When rotary machines became popular, many people had decided that “cushion” or “give”, or the lack thereof, 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 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 dragging (“catching”)sensation 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 sinusoidal waveform, the position in which the needle is contacting the skin. What this does is lengthen the amount of time that the needle is hesitating 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 spend in the skin. The Neuma FOUR gets a needle in and out of the skin very quickly, greatly reducing tissue trauma.
Additional priorities placed on the Neuma FOUR are:
-Ability to autoclave or dispose external housing with ease
-Ease of variability of stroke and waveforms
-Reduced size with no reduction in power
-Emphasis being placed on function over form
-Minimal maintenance, maximum lifetime
-Durability, performance, and simplicity
-Relative ease of manufacturing for the purpose of availability