Boston Engineering Corporation and Moscow Mills Manufacturing Services collaborated to produce this approximately 4 in. x 2 in. x 1 ½ in. stainless-steel pitch-axis subassembly for a goniometer that was part of a brain-tissue-slicing device used in medical research. The component featured tolerances ranging from 0.0002-in. to hand-lapped matched fits. Credit: Boston Engineering Corp. |
Michael Rufo, principal engineer and leader of the Advanced Systems Group at Boston Engineering Corporation, Waltham, Mass., says engineers usually are familiar with the machining operations required to turn their designs into tangible parts.
“Most engineers have built things before,” he says, “but there are always things that you don’t see.” So, to one degree or another, an engineer depends on the machine shop that makes his parts to identify problematic features from a manufacturing process point of view.
As a result, when Rufo contracts a machine shop to build the parts he engineers, he considers the shop’s capabilities and approach to a job. Some shops do, in fact, work on a plug-and-play basis.
“One could make a print and send it to the shop. Perhaps two parts clearly fit into one another. If a dimension on one part is difficult to achieve in manufacturing, or is incorrect such that it won’t fit as intended, some shops ‘just make it.’ If it comes out right or wrong, they are just going to send it off to you,” he says.
For very simple, non-critical parts, that basic level of shop input may be satisfactory and in some cases even cost-efficient. However, when parts and assemblies become highly complex and time is a factor, the engineer/machine shop relationship has to move to a truly collaborative level.
Boston Engineering provides multidisciplinary product development and engineering consulting services to customers in the electronics, medical, and energy/environmental industries, and develops innovative new technologies internally for defense and homeland security applications. For one customer, Rufo participated in a project that developed a machine used in neurological research. The autonomous unit was designed to cut extremely thin slices of embedded brain tissue that would then be imaged via electron microscopy and used to map neural pathways.
The tissue-slicing equipment had to operate within extremely tight tolerances. It was designed to slice a 1-mm cube of brain tissue into 50,000 20-nm-wide slices (within +/- 2 nm), using a diamond blade only 12 atoms thick at the tip. Orienting the blade in yaw and pitch required construction of a precision positioning device called a goniometer.
“We could design it to a certain point, but when it got to determining how we hold the part’s tightest tolerances we needed help,” says Rufo.
To machine the components of the goniometer, Boston Engineering contracted Moscow Mills Manufacturing Services in Stowe, Vermont. Describing the stainless-steel assembly the shop produced, Rufo says, “To produce the extreme reliability required in operation, the tolerances for the components ranged from 0.0002-in. to features that were lapped and hand-fit.”
Moscow Mills is not a plug-and-play shop. The shop machines complex parts for customers in the aerospace, robotics, semiconductor, R&D, and general industrial markets. “Prototype to short-run production is the way I would describe it,” says owner Anderson Leveille. “It’s extremely high-end stuff, a lot of insane parts. They’re made out of exotic materials like titanium, 18Ni-300 maraging Inconel, Celazole, and PEEK polymers, as well as many others.”
In addition to providing machining services, Leveille says, “We provide high value-added support services for our customers. It’s not unusual for our customers to consider us an extension of their engineering departments.”
These stainless-steel assemblies make up a goniometer that was produced via a collaboration between Boston Engineering Corporation and Moscow Mills Manufacturing Services. The device controlled pitch and yaw of a diamond blade in medical research equipment engineered to cut 50,000 20-nm-wide slices (within +/- 2 nm) from a 1-mm cube of brain tissue. Credit: Boston Engineering Corp. |
Regarding that role, Leveille says he sees the machine shop as an interpreter that translates the engineer’s language of 3-D models, dimensions, and materials into tangible items. To fulfill the design’s intent, the interpreter must have comprehensive knowledge and understanding of the engineer’s language, as well as deep familiarity with the tools required to express it.
The tools Moscow Mills employs include a comprehensive array of advanced manufacturing technology. The shop has 3-, 4-, and 5-axis CNC milling equipment, a 7-axis mill/turn machine, CNC and manual lathes, grinders, and equipment for fabrication, heat- and cryogenic-treatment. A 5-axis CMM and other inspection equipment enable precise measurement of complex parts. Software support includes multi-axis CAM and simulation packages matched to the capabilities of the shop’s machines. Other specialized equipment includes a laser interferometer and Renishaw ball bar for assessing the repeatability of machine tools. In addition to possessing the technology, Leveille says, fully exploiting it requires a deep management commitment “to invest in all the correct tooling, all the correct software and the hardware to run the software; you can’t skimp on any of it.”
Complementing newer equipment, Moscow Mills employs machine tools that it custom-modified to maximize accuracy and flexibility.
“We had some 1980s-vintage Mori Seikis that we rebuilt completely,” Leveille says. “We took off the old controls and put on our own and wrote all the software, so now we have some beautiful iron with modern controls on it. We understand how the machines work, why they work, and therefore we are able to do things differently than others.”
Producing parts with tolerances of 0.0002–in. and tighter does require a specialized approach, Leveille says, offering an analogy involving airspeed: “anything above 0.0002-in. is like normal flight,” he said, “but anything below 0.0002-in. requests a different set of rules, like the different set of rules that applies after the sound barrier is reached and exceeded.”
When Rufo sends a complex 3-D part file to Moscow Mills, he says, “I don’t go into the full details. I often won’t bring a part or an assembly all the way to its completion. I’ll send it to Anderson and we work together; he basically consults and advises on the side of the manufacturing, as opposed to the engineering.” By being involved at the design stage, Leveille can proactively address material and manufacturing issues. “There is always good back and forth … ‘we can’t do this, but we can do this,’” he says.
Even with the back-and-forth exchange of ideas, much of Moscow Mills’ work is short-deadline in nature. “We often have to reinvent the wheel on a component, hit the ground running, and get it right the first time,” Leveille says. “Depending on a part’s complexity, it is not unusual for us to go from ‘art-to-part’ in a day.”
Rufo says design and manufacture of the goniometer was subject to strict time constraints. When Moscow Mills was consulted, “This project was within two months of delivery, and the goniometer was a component on the critical path,” he says, “Moscow Mills helped us get the goniometer completed in rapid fashion, such that our team was able to get the entire end-to-end system designed, manufactured, built, and tested on time.”
According to Leveille, Moscow Mills’ responsiveness is driven equally by its advanced manufacturing technology and the attitude and experience of the shop’s team of programmers and machinists.
“We foster an environment where preplanning is an art and a science, where all of the guys are involved,” he says. Leveille pointed out that a purchasing agent might be able to hire a shop that charges a bargain price to simply punch numbers into a CNC, but that approach can put engineers’ time schedules, and their reputations, at risk. Leveille says his goal is to help engineers accurately and cost-effectively execute their designs.
Moscow Mills, Rufo says, “is very good at doing amazing things quickly, and they are always right.” Obviously, timely and accurate delivery of complex projects makes an engineer look good. More importantly, according to Rufo, is minimizing the need for part modifications during integration and testing, when such changes are the most disruptive to time-to-market strategies and overall costs and schedule. In that respect, getting it right the first time can produce significant cost savings and facilitate the project’s overall success.