CNC Point Pin Marker: How Dot Peen Marking Works

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  What a CNC Point Pin Marker Actually Does
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  Depth, Pitch, and Force: The Three Settings That Decide Quality
• 3
  Where the Stylus Can and Cannot Reach
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  Material Behavior Under the Pin
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  Running the Mark Inside the Machining Cycle
• 6
  Dot Peen vs Laser vs Stamping: Which Fits the Part

A CNC point pin marker is an impact marking head, not a cutting tool. A solenoid or pneumatic actuator pushes a hardened stylus into the workpiece, then retracts it. The cycle repeats at 100 to 400 hits per second. While the stylus is cycling, the machine moves either the head or the part along X and Y, so each hit lands a fixed distance from the last one.

The spacing between indents is the dot pitch. At a pitch of 0.1 mm, the dots overlap enough to read as a continuous line. At 0.3 mm, you get a visible row of separate points. Both are legible; the choice depends on how the mark will be read and how the surface will be treated afterward.

Nothing is removed from the part. Material is displaced and pushed sideways, forming a small raised rim around each indent. That rim is why dot peen marks survive shot blasting, anodizing, and most paint lines. A laser mark sits on the surface; a pin mark sits in it.

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  Impact, not abrasionNo chips, no coolant, no tool wear curve to monitor.
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  DisplacementMetal flows around the stylus, so the mark has raised edges.
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  Digital controlThe same CNC program that mills the part can position the mark.

Depth is the single setting engineers argue about most. A typical range is 0.01 mm to 0.5 mm, with 0.05 to 0.15 mm covering most serial-number work on aluminum and steel. Go deeper and you risk a stress riser on a fatigue-loaded part. Go shallower and the mark disappears after a light pass with a deburring tool.

Force and depth are linked. The stylus needs enough force to yield the material, and that force scales with hardness. Aluminum 6061 marks at a low setting. 17-4PH stainless and Inconel need more force, a shorter stylus life, and often a second pass to reach the same visual contrast.

Pitch controls readability more than depth does. For a data matrix code, use a tighter pitch so the reader can resolve individual cells. For a human-read part number stamped on a large casting, a wider pitch saves cycle time with no loss of legibility.

There is a fourth setting people forget: stylus geometry. A 90° cone leaves a different indent shape than a 120° cone. The narrower cone concentrates force, which helps on hard alloys, but the tip wears faster.

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  Depth 0.05–0.15 mmCommon for serial numbers on aluminum and mild steel.
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  Depth 0.2–0.5 mmHeavy-duty tags on castings and forgings.
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  Pitch 0.1 mmFor machine-readable codes.
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  Pitch 0.2–0.4 mmFor text read by eye at arm's length.

The stylus is a straight shaft. It needs clearance above the marking point, roughly 30 to 60 mm depending on the head model. That clearance requirement rules out deep pockets, undercut shoulders, and inside corners where the wall is taller than the stylus body.

Flat surfaces are easy. A cylindrical shaft is also workable if the machine can index the rotary axis and mark along the length, or if the text is short enough to sit within the curvature. Marking across a curved surface with a fixed head changes the effective depth from the center to the edges, so keep codes narrow on small diameters.

Thin-wall parts are the hard case. A 1 mm wall will bulge on the back side if you mark at high force. The fix is a backer, a lower force setting, or a switch to laser marking. None of those three is always right; it depends on whether the back face is a sealing surface.

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  Good fitFlat faces, bosses, shaft ends, and plate edges.
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  WorkableCylindrical surfaces with rotary indexing.
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  AvoidDeep pockets, undercuts, and wall thickness under 1 mm.

Hardness sets the force. Aluminum 6061, 7075, brass C36000, and mild steel 1018 mark cleanly at moderate settings. Stainless 304 and 316 work but tend to smear rather than cut, so the mark looks softer and needs a slightly deeper pass to hold contrast.

Titanium TC4 and Inconel are the boundary. They mark, but stylus life drops and the indent tends to raise a taller rim. On aerospace parts, that rim can matter if the marked area sits near a fillet or a sealing face. Deburring the rim is possible but adds a step.

Plastics behave differently again. POM and ABS deform plastically, so the mark can relax over time, especially if the part sees heat. For plastic parts, a laser mark is usually the better call, and we would say so before quoting a pin marker setup.

Coated and plated parts need a sequencing decision. Mark before anodizing and the oxide layer covers the mark, which can fade it. Mark after plating and you break the coating locally, exposing bare metal. For hardcoat anodizing, mark first and accept a shallower read, or mask the area.

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  EasiestAluminum, brass, and low-carbon steel.
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  Needs tuningAustenitic stainless, titanium, and nickel alloys.
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  Usually wrongSoft plastics and thin elastomers.

The practical advantage of a CNC point pin marker is that it uses the same motion platform as the cutting tools. On a 5-axis machine, the head can be loaded into the tool magazine and called like any other tool. Position comes from the same work offset, so the mark lands where the model says it lands.

That matters for traceability. If the serial number is derived from the same setup that produced the bore, you can tie the mark to the measured dimensions of that specific part. Inspection data and identity stay together.

Cycle time is modest. A 12-character string at 0.2 mm pitch takes a few seconds. A 12 × 12 mm data matrix code at 0.1 mm pitch takes longer, so place codes on a face that is not on the critical path of the cycle.

Marking after the final finishing operation is usually the last step before inspection. At GreatLight, marking sits inside the same one-stop finishing flow as anodizing and bead blasting, which avoids shipping parts out and back between operations.

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  Same offsetMark position inherits the machining setup, so it stays true.
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  Tool-callableHead loads from the magazine like a drill or tap.
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  TraceableSerial number and inspection record share one part ID.