May 2007 Edition

Turning Centers

Lathe Turns Into a Cost Saver

A Wisconsin shop saw a significant time-to-part reduction with a new lathe

Rotating Equipment Repair, Inc., Sussex, WI, took a step forward in its machining technology with the use of a CNC cycle-controlled lathe. By adding the lathe for turning pump shafts and other long, heavy workpieces, RER realized a 33 percent overall reduction in time-to-part, with some jobs involving a 50 percent reduction, based on in-house tracking, according to Bob Merriman, the company plant manager.

The CNC-equipped lathe is a Weiler E70 with a dedicated graphical programming interface designed by Weiler – and based on the open architecture of the Siemens Sinumerik 840D – for the specific needs of the lathe operator.

The machine has been designed so that simple parts can be made in the same way as on a manual machine, only better, according to Andreas Schulz, Weiler U.S. general manager, while complicated parts can be made in the same way as on a CNC machine, only more easily.

As Important as 1-2-3
This is the result of three factors, Schulz said: “First, we built the control to run with a very rugged, rigid, and high-precision machine.

“Second, the control was designed by machinists, based on the input we gathered through our internal marketing operation.

“Third – and perhaps most importantly – Weiler engineers wrote the code graphics, emphasizing simplicity, speed, and information clarity.”

Schulz said an operator doesn’t need extensive G-code or CNC knowledge to get the most from the lathe. He can go from a drawing to cutting in far less time. Plus, he can make adjustments on the fly, especially in the running speeds, to compensate for various factors, without interrupting the basic program.

Weller Machinery, Pewaukee, WI, the local Weiler dealer, sold the unit and provided training to RER. “We installed the Weiler E70 with its 177" bed about six months ago,” Merriman said. “Since that time, we’ve cut our per-part production by at least one-third and up to one-half on some jobs. The constant speed of the machine, the adjustable feed, the non-stop production rates, and especially the programming setup, all contribute to savings.”

According to Merriman, a typical job previously had a 45- hour run. With the new lathe, it was accomplished in 28 hours with better quality. He said the straightness of the part, tolerances held to ±0.0005", and the finish quality even on vertically heat-treated 416 stainless steel – were outstanding.

RER typically works on 3"- to 5"-diameter, multi-stage, high-pressure boiler-feed pump shafts that run at 3,600 to 5,000 rpm.

As a turnkey operation, this job shop also repairs and rebuilds impellers, sleeves and nuts for finished assemblies with tight interference fits in the 0.001" to 0.003" range.

On its largest job to date, a 55'-long pump shaft was machined for a vertical pump with diffusers on the shaft.

Process Flow

The company’s workflow for the Weiler lathe involves a number of steps and operations, Merriman said:
• A pump is delivered, broken down, and analyzed for requirements.
• The engineering department prepares a Pro-E drawing for the shaft work.
• Material requirements are determined and the material is cut to length, usually from RER inventory, on the in-house band saw.
• The machine operator writes the program on a laptop and the material is loaded onto the lathe.
• The program is transferred to the machine and cutting begins.

One-off is the standard at RER, with a typical workpiece starting as a 600 lb billet and finishing as a 400 lb machined shaft. With the look-ahead feature of the Siemens CNC, the Weiler control maintains a constant cutting speed, while adjusting for angle-to-radius changes, especially on precise internal threading.

A Second Opinion

Allen Hock, H&M Machine, Greendale, WI, also purchased a Weiler lathe from the Weller Machinery dealership.

In Hock’s case, he needed to put a 2- pitch internal Acme thread in a 14" I.D. on a 15-3/8" long part. “For the grooving and threading cycles we needed, this was the perfect machine,” Hock said. “The control was clearly made by machinists, not computer guys. It has user-friendly cycles and we can change speeds manually, while the cutting is proceeding

 “The weight and the rigidity of the machine fits our needs, even though we needed to pour a special concrete base for the Weiler. We had another machine under consideration that cost $50,000 less, but we know we made the right decision, based on the performance and the quality of the finished parts we get.”

The Weiler-designed controller, based on Siemens CNC architecture and its Wizard template, is provided to the customer with customized screens for particular machining functions, tool management, thread-cutting cycles, part profiling, and cut simulations.

A drilling axis in X or Z planes also can be selected for machining bore holes and threads.

So Good, They Use It Themselves

Four software engineers at Weiler have Sinumerik 840D CNCs at their workstations to simulate all possible screen variations, based on input from machinists worldwide, so they have firsthand knowledge of what users encounter and how to create improvements.

Weiler research and development A seven-stage water pump assembly is typical of the rebuild work done on the Weiler lathe. The shaft is CA6NM, a modified 400 Series magnetic stainless steel, with high-corrosion resistance. receives application data from the field almost daily, then incorporates the machine motions and tool ma n a gement schemes into the architecture, to make the onsite control as adaptable as possible. Long used in the oil and gas industry for long, heavy sections of drilling equipment and other rotating devices, Weiler lathes are finding applications in the aircraft, steel, and power industries.

At one government facility, an E-Series machine makes the hologram for U.S. currency.

Mobile Pro
Under the leadership of RER owner Kurt Weis, the company performs heavy repair and rebuild operations on pumps, primarily for the power generation industry. In addition to in-house machining, welding, final assembly, and diametrical/runout testing procedures, the company also operates a portable machine-shop-on-wheels that can travel onsite for breakdown, repair, and rebuild operations at the company’s power generation customers. The company is planning another facility to serve customers in its southeast market. While machining shafts are the company’s primary focus, RER also repairs or rebuilds threaded nuts, sleeves, bearings, balance pieces and forgings for its customers.

Weiler

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What do you think?
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