Familiar, reliable equipment series becomes more effective, easier to operate.
Beginning with the Model 107 fusion tube welder in 1979, and the Model 207 in 1989, Arc Machines (AMI) has been developing commercial orbital fusion-welding systems for over 30 years, starting with the Model 107 fusion tube welder in 1979, followed by the Model 207 in 1989. Recently AMI introduced a replacement for the Model 207 — the M217 WDR — which it describes as “the new workhorse of the orbital welding industry.”
For orbital welding customers, the questions will be, “Does the M217 measure up to the reliability and quality of the M207?” and, “Do all the new ‘bells and whistles’ make the power supply more effective and easier to use?”
The first thing a new user will notice about the M217 is how similar it appears to the M207. The familiar ‘red box’ has the same footprint to match up with existing coolers, and the lid and case close together with the splash resistant seal. The M217 is 13 pounds lighter, with a textured finish that resists stains and fingerprints. (See Figure 1.) Connections remain the same, to match up with existing weld heads and accessories, although they have been moved for better spacing.
Opening the lid reveals the first major difference of the M217. In place of the membrane switches and dual-line display windows is a 12.0-in., high-resolution, color touchscreen. To its right are two USB ports, with a new thermal printer to the left. AMI eliminated the openings on the top surface of the M207 that allowed small items (e.g., tungsten electrodes) to fall into the printer or CPU section. Opening the case is simple, with a shouldered socket-cap screw at each corner. Once removed, the upper section folds back, revealing the computer section in the top, and the majority of the electronics in the lower case (see Figure 2.)
Here are some other design observations:
· All components are easily accessible, with no need to remove non-affected parts. Diagnosis and replacement, should a failure occur, is going to be a much simpler task than with the M207.
Figure 3 shows all the sub-systems are arranged horizontally and firmly mounted to metal plates and brackets. This allows for complete airflow and prevents heat from building up. In addition, the primary heat load, the main power unit, is shielded from the rest of the system, and cooled by a pair of high volume fans in a push-pull arrangement. While noticeably louder than the cooling in the M207, this design should keep minimize overheating (the cause of most electronics failures.)
· The M217 contains fewer individual connections than the M207, resulting in fewer potential failure points. All major sub-systems are wired with industry-standard connectors. Fewer pass-through style interconnects, board-to-board headers, or wire screw clamps improve reliability.
· The power unit is designed exclusively for the M217 and manufactured to spec in the U.S. Its design criteria matches the M207 in most categories, and exceed it in one. While both are capable of 5-150A of welding power, only the M217 is capable of auto-switching between line voltages of 110V and 220V. Both units are 100% duty cycle-rated. A power system that is 100% rated means that it was designed and specified for full power usage, and is not being pushed beyond its limits when operated there.
· Another area where the M217 improves upon the M207 is the DC voltage supplies (see Figure 4). AMI chose a third-party supplier that has engineered and manufactured power supplies completely in the U.S. for almost 30 years, and the units included in the M217 have an MTBF rating of 100,000 hours. Fully certified, including UL and CE, they are also qualified for use in the medical industry.
· Also notable is the M217’s controller/interface. The combined touch-panel/ PC is NEMA IP65 rated against moisture and dust, and designed for use in rugged and demanding environments. Eliminating the M207’s mechanical key pads will improve reliability. Containing an Intel processor and running embedded Windows 7, the M217 controller should be a stable platform for the long run. The M217 I n U se Hooking up the M217 is simple.
Facility requirements are the same as the M207, except the fittings for the purge gas lines are compression style, instead of flared. The unit is switched on with its main breaker, in the same location as the M207. Power-up takes about 50 seconds, and displays the M217 home screen when complete.
Navigating through the various screens and operations is very intuitive. One function worth mentioning is the M217’s auto-generated recipe capability. The user enters four parameters (tube diameter, wall thickness, tube material, and the model of weld head) and the M217 pulls all the remaining schedule specifics from an on-board library containing AMI’s best practices.
Select the type of weld you want to perform from the four choices — Auto-pulsed, Auto-step, Auto-tack, and S³ — and the M217 creates and loads the new recipe. Should a user wish to customize specifics or fine-tune a weld, simply touching the schedule field relating to a particular parameter brings up a menu, and allows on-the-fly editing. Another clearly observable improvement over the M207 is in how smoothly the M217 runs the various weld head motors.
Operations are performed from the Weld screen (see Figure 6). Individual displays provide constant feedback as the weld is occurring.
Monitoring of the actual tungsten position as the rotor turns, the output current versus programmed current, weld step countdowns, purge pressure for both lines, and more, are all viewable in easy-to-read, real-time from this screen.
So how does the M217 weld? Using a variety of AMI heads, from the 9-500 to the 9-7500, as well as the 8-2000 and 8-4000, CSI made welds on SS tube diameters from 0.25 to 6.0 in., and wall thickness’s from 0.035 to 0.120 in. Using the M217’s auto-generated four level weld schedules, results were mostly excellent, with a few examples benefiting from small primary amp adjustments to the AMI library values. Bead uniformity, fish-scale, penetration, and color were as good as the best we had ever seen from a M207, and often better.
Another advanced feature examined during weld testing was the capability to perform Single Slope Single Pass (S³) welds. S³ welding is more precise than the current industry standard four-level fusion welds. The four-level weld schedule lowers the weld current every 90º of rotation in an attempt to keep the heat in the work piece constant. But, the heat buildup actually occurs in a linear fashion, not in steps, and can result in what is called the ‘Christmas tree effect’ as the weld bead narrows and widens.
By reducing the weld current in a linear fashion designed to match the heat build-up, S³ welds should be extremely consistent from start to finish. Test coupons using this type of schedule on the M217 looked even better than the four level ones, and might easily become the industry standard as more organizations become familiar with this technique. Fine-tuning the M217 In addition to CSI’s in-house testing, CSI provided M217’s to some external customers, requesting any and all feedback.
Small adjustments to the user interface, added content and form of weld print-outs, durability of painted surfaces, and other enhancements were noted. This feedback, along with CSI’s, was passed along to AMI. Their response to these ‘market’ requests was positive and effective, which will serve them well as they continue to refine the M217.
John Throngard is the senior technology specialist for Critical Systems Inc. CSI leases AMI equipment to manufacturers, and is AMI’s only outside authorized repair center in the U.S. CSI worked with AMI from the design phase through the beta testing of the M217, and has purchased and performed in-house testing on a significant number of M217s. His article first appeared online at www.criticalsystemsinc.com. Contact him at jthrongard@criticalsystemsinc.com or 866-229-2291.
