nesting software

As a manufacturer of trailers for agricultural, scrap, and general industrial applications, Maurer Manufacturing was in the midst of a very busy time in the company's history. In fact, the company replaced its older plasma cutting machine with a new one from Alltra Corp. in November 2006 in an effort to keep up with increased production orders. The table, which came with a 168- by 192-inch cutting table and a Hypertherm HPR260 power supply, was able to keep tolerances of at least 0.030 in. The new plasma cutter was a nice complement to the company's Cincinnati Incorporated CL-707 laser cutting machine, which had a dual-pallet setup, both 72 in. by 144 in. in size, and could reach speeds of up to 8,500 inches per minute.

The cutting tolerances that the new plasma table could achieve actually allowed some family of parts to be cut on either table. Unfortunately, the company's newfound flexibility in cutting plate—mostly 16-gauge up to 5⁄8 in. thick—was plagued by the reality of having to carry two nesting systems, the one that came with the Cincinnati laser cutting machine and the one for the Alltra plasma cutter.

Nesting Software

"The Cincinnati software that we had before was good because it was designed specifically for Cincinnati," said John Tatman, Maurer's production manager. "But we wanted one single software. We were changing over people at the same time, and it was just so much easier to have someone come in and learn one software. And our engineering department could learn one software, instead of having to learn two packages."

For a company that didn't have a lot of time to waste in keeping up with production needs over its two 10-hour-shift, six-day workweek, Maurer Manufacturing didn't see a lot of value in having people sit through additional software training if they didn't need to.

What You See …
All nesting is done offline at Maurer Manufacturing. Because the shop floor works off a weekly production schedule, nests are prepared the week before the jobs are scheduled to hit the shop floor. Tatman estimated that about 25 percent of the nests are standard for popular trailer offerings, while the other 75 percent are unique nests that rely on the software's dynamic nesting capabilities to position the parts efficiently.

So the ability to create master programs for standard nests was an important requirement for new nesting software, as well as the ability to work with more than one brand of metal cutting machine. Maurer managers thought they had both of those requirements covered after witnessing their first demonstration from an independent software vendor.

Three months later, however, they discovered that wasn't the case. What Tatman and his team witnessed in the demonstration couldn't be duplicated at the factory.

The software that was demonstrated did provide basic plasma cutting functionality, but did not provide advanced features, such as feed rate reduction to achieve small holes with reduced taper, autoheight control lockout, and control of the auto gas console. The software also experienced some difficulty producing NC code for the laser.

Cut to the chase

Many applications that traditionally didn't use plasma cutting now can consider it a viable tool. End-user markets for plasma arc cutting have expanded over the last several years.

Newer technologies—such as advanced, digitally controlled inverters—have resulted in developments that can make these systems more affordable and can provide robustness that most typically existed in more cumbersome machines.

In the beginning, plasma development was limited to drooper or chopper technology. Though this technology is reliable, the architecture tends to be large. New inverter technology can provide durability in a smaller footprint. This provides portability, which can be a benefit in construction applications in which cutting often takes place in multiple locations on one site.

Plasma machine

Advancements such as microprocessors, solid-state hardware, and self-resetting fuses add to newer systems' reliability. Other developments include advances in system and torch design, elimination of breakable consumables, and a more cut-resistant torch cable jacket.

In addition, the flexibility of operating equipment with 115-volt input power has brought plasma cutting to the home owner and hobbyist. No longer does a potential plasma user need to be concerned about the complexities of operating the equipment. Today torch design and functionality can improve convenience and ease of use for the unseasoned operator. Nozzle shield technology allows the operator to place the torch on the material when cutting, allowing for greater control and precision.

Many cutting applications can take place in remote areas, where power is not readily available. Welding professionals now can incorporate a plasma system onto their trucks, along with an engine-driven generator and an air compressor, to perform remote operations. Common examples include repairs to construction equipment, such as dump trucks and bucket loaders. Other on-site applications include railcar repairs and bridge construction.

