Introduction to Coil Machine Calibration :

Tattoo Machine Single Operation Cycle:

Power applied, by the power supply, to the negative terminal top post 
and the positive terminal lower binding post of the support structure (frame).

The first and the second electromagnetic coils are charging ,to form an electromagnetic field.

The armature bar is pulled down, by the electromagnetic field,towards the coils.
 Pushing the needle bar and thus the tattoo needleset in a downward motion as a down stroke.

The front spring bends downwards,losing contact with the contact screw.
Thus the circuit opens.The coils cease to charge.
The magnetic field collapses.
A brief kickback current spike is induced.
Some of it's charge is withheld and stored by the capacitor.

Capacitor then discharges,re-energising briefly the coils.
Armature bar is at the lowest position.

The armature bar forced by the tension of the back/rear spring returns to it's 'rest' position.
Needleset is moving off the skin upwards.
The front spring contacts the contact screw.
Circuit closes ,thus coils are charging again.

Front Spring:

Mainly affects the Frequency of the tattoo machine.

A THIN and/or LONG and/or NARROW front spring will decrease 
the Frequency (Speed) of the machine.

Low Tension front springs (Soft Springs) increase the Duty Cycle,also.

On the contrary,a THICK and/or SHORT and/or WIDE frontspring
 will increase the Frequency. 
High Tension front springs,do decrease somewhat the Duty Cycle,also.

Back/Rear Spring:

The back/rear spring deflects the front spring towards

the contact screw.It's power of deflection (tension),

affects mainly Duty Cycle (Coils Charging Duration).

A high angle of deflection and/or a High Tension

(THICK and/or SHORT and/or WIDE) back/rear spring,
will increase Duty Cycle (Somewhat Frequency decreases).

A low deflection angle and/or Low Tension

(THIN and/or LONG and/or NARROW) back/rear spring,
will decrease Duty Cycle(Somewhat Frequency increases).

Capacitor:

The amount of capacitance of the capacitor ,mainly

affects the Frequency of the (dual-coil) tattoo machine.
As the front spring stops contacting the  Contact Screw tip,
the charged coils' magnetic field collapses.
That creates a brief ,but of high voltage 'kickback current spike'.
The larger the inductance of coils (power of magnetic field),
(thus the operating voltage,also) and/or the higher the machine's frequency,
the higher voltage of the kickback spike current.

The Capacitor of the machine 'absorbs' partially & stores the spike's charge.
The larger the it's capacitance,the higher amount of spike's charge “absorbed” .

Or “Stored” instead of “absorbed” .

And that because the capacitor's charge now ,is

charging the coils (just a bit,though ),as the capacitor discharges.

Forcing the armature bar to 'stick' longer with the core of the front coil,
when they contact.

So,a small capacitor of 10 μF, 15 μF or 22 μF,will

increase the operating Frequency,but the machine somewhat 
will decrease in power to pop clean & fast the outer layers of skin .

From the other hand a large capacitor(33,47 or 68 μF) will decrease machine's speed,
but it can assist the coils,onto driving large needle sets clean & fast in and out of the skin,
as the coils remain 'active-charged'from the large discharging capacitor

-while the armature bar has lost contact with

contact screw and is moving downwards.

Contact Screw Gap:

For every given combination of front spring, back/rear spring,
capacitor and magnetic field power

(coils,armature bar & frame/yoke electrical & physical properties-along with operating voltage ),
there is a 'sweet spot' at the gap distance between contact screw tip and front spring contact,
when the armature bar is at the lowest position-in contact with front coil's core.
A gap greater than that 'sweet spot' the Frequency drops ,along with power.

Shorter and the Frequency increases ,but the penetrating power drops considerably.

Needlesets start to 'rip off' the skin easily,also.

(The needleset 'spends' more time being inside the skin.As the artist moves along the tube tip ,
tracing an outline ,shading or packing color,the needleset rips-off the skin,causing excess tissue damage,severe bleeding and excessive wounding with longer healing times).
The severly damaged cellular matrix might not retain it's pigment homogeneity upon healing,
which might lead to dull spots -aka 'Holidays'- or deformed tattoo lines/shades.)

Frequency:

Estimation of machine's optimal frequency ranges,depending on assigned 'role'.

Liners: 120 -140 Hz

Shaders : 100-120 Hz

Fine Shaders: 90-100 Hz

Color Packers :80-90 Hz

Duty Cycle:

The longer the coils are charging,the higher the velocity of the needleset 
( 'Clean' skin penetration ).

Also,the longer the needleset stays off the skin,the faster the handwork can be,
without damaging severely the skin tissue.

The range of 45%-55%,is the one that seems to work best.
Lower Duty Cyclestend to lack power, 
'dully' penetrating the skin tissue and severely damaging it,
while the artist is moving the tube needle tip. 
Higher Duty cycles will overheat the coils.

 

Other factors affecting Dual-Coil Tattoo machine's operation:

-Frame/yoke material,shape and mass.

-Coil Cores & Armature bar's material,shape and mass.

-Needle bar friction.

-Needleset friction.

-Needleset size and type (Round-flat-magnum).

-Rubber-band.

-Coil wire gauge(Resistance) and number of wraps.

-Coil-Core Isolation.
-Correct polarity of Clip Cord.