Everyone wants to engrave perfect images. But perfect engraving requires knowing a few fundamental, unavoidable relationships — not on the software side, but in the machine's mechanical reality.
This guide doesn't cover the images themselves, and doesn't discuss software settings. It covers the mechanical side: what the machine is physically capable of — and not capable of — achieving.
A laser can "print" at print-quality resolution during engraving. For this, though, you need to understand the shared physical limits of your motor, your belt drive, and your microstepping setting.
Most diode laser engravers use a GT2 belt drive, where the belt pitch is 2 mm. The motor and the pulley together determine how many steps are needed for 1 mm of movement.
This number is what appears in the controller board's GRBL settings:
The step/mm value has a critical role because the machine can physically only move to positions reachable by a whole number of steps. There's no in-between position — the mechanics jump to the nearest reachable point.
When engraving, the software draws lines next to each other. The distance between the lines is the line interval. For the machine to achieve this precisely, the line interval has to fit the step grid — meaning it has to come out to a whole number of steps.
80 step/mm, 0.10 mm line interval
0.10 × 80 = 8 steps
A whole number — the machine can move to exactly this position.
80 step/mm, 0.08 mm line interval (318 DPI)
0.08 × 80 = 6.4 steps
Not a whole number — the machine tries 6 or 7 steps. The result is banding.
What happens with a non-fitting line interval? LightBurn jumps to the nearest whole step count — up or down. Because of this, some lines end up closer together, others farther apart. You see this as banding on the finished engraving. LaserGRBL tends to stall in these cases.
The table below shows the matched line-interval and DPI values for the most common motor/pulley combinations. Only values where the required step count is a whole number are listed.
Note: a single-module laser up to 5W, with a 0.01–0.035 mm spot size. For a combined module the optimal DPI may differ.
| Configuration | step/mm | 1 step | Line interval | Steps/line | DPI |
|---|---|---|---|---|---|
1.8° / GT2 20T$100=80 | 80 | 0.0125 mm | 0.100 mm | 8 | 254 |
| 0.050 mm | 4 | 508 | |||
| Other common values (0.08, 0.09, 0.07 mm) don't fit — they cause banding on an 80 step/mm system. | |||||
1.8° / GT2 16T$100=100 | 100 | 0.010 mm | 0.100 mm | 10 | 254 |
| 0.090 mm | 9 | 282 | |||
| 0.080 mm | 8 | 318 | |||
| 0.070 mm | 7 | 362 | |||
| 0.060 mm | 6 | 423 | |||
| 0.050 mm | 5 | 508 | |||
| 0.040 mm | 4 | 635 | |||
0.9° / GT2 16T$100=200 | 200 | 0.005 mm | 0.100 mm | 20 | 254 |
| 0.090 mm | 18 | 282 | |||
| 0.080 mm | 16 | 318 | |||
| 0.070 mm | 14 | 362 | |||
| 0.060 mm | 12 | 423 | |||
| 0.050 mm | 10 | 508 | |||
| 0.040 mm | 8 | 635 | |||
1.8° / GT2 16T (100 step/mm) is the most universal configuration — every common line interval fits it, giving a whole-number step count.
It's not just the line interval that needs to fit — the physical size of the object being engraved also needs to come out to a whole number of lines at the given line interval.
If the size doesn't divide evenly, the machine has to offset the last line — which causes a visible flaw at the edge of the image.
| Size | Line interval | Number of lines | Fits? |
|---|---|---|---|
| 98 × 98 mm | 0.08 mm | 1225.0 | ✓ |
| 97 × 97 mm | 0.08 mm | 1212.5 | ✗ |
| 150 × 150 mm | 0.08 mm | 1875.0 | ✓ |
| 149 × 149 mm | 0.08 mm | 1862.5 | ✗ |
Practical rule: the image needs to be resized so that the physical height (in mm) divided by the line interval gives a round whole number. Then the machine works with whole-number steps the whole way through — no offset in the line order, no banding.