End forming tube with digital technologies, material handling options

Imagine you were born in 2005 and someone handed you the keys to a car built in 1965 and said you could take it for a spin. Certainly you could do it, but you wouldn’t be in your element. Without a remote fob, you’d have to use the key to unlock the door, and after you were in the driver’s seat—and after you had adjusted its position manually—one look at the dashboard would leave quite an impression. All the gauges in those days were analog, you wouldn’t see anything that indicated an airbag, and you wouldn’t be too impressed by the sound system (most likely an AM radio with a single factory speaker). If you weren’t sure of your destination, you’d have to use a map. Cars in those days had power nothing, and you’d probably miss the switch for changing from low beam to high beam.

Believe it or not, the technology used to build end forming machines was on that level until the last decade or so. Many end formers and spin formers that were built in previous decades are still running today, a testimony to good engineering practices, excellent materials, and solid construction. Fabricators often are reluctant to replace machines that run well and do what they were designed to do, so many of these systems are still in use today. However, they’re not as versatile or efficient as their modern counterparts.

Hardware and Control Technology Upgrades

For many industries and many applications, the days of a stand-alone machine that performs just one function are numbered. Rather than design conventional, manually fed end formers that do just one task, the industry is moving forward and taking on new capabilities.

Modern machines help the operator to a great extent. A touchscreen can provide instructions regarding die installation, and if the dies are designed for toolless changeover, the setup is not only easier but faster. Loading and unloading can be automated and forming steps can be programmed so that processes can run unattended for long periods of time. Rather than form cold only, induction heating can be added as an option for forming tube or pipe with heavy walls or made from hard-to-form materials. Onboard sensors can monitor the manufacturing process, and onboard diagnostics can alert an operator when something has gone wrong.

Of course the key to coordinating all of these activities is digital control technology. Digital control has been upgrading manufacturing processes for decades. In a trend that gained a lot of traction in the 1970s, digital control technology replaced analog controls in machining centers, upgraded the capabilities of sheet metal fabrication equipment such as laser cutting machines and press brakes, and found its way into the tube and pipe niche, notably on bending equipment.

The many advances in manufacturing capabilities and control systems—and falling prices—have paved the way for machine designers to develop end formers that are more capable, more versatile, more accurate, and faster than ever before. And while manufacturing always will be a people-based business, end formers follow the trends experienced elsewhere in relying less on hard-to-find skilled labor.

Modernizing A Basic Concept

A conventional end former uses a hydraulic ram to advance a tool that reduces, expands, or otherwise modifies a tube end. An operator inserts a tube into the machine and steps on a foot switch; the machine clamps the tube in place, the ram advances until it hits a hard stop, and the ram and clamps retract. Simple.

Many end forms these days are too complex for a single tool, so multihit machines are becoming much more common than ever before. Many equipment builders use a linear layout, shuttling the tools back and forth on a carriage.

An alternative to that is a radial carousel, similar to that of a CNC lathe or a turret-style punch press. Linear systems often hold enough tools to make a complex end form—usually four or five tools—but a carousel can hold more than 25 tools without making the machine much larger. This means that a carousel-type machine can hold all the tools it needs to make five or six unique parts, whereas a linear-type machine holds enough tooling for one or possibly two unique numbers.

In addition to more complex forms, some of the latest machines form two tubes at once. This doubles the tooling investment and requires a little more hydraulic power, but usually these upfront costs are small in comparison to the benefit: a doubling of the productivity.

Stronger Material, Heavier Walls

While the applications for end forming are countless, a good reference point is an exhaust system component for an automobile. The tube diameter is commonly around 3 in. and the wall thickness typically is 0.065 in., a sweet spot for manufactured goods of all sorts.

One application that far exceeds a typical application is a gas meter set. Near the end of the line for natural gas distribution is the last leg of the distribution pipe, a meter, and the pipe that runs into the building. Meter inlets and outlets often are 1 in. dia., and the material of choice for natural gas often is black iron pipe, Schedule 40 or Schedule 80. At 1 in. dia., the wall thicknesses are 0.133 and 0.179 in., respectively. Approximately double and triple the wall thicknesses of the aforementioned exhaust application, these end forms are nearly impossible to make on conventional machines. They need complex end forms with crisp features to form good, airtight seals.

An updated end former can be outfitted with an induction heater for making such components. Induction heating works by inducing current flow in the pipe; the material’s electrical resistance causes it to heat up. The process is so quick that it can get the material to 1,500 degrees F, cherry red, in just three seconds or so.

Of course this is hard on the tooling. When used more or less continuously, the tooling lasts just a few months in an application like this one. Water-cooled clamps and forming tools last much longer, usually two to three years.

Forming Without Much Labor

Fabricators everywhere need more skilled workers, and many would be happy to hire unskilled workers, but even those are hard to find. End formers these days can be designed and built to require less labor than before.

First, it’s becoming common practice to use a gantry or a robot to load the machine. Whether the tube goes directly from a hopper to the machine, or from a hopper to an induction heater to the machine, a material handling system can greatly reduce the labor on the front end.

