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The art of training a plate rolling expert

5 guidelines for metalworking shops that want to grow plate roll operators in-house

Plate rolling machines in a metalworking facility

Finding a plate rolling expert is hard for many metalworking facilities, so training one in-house makes sense. Images provided

If you want to learn to drive a car, you go to a nearby parking lot where you practice pulling into parking spaces, making turns, driving in reverse, going different speeds, and employing emergency braking. If you want to learn to drive a race car, you are going to need a lot more practice, the right equipment, the right track, and a team behind you. In other words, it’s a big leap from driving a family sedan around an empty mall parking lot to taking Kevin Harvick’s Ford around a NASCAR road course.

The same thinking can be applied to operating a plate rolling machine. Anyone can load material into a machine and hit a button on the CNC to make it go. That doesn’t mean that things go right, however.

Plate rolling is still an art, even in the day of advanced CNC. Material thickness and hardness can vary from plate to plate, while still being within a specified tolerance range, which introduces variability to an already challenging endeavor. Careful operation helps to maintain a safe working environment and encourages precise work, but a shop floor is always under pressure to increase throughput. In an age when set-it-and-forget-it control technology has appeared on everything from laser cutting machines to even automated press brake cells, an experienced hand on a plate rolling machine is always welcomed.

Unfortunately, an experienced operator is not always available. There aren’t a lot of shops that roll plate, and as a result, the industry simply doesn’t produce a lot of skilled plate rolling machine operators. In fact, in certain cities you’ll see a good operator bounce around from one manufacturer to another, claiming small raises at each stop, because companies value the skill this employee has.

Shops that are looking to jump into plate rolling might be forced to grow their own experts. That’s not necessarily a bad thing because a company knows more about the person it might like to be an operator for the machine rather than an unknown quantity coming from another manufacturer. With that in mind, here is some guidance for those shops that may be hoping to develop some plate rolling expertise within their own ranks.

1. Find a Prospective Operator Who Knows How Metal Reacts During a Bending Process.

A person with a basic metal fabricating background is going to be much more aware of how metal reacts during the bending process. For instance, someone with metal forming experience understands that as material is being formed it moves along a stress-strain curve, which has peaks and valleys. Eventually the operator gets to the point where he is able to apply just enough stress on the material, and the process moves down the valley, where it becomes much easier to move the material. But as the operator comes out of that valley, the material becomes much harder to manipulate.

This is not an uncommon problem in heavy fab shops where someone is rolling plate back and forth on a manual machine, gradually bringing the plate down to the needed diameter. When the operator gets close, he brings the bending roll up just a hair, but the diameter gets too tight. The operator has no idea how the material moved so much after being so resistant. Experience would have had him be much more aware of dramatic material changes after having worked it so much in the rollers. A scrapped cylinder made of ½-in. carbon steel is bad news for everybody.

The operator also needs to recognize that differences exist in what might be considered the same material. Different aluminum alloys have different characteristics, with some considered softer and easier to form than others. Also, material properties can change as it ages. For instance, if a shop is just stacking laser-cut aluminum blanks and the workpieces at the bottom are not used because newer blanks are always stacked on top of it, a plate rolling machine operator has to be cognizant that the older aluminum blanks at the bottom are likely more hardened than the more recently cut blanks.

A person with press brake experience might be the closest a shop can come to finding that person with metal forming experience, but it’s not exactly the same as plate rolling. In press brake forming, bending is static. It’s a little easier to measure the load that it takes to get the metal to a certain point. Plate rolling is a constant process where the material and bending rolls are moving simultaneously. It’s a little more complicated. But someone with that press brake experience at least has some familiarity with how metal reacts when it is under bending stress, so he may be a bit more cautious when working with much more expensive material.

2. Invest in Training for All Shifts.

More often than not, training for a newly purchased plate rolling machine takes place during the first shift and the prospective plate rolling equipment operator is there. That’s OK if the company has only one shift. But if the company is running second and third shifts, the operators on those shifts need to be at the training as well. And having the third-shift operator stay over for an extra two hours for two days does not count.

