True numerical control of machining and manufacturing processes, born in the 1950’s, wasn’t just a new way of making parts, it was a new way of thinking about the part-making process.

Tracing machines based on templates had been used for years, and punched paper tape or cards had been used to automate looms in the 19th century, but in metalworking, the pattern or template, by necessity, was a highly accurate model of the finished part. Numerical control replaced the physical pattern with a virtual one, but flexibility was little better than the original copy lathe of a century ago.

Computers changed the game by allowing truly multi-purpose machines. Today, the same principle is taking the CNC machine and adding automation to the cutting tool change and inspection as well as part quality inspection, loading and unloading; removing much of the worker interaction with the production process. While this level of automation improves precision in all manufacturing metrics, the real benefit is lower cost through shorter cycle times.

IS IT WORTH THE COST?

The old adage “it takes money to make money” might have been coined to describe metalworking automation. CNC reduced expensive machinist and toolmaker time, a self-evident cost savings, but an automated cell at first glance replaces much less skilled and lower-cost workers. The business case for high-level automation is less clear for medium and low volume production and job shops. DMG Automation summarizes the profit potential succinctly with a simple graph.

At first glance the return on investment for the automated process is clear, but as important is the effect on the breakeven point. In the DMG example, two conventional machine tools could be purchased for the price of a single automated system, approximating the profit available soon after breakeven, but the breakeven point occurs much sooner. As the cost/revenue curves diverge post breakeven, even two conventional systems can’t match the overall return on investment represented by the area between the curves. Put simply, the automated system makes money sooner and at a faster rate, with fewer supporting resources such as labour, production floor space, preventative maintenance and machine qualification/documentation.

While the benefits of automation are clear for long production runs, job shops that batch-process moderate part volumes also benefit. Reducing the number of part set-ups, and the set-up time is a primary productivity driver, centralizing second or third “op” post-machining processes such as inspection, deburring, marking and labeling into a single process increases single-shift productivity. At lower utilization rates, the automated system boosts throughput without the higher costs and decreased productivity typical of a second shift and when volumes increase, the same technology can allow a second shift supervised by unskilled or semi-skilled labour.

FOUR LEVELS OF AUTOMATION

The case for automation is compelling, but is the gold standard, an integrated “lights out” cellular system, the only option? Modern CNC machining centres offer a range of automatic options covering tool change, part holding and bar feeding in turning centres.  At the Florence, Kentucky manufacturing plant of Mazak Corporation, extensive automation of machining centres has reduced costs and driven a considerable expansion of the Florence operation, despite perceived cost disadvantages compared with offshore operations.

The systems are complex, but George Yamane, marketing manager for Mazak Corporation, describes the basic concept as the “3, 4, 5 Project”, meaning “three levels of controls, four levels of automation and five levels of multitasking.” With automated machine tools literally making other automated machine tools, the Florence lines are complex, but the key concept applicable to job shops everywher is the clear definition of four discrete levels of automation. Yamane uses a typical horizontal machining centre as an example: “The first level is the bar feeder”, he begins, a basic technology so common many shops wouldn’t consider it ‘automation’ in the usual sense. “The second level are gantry loaders. They’re integrated into the machine; not very flexible, but they allow the machine to operate for many hours unattended.”

A gantry-equipped machine not only allows production without the dead time associated with manual loading and unloading, it permits chucking and indexing functions not possible with a simple feeder. With double spindle centres, the productivity advantage of a gantry loader machine is even greater. While gantries speed the chucking process and clear the parts efficiently, more complex operations and multiple jobs running on the same centre require a higher level of automation for efficient operation.

“The third level is the Palletech (Mazak’s pallet system)”, Yamani explains. Compared to gantry systems, palletized equipment represents true automation, combining multiple machining tasks with the ability to switch between different jobs, with different lot runs without direct operator intervention. “You can run the machine for long hours, with a very small cost of ownership”, adds Yamane, who notes that palletized systems also allow more in-machine capability, including advanced options such as automatic inspection.

For many job shops, this level of automation offers the best price/performance ratio for short to medium-run parts. The next step is towards the ultimate in machining flexibility and performance, says Yamane. “Another formation is customized automation using robots. You can use it for simple loading and unloading or ‘go the whole nine yards’ with conveyors, continuous part feeding, machine vision systems and robots with the ability to change end of arm tooling.”

This “Cadillac” level of automation is the ultimate in flexibility and is typically the most expensive, requiring integration of robotics that are frequently outsourced. Shops going the robotic cell route have the option of using a third-party integrator who sources machine tools and robotics separately, or purchasing a system from a machine maker who is certified by a robotics supplier to build OEM systems. Both approaches are viable; frequently the decision to use either an independent system integrator or an OEM is based on prior experience with stand-alone machine tools and a good working relationship with their supplier. Yamane’s four-stage description of machine tool automation is also a typical incremental pathway for a job shop; few will jump directly to robotic cells without prior experience with in-machine automation.

With a mature robotic technology base and an improving price/performance ratio in automated machine tools, Canadian job shops can cost-effectively upgrade to equipment that can allow a small to medium-sized operation to bid on contracts of larger volume and sophistication at lower overall risk.

No single article can cover the rapidly advancing state of the art in machine tool automation … look for continuing coverage in Canadian metalworking.