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Peace of mind with single-piece flow

New fabricating technology allows an OEM to execute a simple lean manufacturing principle

Figure 1
Unison Comfort Technologies was seeing increased demand for its HVAC units, which put a strain on its metal fabricating efforts at its Minneapolis production facility.

Busy is good, but it’s not easy. Without a doubt, manufacturers would rather see a shop floor buzzing with activity than not. That level of activity is typically associated with purchased products being shipped to paying customers.

Any stress points that begin to appear during these extremely busy periods have to be addressed in a quick and effective manner so that current production is minimally affected. It’s a tricky walk on a tight rope, but a necessary one.

Unison Comfort Technologies (UCT), Minneapolis, found itself in such a situation a couple of years ago. The 200,000-square-foot manufacturing facility had reached capacity fabricating parts for the company’s Innovent and Valent brand HVAC units. The operation was running 24 hours per day trying to keep up with the robust production schedule, and work-in-process crowded the floor.

With no floor space available, UCT decided to modernize its fabricating technology in an effort to create more room. It wanted to combine two separate fabricating cells for the Innovent and Valent brands into one cell.

The move to more automation also brought a chance to dictate the pace of the fabrication. Single-piece flow was the way to go.

HVAC Business Gets Hot

UCT (see Figure 1) was established in 2010 as the parent organization of Innovent and Valent, as well as Precision Coils, a manufacturer of coils for HVAC OEMs and for the replacement market. Innovent Air Handling Equipment, which traces its history back to 1981, designs and manufactures air-handling products that ventilate, dehumidify, filter, heat, and cool air. While it focuses on custom equipment, Valent Air Management Systems has a much more focused product lineup.

The Valent brand is less than 10 years old and has grown rapidly over that time. As the growth occurred, UCT’s Minneapolis facility struggled to keep up with metal fabrication requirements. Because the commercial HVAC units of both brands require plenty of sheet metal panels (see Figure 2), the three hydraulic punch presses were always crushed with jobs. The panels, typically mild steel sheets ranging in thickness from 16 to 22 gauge, weren’t complex, requiring a few knockouts and screw holes if anything; they were just plentiful. The punch presses could barely keep up.

Meanwhile, UCT’s 2-year-old Prima Power FastBend panel bender was handling a lot of the bending chores. The machine required an operator to load the part and square it off manually, but it would then take the part, move it into position, and create all of the forms automatically on one side of the part. Everyone acknowledged what that type of technology meant for bending, but attention at the time was focused elsewhere.

“It was definitely front of mind because you could see the type of quality that you could get out of a panel bender, but we really needed to have punch capacity,” said Jacob VandeHei, a Valent manufacturing engineer.

The company looked at combination machines, but found that they simply didn’t need a laser’s cutting prowess. The rectangular shape of a majority of the panel parts lent itself to a different type of combination machine: a punch/shear.

Figure 2
This Valent HVAC unit shows the many basic sheet metal panels necessary to assemble a complete product.

The manufacturing team was drawn to the Prima Power punch/shear combination machine, but as they fine-tuned the project and explored the options, they realized the shop floor could benefit from a complete automated fabrication line. Something that could tie punching and bending together also could help them maintain a production flow that would eliminate the WIP that used to occupy valuable manufacturing real estate.

UCT selected the Prima Power PSBB line that included a Shear Genius® servo-electric punch/shear (SGe8) combination machine, buffer tables, a servo-electric Express Bender (EBe6), material handling automation, and control software. It was installed in the early fall of 2014.

Clearing out Room

When a manufacturing facility has no room for additional production capacity, it has to make room to accommodate new equipment installations, particularly a fully automated production line. VandeHei said virtually everything in the facility, excluding the welding cells and paint booth, moved.

Because it was getting an automated panel bender, UCT parted with its FastBend. The new punching and bending line actually occupies the same space where the Valent-only assembly line once sat.

“What we did when we brought this in is focus on single-part flow,” VandeHei said. “It’s prioritized right from the get-go. It follows through. The vast majority of the WIP is now gone from our foamed panel production processes.”

In most cases, UCT has the luxury of a relatively predictable production schedule. It uses its SAP enterprise software to determine when a build process needs to start for an HVAC unit to be delivered on time. When that date is determined, the job then can be scheduled on the shop floor and for the metal fabricating line (see Figure 3).

The production schedule is typically planned out about two months in advance, but it’s solidified a week ahead of time. The shop floor has a bit of wiggle room to move production jobs around, but everyone tries to avoid that as it can disrupt other assembly processes downstream.

The automated fabrication begins with a two-pallet system that loads material into the SGe8 and prepares the next sheet metal delivery while punching and shearing is taking place. The 30-ton punch/shear combination machine has a 1,000-hits-per-minute stroke speed, a 250-RPM index speed, and 492-FPM (150m/min.) sheet positioning speed. The right-angle shear can handle mild steel up to 0.157 in. (4 mm).

VandeHei said common-line cutting can be accomplished with the right-angle shear, something the older punch presses couldn’t do. He estimated that on the older machines there was about 0.75 to 1 in. worth of space between parts. Common-line cutting has led to better nests and improved sheet utilization.

