What Does ±1.00 mm Mean, and Why Does It Matter?

What does accuracy measure?

In a laser positioning system, projection accuracy is the deviation between the position the control system targets and the centre of the line projected onto the working surface. ±1.00 mm means that if the system is commanded to 850.0 mm, the centre of the line falls between 849.0 and 851.0 mm.

That figure comes not from a single component but from a chain : the positional accuracy of the servo axis, mechanical backlash, the mounting plane of the housing, the angular tolerance of the laser module and the working distance. Break any link in that chain and even the best servo will not hold the figure.

Line thickness is not accuracy

Two figures sit side by side in catalogues and are routinely confused: line thickness and accuracy. Line thickness is an optical property: the width of the strip of light the laser puts on the surface. Accuracy describes where the centre of that strip falls.

A 1 mm line can be positioned to 0.1 mm accuracy, and the reverse is equally possible. In practice the two only make sense together: the operator judges the centre of the line by eye, so a thick line gives back at the reading stage what a precise axis gained.

What does working distance change?

As the distance between the laser module and the working surface grows, two things happen. First, the line gets thicker — focus is adjustable, but only within limits. Second, and more importantly, a small angular deviation in the module mounting is multiplied by distance and becomes a linear deviation on the surface.

An example: a mounting tilt of 0.05 degrees produces about 0.9 mm of offset at one metre. The same tilt gives 1.7 mm at two metres. An accuracy figure is therefore incomplete unless it states at which working distance it applies.

How much do you need on your line?

The right question is not “which system is most accurate” but “what is my tolerance”. Check three things:

• Slit width tolerance. If your customer accepts ±2 mm, an alignment reference of ±1.00 mm leaves a reasonable margin. If ±0.5 mm is required, reassess the whole chain.
• Blade or cutter width. The cutting element itself is often wider than the laser accuracy, so a tighter reference may bring no measurable gain.
• How it is read. If the operator aligns by eye, human reading uncertainty typically sits in the 0.5–1 mm band. Pushing the system far below that adds cost without a return in the process.

How is it verified on site?

We run a simple but effective check during commissioning:

1. Establish a reference pointChoose a measurable, fixed edge on the line and treat it as zero. Use a fixed gauge rather than a tape measure where possible.
2. Command five different positionsEnter five target positions spread along the travel, then measure the centre of the line at each and record the deviation.
3. Return to the same positionsChange the recipe and come back to the first positions. The difference between the second round and the first is your repeatability.
4. Repeat at the endsThe ends of the travel put the mechanical chain under most strain. If a system that holds at the centre does not hold at the ends, look at the mounting plane.
5. Keep the recordThat measurement is the baseline to compare against if a deviation is ever suspected. File it with the commissioning record.

Summary

ServoMotion systems we set ±1.00 mm as a level that holds under realistic mounting conditions and pays back in the process. If your line’s tolerance calls for a tighter reference, assess it together with the working distance and the mounting structure — that is a design decision, not a product selection.