A PMU Cartridge Is More Than Just a Needle: How Its Construction Affects Machine Performance

When choosing a permanent makeup cartridge, we usually focus on three specifications: needle diameter, configuration and taper. We see a label such as 0.25 1RL LT or 0.30 1RL LT on the packaging and assume that this tells us how the cartridge will perform.

But that is only part of the picture.

A PMU cartridge is not simply a needle placed inside a plastic housing. It is a complete mechanical system consisting of the needle, needle bar, membrane, guiding system, tip and rear component that connects with the machine’s drive pin.

Each of these elements can affect resistance, stability and the way the needle moves. This is why two cartridges labelled 0.30 1RL Long Taper may behave differently, even when their specifications appear identical on paper.

The Cartridge Becomes Part of the Drive System

Once a cartridge is installed, the machine’s drive pin is no longer moving only its own internal mechanism. It must also overcome the resistance of the membrane, accelerate the mass of the cartridge’s moving components and maintain their movement throughout the entire operating cycle.

This means that the cartridge creates a real mechanical load on the motor and its control system.

This is easy to observe in practice. The same machine may sound and respond differently when running without a cartridge than it does after one has been installed. Changing the cartridge brand may also affect the sound, perceived resistance, needle response and machine behaviour at low frequencies.

This does not automatically mean that one cartridge is good and another is bad. It simply means that their mechanical construction is different.

The Membrane Performs More Than One Function

The membrane is primarily associated with protecting the inside of the cartridge and the machine grip from pigment and bodily fluids. This is an extremely important function, but it is not the only one.

In most modern cartridges, the membrane:

• creates a physical barrier that restricts fluids from travelling towards the machine,

• helps retract the needle after each drive-pin impulse,

• stabilises the movement of the needle assembly,

• creates a specific level of resistance that the machine’s drive system must overcome.

EN 17169:2020, the standard addressing safe and hygienic tattooing practices, specifies the use of sterile, single-use needles or cartridges. It also highlights the importance of a physical barrier that prevents fluids from entering the grip. A product should not be used if its sterile packaging is damaged or has expired. However, the statement “cartridge with a membrane” alone does not replace manufacturer documentation confirming the effectiveness of the barrier. EN 17169:2020

A Softer Membrane

A membrane with lower resistance requires less force to deform. It may make the needle movement feel more dynamic because less of the drive system’s energy is used to overcome the cartridge’s internal resistance.

However, this does not automatically mean that the needle will work more gently in the skin.

When the needle moves against less resistance, the artist may perceive the impulse as faster or more direct. The tissue response still depends on the technique, frequency, stroke length, needle protrusion, working angle and hand pressure.

A Firmer Membrane

A firmer membrane generates greater counterforce. It may create a stronger sense of stability or a more distinct needle return, but it also increases the load placed on the drive system.

This difference is especially noticeable when working:

• at low frequencies,

• with a machine that has limited torque,

• with a larger needle configuration,

• with a heavier cartridge needle bar,

• with a longer stroke.

For this reason, “soft” and “firm” membranes should not be treated as synonyms for gentle and aggressive pigmentation. These terms primarily describe the mechanical properties of the cartridge.

The Same Frequency Does Not Always Mean Identical Needle Movement

If a machine displays 60 Hz, its target is 60 operating cycles per second. However, this does not tell us everything about how the needle behaves under load.

In machines without active speed control, greater cartridge resistance may cause a more significant drop in actual speed. In systems that measure and electronically correct speed, the controller can increase the motor response to maintain the selected frequency.

Even then, two cartridges may feel different during treatment. The controller may control the drive speed, but it cannot change the cartridge tip design, guiding friction, needle-bar mass or the elastic characteristics of the membrane.

Machine settings should therefore always be evaluated with the cartridge installed.

Needle Diameter Is Not the Diameter of the Needle Tip

A measurement of 0.20, 0.25, 0.30 or 0.35 mm refers to the nominal diameter of a single needle shaft before it is sharpened. It does not describe the diameter of the point that contacts the skin.

This distinction matters because the shape and characteristics of the needle tip are also determined by its taper.

For example, two needles with a diameter of 0.30 mm may have completely different points. One may narrow to a point over a shorter distance, while the other may taper gradually over a much longer section.

Therefore, the 0.30 mm designation alone does not tell us whether a needle will feel rigid, flexible, sharp or stable.

What Is a Needle Taper?

The taper is the length of the section over which the needle gradually narrows to a point. Cartridge specifications most commonly use the following abbreviations:

• MT – Medium Taper,

• LT – Long Taper,

• XLT or ET – Extra Long Taper.

These terms do not always represent exactly the same taper length across different manufacturers. One brand’s Long Taper may differ from another brand’s Long Taper. Comparing abbreviations alone, without checking the manufacturer’s specifications, can therefore be misleading.

A longer taper creates a longer, slimmer point. A shorter taper leaves more material closer to the tip. This affects the rigidity of the point, how it interacts with tissue and how pigment behaves on the needle.

This does not mean that a longer taper is always gentler or better. The appropriate choice depends on:

• the type of tissue,

• pigment viscosity,

• the desired dot characteristics,

• hand movement,

• needle protrusion,

• machine configuration.

Why Is a 0.25 mm Needle Not Always Gentler Than a 0.30 mm Needle?

A thinner needle has a smaller shaft diameter, but it does not work in isolation. If it is installed in a cartridge with a very soft membrane, a long taper and a looser guiding system, it may behave more dynamically than a thicker needle placed within a more stable system.

An artist may also compensate for a thinner needle by making more passes, increasing the frequency or applying greater pressure. In that case, a choice that is nominally considered “gentler” may not produce a milder tissue response.