As for productivity on the new punching machine, VandeHei said it is twice as fast as the previous machines. The older turret punch presses took approximately 7 to 8 minutes to process a sheet, whereas the new punching machine can do the job in about 3.5 to 4 minutes.

Figure 3
The one operator needed to oversee the automated punch, shear, and bending line uses the system’s control software to track jobs and schedule special tasks, if necessary.

Another time-saver is an inkjet printer option installed on the side of the turret frame. VandeHei said it saves time when compared to marking parts with turret tooling or manually marking parts downstream.

A buffer system is in place between the punching machine and the panel bender. If the panel bender is ready to go, the buffer allows blanks to pass from the punching machine directly to the panel bender. If the bender is busy, a material mover, which VandeHei describes as a kind of baker’s rack, lifts the blank and removes it from the flow. The buffer system can do the same for other blanks, allowing the punching and bending machines to continue at their own pace. The key is that the punch/shear continues to operate as fast as possible with no delays because of downstream machine functions.

(VandeHei mentioned that the current line is arranged in such a way that it could accommodate a robotic arm to coordinate different blanks in separate stacks on multiple tables. That option wasn’t implemented with this installation, but UCT could choose to add that in the future if it needs more flexibility in this buffer area. Right now, the last parts positioned in the buffer area are the first parts to be sent to the bender when the time is right.)

When the blanks leave the buffering area (see Figure 4), they head for the panel bender. UCT has about 70 different bend profiles in its part catalog, and the bender is ready to run any of those based on the program instructions tied to the blank.

“Basically you have this blank that has been punched and sheared out, and the bender knows what parametric bend program to use,” VandeHei said. “It will take the dimensions of that blank and stretch it and make the bending program on-the-fly. It’s pretty slick. It saves us a bunch of programming time.”

The EBe bender has a maximum bending length of 11.6 ft. (3,550 mm) and a maximum opening height of 8 in. (200 mm). NC servo axes actuate the bending blade and upper tool movements.

VandeHei said the ability to bend negative and positive flanges on the machine without flipping the part over has been a real productivity enhancer.

“That’s an important feature because we have door panels that have 12 forms with four negative bends on them,” he said. “To form that part on a traditional brake, we would end up flipping it eight times. Now we can form that part in 45 to 50 seconds.”

One operator oversees the entire operation. Many times that operator ensures the line is running smoothly and engages in another activity.

Sorting Through Benefits, Not Parts

VandeHei said the new line, which has been in place for less than a year, has been just the right addition to the machine mix on the shop floor because it has been able to absorb the increase in production during a time of continued growth. Even as things have gotten busier, the manufacturing process is less stressful because scheduling doesn’t have to be perfect to keep up with 24/7 production. The new capacity has created a new production environment.

Figure 4
After the buffering area, a device turns the blank over. All of the punching is done with the finished side up. After the blank is punched and sheared, it needs to get flipped over before entering the panel bender.

VandeHei added that maintenance personnel now have scheduled downtime to perform service on not only the new line, but the other three punch presses, which were retained for smaller and more feature-intensive parts. Sometimes when production calls for as much machine uptime as possible, maintenance is pushed to the side. That doesn’t have to be the case any longer.

But the ability to establish the single-piece part flow through the shop is perhaps the biggest improvement, VandeHei said. As an example, he pointed to the foam prep area.

This is the production step before foam is shot into panels. (The inner and outer panels are joined, and foam is shot in between the panels.) The panels are used as thermal breaks in these HVAC units.

Some prep work has to occur before the panels are filled with foamed. Foam strips have to be placed on the interior of the panels, and tape has to be placed over holes and corners to prevent foam from escaping during the foaming process.

Before the new line was installed, workers in the foam area stacked a lot of panels on the floor and spent quite a bit of time handling the parts in and out of the carts as they kept pace with the panels that were sent their way from metal fabricating. Now they are prepping the panels that are needed at the moment. The panels slide down rollers as they exit the panel bender, and workers grab them as they become available.

“I know that just with this operation alone, which really isn’t directly connected to the machine, we just reduced the nonvalue time by almost 50 to 60 percent,” VandeHei said. Operators handle the panels once and place them in carts for assembly. They aren’t stacking panels in carts and then going back to the carts later to put the panels through the foaming process, only to return them to another staging cart later.

This type of production improvement is indicative of the major impact the automated punching, shearing, and bending line has made on the shop floor. It used to take two to three days for sheet metal to be turned into a foamed panel; now it takes just a few hours.

“It has been a real game-changer, and we shudder to think what would have happened if the line had been installed a few months later,” he said.

About the Author
The Fabricator

Dan Davis

Editor-in-Chief

2135 Point Blvd.

Elgin, IL 60123

815-227-8281

Dan Davis is editor-in-chief of The Fabricator, the industry's most widely circulated metal fabricating magazine, and its sister publications, The Tube & Pipe Journal and The Welder. He has been with the publications since April 2002.