Peter Zelinski has been a writer and editor for Modern Machine Shop for more than a decade. One of the aspects of this work that he enjoys the most is visiting machining facilities to learn about the manufacturing technology, systems and strategies they have adopted, and the successes they’ve realized as a result. Pete earned his degree in mechanical engineering from the University of Cincinnati, and he first learned about machining by running and programming machine tools in a metalworking laboratory within GE Aircraft Engines. Follow Pete on Twitter at Z_Axis_MMS.
Mechanical engineer Dakota Bass is seen here with one of the machining centers used to manufacture satellite launchers at CubeSat.
Employers and industry groups have struggled with the question of how best to reach out to young people who might fill the so-called “skills gap” in manufacturing, and fill the need for talent in CNC machining in particular. Dakota Bass thinks this last part of the question answers itself. For him, machining was the outreach. He became fascinated with machining the first time he had a chance to make a machined component as part of his mechanical engineering coursework at California Polytechnic State University. He bought his own small CNC machine and began to experiment with machining in his own time.
He has worked with or near CNC machine tools at each stop in his career since, which so far has involved manufacturing positions with Apple and CubeSat. He recently accepted a position with SpaceX and will begin working there soon.
“Among younger people who are looking at manufacturing, I think the ones who can fill the opportunities in machining will be self-selecting,” he says. Modern CNC machining is fast, automated, and amenable to innovation in a way that is not quite like any other manufacturing process. If continued automation of machining processes leads to an industry in need of fewer employees, but demanding high engagement from the employees who do oversee the work of machining, then it wouldn’t be hard to imagine the work being carried out by a corps of self-selected enthusiasts like Mr. Bass.
In fact, I first heard from him because of an idea that developed from his enthusiasm. Ballnose tools are not the only end mills than can do 3D surface milling, he realized. Recently, he has been experimenting with using much larger, flat-bottom tools to machine smooth, curving surfaces. The key to using the square tools in this way is small stepover increments, he says. The nose rest of the sunglass form below was machined with a 3-inch-diameter face mill—and he says it was machined faster than a ballnose tool could have produced the same form.
The external contours of the nose piece were milled using a 3-inch-diameter flat-bottom tool. Mr. Bass wrote a white paper about surface with large, square tools.
One of the challenges to this approach is that the programmer has to draw the spline defining the tool path for this cutter, because CAM systems don’t automatically generate contouring routines using a tool such as this. Partly for this reason, the technique so far remains his own thought experiment and has yet to find a production application. Even so, you can download the paper Mr. Bass wrote about surfacing with a flat-bottom tool.
Here is a wonderful clip from CNN showcasing CNC machining students who are part of North Carolina’s “Apprenticeship 2000” program. The employer cited in this report, Ameritech Die & Mold, describes how students receive manufacturing employment and paid tuition at a local community college, with the likelihood of a skilled manufacturing job after graduation. By their mid-20s, graduates of this program have high-paying jobs (Ameritech cites the figure of $50,000 to $60,000 per year, plus health benefits) combined with zero college debt. The only price the students pay for this, as the report astutely points out, is that they sacrifice the social experience that is typically part of college.
The compensation alone isn’t the point. A student at the end of this piece describes the real reward, saying, “This is so much more than a ticket through college. This is your life—a career you can build off of.”
Tech Manufacturing runs the spindles hard on its five-axis profilers. The Missouri shop uses these machines to take heavy cuts at high speed for machining large aircraft parts. Periodic spindle replacement is a fact of life and an acceptable cost for this shop.
But the problem was that spindle failure was occurring by surprise. Analysis of machine performance data revealed spindle replacement to be the leading cause of unplanned maintenance downtime for the shop. If this event could instead be planned maintenance downtime, so the shop could schedule spindle replacement within its workflow, then that change would represent a meaningful efficiency improvement. In short, the shop needed to find a way to predict that a spindle was about to fail.
The team members here searched for the telling clue. They tried periodic tap testing. They tried drawbar force tests.