Determining whether your application is an appropriate candidate for plasma arc cutting can be as simple as answering a few questions about the work you do:

1. What are the primary costs in your production or repair processes? If the primary costs are cutting or finishing steps, plasma can offer savings.
2. What are the critical issues or quality parameters? If conformance to specifications and high quality are critical, plasma systems can offer a controlled arc that minimizes metal warping.
3. What new capabilities could plasma cutting bring to your operation? Plasma can gouge existing welds and cut thin-gauge material with minimal warping.
4. What is your skill level in welding and maintenance?

The plasma process requires slightly greater welder skill and training than oxyfuel welding. Also, maintenance skill and training must be greater than for gas tungsten arc welding (GTAW) because the equipment is more complex.

Applications
Aside from the well-known applications for plasma cutting, it can be used in many other, less familiar operations.

Time to Cut the Old Technology Loose

With its 14-year-old machine no longer meeting its needs, ButlerBuilt looked for a change in 2007. Butler and Ashleman considered two options: upgrade the existing plasma cutting system or purchase a new system.

The manufacturer of the original plasma power supply was in the process of discontinuing all support on the plasma system ButlerBuilt purchased in 1993. Additionally, the drive carriage on the plasma cutting system had an outdated rail design, and the drive capabilities were considerably less than newer machines on the market. An upgrade would cost almost as much as a new machine.

The decision was made to purchase a new machine, and Ashleman began an intensive process to research the best systems to meet their needs.

"Our first plasma system gave us good service for almost 15 years, but we chose to refresh with a new machine, new warranty, and new technology," Butler said.

All About the Accuracy
After mapping out ButlerBuilt's specifications and thoroughly researching several plasma systems, Ashleman determined the final decision on a machine would be based on three factors: part repeatability, tolerance of a finished piece over the life of a consumable, and optimal cutting speed.

"With our old system, as the consumable life grew, so did the part tolerance," he said."It was something we were trying to minimize, and it worked out great to find the machine that would do it for us."

ButlerBuilt selected a Genstar cutting table and a KALIBURN Spirit 150a plasma cutting power source from Westwood Robotic Technologies in Elizabethtown, N.C., in the spring of 2007.

The Spirit150a is a 150-amp machine, which gives the seat fabricator the power to maintain repeatability over the consumable's life span. The power source is more than double the size of the company's previous 70-amp system.

The new plasma cutter also gives ButlerBuilt the capability to cut materials up to 1-inch-thick plate, if necessary, and ¾-in. plate on a daily basis.

The majority of our production is 0.090-inch through 3⁄16-inch aluminum, but we were maxed out at high-tolerance cutting of ¼-inch pieces. Now we can quality-cut as much as an inch thick if we need to," Ashleman said.

ButlerBuilt's 150-amp system delivers the speed and cut quality it needs for a majority of the aluminum it cuts. But it also provides the strength necessary to mimic the same results on harder aluminum alloys, which can be comparable to cutting carbon steel.

Orbital Welding

Orbital welding is Automatic Tunguston inert gas welding. It eliminates chances of manual errors in welding. It produces identical welds for hundred of times hence accuracy in welding.

Orbital welding was first used in the 1960's when the aerospace industry recognized the need for a superior joining technique for aerospace hydraulic lines. A mechanism was developed in which the arc from a tungsten electrode was rotated around the tubing weld joint. The arc welding current was regulated with a control system thus automating the entire process. The result was a more precision and reliable method than the manual welding method it replaced

Orbital welding became practical for many industries in the early 1980's when combination power supply / control systems were developed that operated from 110 V AC and were physically small enough to be carried from place to place on a construction site for multiple in-place welds. Modern day orbital welding systems offer computer control where welding parameters for a variety of applications can be stored in memory and called up when needed for a specific application. The skills of a certified welder are thus built into the welding system, producing enormous numbers of identical welds and leaving significantly less room for error or defects.

