General issues: |
The laser cuts at a slight taper (1-2 degrees) since the laser beam is shaped like a cone (it gets focused from a larger spot to a small point). The tapering causes one side of a laser-cut part (the side facing up during laser cutting) to be slightly smaller than the other side. The taper is almost unnoticeable in 1/8" material; the thicker the material, the more noticeable the taper. When using laser-cut parts such as wheels or gears, you might need to position the parts in an alternating pattern so that the tapers "cancel out".
The kerf (the thickness of the laser beam) is about 0.010".
Small circles (usually for screw holes) will not be perfectly circular. Also, the holes will be conical due to the slight taper of the laser cut as described above. If you need the holes to be more circular and cylindrical, we suggest that you have us laser-cut small starter holes, which you clean up with a drill.
Plastic thickness can vary by + or - 10%, so you cannot count on the thickness to be exact when designing your parts. If you are designing interlocking parts with slots and tabs and you are trying to create a tight fit, keep in mind that you can only control the dimension being cut by the machine (not the material thickness). You will have to decide whether to design the part so that the dimensions you control are slightly too big or too small (so that to achieve a tight fit, you might have to either sand some parts, or use glue or add some shims).
The edges of some materials including wood, paper, felt, and cloth, will get charred from the laser. The degree of charring depends on the material. The back side might show more charring or some scorching (the laser bounces off of the metal grill on which the material sits and hits the back of the material, leaving scorch marks). You can mask the material to decrease the charring and scorching on the material surface, but the edges will still be charred. Most plastics that we cut, including acrylic, PETG, and ABS, do not char.
Sharp, thin pieces, especially those that taper to a needle-sharp point, might warp from the laser¿s heat, or crack when taken out of the scrap. This is true especially if the width of a piece is the same or less than the material thickness.
If you have parts that taper to a thin, sharp point, note that once the two converging lines are closer than 0.01" apart, the laser beam (which is roughly 0.01" in diameter) will eat away any material left between the two lines. The material at the end of the tip will become paper-thin and brittle and will probably break off in an unpredictable spot. We would suggest that you round off any acute, sharp corners where the two converging lines are no less than 0.018" apart.
The material sits on a metal grid during cutting. When the laser cuts through the material, it hits the metal grill and bounces back and hits the bottom of the material, causing a small dent or mark. The backs of the parts will usually have small dents along the cut edges of the part wherever the laser, metal grid, and material meet.
Many plastics including acrylic and PETG come with a protective masking on both sides. Other plastics, such as ABS and styrene, do not have any protective masking. The masking helps to decrease denting on the back side described above, and protects the material surface from any flames or residues that are created during cutting. If you would like us to mask your material, please request this in the special notes section of our quote request form. |