A second feature is die lift assist. Some of the dies weigh more than the safe handling limit stipulated by many employers, commonly 35 lbs. Rather than rely on two hard-to-find employees, or rely on an employee to go off to find some sort of a hoist, the lifter can be built into the machine.

Toolless changeover also is a big help. Fabricators don’t pay their employees to walk back and forth across the shop floor, chasing tools; they pay them to fabricate products, so toolless changeover helps to downtime between jobs to a minimum. Whether it’s a machine that handles single tubes or pairs, and whether it has one tooling set, a linear tooling carriage, or a carousel system, toolless changeovers help fabricators of every sort get the most productivity from their end forming system. To this end, quick-change tooling often is installed by placing the tool onto a shaft and turning a collar until it locks into place; to remove, the operator presses down on a release button and turns the collar in the other direction.

Another handy feature is weld seam orientation. Everyone knows that orienting the weld seam along the neutral axis can be critical in bending, so many bending operations start with some kind of a system that detects the tube’s weld seam and orients the tube appropriately. Some end forming operations also benefit from proper weld seam orientation, and end forming machines often perform the same operation.

End formers these days go one step further, maintaining the weld seam’s orientation as the tube is discharged from the end forming cell. For operations in which the next process is bending, the tube arrives at the bending station ready to go.

Monitoring Process Consistency Without Much Labor

Conventional manufacturing relied heavily on a person to perform part inspections to determine whether components formed properly and met the dimensional criteria. These days, sensors and software can be combined to assist in such endeavors by monitoring the machine for process consistency. Any change in a consistent, repeatable process often indicates a bad part.

In many metalforming operations, the difference between a good part and a bad part is reflected in the machine’s performance. If the machine is hydraulic, a consistent and repeatable process relies on a consistent forming force and ram travel distance. Key machine components are a load cell and linear variable-differential transformer (LVDT). The first monitors the amount of hydraulic force developed during each stroke; the second monitors the distance that the ram travels on each stroke.

Understanding how these change is a key in understanding how a process is changing. For example, a slowly rising amount of hydraulic force can indicate tool galling, which eventually can lead to bad parts. A sudden change in one cycle likely indicates a part that didn’t form correctly.

This isn’t to suggest that every change in a reading at the load cell or LVDT indicates a bad part or parts. A sudden change in every cycle may indicate a change in the raw material—the end of one heat lot and the start of a new one—because a change in material strength can accompany a new batch of steel.

In cases when a sudden change seems to indicate a bad part, programming options include the ability to stop the machine after a single bad part (or some other quantity). An additional option is a diverter that sends every suspect part to a specific bin, allowing 100% inspection of any that are questionable.

An LVDT does more than merely indicate the dramatic differences that can distinguish a good part from a bad part. It’s more sophisticated than that, helping to monitor subtle features of the process, such as over- and underforming. An LVDT can help flare an end to 3 in. +/- 0.005 in. consistently. It also assists in developing the most efficient process possible. For example, rather than retract the ram the full stroke, the program can retract the ram just enough so that the tooling clears the tube and the next tool can be indexed. An LVDT provides the feedback that makes this possible.

Errorpoofing

Making end forms isn’t too difficult, but selecting the right tooling, getting it mounted correctly, and feeding the right tube into the machine to fulfill each order can be challenging. Many shops have dozens of tools for expanding, reducing, beading, flaring, dimpling, and notching. The types and styles of tooling vary quite a bit too—ID tooling, OD tooling, I/O tooling, segmented, and single-piece. It’s difficult to keep it all straight.

Meanwhile, all the tubing looks pretty much alike, so matching the raw material to the customer’s order can be a vexing problem. Sure, it’s marked, but who has time to decipher the markings?

A modern end forming machine can make simple work out of this. A key component is the RFID tag. Whether the tag actively transmits a radio-frequency signal or does so passively, the tag is handy for identifying nearly anything. Affixed to a shipping carton, a pallet of parts, or a mobile cart, the RFID tag identifies the contents. When an operator uses an RFID tag reader, this information can be sent to the company’s enterprise resource planning system to update the production schedule and so on.

End Forming Beginning to End

A state-of-the-art end forming process has many capabilities to consider. An upside is that the process is easy to get started when using bar codes, which identify each length of tube, or RFID tags, which identify carts or pallets of raw material. An emerging practice that is becoming common is to attach RFID tags directly to the tooling and mount a reader to the end former.

To start a production run, the operator scans the bar code or the RFID tag. The machine’s display shows the operator images of the tooling he needs and provides mounting instructions so each tool gets mounted to the correct station. If the machine has been programmed to act as a poka-yoke system, it won’t start until all of the correct tools are mounted in the right positions.

The machine’s controller pulls up the correct program, the operator presses “start,” and the loading-forming-unloading process commences.

At the other end of the process is an improved output, a part made to a tighter tolerance than before. These days end formers can achieve tolerances as tight as +/- 0.005 in., which is half to a quarter of the tolerance end formers typically achieved 25 years ago.