An electromagnetic tattoo machine is assembled with a pair of electromagnetic coils and a reciprocating armature bar. This is a what visually and functionally characterizes the electromagnetic tattoo machine and separates it operationally from a rotary machine, or a pneumatic machine. We all know that the coils are the main machine part responsible for attracting the armature bar which holds the needle bar with it's attached needle groupings, and forces the "down ward motion" which make the needles penetrate the skin. Inexperienced artists often blame the coils for a machine not functioning or running properly. So some myths and assumptions about coils must be addressed.
Lets talk about the function of the Coil, starting with electrical current.
Current is made up of electrons. Electrons are invisible atomic particles. Voltage is the force that causes current, in the form of electrons, to move through wires. Electrically charged particles move through material, they can move through water as well. Electrons are the most common moving charges. In our use, the coil uses copper wire. Copper is an excellent conductive metal because copper atoms contain very loose electrons. Even though this is true of all metals, copper is the preferred type of wire for our intended use.
In a copper wire, the energy due to room temperature is enough to make any of these electrons float around inside the metal. When connected to a power supply, electrons are pushed, they will move through the wire in a continuous loop of charge, like water through a garden hose. When electricity moves through a wire it creates an electromagnetic force. When running an electric current through a machine coil with a steel or iron core, a magnetic field is generated. A final note, the closer the wire is wound together, the better the quality of the magnetic field. Look at some of these "machine" builders coils...check the closeness of the winds.
First, before we proceed to the next topic, the term "wrap" used as "8 wrap" or "10 wrap" referring to the wire winds on a coil is incorrect, each time the wire completes a turn around the coil post, it is referred to as a "wind" or a "turn". The winds added up from the lower retaining washer/cap to the top washer/cap is called a layer. An 8 layer coil (D.H.D. round coils) may have 296 turns or winds around the post. So the correct terminology is "8 layers" or "10 layers" NOT "8 wrap" or "10 wrap". There are few simple ingredients which make up a coil's construction:
* an iron or steel post
* insulation tape
* nylon, neoprene or plastic retaining washers
* magnetic copper wire
Lower retaining washer.
Coil post / core. Made from Iron or steel.
Upper retaining washer-plastic, nylon neoprene...anything but
The construction of a coil bobbin consists of (starting at the center): a machined or milled iron core-recommended steel is 1018 or 1025, not stainless, this core is then wrapped with a layer or insulation tape, followed by windings of magnetic copper wire to the desired number of layers, which are held in place with a nylon, plastic or neoprene retaining washer inserted into grooves which are machined distally (on each end) on the core for the purpose of accommodating the said washer(s), and finally, the coil is finished with an insulating material wrapped around the "bobbin" of wound wire (sticker, insulation tape, heat shrink.). This is a simple construction.
Not true, the construction of a "coil" will not permit a coil to "burn out" or "go bad". One way a coil will become useless is if the wire wound around the post is broken. This will interrupt current flow and the machine will not run. Another way is for any part of uninsulated wire to make contact with the frame, or the yoke (grounding). This is not to say that a grounding problem would be solely linked to the coil wire itself, it is common for inexperienced artists to not insulate the screws which secure the binding posts (see binding post assembly illustration p. 53).
The construction of a coil consists of (starting at the center): a machined or milled steel or iron core-recommended steel is 1018 or 1025, not stainless, this core is then wrapped with a layer or insulation tape, followed by windings of magnetic copper wire to the desired number of layers, which are held in place with a nylon, plastic or neoprene retaining washer inserted into grooves which are machined distally (on each end) on the core for the purpose of accommodating the said washer(s), and finally, the coil is finished with an insulating material wrapped around the "bobbin" of wound wire (sticker, insulation tape, heat shrink.). This basic construction cannot "burn out" and will not be damaged by heavy use.
Let's address some myths about coils.
Myth: "Coils burn out.
Myth: "12 layers are better than 10, 10 layers are better than 8, 8 layers are better than 6."
Not so...The more layers of wire wound around a steel/iron post, and the thicker the wire, the longer the current takes to flow through, from the lower binding post around one coil, around the second coil and ending at the terminal at upper binding post. Remember, the longer the wire, the more resistance the current will encounter in it's movement through the wire, and the more heat will be produced. The wire gauge and length are the key factors here...the thicker the wire, the more current will flow through but the slower it will flow. Is it really better? Not necessarily, there are variables which can be changed: spring thickness and tension, frame specifications, armature bar weight and capacitance measurements to compensate for and even improve what a coil's performance may lack and may even make the magnetic field of a coil with less layers, function similar to a coil assembly with more wire layers, just by changing the wire gauge to a thicker gauge. But no matter how many layers of wire, the electromagnetic coil will still do what it was designed to do: allow current to pass through the wires wound around it's steel or iron posts causing a magnetic field which pulls down the armature bar, moving it and it's components (needle bar, needles...).
