The dot resolution of the blackTooth is a combination of two specifications of the machine:
- The steps/inch (or steps/mm) which is the resolution but not the dot size
- The size of the actual dot, which is not specifically related to the resolution.
The steps per or resolution can actually be a range, since the driver microstepping can be modified.
A simple formula can be used to determine the resolution:
step per inch = (motor steps * microstepping) / (travel at one turn of the motor in inches)
if microstepping is set at 16 (1/16 on the driver) and you are using a pulley that has a pitch of .08 inches and 20 teeth on the drive sprocket
= (200 steps * 16 microsteps) / (20 teeth * .08 inches)
= 3200 steps / 1.6 inches
= 2000 steps per inch
To increase the resolution, just increase the microsteps on the driver.
The actual dot size will depend on the lens you are using, the material being lased, the time period that the laser energy is applied to the material, and the focal height of the lens to the work surface material. The energy from the laser will converge to a point and create a dot on the surface (which is different than the kerf of the laser cut into the material).
The dot will appear in different sizes depending on the material because, say wood, will burn causing a dot that burns the fibers of the wood and spreads a bit. The dot lased on the surface of a plastic, say Plexiglas, the dot will be smaller because the energy is absorbed only at that point, but since Plexiglas is a thermoplastic, a bit of the energy will melt the dot edges depending on the time frame (period) that the energy is applied to the surface.
The focus of the laser energy from the lens looks like a cone converging to a point, then diverges outward after that point. Depending on the distance from the lens to the surface of the material, the dot will be bigger or smaller. You want to find focal point (where the energy is focused into a point). You can use the technique where you lay a material on a slope and lase that material along the slope to find the sweet spot (dot) and that will be your smallest dot, or kerf location. Remember that the kerf will widen or narrow within the material thickness depending on the focal length lens specification (the cone will be shorter or longer depending on the lens focal length).