Engraving powder paint tumbler problem

Perfect! Is there like a formula to calculate that number? Or just try-error method?
Do you recommend another software to work with the machine?

Hmmm…So if you are using the 0.002 as a scanline step that should actually be fine as the laser beam should be around 0.0055". Are you using a rotary setup? If you are then it’s probably related to that actually.

For a stock k40 controller K40 whisperer or Meerk40t are the only real options.

Yes, I am using a rotary accessory and the rotary settings. Is there a way that using rotary settings I can correct that?

Also, I have powder paint tumblers and I have not been able to engrave them and achieve a clean engrave. Actually to the point of not been even able to remove the paint. I have tried different height, power and speed but same result. Any idea or suggestion?

Tell us more about your machine and setup. Do you have an analog ammeter? Have you done a ramp focus test?

Here is a video about calibrating and using Whisperer with a rotary. Not sure if you have seen this one. At about the 5:30 mark it gets to the software.

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Thanks, I went thru that process and it worked perfect for the design scale purposes. Although it worked I still getting the dirty engrave result.

Hello, I am using a rotary accessory and settings.
I do not have a ammeter in my machine.
Can you tell me more about the ramp focus test? I have not do it.

Without an analog ammeter, you don’t know whether you are overdriving your tube and degrading it permanently; a common form of degradation is loss of power. Analog ammeters are cheap parts, and any seller who doesn’t include an analog ammeter is doing a major disservice to their buyers.

The K40 Intro at the top of every page has / links to detailed information that is very useful for running a K40 or any similar laser. Much of it is really critical to running your laser safely for you, the laser, and your house, and I strongly recommend reading the whole K40 Laser: Getting Started category. It is edited by moderators to be limited to information and is not full of random discussion, so it will repay your time to read it.

However, with respect to your particular concerns, directly from the K40 Intro:

… use an analog meter to check tube current. Add an analog current meter of 0-30ma range to do power checking if an analog meter was not included in the unit you purchased.
… study online sources for how to adjust and set up your laser. You may need to do these things before ever using your K40. This includes: How to adjust focus

You can also do a site search (use the :mag: icon at the top) for “ramp test” to see related posts.

We want to continue to improve the getting started documentation, but what is there is a substantial and useful collection of information.

Thanks so much for the info.
I will look at it carefully and get back to you with feedback.


When you say “dirty engraving “ are you taking about the lines like in this picture?

Yes, that is correct. And in some powder paint tumblers the paint is not completely removed.

What is your scanline step set to?

Hi Ned

It is set at .002in

Have read through this, maybe your rotary needs adjusting. Perhaps check the nema 17 stepper is 400 steps like the others.


You can trying lower it to 0.001" which is the lowest it can go in K40 whisperer. Just to check, are the lines in that star part of the actual graphic?

If you are having trouble getting through some of the power coat check the height from the surface to the lens. Stock k40 lens focal length is typically 50.8mm or 2". This is why the ramp test was suggested so you could verify your focal length.

For the smallest beam spot (most power per unit area) your work surface needs to be at the focal point of the laser. The laser beam diameter diverges (get larger) on either side of the focal point like a hourglass. With a 2" focal length lens you typically have a couple of mm on either side of the focal point that you can work with before the beam width starts getting too wide.

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Hello, thanks for your feedback.
I changed it to .001 in and improved a bit.
No, the lines are not part of the design.
Even with the set of .001 in and the rotary accessory it keeps leaving some paint lines in the engrave.

What stepper motor is your rotary using and what type of belt pulleys?

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I looked for motor information but nothing attached to it.

Usually the stepper motor will have a part number somewhere on it, and that can almost always be decoded. It’s usually on the back.

It could be that this is simply rotating further than it should for each step due to the choice of stepper motor and gear ratio on the pulleys.

Engrave two lines a substantial distance apart (say 50 mm) and then measure the distance between them with a flexible tape wrapped around the object. If it’s longer than it should be, then that’s where your problem is.

From zooming in on your picture earlier, it looks like a GT2 belt with a 20 tooth drive pulley on the stepper and a larger — but I don’t know how much larger — pulley on each rotary wheel:

It also looks like it’s at least partially a 3d printed kit. Share with us all the information you have on your rotary kit. Don’t hold back and make us guess.

With regard to:

This is where not having an analog ammeter might have hurt you; it might be that your tube is damaged from over-driving it (very easy to do without an analog ammeter) and just doesn’t have enough power for that paint. Alternatively it might be poor focus, thus the ramp test.

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