Metal fabricators are looking to eliminate secondary tapping operations
October 1, 2009
Whether in the guise of bolt-on tapping units or actual tapping tools that are housed in a turret, precision punch presses can handle tapping chores like never before. As a result, metal fabricators are considering these options to take the manual activity out of the fabricating mix.
By having their precision punch presses put taps in sheet metal parts, fabricators are saving time and money because they no longer need an operator to transfer parts from the punch to a manual tapping unit. Photo courtesy of Prima Finn-Power North America Inc.
Three years ago Sureway Tool & Engineering, Franklin Park, Ill., purchased a new precision punch press. Today the company is starting to tap into its full capabilities. The company was no stranger to punching, having been involved with CNC machines for more than 10 years before the purchase of its Pullmax 720 with a 20-station turret. But with this new piece of equipment, it wanted to expand its horizons. The company requested that a six-station tapping unit (see Figure 1) be included with the equipment.
The reason? Sureway management saw the chance to get away from a tedious manual process that involved excessive material handling and the need for a large inventory of hardware insertion components.
It's a scenario familiar to many shops. An operator has to take the sheet from the punch press, where the appropriate hole sizes have been punched, and take it to a stand-alone tapping unit or a press brake that has been set up to install taps. The operator has to make sure the right tap is put in the right place and on the right side of the sheet metal part, a task that sounds simple, but mistakes occur more frequently than anyone on the shop floor might care to admit.
"We were trying to reduce the need for hardware insertion. It's a lot cheaper than inserting fasteners or weld nuts. Those are the two primary things that we have been using up until this point," said Carlos Rivera, Sureway's director of engineering. "We are getting away from those little by little."
The departure from hardware insertions started with much gusto when the engineering staff began to explore the true capabilities of the punch press's tapping abilities just over a year ago. The company had wanted to grow comfortable with its newest piece of equipment and its basic functions before dabbling with its optional fabricating capabilities.
During this investigatory phase, Sureway engineers learned that this was not a simple one-tool solution. In addition to the tapping tool in its six-station add-on, the turret had to have a corresponding punch to make the hole and a tool to extrude the material that would ultimately become the tap. They discovered a real limiting factor in some jobs was the requested combination of sheet metal gauge and tap size. For example, the engineering staff learned that they could tap and extrude as thin as 22 gauge with 6-32 or 10-32 taps, but to tap 22 gauge sheet with a 1/4-20 tap wouldn't work. They also learned that taps wouldn't work in certain places on a sheet metal part, such as an area close to a bend.
Once the engineers and shop floor technicians felt comfortable with the punch press's capabilities, Sureway sent out sample parts with different-sized tapped holes to its customer base, many of which are manufacturers of racks and shelving for retail outlets. Rivera admitted that everyone wasn't sure "if people would go for it."
The company doesn't worry about that much anymore. The Pullmax 720 is usually busy over the company's two shifts, often tapping in addition to punching and forming.
"We have two or three customers that won't allow us to use anything but this," Rivera said. "They won't allow us to manually insert [hardware]."
If a potential tapping project falls between 12 and 20 gauge, Sureway has no qualms about throwing the job on its punch press. It also maintains its press brake tooling for insertion of PEM nuts and its spot welders for weld nuts in case a small job needs to be turned around quickly or a customer spec hasn't changed with Sureway's newest technology offering.
But it's the automated tapping capabilities that have really helped to keep the shop floor active, especially during the early part of 2009.
"Now that the customers know about it and want it, we couldn't operate without it," Rivera said.
Sureway Tool & Engineering is not alone when it comes to exploiting new technological capabilities. The economy has forced other shops to think creatively as well.
"In this type of economy that we are in right now, [tapping] is getting a little more attention. Customers seem to be looking to get more out of their machines," said Glen Shuldes, applications engineer, Wilson Tool International®. "In the past they may have just purchased another machine. That really isn't much of an option right now for them."
But the options on a punch press make a lot of sense. A precision punch press is valued because it can do so much, and in the job shop world, that versatility is gold.
"In general, when you want to do tapping [in a punch press], you don't have a high volume, but you have a high mix. And you want to add as much value as possible when processing raw material and making the finished goods," said Lutz Ehrlich, production manager, punching and automation, Prima Finn-Power North America Inc.