In the orbital welding process, tubes / pipes are clamped in place and an orbital weld head rotates an electrode and electric arc around the weld joint to make the required weld. An orbital welding system consists of a power supply and an orbital weld head.

Power Supply: The power supply / control system supplies and controls the welding parameters according to the specific weld program created or recalled from memory. The power supply provides the control parameters, the arc welding current, the power to drive the motor in the weld head and switches the shield gas (es) on / off as necessary.

Weld Head: Orbital weld heads are normally of the enclosed type and provide an inert atmosphere chamber that surrounds the weld joint. Standard enclosed orbital weld heads are practical in welding tube sizes from 1/16 inch (1.6mm) to 6 inches (152mm) with wall thickness' of up to 0.154 inches (3.9mm) Larger diameters and wall thickness' can be accommodated with open style weld heads

The orbital welding process uses the Gas Tungsten Arc Welding process (GTAW) as the source of the electric arc that melts the base material and forms the weld. In the GTAW process (also referred to as the Tungsten Inert Gas process - TIG) an electric arc is established between a Tungsten electrode and the part to be welded. To start the arc, an RF or high voltage signal (usually 3.5 to 7 KV) is used to break down (ionize) the insulating properties of the shield gas and make it electrically conductive in order to pass through a tiny amount of current. A capacitor dumps current into this electrical path, which reduces the arc voltage to a level where the power supply can then supply current for the arc. The power supply responds to the demand and provides weld current to keep the arc established. The metal to be welded is melted by the intense heat of the arc and fuses together.

Using plasma arc cutting to clean-cut stainless steel sheet and plate

To cut stainless steels and other metals with plasma successfully, fabricators need the following tools:
To clean-cut stainless steel sheet and plate, fabricators first must choose the right CNC cutting equipment and then set the correct process-related variables. Precise machine motion controls, torch-to-material distance control, and the correct plasma and assist gases all are crucial to producing weld-ready plasma-cut edges on all stainless steel thicknesses.

1. Precision machine motion controls
2. A smooth linear drive system
3. Software controls that automatically compensate and provide proper speed and acceleration and deceleration for various part features

During the plasma cutting process, material is in the molten state inside the kerf zone. Mechanical problems such as motion irregularities cause vibrations, which transfer through the machine axis into the cut edge. These vibrations are solidified into the cut surface and can be easily mistaken for process problems. These motion irregularities and/or vibrations cause a rough-cut surface, nonlinear cut edges, and overall poor cut quality.

Plasma Cutting Machine

To initiate the cutting process, a pneumatic probe locates the material position and provides an accurate and repeatable pierce height. After the pierce is made, the plasma arc cutting (PAC) voltage from the plasma power unit is used in a closed-loop process control system to maintain torch-to-material height while cutting.

Automatic voltage control precisely maintains the torch tip-to-material distance. This is vital when processing thin sheet and stainless steel plate.

Fabricators can process stainless steel with clean-cut surfaces by using nitrogen or a blend of oxygen and nitrogen as a plasma gas. These plasma gases provide a nonoxidizing plasma arc, which produces a clean-cut edge that is weld-ready without secondary operations.

Nitrogen also increases electrode life by preventing oxide formation on the tip of the halfnium electrode. Halfnium is used as the metallic element in the electrode, which also is compatible with oxygen as a plasma gas for steel cutting.

Pure oxygen is not recommended as a plasma gas for stainless steel cutting because of its oxidizing characteristics, which leave an oxidized, contaminated cut edge.
Compressed air is not used for cutting because it often is contaminated with water, oil, or other contaminants. These contaminants can cause regulator and solenoid valve breakdown, as well as plasma double-arcing.

The type of stainless steel assist gas (or shield gas) to use varies according to the material thickness and the desired cleanliness of the cut edge. Based on each assist gas type and the material thickness, different conditions and chemical reactions result.