This plate rolling machine is used to bend thick plate into large cylindrical forms.

When plate is being rolled on machines of this size, the job has to be done right. Shops can’t afford to scrap a workpiece that doesn’t meet customer specifications.

3. Coordinate With Upstream Processes.

Rolling with the plate’s grain structure is going to require less force than working against the grain because the material’s ductility is readily stretched when the plate is made at the mill. The problem is that no computer on a plate rolling machine can tell what the grain direction is on a plate that is loaded into the rollers. That’s left up to the operator.

But upstream processes can help. Instead of a laser cutting machine operator just cutting blanks and stacking the pieces in some random way without taking into account grain patterns, the operator can take the time to ensure that each laser-cut blank is stacked so that the grain pattern in each piece flows in the same direction. That way the plate rolling equipment operator can load in the blanks and expect the pieces to form somewhat similarly without having to worry about the random plate piece that will have him rolling against the grain.

4. Don’t Rely Totally on a Tape Measure.

When a shop gets a new plate rolling machine, many will rely on a tape measure to check the radius. That literally means that they take the rolled plate off of the machine and then use the tape measure to check it.

Creating a template makes a lot more sense. Fabricators have the plasma or laser cutting machine nearby, so they should cut a template of the specified radius. Then the template can be applied to the rolled plate while it is still in the rollers. If it’s not the correct size, the machine can be engaged to put the finishing touches on the rolled shape.

5. Consider a Four-roll Plate Rolling Machine.

A four-roll machine is easier to operate for anyone new to plate rolling. First, it’s easier to load the plate into the machine than a three-roll machine because the rear bending roll can be used like the backgauge of a shear.

The operator lifts the rear bending roll as the plate is being loaded into the machine and moves the material until it hits the rear bending roll in the center, squaring it up like a press brake operator would do with a workpiece and the backgauge. The bottom roller is then brought up to pinch the material. With this four-roller arrangement, the material is held by the rollers for the entire bending sequence.

Now, a four-roll machine is not as versatile as a three-roll machine because of the four-roll machine’s limited opening between the top and bottom. Also, when the material is pinched in the four-roll machine, the equipment is subjecting the plate to the crown of the rolls. (The rolls are crowned to help deal with deflection during the bending process.) It is almost inevitable that a four-roll machine will impart some sort of odd shape to the material, although in most instances the barrel or hourglass shape is still well within tolerances for the job.

If budget were of no concern, a manufacturer interested in processing 16-ga. to 0.5-in. material could buy a four-roll plate rolling machine with 18-in.-dia. rolls that are straight instead of crowned. (The straight rollers can handle the deflection because they are much larger than typical rollers for a machine that can roll the same material thicknesses.) The reality, however, is that few companies are interested in buying an oversized machine with straight rolls. Most shops have distinct applications in mind when purchasing a plate rolling machine so they are looking to get the most for their investment.

Getting a Good Part From the Start

Plate rolling results are better when an experienced operator can oversee the operation, but that doesn’t mean that less experienced operators can’t make good parts. If management can put someone in place who has a desire to learn about the forming process and is comfortable around controls that are similar to mobile phone interfaces, the company is in a good position for success.

Early training from the machine tool supplier won’t cover every scenario that the fabricator is going to encounter with its new plate rolling machine, but the supplier should be available for immediate consultation. Challenges are to be expected. Luckily, they make the engaged plate rolling machine operator that much more capable and better prepared for the next challenge that is ultimately going to arise.

An engage machinery operator helps to deliver quality plate rolls on a consistent basis.

Getting consistent rolled plates is much easier than it used to be thanks to modern control software and machinery advancements, but an engaged operator also is an integral part of the process.

About the Author

Allan Flamholz

President

4610 Mercedes Drive, Suite 410 P.O. Box 70

Belcamp, MD 21017

410-272-3600