Author: Mary-Jane Owen

Medical CNC machining has been the de facto standard for producing medical devices and machine parts for decades.  In recent years, though, 3D printing has entered the field.  Sometimes it can be confusing trying to figure out which technology is better suited to a particular situation.

Nothing in Common

It would help if the two technologies were more compatible.  Medical CNC machining is a subtractive technology -it removes material to form the desired part.  3D printing, however, is additive, layering the fluid material to form the part.  There is no native file format shared between the two technologies.  The language of 3D printing is concerned largely with layer thickness and supporting the part during printing, while the languages used for medical CNC machining have completely different focuses.   3D printed parts also shrink during curing, which means their files have to specify in what directions and to what degree the part is printed oversized.  That’s simply incompatible with CNC machining.

Form Ultimately Follows Function

Medical devices often rely on prototyping during development.  Prototypes can range from non-functional placeholders to see how a component fits into a device, to perfected pieces that have been tweaked for features, functionality, and production steps.  3D printing can be a suitable technology for those early-stage prototypes.  They are seldom concerned with surface finishes, and often the fitting isn’t critical.

As a medical device moves through the development process, however, prototypes necessarily become more refined and functional, with fittings, measurements, finishes, and functionality being incorporated into the design.  In the background, this also involves supports, hold-down tabs, and other fittings required for the production of the part.  If the functions of the part are better suited to CNC machining, it makes little sense to prototype it via 3D printing and then translate that experience to CNC code for manufacture.

The Shaping of Things to Come

There is no question that 3D printing has a tremendous role and promise in creating models of medical imaging for surgical preparation.  Technology has revolutionized many procedures.  This often extends to custom medical implants based on a specific patient’s needs using a wide variety of materials, including ceramic and sintered metal.  These, however, are one-off or limited-run applications, not standard production.

Medical CNC machining, on the other hand, works with an even greater variety of materials and is far better suited to production.  It produces far better surface finishes than 3D-printed parts.  The hardest or strongest 3D printing materials simply are not as durable as materials that can be used in medical CNC machining.  Lastly, the shrinkage inherent in 3D printed parts -especially in materials that require firing- creates greater difficulties in meeting exacting specifications for medical devices.

It’s easy to think of 3D printing as being faster than medical CNC machining, but that’s simply not the case.  3D printing is slow even in the best circumstances.  It’s even slower when printing medical devices because the layers are at the finest level possible to provide the best possible finish.  If a part has been designed by medical CNC machining, that design can be tweaked and the part is re-created from scratch faster than it could be reprinted.  Medical CNC mills can often run lights out, allowing multiple copies to be produced.  3D printers rarely have that capability due to the separation, cleaning, and curing processes that are required following printing.

3D printers have their place in the medical industry, and no doubt their roles will expand as the technology matures.  That said, now and for the foreseeable, medical device design and production is almost exclusively the realm of medical CNC machining.

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• CNC Turning or CNC Milling: The Difference And When To Use

 

In most cases, the choice between using CNC turning or CNC milling to produce a part is obvious.  There are times, however, when the decision is less cut and dried.

CNC milling holds the raw material still while tools move around it, removing what doesn’t belong in the final part.  CNC milling is the obvious choice for flat, square, and otherwise irregularly shaped parts.  CNC turning, on the other hand, spins the raw material while the tools move very little.  This lends itself to cylindrical parts, of course.

The Symmetry of the Part

Parts which can be produced from symmetrical stock are usually best suited to CNC turning.  Symmetrical stock isn’t just cylindrical stock.  Square and hexagonal stock are sometimes turned.  The connotation of symmetrical stock is simply stock that’s about the same thickness no matter which way you turn it around its long axis.  Two-inch by half-inch bar stock is something that would almost never be used for CNC turning -it’s too asymmetrical.

The Roundness of the Part

While round parts are made with CNC milling, it’s far more common to find CNC mills cutting parts with corners and angles.  All things being equal, if you need a round shaft, you will look to CNC turning to produce it.  But if you need a round shaft protruding out of a large flat plate, you need to consider CNC milling.  Flat or boxy shapes are definitely candidates for CNC milling.

On the other hand, consider something like a crankshaft from an internal combustion engine.  It’s not exactly what you’d call symmetrical, with off-axis journals along its length to push pistons up and down.  Yet probably every crankshaft on earth was finished on a lathe.  CNC turning is the go-to technology to balance the weights and fine tune the bearing surfaces to give the crankshaft years of reliable service.  The key is to notice the roundness.  Pretty much every point on a crankshaft is curved.  That’s how you can tell it’s best suited for CNC turning.

The Surface Features on the Part

CNC milling excels at producing surface details.  Milling sealing surfaces perfectly flat, cutting gasket channels around cooling ports, drilling screw holes, even carving decorative or functional finishes or cutting irregular shapes on a part -these are all the bread and butter of CNC milling.  CNC turning has some limited ability to produce surface features -knurling handle grips, for example.  But for the most part, this is the domain of CNC milling.

Sometimes the Answer is Both

It’s always economical to simplify the design of a part.  Minimize the number of features, or concentrate them on one side of a part so it doesn’t have to be repositioned in the mill.  Plan the design so the CNC lathe can form the part while holding it at one end without having to remove it and turn it around.

That’s not always possible, though.  Often your part will require repositioning, which involves truing it up in the machine all over again.  And sometimes a part may require both CNC turning and CNC milling.  It happens that one is far superior at one function you need, while the other is the only way to include another required feature.  Consider that crankshaft again.  Many crankshafts depend on oil being sent through special passageways, and those holes can’t be drilled on the CNC lathe; the part has to be set up on a CNC mill just for that feature.  Features like that obviously increase your costs quite a bit, so consider them carefully, and consult with your CNC professionals to see if you can find another way to accomplish the same job for less money.

