- May 20, 2014
How far can advances in "intelligent machining" for turning go?
Given how quickly machining technologies are changing, "lights out" manufacturing–typically a shift run with minimal human involvement–may soon be referred to as "autonomous" manufacturing in which permanent unattended machining will be the norm.
At least that seems to be where we're heading based on discussions with machine tool builders about intelligent turning technologies.
When people consider "intelligent machining" typically the first thing that comes to mind is software technology. And while they are partially correct in this thinking, the design of the machine and how components and mechanisms interact in the machine tool should also be considered in the definition.
"With CNC machines the focus is on the controls but we've taken a ground up approach to how we design smarter machines," says David Fischer, lathe product specialist with Okuma America Corp., Charlotte, NC. He cites Okuma's Thermal Active Stabilizer (TAS). Fischer says TAS is a result of R&D that focused on what happens to machines and their dimensions when they heat up and cool down during machining.
"For many people, the first thing to focus on would be the control and in how the control can compensate for the heating up and cooling down occurring in the machine. Problem is, you need to write algorithms to make such adjustments and these algorithms can become very complex. What Okuma has done is focus on the machine design."
Smarter machine design
Years ago, flat bed lathes were the norm and the most thermally stable machines, but when slant bed lathes emerged, because of their design, it was difficult to predict the heat patterns, so Okuma created a new design for its slant bed lathe to address this issue.
"We've broken down that slant bed lathe into two parts," explains Fischer. "The way system is on one casting, so it's a cube and achieves the thermal stability. This structural casting is then mounted on an angled base. So now we get the thermal stability and thermal predictability of a flat bed lathe combined with the benefits of a tilted base for ergonomics and better chip evacuation."
It's a similar concept that DMG MORI (DMG MORI ELLISON in Canada) uses for some of its mill-turn multi-tasking machines. Called duoBlock, it achieves thermal stability by building the machine with two cast iron blocks in conjunction with three guideways in the X axis and a three-point support.
In contrast to the two-piece concept for the bed, Doosan Puma's new GT2100 series CNC turning centres feature a single piece slant bed design that Glenn Pedersen, director/product management team at Doosan Infracore Machine Tools, Pine Brook, NJ, says "reduces the centre of gravity of both the spindle and the cross slide by 12 per cent. The Natural Frequency (NF) is a critical factor that affects the machine's contouring performance and surface finishes. The NF of the Puma GT2100 bed is 42 per cent higher, delivering great dynamic stability in high speed operations."
Multi-tasking machines are perhaps the best example of smarter machine tool design. Increasingly, machine tool builders are using the basic lathe design to create machines with dual and B axis milling spindles combined with 360° rotary turning tables that mill, turn, drill, bore, grind and finish parts on one machine with one set-up. Mazak calls the concept "Done in One."
To illustrate the efficiency of multi-tasking, Mazak compares the production of a rotor shaft machined with a conventional process and with the Done In One concept. Mazak cut in-process time from eight days down to two days using the Done In One concept.
DMG MORI ELLISON's Siroos Akari, technical sales manager for the company in Mississauga, ON, says smarter designs for turning machines should also include an ability to accommodate automation such as robots and gantry loaders, "and fast set-up features for quick work change-overs, such as using machining tool presetters, quick jaw change chucks and quick change tooling."
There are lots of "smart" technologies available today from collision avoidance software to on-machine tool and part load monitoring, but manufacturers have to ask themselves an important question: do they need these technologies?
"Smart technologies are out there and Mazak has introduced many concepts for our approximate 300 models of machine tools with approximately 97 being multi-tasking," says Chuck Birkle, vice president of marketing, Cybertec Division for Mazak Corp., Florence, KY. And while these smart technologies offer benefits, "we want to give manufacturers choices based on their applications so they don't have to buy functions on a machine they might not need."
It is a good consideration to keep in mind when purchasing new machine tools because the most significant advances in smarter machining technologies have occurred in machine controls and machining software.