The question should therefore not simply be:

Should I choose 0.25 or 0.30 mm?

A better question is:

How does the complete cartridge interact with my machine, pigment, technique and the specific tissue I am working on?

Needle Guidance and Tip Construction

During operation, the needle should not move unpredictably inside the cartridge tip. The guiding system affects lateral stability and determines whether movement from the drive pin is transferred along a consistent axis.

Excessive clearance may cause:

• more pronounced lateral movement,

• irregular sound,

• changes in the way dots are deposited,

• pigment splatter,

• less precise feedback when the needle contacts the skin.

An excessively tight guiding system, on the other hand, can increase friction. The machine must then overcome not only the resistance of the membrane but also the additional resistance created between moving components.

The shape of the cartridge tip is also important. A narrow tip may provide different support and pigment flow than a wider one. An open-tip design can improve needle visibility, while a more enclosed design may retain pigment inside the tip differently.

None of these options is universally superior. The design must suit the technique, pigment and the artist’s working method.

Why Doesn’t an Identical Label Guarantee an Identical Result?

Two 0.30 1RL LT cartridges may differ in the following ways:

Component	Possible difference
Membrane	Resistance, elasticity and return force
Needle	Steel, polishing and straightness
Taper	Actual length and geometry
Needle bar	Mass and rigidity
Guiding system	Lateral clearance and friction
Tip	Width, profile and pigment flow
Assembly	Needle centring and connection quality
Barrier	Seal integrity and protection against fluid ingress

This explains why changing cartridges may require the artist to readjust the frequency, hand movement or method of loading pigment.

How Should You Test a New PMU Cartridge?

A new cartridge should not be assessed solely on the basis of the first few seconds of working on a client. Begin with a visual inspection and a test on latex.

1. Inspect the Packaging

The cartridge should be sterile, intended for single use and sealed in undamaged packaging. ISO 11607-1 describes the role of sterile barrier systems in maintaining product sterility until the point of use. ISO 11607-1:2019

Do not use the cartridge if its packaging:

• is open or torn,

• is wet,

• has a damaged seal,

• does not display a clearly legible expiry date or batch number,

• has passed its stated expiry date.

2. Observe the Needle

Before starting work, check whether the needle:

• is centred inside the tip,

• is not bent,

• does not visibly rub against one side of the tip,

• moves along a consistent axis,

• retracts smoothly after every cycle.

3. Listen to the Machine

An unusual sound after installing a cartridge may indicate increased resistance, friction or a defect in that specific module. If one cartridge sounds noticeably different from others in the same batch, replace it.

4. Begin With Familiar Settings

Use settings whose behaviour you already know instead of changing the cartridge, frequency, pigment and technique at the same time. This makes it easier to identify which variable is responsible for the difference.

5. Evaluate the Dot, Not Just the Sensation

When testing on latex, evaluate:

• dot consistency,

• the amount of pigment deposited with each contact,

• pigment splatter,

• performance during slower and faster hand movements,

• response at different frequencies.

The Most Common Mistake: Adjusting the Machine to Compensate for a Defective Cartridge

If a cartridge operates unevenly, becomes stuck or produces a noticeably different sound, the first response should not be to increase the frequency or apply more pressure.

Replace the cartridge first and check whether the problem continues.

Attempting to compensate for a defective or poorly matched cartridge can lead to unnecessary changes in technique. The artist may begin working faster, pressing the machine harder or repeatedly passing over the same area, even though the source of the problem lies within the cartridge itself.

FAQ

Is a soft membrane always better for permanent makeup?

No. A soft membrane creates less resistance, but it may also produce more direct needle movement. Its suitability depends on the machine, stroke length, needle configuration and technique.

Do cartridges with the same specifications perform identically?

No. The label primarily provides information about needle diameter, needle count, configuration and taper. It does not describe membrane resistance, friction, needle-bar mass or the quality of the guiding system.

Which needle is better: 0.25 or 0.30 mm?

There is no single answer. Diameter is only one variable. You must also consider the taper, tissue, pigment, membrane, machine settings and the result you want to achieve.

Does the membrane completely protect the machine?

Only an effectively sealed and verified barrier can restrict fluids from entering the grip. The marketing statement “with a membrane” is not sufficient evidence that the cartridge provides an effective seal.

Does a universal cartridge work with every machine?

The fact that a cartridge can be physically installed does not guarantee identical mechanical compatibility. Differences in needle-bar length, membrane resistance and rear construction can affect machine performance.

Do I need to change my settings when switching cartridge brands?

Not always, but the needle’s behaviour should be reassessed. If the resistance, pigment flow or nature of the contact changes, you may need to adjust your technique or frequency.

Conclusions

The machine generates and controls movement, but the cartridge ultimately transfers that movement to the needle.

It should therefore not be treated as a neutral consumable. The membrane, taper, needle diameter, needle-bar mass, guiding system and tip profile form a single interacting system. Changing any one of these components can affect the behaviour of the entire system.

It is also important to understand that a cartridge may be poorly designed, incorrectly assembled or inconsistent in quality. The needle and membrane are not the only elements that matter. Connection quality, component fit, needle-bar guidance, tip design and the air vent are also important. Each of these elements can influence resistance, smoothness of movement, pigment flow and the way the needle responds under load.

If a machine is not operating correctly, the machine itself is not always the cause. The problem may lie with a specific cartridge, its construction, manufacturing quality, a particular production batch or a lack of compatibility with the machine and selected technique.

An informed choice is therefore not about finding one “best needle.” It is about finding a cartridge that works with the machine, technique, pigment and tissue in a way the artist understands, can use intentionally and can reproduce consistently.