronics, plumbing and heating, musical instruments, and electric motors. The company produces parts for OEMs in the U.S., Canada, Mexico, the U.K., France, and Germany.
Howard Engineering's jobs include many difficult configurations of deep drawing, Keefe explains. Deep drawing is a specialized process that is used to form deep objects, no matter what their shape. Whether the part is an aluminum bottle cap or a large food canister, deep drawing is required to form the part. Deep drawing is described as the ratio between the diameter and length of the part. If the overall height is more than 11/4 times the diameter, it is considered to be a deep drawn part. Relatively few job shops attempt the process because it is so time consuming, much of it involving complex designs and detailed calculations before production can even occur.
Another reason for its complexity is that many forming operations, each needing separate tooling, may be required. Additionally, the faster the part is run, the more heat that builds up on the part and tooling, which can corrupt tolerances. Consequently, lubricants and coolants must be used, and each station must be set up properly for the entire part to come out right.
The company's transfer machines perform a legion of punching and bending operations, including piercing (side-stabbing), knurling, beading, and threading. One part made by the company is a screw shell to hold light bulbs; it requires threading and a very complex procedure called side piercing.
The company also makes a Harley-Davidson motorcycle part that is basically a drawn shell with a square, side-stabbed hole on the side. The trick is to get enough force in a side motion. To accomplish this, the firm uses a hydraulic pump attached to a piston on the press, with a special setup to force the piercing tool in with more pressure.
Staying Competitive at High Volumes
One of the main advantages of punching and drawing with transfer machines is the ability to throughput high volumes with very close tolerances.
"We do eyelet transfer production runs that range between 50,000 and 50 million parts," Keefe enthuses. "However, many of our jobs are in the two-to-three million range. Our most common sizes range from round, 1/10-inch-diameter flat parts to those that are the size of a lipstick tube cover at 3 3/4-inches long and 3/4-inch diameter. On the larger parts we usually hold 0.005 inch on length and 0.004 inch on diameter. On the smaller parts we hold 0.003 on length and 0.002 on diameter."
At this venerable shop, problem solving is an integral part of the company credo during all aspects of design and production. In several instances-for consumer electronics customers using solid stock in screw machines or castings for their parts-the stamping company saved them time and money by shifting the parts-making process to eyelet machines.
"We've saved these customers between 25% and 30% per part, tens of thousands to hundreds of thousands of dollars per year," Keefe proudly asserts. "We did this by helping them change the design of the part, and by running the part faster in our machines with less material consumption. We always try to add extra value to our end product."
The high-volume manufacturer has many cost-effective methodologies in place for competitive production. Most of the firm's machinery runs automatically, with metal feeding the equipment in large coils. Human interaction with the machinery is minimal, with one operator usually watching several machines at one time. The few employees on the shop floor are machine setup personnel.
For the larger production runs, the metalforming company operates with annual blanket orders, which allows the firm to produce parts competitively with minimal setups. In turn, Howard carries a large parts inventory for these clients, then releases the parts as needed. For example, on a 20-to-30-million parts run, the company might dedicate one transfer machine to a particular part for the whole year, shipping a specified quantity of parts every week.
In another situation, a few million parts might be needed yearly. Instead of setting up and making a new batch of parts each month, the stamper will manufacture six or seven months worth of parts on one large production run. It will then ship out a set quantity every month.
"All of our work is just-in-time delivery, even the smaller runs," says Keefe. "Nowadays, clients don't say 'we'll need a particular part in a couple of weeks;' they say 'we'll need that part next Wednesday.' So we have to have a certain amount of parts on hand for everyone, or be able to manufacture them very quickly. Luckily, we have a very large warehouse for stocking the parts inventory."
Another way that Howard Engineering stays cost effective is by stocking a large inventory of coiled metal. "We buy a lot of material on a regular basis; therefore, we get an excellent price range from our metal vendors and also excellent quality," Keefe insists. "We routinely put out orders for 50,000 lbs. of a material, and then have them deliver it to us in 5,000-lb. lots every week. We pay a high price for stocking all of this inventory, but it keeps us very competitive."