When rotary machines became popular, many people had decided that lack of “cushion” or “give” is the main differentiating factor between coil machines and rotary machines. Coil machines have an inherent “give” and rotary machines do not. This creates a number of issues with rotary machines, related to the way a needle is interacting with the skin.
To begin, needles push back against the resistance of the skin, whereas a coil would normally back off. This action can cause additional trauma/damage to skin tissue, when using a rotary. In addition, when the needle is inserted into the skin, there is a significant amount of dwell time the needle experiences. Roughly 40% of the duration of a stroke cycle the needle is inside the skin, versus roughly 10-15% of a cycle that is spent in the skin for a coil machine. The resulting effect of this is a snagging (“catching”) effect that results in more tissue damage.
When a “cushion” is integrated to a rotary machine, the needle is no longer forced to complete all of its downward stroke. However, this is actually creating a flat spot in the worst possible position of that stroke cycle, the position in which the needle is contacting the skin. What this does is lengthen the amount of time that the needle is dwelling inside the skin to about 50% of a stroke cycle, thereby causing even more tissue damage.
This began an exploration by Neuma developers of possible ways to manipulate the shape of a cam in order to reduce the amount of time a needle would dwell in the skin. The Neuma FOUR’s original (20%) cam gets a needle in and out of the skin very quickly, greatly reducing tissue trauma. Additional cams have also been developed to create different results. The 28% has a slightly slower insertion speed with the same fast recoil of the original cam, and the 33% has an even slower insertion speed with that same recoil. These two cams are great for use with softer shading or multi-pass layering, as compared with the 20% which has been touted as an amazing liner. The 40% cam is great for packing, when single-pass solid packing is desired.
Additional priorities placed on the Neuma FOUR are:
-Ability to sterilize or dispose of external housing with ease
-Ease of variability of stroke profiles and lengths
-Reduced size with highest power available in a pen
-Emphasis being placed on function over form
-Minimal maintenance, maximum lifetime
-Durability, performance, and simplicity
-Endless possibility for different configurations