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Acquiring Complex Machined Parts in the 'No Bid Zone'
A complex part, precision machined by Silicon Valley Manufacturing & Machining, illustrates the difficulty of achieving tight tolerances on a part with numerous features of varying dimensions. According to the company, the part is an example of "ultra-precision machining." Photo courtesy of Silicon Valley Manufacturing & Machining.
Pharmaceutical companies are partnering with machine shops capable of producing ultra-high tolerance parts for enhanced reliability
By Jeff Elliott
To safely produce reliable, life-saving drugs with consistent dosing, the pharmaceutical industry often requires machined parts of exceptionally high tolerance and complexity within its production equipment.
The difficulty is that most machine shops–even high precision operations–typically machine parts down to 0.001-inch tolerance. However, when ultra-high tolerance parts (up to 0.0001 inch) are required, a significant number suddenly enter the "no bid zone," where contract part manufacturers pass on jobs that are too difficult or beyond their capability.
"Many machine shops will not bid on an ultra-high tolerance part because they are concerned about the amount of time and effort it will take to meet the required tolerances," said one longtime engineering manager at a pharmaceutical company that designs and builds its own equipment for filling and packaging.
"The fact is that [in the pharmaceutical industry] a part that is 99 percent 'right' may not be good enough," he added. "For one job, we sent some ultra-high tolerance work to a machine shop and they made about 30 parts, but we had to reject them because they failed independent third-party measurement and functional testing."
Fortunately for pharmaceutical equipment manufacturers with complex components in the "no bid zone," there are machine shops capable of producing ultra-high tolerance parts consistently. When they do, it is not usually a matter of having superior CNC equipment, but rather a combination of experience along with a knowledge of unique challenges of machining and inspection required to hit the mark every time.
Overcoming Precision Machining Challenges
When pharmaceutical production equipment is used to handle, mix, process, and package medications in precise quantities, the CNC machining of the component parts must also be excruciatingly precise. This includes parts with tolerances down to 0.0005 inch and sometimes less, machined out of 316 stainless steel or exotic metals such as titanium, Invar, Kovar, and Nitronic 60. However, an increasing number also want high tolerance parts that are made out of ceramics and plastics like PEEK (polyether-etherketone).
To avoid the substantial downside of dealing with failed parts, pharmaceutical engineers send higher tolerance work to machine shops with a proven background in handling such items. One example is Newark, California-based Silicon Valley Manufacturing & Machining (SVM), a shop that has specialized in ultra-high tolerance precision CNC milling and turning services, as well as CNC 5-Axis prototype manufacturing, since 1997. While the company offers services from prototyping to high volume, "lights out" manufacturing, its focus on consistently holding extremely high tolerances down to +/-0.0001 inch is typically the reason pharmaceutical equipment manufacturers seek them out.
"We go to SVM because they will machine really difficult parts that many other firms will turn down and not even bid," said the engineering manager. "This includes both round and tapered parts with tolerances in the range of 0.0001 inch to 0.0002 inch.
Another part, delivered by SVM, that required "ultra-precision machining." Many shops are unable to take on jobs that require machining of parts to ultra-high tolerances of up to 0.0001 inch. Photo courtesy of Silicon Valley Manufacturing & Machining.
"It can be tough to match such high tolerances in every way because in every component, there could be 100 dimensions that all must be near perfect," he said. "SVM is able to make highly precise parts that match the print."
Success in the 'No Bid' Zone
To achieve extremely high tolerances, machine shops must pay attention to minute details and factors that go well beyond what even "precision" parts require. Silicon Valley Manufacturing & Machining owner Mark Serpa said that really begins with a mentality amongst the employees that "no part is too complex to figure out."
"We can hire extremely experienced people or train employees, but if they do not have the right mindset, no years of experience helps because these type of parts cannot be machined like 'all other parts,'" said Serpa. "It requires a team of different personalities, education, experience, and age levels working together. That makes a huge difference."
To ensure that ultra-precise tolerances are achieved on every part, state-of-the-art quality control systems must also be in place.
In the case of Silicon Valley Manufacturing & Machining (www.svmfg.com), the company's measuring equipment includes a Zeiss Contura G2 with scanning coordinate measuring machine (CMM) capability for inspection down to 0.00005 inch; a MicroVu Vision System with 575x magnification; and a Starrett 14-inch Digital Comparator with 50x magnification.
Serpa said that ultra-high levels of precision may even dictate that the same style and brand of inspection equipment be used on both ends.
"To enhance reliability and ensure an 'apples to apples' comparison, we have even had to purchase inspection equipment that matches what our customer uses in their facility," said Serpa.
Even the way each part is handled and moved from point to point can affect how accurately it is measured.
"You have to think about where the part sits and how it is handled," said Serpa. "You have to think about how it is moved from machine to machine, from person to person, because all of these factors can affect measurement when tolerances are that extreme."
In some cases, a short period of time may even be required so that parts can acclimatize to a new environment.
When pharmaceutical production equipment is used to handle, mix, process, and package medications in precise quantities, the CNC machining of the component parts must also be excruciatingly precise. This includes parts with tolerances down to 0.0005 inch and sometimes less, machined out of 316 Stainless or exotic metals such as titanium, Invar, Kovar, and Nitronic 60. Photo courtesy of Silicon Valley Manufacturing & Machining.
"Different types of materials expand or contract with temperature at different rates. This must be accounted for when extreme tolerances are required," said Serpa. "You cannot simply grab a part off a shipping shelf and test it, or you may get a different result."
When ultra-high tolerances are involved, the role of quality control (QC) personnel must also shift from simply assessing pass/fail of parts to "engineering support."
"QC inspectors have to not only tell the machinist if the part is to print or not, but work with them to solve issues in manufacturing that are contributing to the parts not passing," explained Serpa. "This is not the standard mentality in the industry; it is a different skillset, level of work, and responsibility."
Since the pharmaceutical industry must maintain safety at all stages of production, the hygiene and cleanliness of production equipment components is a top priority.
In another example from the pharmaceutical industry, the ability to easily disassemble and clean equipment was a major consideration. Part count reduction and tool-free assembly are also high-priority design goals, which often led to fewer, but more complicated, parts.
Many of the parts were also very high tolerance because they were part of precision mechanisms. Other parts needed high precision to fit together well and ensure that the custom filling equipment would not allow any product to leak.
According to Serpa, the components that SVM delivered were generally made of 316L or 630 stainless (commonly known as 17-4), along with a few made of PEEK or Acetron GP. High precision plastic and steel parts were used together to allow trouble-free motion guidance in an environment where lubrication is not permissible.
For such a demanding application, Serpa suggests it is critical that the customer understands the value added in engaging in an ongoing collaboration with their vendor.
"As a result of the collaborative process, we are able to discover together how to make extremely complex parts more accurately and reliably," said Serpa.
Jeff Elliott is a Torrance, Calif.-based technical writer.
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