Bringing laser cutting home

A modernized machine shop delivers in-house control to manufacturing and inventory

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Many businesses continue to outsource their machining to job shops while others, like Griswold Controls (Irvine, CA), are embracing new technology to reduce costs and control processes. The company has manufactured flow control valves for heating and air conditioning systems for more than 40 years. In 1960 the company introduced a valve with a patented stainless-steel cartridge that controls the flow of air or water to ±5 percent accuracy under any pressure. Its products can be found in office buildings and hotels all over the country.

A year and a half ago, Griswold wanted to modernize its machine shop to bring more control to manufacturing and inventory, so it brought the CNC machining and laser cutting in-house. Because many of its products contain complex turned parts, the first purchase was an easy decision—a Swiss turning center. But when it came time for a laser cutting system, the company soon discovered there was very little available in its price range.

Told to bring laser cutting in-house, Hemant Shah, director of manufacturing, says, "I had no clue what a laser machine was. So I started looking, and the lasers I saw were priced up to $500,000. And that's not the price we were looking for. But I talked with the people at the Haas Factory Outlet in Anaheim (Calif.), and they told me that the company was coming out with a laser machine."

Haas Automation's Z series laser-cutting systems are based on the company's shop-proven vertical machining center platforms and feature the user-friendly Haas control. A Coherent (Santa Clara, CA) Diamond series pulsed CO2 laser is then integrated into the machine in place of the spindle.

After looking at the possibilities, Griswold chose a Z3-500 laser cutting system for its shop. This system has travels of 40 in. × 20 in. × 25 in. (XYZ) and provides positioning accuracy of ±0.0002 in. It comes equipped with a 500W (average power) CO2 laser that yields a peak power rating of 1.5 kW.

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Figure 1. A key component of the flow-control valve is the stainless-steel cartridge cup with laser-cut parabolic openings that maintain a constant flow rate within a broad pressure range.
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The key component of Griswold's flow-control valves is a stainless-steel cartridge cup with parabolic openings cut into it to maintain a constant flow rate within a broad pressure range (see Figure 1). "The openings have to be precise," says Shah, "because we put a spring in the cup that controls the flow to ±5 percent. We are the only one in the industry who promises ±5 percent, and that's why our valves are so popular."

Depending on the size of the cartridge and its use, there can be up to 20 different profiles for the openings. "The profiles are all computer generated, and they're designed to meet flow and pressure specifications," explains programmer Jim McCulloch. "There are 15 different configurations that come out of the same half-inch cup, depending on what type of flow and volume the valve has."

In the past, Griswold sent the cups to outside suppliers to have the profiles cut using laser cutting systems or EDM, but it made more economic sense to bring the job in-house. "We were spending approximately $300,000 a year for outside processes," says Shah. "The price of the Haas laser system was more in line with what we were looking to spend, and it will only take us a year and a half to pay for the machine."

Griswold's laser system was installed in January 2003, and the first task was to design an effective fixturing system for the 0.0030-in. thick cartridge cups. To increase throughput and take advantage of the machine's large travels, Griswold installed a Haas HA5C quad-spindle collet indexer, which provides simultaneous four-axis machining and allows machining of four different cups in a single setup. McCulloch then worked with the engineering department to design a vacuum system to hold the cups in place. "All we have to do is screw in a different mandrel to hold a different size cup," he says. "Right now, we have the machine set up to do two 3/4-in. cups and two 1.5-in. cups (see Figure 2).

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Figure 2. The laser cutting machine currently is set up to process two 3/4-in. cups and two 1.5-in. cups.
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"We built it this way so I could run any size, at any profile, at any location," McCulloch continues. "It's programmed using macros, so I simply tell it what size cup is going where and what profile is going there, then press Start. Now that we've developed this system, we can do practically any part in our product line."

One of the difficulties Griswold had with outsourcing was inventory control. "We had to order 1000 of each size to get the price we wanted," says Shah. "We used to place an order and wait two weeks for delivery. Then the finished parts would sit on a shelf. Now, with the laser, we are cutting cups when we need them."

And the accuracy is better as well, Shah adds. "Our quality is better in-house than from outside suppliers," he says. "And our assembly is faster, because we don't have to drill any holes or do anything extra. In the past, that wasn't always the case. But we wouldn't send the parts back. Instead, we'd have to drill a little hole in the cup to make sure the flow was correct, or add a shim to make sure the spring wouldn't compress too much. Now, every part is perfect."

McCulloch agrees, adding, "The cups we're making on the laser are also more accurate because we have a better program to cut the profiles. The program that was developed in conjunction with engineering is completely adjustable, depending on what we need," he says. "The machine is extremely accurate, so if engineering develops a profile that is of a given size we get exactly that profile from the laser. We have mechanically inspected the profiles, and they're exactly what we've designed."

Bringing the laser processes in-house also enables Griswold to prototype new profiles easily, and respond to customers' demands quickly. "If someone from the assembly floor comes in with a hot order, we can react instantly," says McCulloch. "If someone says they need two of this and three of that, then that's what we'll run. All I have to do is call up the program and the machine cuts just what we need. And now, engineering is having us make prototypes for them rather than having to send those to outside suppliers."

Griswold's engineering group uses SolidWorks software to design new profiles. "Then they send it over to me and I take it into MasterCam to create the toolpaths for the laser," McCulloch says. The laser also engraves each cartridge cup with a number that describes the profile, which helps with part identification and inventory control.

It only takes the laser about 45 seconds to cut the profiles and engrave the number on each cup. The vacuum fixturing system not only holds the cups in place, but also evacuates slag and small particles generated during machining. When each batch of four cups is done, the vacuum system automatically shuts off so the parts can be removed.

Griswold found other uses for the laser system as well. Cutting plastic inserts for the company's Griswold Optimizers is one example. This patented part goes inside a ball valve to control the flow of water. Shah says, "We used to have different molds for different inserts, but now we can buy just one size of material and use the laser to cut the insert. We don't have to pay for more molds, so we're saving on capital investments."

In the future, Griswold will be going to more just-in-time inventory. "Right now we're running one shift, but we'll probably go to two shifts as we use up our inventory of cups," says Shah. "And instead of having to order a thousand cups, we can make just what we need."

So while many companies continue with what works, Griswold Controls has taken advantage of new technology to bring laser cutting in-house. And with the change comes the benefits of reduced costs, increased accuracy and better control of processes and inventory.

Scott Weersing is a staff writer/photographer at Haas Automation Inc., Oxnard, California. Contact him at sweersing@haascnc.com.

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