Optimizing Tumbler Settings

Applies to: all AEON CO2 lasers with a rotary

This guide walks through the tests that find the best settings for engraving a tumbler or similar cylindrical object. Use it when you first set up for tumbler projects, before a production run, or when you switch to a different tumbler brand or coating.

What you need

• Tumblers to test
• Focus gauge
• Notebook

Before you start

The procedure below is geared towards a full wrap, but it works just as well for a design of any size. The aim is the shortest cycle time that still gives a finished product you would be happy to sell.

This is the process we used in our shop to find the best settings for a full wrap on a tumbler, written in the order we ran it. The tests and conclusions are examples. Your tumbler will likely have different dimensions or a different coating, and may give different results.

Speed test

This test finds an engraving speed that balances efficiency and quality. Start with a long, thin rectangle that spans the full height of the cup, so you can find the most efficient scan speed with minimal overscan. For a smaller design, make the rectangles the length of the design.

Settings

• Machine: MIRA 7, 60 W
• Power: 100%, because high speeds are being tested
• LPI: 400, roughly the median for most materials. Changing LPI has a significant effect on both output and job time.
• Lens: 2.5 inch (63.5 mm). This is not the standard MIRA lens. Its deeper focal depth gives a wider usable focal range.
• Test shape: 180 mm wide by 5 mm tall. The engravable area on the cup was 180 mm from mouth to base.

Procedure

We tested 300 mm/s to 1200 mm/s, nearly the full range of the machine, then filled in 350 mm/s to 1150 mm/s in 100 mm/s steps for more precise data. All times are within 0.5 seconds.

Result

Times varied widely across the range, as expected. Speeds from 700 to 1000 mm/s differed by only about 5 seconds and gave good quality.

At the low end (300 to 450 mm/s), the coating burned onto the cup instead of ablating properly, because of the power used at such low speeds. At the high end (1000 to 1200 mm/s), the result looked good from a distance and was notably faster, but the edges of the engrave were poor.

The goal is a speed that is fast and still gives a usable result, so we chose 950 mm/s.

Focal depth test

This test finds the usable focal depths for a quality engrave with a 2.5 inch lens. Most lenses have a range of 1 to 2 mm above and below the best focal point, called the defocused range, where the machine still engraves effectively with a larger dot.

Using a larger dot helps smooth the edges of the design. It also cuts job time, because a larger area is exposed to the beam.

Lens

• Diameter: 18 mm
• Focal depth: 2.5 inch (63.5 mm)

Procedure

We focused with the manual focus gauge, because the standard autofocus configuration is for a 2 inch (50.8 mm) lens. Autofocus corresponds to approximately 8.5 mm on the manual gauge. Adding 1/2 inch (12.7 mm) gives a manual focal depth of about 21 mm.

With the 1 to 2 mm range either side of the focal point, the usable range for this lens is 19 mm to 23 mm on the manual focus gauge.

A basic focal ramp test fine-tunes the range. Set the depth to the calculated focal point (21 mm on the manual gauge in this example), then move the bed up or down 1 mm at a time. Pulse into scrap material at each depth and look for the finest pulse marks. That gives you the effective work area and the defocused range. Beyond that range, quality drops sharply as the beam spreads.

Result

A range of roughly 5 mm gave an effective result. Knowing your range matters for tapered tumblers, such as a Stanley cup. The whole surface of a tapered cup cannot be level and in focus at once. Once you know the effective range, you can position the cup on the rotary so its surface stays within that range across the whole tumbler.

LPI test

This test finds the ideal LPI: a balance of speed and complete coating removal without spoiling the finish. A low LPI gives a quicker job, but too low and the coating is not fully removed, which makes the result unusable.

This part comes down to personal preference. Cycle time matters, but LPI has a large effect on finish. If you want a matte finish and a higher LPI gives you that, use the higher LPI.

Settings

• Speed: 950 mm/s, the speed found in the speed test
• Power: 100%, because of the high speed
• Lens: 2.5 inch (63.5 mm), focused to the depth found in the focal depth test
• Test shape: 50 mm wide by 5 mm tall, closer to the size of real engraved areas and quicker to test

Procedure

We tested 100 LPI to 1000 LPI, then filled in 350 LPI to 750 LPI in 100 LPI steps across the range most often used. Finish results are based on visual inspection and opinion. All times are within 0.5 seconds. Every value was tested over the full focus range found in the previous section.

Result

The test gave an effective range of LPI values with different finishes. Based on the look, the times and our judgment, the effective range is about 400 LPI to 800 LPI, depending on the finish you want. A standard gloss finish is the most common. With that and cycle time in mind, we chose 400 LPI.

Full wrap test

This test checks the engraving quality of a design that wraps fully around a tapered tumbler, to confirm it stays uniform and precise across the whole surface. Curvature and taper both affect the engrave.

Settings

• Speed: 950 mm/s
• Power: 100%
• LPI: 400
• Lens: 2.5 inch (63.5 mm), focused to the depth found in the focal depth test
• Rotary: PiBurn Grip. At these speeds a chuck style rotary is best because it holds the cup most securely. We used braces and magnets to hold the rotary in place against the vibration that comes with high speeds.

Procedure

We engraved a design that wrapped entirely around a tapered tumbler to check consistency and quality across its contours and depths. To make the design wrap fully, we set the file dimensions to match the circumference of the tumbler.

Result

The full wrap came out well, and would easily pass as a finished product. The settings gave a uniform appearance over the whole surface, with consistent, clear detail. Total job time was 19 minutes 40 seconds.

Summary

Test speed, focal depth and LPI one at a time, and you can tailor your file settings to any tumbler, whether for a full wrap or a smaller design. The same approach carries over to new materials and coatings, so keep experimenting with your machine.