Beveling success

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by Kip Hanson

Ontario manufacturer sees big benefits with new high-tech plasma machine

The Problem
High cost of out-sourced beveling

The Solution
A plasma machine with beveling capabilities 

There was nothing wrong with the old machine. In fact, it wasn’t even that old—Guelph, ON-based AWC Manufacturing Inc.’s first plasma burner, a Koike Mastergraph II, had been purchased just six years earlier.

The problem was with the ‘horse collars’ AWC was making for Komatsu Mining. Since the Mastergraph only burns vertical I-cuts, the Ontario fabricator was spending $275 apiece to have a local machine shop bevel the big U-shaped parts. Operations manager Don Savage explains: “at that time, we had a 20-year old machine that we’d retrofitted with a plasma head and an NC controller. So for most of our work we’d burn everything on the Mastergraph and then use the old retrofit machine for beveling. But the horse collar has so many large arcs and complex bevels there was no way we could do it in-house.”

The subcontracting for that one part alone was costing AWC over $150K annually. Adding insult to injury, their homemade beveling machine was on its last legs. “The drives and the controller were breaking down a lot and we were getting nervous. The beveling for the horse collars was under control (at a cost), but there were also many other parts for Komatsu, as well as outriggers and upper frames for Link-Belt and axles for Hitachi. All of these require beveling, as do most of our commodity parts.” Savage says the machine shop route was too expensive, so AWC tried sending some of its more complex work out for plasma beveling at some of the local plate houses. “They couldn’t hold the tolerances we required. That’s when we called Linde.”

Linde Canada Ltd., Mississauga, ON, distributes welding, cutting and safety supplies throughout Canada, and is a reseller of Koike Aronson cutting machines. AWC challenged the company with the horse collar. “This is 1-1/4 in. [31.75 mm] plate steel with a number of bevels, ranging from ½ in. (12.7 mm) x 45° on the inside diameter to 30° and 17° bevels on the outside,” says Savage. “The tolerance on the root face has to be held to +/- 1.5 mm.”

Wayne Gergens, cutting specialist at Linde, pointed AWC to a Mastergraph Extreme from Koike Aronson, Arcade, NY. The Extreme navigated the horse collar’s complex requirements with ease—AWC was convinced, and ordered its new machine in August of last year.

That’s not to say AWC didn’t shop around. But since the company already had a relationship with Linde from the purchase of its first Koike, the decision was much easier. According to Savage, the machine’s “simplicity of design” means fewer things to go wrong, an important factor in the demanding environment of plasma cutting. “Unlike some of the other machines we looked at, the Koike doesn’t use a PLC to drive the head. It’s just software, CNC, and the head itself.” Also, by sticking with the same equipment brand, AWC was able to get both machines running on the same set of rails. “This was a huge advantage to us. As we went through the learning curve, it was nice to have the old machine there for those situations where we got stuck figuring things out. It worked out very well for us.”

That learning curve is probably the only “gotcha” that AWC experienced through the entire machine implementation. Looking back over the past year, Savage says they probably underestimated the time it would take to get up to speed. “A machine with a bevel head is more difficult to program and setup than straight plasma cutting. One of the things you don’t realize up front is that you’ve got to spend the necessary time cutting test pieces to get the right offset and parameters for each thickness bevel type. Also, proper torch calibration is critical to getting the correct dimensions on your part. It’s far more important than on standard plasma. On the other hand, you’re asking the machine to do much more, so it’s all relative.”

Those test cuts are used to populate a database in the ProNest CAD/CAM system by Hypertherm, thus establishing a library of settings the software uses during programming. Savage says this is far different than with regular I-cutting, since the machine now has to be told how far to move the head in the Z axis, as well as angular information, during bevel cuts. “Basically, you have an AutoCAD drawing of the profile that gets imported into ProNest. You generate the toolpaths, and if there are any bevels, you tell the software what type you want and on which line of the profile. After that, you post the code, send it out to the machine and press cycle start.”

Savage says it took AWC several months to work through all of the different bevels it typically uses. In the event of a new requirement, however, setup is no more difficult than throwing a drop of the correct material on the table and making a few test burns. “It probably takes an hour to establish parameters for a new bevel. Aside from that, there’s a head calibration routine we have to run every couple of months. When we first got the machine, that routine took us an entire day to go through, but now we can do it in a few hours.”

That might sound like a hassle, but Savage admits they were making parts three weeks after taking delivery of the machine. “The installation took a little over a week, followed by two or three days of training. The first part we cut was our horse collar, which we did on Friday afternoon right after the service tech from Linde went home. We were all very pleased with the results.”

One year later, things are running smoothly. Aside from the “one stop shop” processing of its complex parts, AWC sees significant speed improvements as well. The Mastergraph Extreme boasts a 400-amp power supply, a 50 per cent increase over the old Mastergraph II. In one-inch plate, this means 70 in. per minute (ipm), compared to 40-50 ipm previously.

The other consideration for would-be plasma machine purchasers is table choice. Savage explains that AWC went with a water table over a downdraft because it wanted to eliminate its smoke stacks. “It was a tough choice. Aside from the air quality considerations, we felt the water table would give us better table life.” But what AWC discovered was that, when you’re cutting at an angle, more of the support slats underneath the workpiece are exposed to the plasma than with vertical I-cutting. “Table maintenance is actually quite a bit higher when you’re cutting a lot of bevels.”

Maintenance costs aside, the bottom line is this: AWC is well on its way to a two-year payback on its new machine, running just the horse collar. “Volumes have gone down a bit, but we’re still well on target. What once cost us $275 each to send out can now be done in-house in just over 20 minutes. Yes, we had to learn some things along the way, but overall the machine has done very well. We’re very happy with our decision,” says Savage. SMT

Kip Hanson is a contributing editor. [email protected]

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