It may seem like a simple question at first, but like most things, the more you dig into the details, it gets more complicated.  That’s why working with qualified engineers who are well versed in CNC milling and CNC turning is critical to getting what you want at a price you can afford.

No field presents more challenges to manufacturers than the medical industry.  The extreme tolerances are always there, but the rapid rate of change constantly creates new demands, and once in a while, curveballs can come hard and fast.

The Leading Edge

MacFab’s Swiss turning machines, precision milling and lathe work keep us on the leading edge of the medical industry.  The molecular precision of mass spectroscopy and mass cytometry means not only the machining but also the surface finishes have to be exactly right.  It’s that way with a lot of the components we manufacture.  Fittings and connections have tolerances down to a ten-thousandth of an inch.  Surface finishes must be flawless to prevent cross-contamination.

We’re capable of milling medical components without coolant to avoid chemical contamination.  We can also create parts with an eye on the annealing temperature to avoid changing the crystalline structure and therefore the hardness.  We understand that medical parts are dynamic -they’re never just a lump of metal.  The work we do to create a component can render it useless if we don’t do our jobs right.  We never lose sight of that.

Innovations

New innovations appear all the time, and Macfab is always adapting.  Many of the changes push manufacturing to the limits.  With our operators, our Swiss turning machines can generate components that could hardly be imagined a few years ago.  We maintain the latest technology, tooling, and processes.  Our operators routinely have to learn new technology so we can keep up with the most advanced needs of our clients.

We have the capacity for production runs -not just prototyping.  Our nine-axis Swiss turning machines give us the accuracy our clients need.  They can handle the complexity of these intricate parts, too.  They often can produce those parts with a finish-quality surface.  If not, we can provide Alodine, anodyne, and electropolishing, along with more commonplace finishes to provide the required surface properties.  As new surface treatments are developed, we bring them in-house.

The Curve Balls

The pandemic taught everyone what can be vital and new ways to adapt.  Overnight things as innocuous as masks, gloves, and gowns became both vital and scarce.  Eventually N95 mask production exploded as much as 8 times pre-pandemic levels.  Manufacturers of all sorts suddenly found themselves faced with challenges no one had foreseen.  As you might expect, manufacturers already working in the medical industry were the first to respond.  Then supply chain problems appeared across the globe and created a new set of issues.

MacFab has extensive supplier relationships to ensure availability for the metal, alloy, and plastic materials we machine.  Our software keeps all of our people on top of every project.  Changes in an order, whether they’re related to design, quantity, or timeline, are propagated out immediately to everyone.

The lessons learned are taken to heart.  Whatever the next curve ball is, MacFab will be as prepared as possible.  We understand how crucial the medical industry is, and we take our responsibility to our clients very seriously.  In the meantime, we’re going to keep innovating and growing,

Clean rooms in are nothing new, but their use in assembly is growing dramatically now.  This is especially true in CNC machining for the Medical industry.  More than ever, medicine today relies on devices -both implanted and external- which are amazingly sensitive and complex.  Clean room assembly is required for many of these.  Even more or less standard devices like lasers and masers have to be built in clean room environments if they’re destined for use in medical applications.

The Pitfalls

Establishing and maintaining a clean room requires painstaking attention to detail.  A single person failing to follow one protocol can shut down a clean room for days.  Clean room assembly calls for special arrangements to bring components in and out.  Filters must be replaced on regular schedules and the air monitored and logged constantly to ensure the proper particulate levels are not breached.

Clean room assembly calls for individual components to be suitably prepped, finished and packaged to enter the space.  Each new shipment is another opportunity for problems.  Each discrete component is another opportunity for a supply chain disruption and another inventory item to maintain.

Sunk Costs

Your job is developing and improving life-saving equipment and devices and getting them out to patients.  Time and money you spend worrying about clean room supply, support, and maintenance is nothing but sunk costs to your business.  Still, those considerations are necessary.

Contract clean room assembly is the only solution that makes sense when one little mistake can cost so much.  MacFab has the procedures, monitoring equipment, and installations to virtually eliminate those situations.  It’s what we do for a living; of course we’re going to be better at it than a company that doesn’t focus on this all day, every day.

The Solution

When MacFab takes on your medical clean room assembly needs, components can be manufactured onsite.  They can be finished onsite -whether that means water or solvent cleaning, vapor degreasing, electro-polishing, or passivation.   They can then go into your assemblies without delay.  Our medical clean room facilities are designed to exceed ISO standard 14644-1 class 7 standards.   Our safeguards and procedures simplify your regulation compliance in every way possible.

The Benefits

You get faster service because the components we produce don’t have to be packaged and shipped before being assembled into your base parts or finished product.  The pieces we produce can go immediately from production to assembly.  The savings in both time and cost can be tremendous.

We minimize your supply chain disruptions.  We have excellent supplier networks and can warehouse assembly components.  We can turn those 20 or 30 individual inventory SKUs into the assembly or part you actually need to stock.  You avoid some out-of-stock piece making your entire product unavailable, and your logistics only have to track one SKU that arrives pre-finished and pre-packaged exactly as your line requires.

Macfab’s medical clean room assembly and manufacturing offerings are tailored to allow you to do what you do best -improve and save lives- while minimizing the headaches that can surround these highly critical facilities.  Boost your profitability and maximize efficiency by turning over your cleanroom requirements to a company that focuses on exactly that.

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