The reliable indicator proved to be temperature.
Just after a milling cycle, the temperature inside one of the profiler’s spindle tapers is generally about 120°F (49°C). But observation of this temperature over time revealed that it reliably increases as the spindle begins to near the end of its life. The increase comes early enough that the shop has time to order a new spindle and schedule the needed replacement.
Now, the shop watches this indicator. Employees routinely measure spindle temperature in search of this increase. They use a digital thermometer for this measurement, but it is possible that this precise device is not even needed. Now that the team members running the profilers are aware of this effect, they can often detect it in the heat of the toolholders when they are manually changing out tools between jobs.
Transforming unplanned spindle replacement into planned maintenance was part of a broad process improvement effort for Tech Manufacturing. Read more about that effort.
Open capacity at 3D-Machine can sometimes involve large-capacity machines, such as the one seen here. The shop uses the distributed manufacturing platform to obtain business from unknown companies without any of its own sales efforts.
MakeTime, the young company connecting buyers and sellers of machining services through a distributed manufacturing platform, describes itself as a “virtual machine shop of CNC machining services from qualified U.S. suppliers.” (In a nod to the popular lodging rental website Airbnb, the company also describes itself as “AirCNC.”) We first wrote about MakeTime in detail in this article, which is still essentially correct. But one important change is this: The company no longer requires shops involved in the platform to spend time on bidding. To improve efficiency, MakeTime now generates fair-market pricing for every job, with buyer and seller simply choosing whether to accept that price.
Removing bidding helps reinforce a point the company takes pains to stress: It’s not an RFQ site. Instead, the idea underlying MakeTime is capacity matching. Buyers upload machining projects, while sellers (machine shops) list their machine tools and their windows of open capacity. MakeTime’s automated process then puts the jobs and capacity together. In addition to performing costing, MakeTime also provides for file preparation, payment management, materials procurement and logistics scheduling. The company does not charge a fee, but collects a percentage of the payment for each successful job.
A recent press statement from the company included two quotes from users of the platform. From a machine shop:
“MakeTime has helped us grow our business without hiring outside salespeople,” says Greg Richardson, owner of 3D-Machine, a Georgia-based independent machine shop. He says the platform also “enables us to tap into a much larger customer base.”
And from a buyer of machined parts:
“Before MakeTime, we were doing most of our production overseas and trying to juggle expectations with different vendors,” says William Davidson, owner of Hybrid Racing, a Louisiana-based aftermarket auto parts supplier. “Now we’re able to move some of our production back to the U.S. because I can get my parts quicker while remaining cost-competitive.”
What machining capability is the right complement to additive manufacturing? For Star Prototype, the answer is a UMC-750 five-axis vertical machining center from Haas Automation (seen here when it was newly purchased in June 2015) programmed using Delcam’s PowerMill software.
The British-owned company based in Guandong Province, China, combines metal 3D printing and five-axis machining to quickly deliver complex, low-volume components that might previously have required the work of two separate suppliers. It calls this service AddSub Manufacturing.
“Many metal 3D printed parts are no longer used as prototypes but as complex low-volume manufactured components,” says Gordon Styles, president of Star Prototype. “As a result, many of these parts need certain high-precision features that are virtually impossible to produce with 3D printing alone.”
The company uses a Renishaw AM250 direct metal laser melting machine to produce dense, complex metal parts in titanium, stainless steel and aluminium. The challenge of machining those parts is not the amount of stock to remove, because the parts are so near to net shape. The machining challenge instead comes from the geometric complexity that additive permits, which led to the five-axis machine purchase. (Indeed, the connection between complex machining and additive manufacturing is a point Delcam recently highlighted in a test case with additive production.)
Star uses five-axis machining to add features to additive parts such as mating faces, precision bores and tapped holes. Whenever possible, the company says, parts are built on the AM250 in a useful orientation for machining, with supports designed so that the build plate can be transferred directly to the five-axis machine.