PVDcoating

I needed to replace a motor. The shaft on the old motor was 3/4 inch in diameter. The shaft on the new motor is 7/8 inch in diameter. Expanding the diameter of the shaft hole was not difficult, but I needed to add an internal keyway.* I decided to file a keyway by hand because that fit the tools I have available, and I successfully did it once before on a smaller collar.**

If left unprotected, electronics of all sorts would fall prey to electromagnetic interference (EMI). Nearby waves would contact their circuitry and disrupt their function. This interference might be annoying for a casual smartphone user, but it would be downright dangerous for an overseas military member unable to communicate with their team.

PVD vs CVDadvantages and disadvantages

While transitioning metals into gases requires high temperatures, the difference between evaporation and chemical deposition is that this variation doesn’t require heating the substrate itself. Also, because PVD doesn’t rely on chemicals, the handling and disposal process is safer and easier.

Notice the yellow line. Put the assembly in a vise so one of the jaws covers the yellow line. The other jaw will cover the same area at the opposite end of the EMT. The pulley or collar will be able to turn a little on the EMT. Lock it in place by lightly driving the wedge end of a straight screwdriver between the pulley or collar and the vise jaw where the green arrow appears in the graphic.

CVD vs PVDinserts

The internal keyway cut inside the shaft hole must be parallel to the existing keyway on the motor shaft. Anything done by hand with a file quickly wanders off of a desired straight line.

CVD vssputtering

It can be a slow patient process, but the EMT filing guide allows you to produce a good keyway. The depth of the keyway needs to be even at both ends and through the middle. You may need to do some final adjustments with the file as you attempt to fit the pulley or collar over the key and on the shaft.

Fit the EMT to the shaft hole by either compressing or expanding its diameter. (Squeeze it evenly in a vise if too large, or pry the edges of the opening apart a little until the EMT fits the hole somewhat closely.) Insert the EMT in the pulley or collar shaft hole. Rotate the opening you cut until it is where the keyway should be. Normally, there will be a set screw and the keyway will align with it.

Meanwhile, physical vapor deposition (PVD) is—unsurprising, given its name—deposition by physical rather than chemical means. One of the more popular physical methods, the one Deep Coat uses when vacuum metalizing plastic, is evaporation. This process involves heating the deposition metals until they convert to a gas, then feeding them into a vacuum chamber where they form a layer of metal capable of attenuating EMI.

CVD PVDdiamond

See the second graphic. The precise cut you made in the EMT is positioned just above the yellow line. Use light downward pressure on the file to keep the cut straight and parallel. Apply most of the pressure during filing against or toward the point of the large green arrow. Loosen the pulley or collar on the EMT by removing the screwdriver wedge, shift the collar or the pulley a bit to make the keyway cut the desired width, and lock in place with the wedge end of the screwdriver. Continue filing.

See the third graphic. Make a second cut to remove a piece from the EMT about a quarter of an inch wide. This second cut may not be as precise as the first cut. That is fine as long as you can always know which is the cut precisely parallel to the side of the EMT.

Cut a piece of EMT close to the internal diameter of the shaft hole so it is just 1/16 to 1/8 inch longer than the pulley or collar is wide. A tubing cutter works very well, but a hacksaw will suffice. Cut the tube as squarely as practical.

Cvd vs pvdcar

Chemical vapor deposition (CVD) is the process by which a deposition material mixes with a precursor substance and then bonds with a substrate. This deposition material can vary by project, while the precursor—often a halide or hydride—is the medium that prepares and transports the deposition material to the substrate or intended surface. This combination enters a vacuum chamber, the deposition material forms a uniform layer on the substrate, and the precursor breaks down and exits via diffusion.

Chemical vapor deposition

Lay the EMT piece on a flat surface. Bring a piece of wood up to the EMT and use a marker to make a line along the length of the EMT. Note the orange colored line in the first graphic. Very carefully cut along the line as shown in the second graphic. Use a hacksaw or a Dremel tool with a cutter disc to make a cut that very precisely follows the line you made. Mark the EMT to indicate the very straight cut and distinguish it from a second cut described in the next paragraph.

Disadvantages ofCVD

* As I began enlarging the shaft hole, I believed enough of the old keyway would remain that I could simply deepen it with a file, but enlarging the shaft hole removed the entire keyway. I would have saved a lot of time and effort if only I had made the original keyway 1/8 inch deeper before enlarging the shaft hole.

If you have further questions regarding the differences between PVD and CVD and how to choose one for shielding purposes, get in touch with our knowledgeable Deep Coat team to learn about our extensive capabilities.

This process requires extremely high temperatures. While this necessitates a substantial heat source, the more significant disadvantage is that some substrates cannot withstand heat upwards of 900 degrees Celsius. In addition, the chemicals involved are toxic. Companies must find safe ways to handle and dispose of them to protect workers and the environment.

** An alternate method for cutting an internal keyway is to mount a cutter the size and shape of the desired keyway on a bar and manually crank the tool holder down the lathe bed so the cutter removes no more than 1/1000th inch per cut.

In response to the need for EMI protection, many companies developed efficient and effective shielding methods. Deep Coat utilizes vapor deposition, but even within that subset, there are options. If you want more information on the differences between PVD and CVD and how to choose between them, read this simple guide to both.