"Everybody is creating more and more software for machine controls and that software has to control cutting conditions and offer a variety of functions to help improve efficiencies, says Kevin Smith, application engineer with Elliott-Matsuura Canada Inc., Oakville, ON, who supports the Nakamura-Tome turning machines line. "Smarter turning is about making it easier to set up and operate the equipment and includes such things as onboard collision detection and crash protection."
Mazak has broken down its machines into categories to help manufacturers select the right level of machining intelligence for their machine selections: five levels of multi-tasking machines, four levels of automation and three levels of CNC controls.
With its CNC controls, level 1 includes its Smart CNC control for easy programming and fast job set up. Level 2 features the Matrix Nexus and Matrix Nexus 2 for optimized multi-tasking programming. Level 3 has the Matrix and Matrix 2 for advanced programming. "Each control has different levels of intelligent functions," explains Mike Finn, development engineer in Mazak's applications engineering department.
For instance, a Level 1 Smart control features "Intelligent Thermal Shield" for heat displacement control. A Level 3 Matrix control offers a voice advisor for machine set up and safety, volumetric error compensation and virtual machining for collision avoidance.
"The spark for our intelligent machine concepts comes from our Technology Centres," adds Birkle. He cites two examples: an "intelligent bar loader system" that schedules and optimizes bar material cutting, and the "intelligent balance analyzer" which shows the required weight and locations to eliminate unbalance in the machine table.
The controls on machine tools today and associated software that provide the "intelligent" functions are part of the growing importance of the human-machine interface (HMI) helping manufacturers improve productivity.
A recent example is DMG MORI's Celos, which made a big splash at EMO 2013 and was a key highlight at the company's Pfronten, Germany, open house in February.
"It helps improve productivity," says Nitin Chaphalkar, team leader, MTL, DMG MORI, who spoke with Shop Metalworking Technology Magazine at EMO 2013. "This is a full analytical package of data that stores details about the machining process, tooling and other parameters. The information in the database can then be used to help improve the process. For instance, we had a customer that was concerned because it was taking too long to make a part during the night shift. With the information he was receiving on his cell phone he knew that the people working the night shift were turning down the speed so they could rest. So owners and process managers can more easily identify problems and rectify them."
An area controls need to address is high speed machining, says Smith. "Higher speed machining will become more prevalent and that means machine controls will require extremely responsive servo motors, drives and control packages to allow such things as high speed turning and threading at two and a half times the normal maximum speed. The other function is high speed synchronization between two spindles on the two turret, twin spindle models. The way the [Nakamura-Tome] machines work, they reduce ramp up time by almost 40 per cent to where they used to be in previous models."
The move to smarter turning in machine design and software is just part of the growing trend towards more intelligent machining. Other technologies not touched on in this article include the increasing use of "machine-to-machine" communication, of which the most prevalent is MT Connect, a machine tool standardized protocol being adopted by many machine tool builders that allows communication between different types and different brands of machines. (Read the article on this subject in the June 2014 issue.)
Ironically, the biggest deterrent to adoption of this technology is manufacturers. "The industry faces a lot of difficulty getting customers to embrace new ways of doing things," says Fischer. "An example is quick-change technology. It's been around more than 40 years but most of the shops I go to haven't adopted it and I ask why? The cost is more, but the savings in the long run are much higher."
Mazak's Chuck Birkle concurs. "Manufacturers are intimidated by the intelligent functions we're adding to our machines. Given the current shortage of skill sets in this industry, our greatest challenge is to get customers to use the smart technologies that exist today on machines. The Mazak Pyramid of Learning, which we've established, helps customers pick the levels of training that they need."
Other machine tool builders have also launched similar in-class and online educational learning programs.
Smarter machining technologies have a higher upfront cost, but as Siroos Akari from DMG MORI ELLISON says, "history and experience have shown that companies that embrace new technologies are more successful in the long term." SMT