With dazzlingly precise multi-axis machines, better technology is leading to better tools, design ideas, and better gears. It’s no surprise: metallurgists have been thinking 20 years ahead since, well, forever. When they invent something that takes gear manufacturing to the next level, it opens up a market for more improvement.
But I’ve been wondering lately if there will ever come a fever pitch. I mean, how precise can you be? Down to these ridiculously small measurements, microns? At some point, it’s just crazy.
Gears are the same thing. But the technology used to make a gear is way more complicated than to make a pencil. I spoke to three of the manufacturing experts I could find about how precision technology has revolutioned, well, everything.
“Gears have complex features to machine. Previously, many of the original methods of making gears took that complexity and put it into the tool design. So all the precision was in the tool. As the tool wore out, the quality of the gear deteriorated.
In precision technology, with complex objects converted into complex tool parts, five axis machine motion became important. That’s where quality machine tools and cutting tools come in. The cutting tools are typically ground to a specific diameter with very minor tolerances. At the same time, we have measurement techniques on the machine tools like laser-based measurements. You predict, to the micron, the diameter of the tool. The machine tools have significantly improved the resolution of the machine. Most of DMG Mori’s machine have 5 micron positioning accuracy. So by combining the correct tool measurement techniques and the positioning accuracy and the volumetric accuracy, which is important on a 5-axis machine, we can make pretty accurate gears that are replicable.”
Important things in precision gear technology:
1. Getting the surface of the gear (with modifications) correctly modeled.
2. Preparing a toolpath based on the surface model.
3. Measuring the tool dimensions correctly.
4. Executing it to the highest accuracy possible. It will improve the overall quality of the gear. That is a common thread in how precision and machine tools are dedicated to the quality of the gear that can be machined.
Five axis technology has been being developed for a long time. We have perfected it while applying it to machine aerospace parts such as blades. We are now applying it to the gear machining.
“In gear production, operators need to tilt rotary tables around to get to the different teeth. With our product line, there’s a quick-set function used to calibrate a rotary table or calibrate the five axes on a machine so it knows where all the pivot points are. It previously took hours and hours, maybe even a couple days of work, to do all the calibration and measurements. It’s now in the hour-range. Users can perform their own calibration and check it monthly, quarterly, bi-weekly, so they can calibrate very quickly.”
In the past, the machine would be out of commission for a day or two, and the manufacturer would end up having to do it during a plant shutdown once or twice a year. Now they can do it on a Friday and it’s ready on a Monday morning.
The more things can get done quickly, the more things people want to do to maintain the precision of the machines. Mechanically, there’s still a lot to be done: preventative maintenance, condition monitoring, power consumption, being as green as possible. But with these monitoring functions, it’s easier to maintain and predict maintenance points that need to be addressed.
“The high precision cnc machines have made it possible for manufacturers to achieve much higher quality levels. As we see in the gearing world, a gear is only as good as all of the processes that it takes to manufacture the gear. That translates into better process control starting with your blanking process which provides a higher quality blank to Scud or hob and the benefits just continue to pile up as you march down the production line. The result of high quality equipment, other than high quality parts, is cost reduction! If the machinery is not having to work as hard as it once did in manufacturing/correcting the parts you will automatically achieve better cycle times, which increases your throughput and capacities as well as increasing tool life. This all adds up to increased savings. Our interpolator is a NURBS interpolator. We do everything internally as a spline.”
As most parts are done as a point-point program, essentially every part that comes off a machine is a faceted part. Siemens technology takes all those points and runs a curve through the points to minimize the stops, making a smoother transition from point to point. We’re using a velocity profile, as opposed to a geometry profile. It reads ahead for getting the correct speeds for reversal and stopping, as opposed to relying on geometry.