by Nestor Gula
Assessing the best cutting system for your shop
It’s a conundrum that most expanding shops have faced–which automated cutting technology to purchase.
If money, for the initial purchase and the subsequent running costs were no object, the decision would be an easy one. But these systems come with a high price tag and the running costs can vary. You need to assess your ROI and balance that with the cutting capabilities you require today and in the future. Paul Silva, application specialist, technical sales for Machitech Automation, says laser cutting machines are a good choice for light manufacturing, but plasma offers more flexibility for cutting thicker materials.
“We can go from thin gauge all the way up to a two-inch split. There is no way you can do that with a laser. Plasma can do thin gauge with lower amperage but the fine detail is not there compared to a laser.”
The systems are complex, but so are the needs of most shops, so choosing an automated cutting system is never about choosing one system over the other, says Kal Shergill, president of MicroStep Canada.
“It depends on a shop’s needs: what type of material you’re processing. What are the tolerances required in processing that material? And the most important thing to consider is how much production do you have for one type of material over another?”
One technology doesn’t displace another type of cutting technology, adds Shergill. He suggests fabricators consider the type and thickness of material typically cut in the shop and the volume of production.
Plasma
When looking at cost, a plasma system has the lowest price for entry. Most small metal shops typically start with a handheld plasma system, so the technology is familiar and accessible. General fabrication and welding shops usually use plasma technology for jobs that don’t require completely clean plates, says Silva. They may be “mill plates that have scale, or may be rusty, and can leave them in the yard.”
Plasma has a large dynamic range for cutting different types of metal – mild steel can be cut from thin gauge up to two-inch slabs with modern high definition plasma. “You have very good cut quality up to one inch,” says Shergill. “But at lower thicknesses of about six millimeters, fiber laser would outperform plasma by the speed of cutting and the accuracy that you are going to get. Laser has a much finer beam than the high definition plasma but you would be limited at the top end. You couldn’t, for example, get the same kind of speed [with laser] at one inch. It just drops off quite drastically.”
Flexibility on thicknesses of metallic sheets is one of the strengths of plasma as is the cost of purchasing and running the system. “A high definition good quality plasma starts at about $150,000. Depending on the size of the machine, it can go over half a million easily, but the average of what we sell is between $150,000 and $250,000 Canadian for a complete production level machine,” says Silva. “Our smallest fiber laser is a five by ten with two kilowatts and that’s going to cost you about $400,000 US.” Running costs are low as well because a plasma system runs at nearly 100 per cent efficiency. “A total cost of running time per hour of the process itself, that’s power, gases and consumable, is about ten bucks an hour.”
Waterjet
Waterjet cutting is a slower process than plasma cutting and is a bit more expensive to buy. “You can cut a variety of materials and a range of thicknesses on a waterjet and that is one of the great advantages of a waterjet system,” explains Jamie Larson, marketing manager for Jet Edge. “You can use it for many different applications, you can cut virtually anything with a waterjet, and it has no heat affected zone like plasma or laser has.”
Heat affected zones can cause problems for secondary processes like welding or milling. “With lasers and plasma, one of the biggest consideration is of course the creation of heat affected joints. Heat generated by the cutting component can result in chemical and mechanical changes and in many instances, that is going to negatively impact the part,” explains Stephen Bruner, vice president of marketing for OMAX Corp. “The part may have to maintain its mechanical and chemical integrity from the edge of the part all the way to the middle of the part and this creates a bit of a problem.”
While the speed of a waterjet may be slower than laser or plasma, you can multiply the speed of production with additional heads. “You can add multiple cutting heads to a waterjet to increase productivity and get a better return on investment,” advises Larson. “We have had several customers that have mounted 10 or 12 cutting heads on a machine so you are processing multiple cuts at one time. The ones that are ten heads are 2D systems, but we also have a system with two five axis cutting heads as well.”
One of the main strengths of waterjet is its versatility. Plasma is restricted to cutting conductive materials and laser cutting does have limits in thickness and some materials. Waterjet has none of these. “It’s hard to quantify what is the return on investment of being able to go to a shop that’s got a machine that really doesn’t have any limitations,” says Bruner. “Somebody walks in the door and says I’ve got this piece of acrylic and I need it water jetted to these dimensions or I need a sign or this type of a cut. We believe that the flexibility that waterjet offers, being able to cut virtually any type of material, has an impact on the business and we think that delivers a return on investment.”
Laser
What makes laser cutting a powerful cutting system is its speed, accuracy and flexibility. While it won’t cut all the materials that a waterjet can, it will cut most. “A laser might make for the most well rounded overall tool as far as speed, accuracy, and part quality,” says Dustin Diehl, laser division product manager for Amada America. “The operating costs are probably what gives it a nice ROI.”
While the initial investment is the largest of the three cutting systems, “the laser process is really going to offer an ultimately cheaper part. In a shop where you have a lot of sheet metal work, gauge materials maybe up to half of an inch or even as much as one inch, the laser will cut the parts for less even though the system tends to cost more,” explains Brett Thompson, sales engineer for TRUMPF. “So really what it comes down to is just throughput. It’s going to be the quickest way to cut the vast majority of the different materials.
If a shop has very low volume runs, it may be difficult to justify the cost of a laser when it could be as much as two or three times the cost of a waterjet or a plasma cutting system, says Thompson. SMT