It doesn't take a 30-year Toyota veteran to know that simple elimination of material handling is a way to boost productivity and increase the chance of improving quality because human hands are less involved with the process. Jack Kimberlin, president, Pullmax Inc. USA., reinforces that point with his tale of a customer that moved a complex sheet metal part to a punch press from a manual three-station process. The customer needed almost a minute to punch several holes and notch openings on a punch press, just under three minutes to tap 19 holes in three different sizes on a tapping unit, and just over three-quarters of a minute to make four bends on a press brake—which all added up to just under 4.5 minutes to complete one part. By moving that same part to a punch press with a six-station tapping unit, the customer was able to produce the part in about 1.5 minutes.
"The whole point here is to leave it on one machine and don't touch it," Kimberlin said.
The six-station add-on unit is not the only way to go for tapping. A more traditional one-station tapping unit (see Figure 2) is a common sight, and a six-station tapping unit in an autoindex form (see Figure 3) is another way to go.
As with many fabricating technologies, advancements are made every year. Those metal fabricators that have been thinking about the possibility of tapping on the punch press have some new developments to consider. These options don't involve separate punching units, however; these options fit right into the turret.
Literally, these tapping tools install just like any upper assembly and die. Changeout takes place in a matter of seconds.
They differ from add-on units in the sense that the tapping action is done by the machine ram travel rate matching the pitch of the tap to the rotational speed of the autoindex. Using this type of tapping tool, a punch press can tap pretty much any thickness of material that the press's clamps can hold, provided a hole can be prepunched in the material, according to David Berry, product engineering, Mate Precision Tooling. Harder material may pose a problem, but as long as the material is under about 35 on the Rockwell C hardness scale, it can be tapped.
This type of tooling can accept taps up to 8 mm and 5/16 in., rivaling the range of other tapping methods. Additionally, the design uses standard taps and easily obtained collet brands to produce threaded holes.
These types of tools create formed threads and do not produce the metal shavings that result from more traditional cutting tools used to create threads. Those shavings are sometimes a hazard as they can harm the material being tapped and the actual tapping unit and the punch press if the operator is not careful.
One benefit of this "rolled thread" approach is that the threads have a higher tensile strength, according to Shuldes.
"By forming the threads, you are working the material, and you end up with a stronger thread actually," he said.
Lubrication systems, a necessity for this process because of the pressure and heat generated, for these types of tapping tools can contribute to a lengthy tool life. A built-in tapping fluid injection system that is synchronized with the punch press's machine stroke helps to reduce the wear and tear on the tooling.
The amount of lubrication can be adjusted easily. Also, a simple adjustment of NC code can distribute lubricant to every second or third hole tapped, Berry noted.
For fabricating job shops or OEMs looking for something more permanently integrated into their punch presses, Amada has introduced a combination laser/punch with a built-in, multipurpose turret in the main turret that can hold four 1.25-in. stations for tapping tools (see Figure 4). Again, the tapping tools are driven by the turret's autoindex mechanism.
"So I can have 10-32, 6-32, M4, and M6 taps all in one machine at one time, which gives you a lot more flexibility if you are a job shop," said David Stone, Amada's product manager, punching and stamping.
Sometimes customers aren't so flexible, and a job shop may be stuck with a request for cut taps instead of roll formed taps. After all, specs don't change overnight.
Stone said that can be accommodated in a punch press that uses dies that can suck chips and slugs down and away from the sheet metal. These "vacuum dies" have holes in the sides and high pressure air is injected into them, creating a powerful vacuum during the tapping process. The remnants of the cutting process are removed before they have a chance to stick to a punch and sabotage subsequent holemaking or forming.
Stone is candid about why he thinks more shops are going to consider some sort of tapping if they have punch presses.
"You have the [punching] equipment, and a guy is running the [tapping] machine. There's no value there," he said. "When the customer orders the part, he doesn't care if it takes him an extra 15 seconds or 15 minutes to finish the part on the tapping machine... He's going to pay you as little as possible in the first place. He doesn't care."
That's a realization hitting many shop owners and managers: Customers will pay only for certain activities. If they see waste, they see an opportunity to cut their own costs, either with that metal fabricating operation or some other company that will do the job more efficiently.
That's why tapping in a punch press is generating more and more interest in the metal fabricating community. It's not a new capability, having been developed several years ago by d/k technologies, Placentia, Calif., the company that also makes the tapping tools for Wilson Tool, but it's a proven technology that now is available in a variety of options. It's up to the metal fabricator to see the opportunity.
"The biggest hurdle is doing the cost justification," Shuldes said. "It's hard for them to look at their current operation and understand what it is truly costing them. That's the real deterrent. Only after they understand their current costs can they determine if tapping on their punch press is cost-effective."
Metal fabricators may be entering the age when they don't have a choice but to understand the total costs. If they don't, their customers may tap someone else for the job.