Issue engraving powder coating bottles

[Claudia Odorizzi]

Hello,

For a few months I have owned and worked with a 30w Chinese laser engraving machine making bottle customization. For a few days now I have a problem with the upper part of the engraving that remains white or with dots that the laser cannot remove. In other words, when the laser moves away from the central area it seems that it is losing power and every time less material is removed. Specially in the upper side when bottles are place horizontally (same position as engraving). I have tried changing the angle, the hatchs, power, other calligraphies, etc without being able to solve the problem.

The parameters I use are 2 x power 70 speed 500 double hatch and 1 x power 60 speed 500 double hatch.

Since I have the machine, the engraving end sometimes presented problems but now they are more accentuated. If I try to clean them the bottom ends up burning.
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Could you help me? I no longer know how to try to solve this problem!

[John Lifer]

Looks like focus issue to me. That is assuming you are using this laser flat and not with rotary. The center is clean, outer edges (sides) are not. Lower your focus just a bit and see if that doesn't help. BTW, this is why I use my CO2 and rotary for removing PC. Focus is always the issue.

[Claudia Odorizzi]

Looks like focus issue to me. That is assuming you are using this laser flat and not with rotary. The center is clean, outer edges (sides) are not. Lower your focus just a bit and see if that doesn't help. BTW, this is why I use my CO2 and rotary for removing PC. Focus is always the issue.

Thank you, the problem was focus... We were working with same parameters as used last time but I do not know why sometimes work well and not others...

We are thinking about buy a new machine to engrave our bottles. It is too complicate too have the right focus when we have bottles of different diameters and laser goes up and down... Do you say C02 is better to engrave PC?

[Glen Monaghan]

One of the major reasons that you get differing results when engraving powder coating is that the thickness of the coating can vary widely, even on the same bottle. Consequently, the thinner areas may ablate completely while thicker areas don't get removed down to the metal.

Also, it sounds like you are "flat" engraving as John said, in which case the power density of the beam will drop significantly as you attempt to engrave farther down the curve of the bottle, especially if you are focused on the high point. You will get best results by focusing midway between the highest and lowest engraving points (which is not simply half way between those points because the curve of the bottle is in fact a curve and not a straight line). One way some people help with this is to use a lens with a longer focal length, but the overall power density will be lower than for a shorter lens, and so longer lenses aren't generally suitable for low powered lasers like yours. Your best bet is to use a rotary device.

[John Lifer]

Rotary can work, but on a fiber it is both slow and works so much differently than flat engraving. I ONLY use a CO2. But others do use fiber with good results.

[Kev Williams]

I'll use a fiber on powdercoated bottles AS LONG AS the engraving is just text, or the logo/graphics are 'in pieces' small enough that each individual piece can be engraved without rotating. Blazing fast. Love the 'rotary text mark' and 'hatch one by one' features :)