I might not be talking about making a person stronger, faster, and better then he was. But taking this phrase from the popular 70’s TV show, the machine tool industry has and will continue to build machines that help the medical field. With stronger precision tool used in the operating room, help mend bones faster with braces and bone saw guides, and make even chewing food better for some in the dental field.

Take, for example, EDM machines.  EDM has been used to produce parts for the medical field for many years. What might not be known by all, is that in the last couple of years the EDM industry has focused on the medical field with the goal to “make it better” for this industry. There are several specific EDM innovations that were developed specifically to “make it better” for the medical field.

Generators:

One innovation was the creation of the new generators which cut exotic materials and reduce, or in some cases eliminate, the recasting of impurities harmful to internal organs onto the medical implants and instrument. In the past there had to be an expensive cleaning process to remove these impurities from medical instruments. Now this cleaning process has been virtually eliminated.

Here’s an example from GF AgieCharmilles:

B-axis Control:

Another innovation for wire EDM has been the full control from the HMI of three different types of b-axes.

• Spin b-axes do exactly that, spin at high RPM’s allowing the wire EDM to produce small grinding pins that clean out the smallest arteries of material that cause heart-attacks. The newest Spin B-axes, also index allowing the wire EDM to cut a key notch in the exact location on these grinder pins. This reduces the cost of the part by eliminating this second operation usually done on another machine.
  
  
• Indexer b-axes have been used to produce bone saw guides as well as other medical instruments. Think of a bone saw guide as a miter box, which allows cutting (in this case, the bone) at a precise angle which helps a broken bone heal stronger.
  
  
• Servo controlled b-axes are new to the medical industry, but have produced some of the most interesting looking medical inserts as well as instruments. One example medical insert (see photo) is made of titanium.  Wire EDM is used to cut a spring in the part to allow it to be used in joint replacement.

QC documentation:

Both the Medical industry and the Aerospace industry requested a way to prove the EDM machine performed the same when cutting the master accepted part and every part after that.  Software developments have now made it possible to record the generator performance so that if during production the generator is not cutting the part exactly the same way as the recorded master (due to either maintenance needs, modification to the program, or a faulty board) the machine will stop with an out-of-tolerance master message. This gives the manufacture of medical components proof that every production part has been cut to the standard set and approved.

Thermal Stability:

When is comes to sinker EDM, the dental industry has benefited from several innovations sinker EDM. Here’s one example of how thermal stability can work: Pumps push chilled dielectric through the casting keeping the base at a constant temperature. At the same time air is cooled through a radiator system at the same temperature as the casting which cools the rest of the machine internally. In order to further increase the accuracy, it’s also possible to have the HMI allow the operator to see if the part being setup and measured on the worktable is at the same temperature as the rest of the machine. This increases the pickup accuracy and eliminates the possibility that the workpiece will move once the cooled dielectric touches the workpieces. All these things together ensure a machine which is not affected by the external air temperature and allows the accurate manufacture of micro parts like medical molds and dental braces.

The diesinking EDM process allows users to burn (cut) small rectangular openings (e.g. 0.02” x 0.013”) through the needle wall without burrs, which eliminates the need for additional deburring.

Up to this point I have talked about EDM only, but milling has also made many advances to make better medical instruments and medical implants.

3+2 milling:

Some parts manufactured on 3 axis milling machines are only part of the medical instrument. One such part is a mass-produced hinge that has to be reliable because it is part of a disposable clamping instrument used in operations. Milling machines are being used in conjunction with die-sinker EDM machines to make thousands of these parts each year. Another part, a titanium clamp implant used fix spinal trauma, is manufactured using a process called 3+2 where the part is index and then machined. There are special milling machines that make short work of parts like these, especially when thousands are needed.

5-axis (aka 5-sided) milling of special materials:

From heart valves to dental implants, small titanium parts are produced day-in and day-out on 5-axis milling machines. A full 5-axis machine is able to produce continuous 5-axis motion at high cutting speed. However, when it comes to milling titanium or stainless steel, there are a few things to remember. One, is that titanium is flammable. Get it hot enough during high speed cutting and it will catch on fire. To prevent this, coolant is usually used to keep the part from over heating. Coolant also helps prevent the second issue, surface hardening. Titanium used in medical implants is a purer form of titanium and, during high speed cutting, over-heating will cause the material to surface harden. Third, is a catch 22, because since coolant is being used during high speed cutting to prevent fire and surface hardening, cutters (especially carbide) will fracture or crack. The solution is to use a milling machine with a spindle strong enough to rough-cut out the material using coolant to make sure the part doesn’t over heat; and then finish-cut using a higher acceleration speed and feedrate to produce a fine finish and increase the accuracy of the part.

Dental implant made of titanium and a heart valve made of graphite coated in titanium.

Here are two larger, full 5 axis parts – these are bone scrapers used in hip replacement surgery.

EDM and high speed milling (HSM) are widely used in medical manufacturing.  In this article I have only shown a small portion of innovations that are helping to make the quality of life better for all.

To continue this discussion with an expert on the subject, click here.