Myth: "Coils must always be used in Pairs"
Not so, there have been machines made using only one coil. The weight of all components being moved by this one coil must be such that this one and only coil can move them with minor effort in order to make this one coil machine run well.
The thickness of any wire is called it's "gauge". These thicknesses / gauges, are measured in numbers. The tattoo industry standard gauge for magnetic copper wire wound around coils is AWG 24.
Wire gauge measurements / numbers, are opposite to the measurements of spring gauges in the way that the thinner the wire, the larger the number and the thicker the wire, the smaller the number. The measurements of the magnetic copper wire are preceded by: AWG, this abbreviation stands for "American Wire Gauge". The standard industry coil bobbin is wound in AWG 24. Thicknesses of wire will affect current flow. Thin wire (AWG 25, 26.) allows current to pass faster with less resistance, the thicker wire (AWG 23,22,21), though it allows more current to pass through, it actually causes more of a resistance because there are a greater number of electrons present in the thicker gauges of wire. Regardless of wire gauge, the closer the winds are together the better the magnetic field will be. An inconsitently hand wired coil bobbin will not be as efficient magnetically as a tightly wound coil bobbin. If winding your own coils, do it right, wind them tight!
These "V-twin" coils (patent pending) are wound in 6 layers of
Most of the magnetic copper wire manufactured is sold pre-insulated so if the wire is being wound around a round coil, it is not always necessary to apply a layer of insulation tape to the coil post...but, it depends on the thickness of the insulation material covering the wire. The main reason to apply the layer of tape is to be sure that no grounding will occur by any exposed wire directly touching the coil post or any other metal part on the machine. Remember, we want the current to pass through the wire, NOT through the frame, the steel / iron coil posts or the yoke, so make sure any exposed wire is insulated! Any coil core which has angles in it, square, rectangular, octagonal, should have a layer of insulation tape around the bobbin core to prevent any possibility of sharp edges or angles from cutting through or wearing down the wire's own insulation and causing a grounding problem. Grounding in a tattoo machine is caused when an un-insulated exposed wire or terminal directly touches any other metal part of the machine components other than the terminals attached to the upper and lower binding posts.
Coil Assembly (Assembling coils)
Every coil has a starting and stopping point where the wire wound around the bobbin starts it's winds and ends-a hole is drilled or punched into the retaining washer next to the center of the coil core/post and it starts it's winds usually from the bottom or base of the coil post, to the top retaining washer and back down repeatedly until the number of layers desired is reached. The end of the wire commonly ends on the outside of the same retaining washer where the winds are started and exits through a hole drilled near the outside diameter. It is not wrong to have a coil wire end and exit through the top retaining washer. We have made coils of odd numbered layers-5, 7, 9 which start winds at the "bottom" of the post and exit at the top retaining washer. This made the distance from the top of the coil to the upper binding post shorter which cosmetically, created one less wire to try and hide or tuck away and made for quick assembly of the coils to the frame / binding posts, it also gave the machine a front coil with an odd number of layers and a rear coil with an even number of layers. Functionally, the difference was slightly noticeable. Our theory was that a frontal coil with more winds and another layer would make for a stronger magnetic pull and add versatility to the machine's function.
The inside wires (or starting wires at the inner base of bobbin) from each coil must connect to each other, the outside wires (or end wires) will connect to ring terminals which will be attached to the upper and lower binding posts. The sizes of these ring terminals are #8 or #10 (see p. 39, "Understanding screw threads"). We recommend that no solder be used when connecting coils to each other. This makes for easy separation of the coils if separating them from each other becomes necessary. It is also not necessary to solder the outer wires to the terminals if the terminals used are the type that can be pinched to secure the wire to the (although unsoldering a wire from a terminal is easy). These are called solderless ring terminals. They Can be pinched with pliers. All exposed wire must be insulated and it is not a bad idea to insulate part of the terminals to prevent potential grounding on the machine's frame.
Coil assembly wiring diagram
Wire ends connecting to terminals, or to other wires, should have the red insulating material removed before attaching them to the terminal. Simply scrape this material off with a pair of scissors or a small file, be careful when using any blade as the wire may accidentally be cut off.
If a wire breaks, at the bottom of the coil at or under the retaining washer, the coil can be repaired by partial removal of the retaining washer and careful unwinding of the broken wire to the desired length. This must be done with care so as not to accidentally cut any part of the wire winds. This can be a tedious process, so be patient, take your time. Think of it as brain surgery. DHD coils are manufactured for easy disassembly in case such an emergency arises.
This is a perfect example of a pair of coils, carelessly joined together with solder, leaving the bare wire exposed. If you look carefully, you can see the exposed capacitor behind the exposed wires. Capacitors are also capable of causing a grounding problem so it is strongly adviseable to heat shrink the capacitor as well. The coils should have been more presentably heat shrunk. This is a perfect example of careless work, imagine if you dropped your car off for repair and the car looked like this when you picked it up!
Please, to more fully understand the function of the coil and it's magnetic field and it's application in the act of tattooing, read the power supply section on page 62.
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