How to use it
- Measure the cup: the diameter (or circumference) at the rim and at the bottom of the taper, and the height of the tapered part.
- Choose a chuck or roller rotary. With a roller, say which end of the cup sits on the motor-driven wheels: a roller turns the cup by that diameter, whatever diameter you type.
- Pick your laser software, then the design's size and how far below the rim it starts.
- Type the numbers shown into your software, and either engrave the pre-warped PNG or SVG at 100%, or use your software's own taper correction. Never both.
- Engrave the test file on masking tape first and measure it. If it is stretched or squashed, "Fix stretching" gives the corrected setting.
Why logos distort on a tapered cup
A rotary turns the cup by the same angle for every row of the file. On a taper the cup is narrower further down, so the same angle covers less surface: a row at diameter d comes out d / D as wide as drawn, where D is the diameter the rotary turns by (the Object Diameter on a chuck, or the cup where it rides on the driven wheel of a roller). The fix is to stretch each row of the file by D / d.
Worked example: a 20 oz tumbler 3.45 in at the rim, 2.81 in at the base and 6.38 in high, with a 2.25 in logo starting 0.5 in below the rim. The logo's top, centre and bottom rows sit where the cup is 86.4 mm, 83.5 mm and 80.6 mm across. With the chuck set to the rim diameter (87.6 mm), the logo comes out 4.7% narrow at its centre and its bottom edge shorter than its top, so the rows need stretching by ×1.015 to ×1.087. The often-quoted "add 10%" is two separate effects: this one, which depends on where the logo sits, and the fact that a flat logo wrapped round a cup looks narrower from the front.
LightBurn, xTool and other software
- LightBurn: on a chuck, the Object Diameter decides the scale; on a roller it does not change the output. Taper Warp asks for a top and bottom diameter and a length in millimetres. Its exact reference is not documented, so the calculator gives values for the design's own band (correct either way) and the full-cup values, and the test file checks them.
- xTool Studio: automatic taper correction works on P-series machines with the RA3 rotary; the calculator gives the Taper builder numbers, including the image centre's height above the base. Other machines and full wraps need the pre-warped file.
- xTool Creative Space, Creality Falcon Design Space, LaserGRBL and others: type the diameter shown and engrave the pre-warped file at 100%.
If a test comes out the wrong length all the way round, a rotary setting is off rather than the taper: see rotary engraving stretched or squashed for the correction and a worked example.
Full wraps
A full wrap must be exactly one turn long: π × the diameter the rotary turns by. On a taper every row turns the same angle, so the ends meet all the way down even though the cup narrows. Do not use a taper warp on a full wrap; it makes the ends miss.
Examples to start from
- 20 oz tumbler, 2.25 in logo, chuck, LightBurn
- Pint glass 86.5 / 60.5 / 148 mm, 60 mm logo at mid-height
- Full wrap on a roller rotary
- xTool P-series + RA3, logo that looks round from the front
- Fix stretching: drew 40 mm, it came out 70 mm
Limitations
- Nothing here has been engraved by us: the maths is checked digitally. Always run the test file on masking tape before a real cup.
- Straight-sided tapers only. Curved and stepped cups (wine tumblers, the lower part of a 40 oz tumbler) are not covered yet. Designs are warped as images; vector warping is not done here.
- Software features change. If your software has its own taper correction, use either it or the pre-warped file, never both.
- Laser safety, power and speed settings are your machine maker's.
Frequently asked questions
- What diameter do I enter for a tapered tumbler?
- On a chuck, the diameter where the top of your design sits (or any diameter, as long as the file is warped for it). On a roller, the setting is ignored: the cup's diameter on the driven wheel decides the scale.
- Is it always "add 10%"?
- No. It depends on the cup, where the logo sits and which diameter you type; the calculator shows the real figure.
- My engraving comes out stretched or squashed. What do I change?
- Engrave a line of known length, measure it, and use "Fix stretching" for the corrected MM per rotation, steps per mm or diameter.
- Is my design uploaded?
- No. Your image is processed in your browser and never leaves your device. Your settings (not the image) are kept in the page address so you can share them; see privacy.