Very small parts, smallest possible engravings.

[Glad]

Hi guys,
I’m working on a very small scale projects like wrist watch cases, dials, bridges and main plates. Sometimes machining new parts and decorating movements inside and out.  As a result I’m trying to do the smallest possible engravings on brass and steel. Diamond drag is not an option; it wouldn’t give me enough depth to change color of the engraving. If any of you had any experience with small scale engraving please respond.  Here is an example of what I was up to: letters on the photo are 1mm high and 0.5 mm wide.
Glad.

[budman68]

Looking good, Glad, how deep are they and what will you use for color "fill"?

Dave

[RICH]

Glad,
The smallest possible engraving is limited by how accurate your machine is, the cutter type used / size and depth of cut.
You may want to have a look at this thread as it shows some small lettering work.

http://www.machsupport.com/forum/index.php/topic,13398.msg87957.html#msg87957

Let me elaborate some....
The best point you will put on an engraver / cutter  is say .001 wide and even that breaks in butter, so lets say .003" in dia.
Then lets say you have .002" runout at the tip of the cutter. So the width of a line is approx .005" wide , but if you go .002" deep
it may be .006" wide. Now lets just take the letter "E" which has three lines and two spaces ( lets say .003" clear  to edges of cut  / that's a human hair) , then total for the letter "E" would be about .024" high. Do some testing with your machine and cutter and see where it's no longer visibly a letter.

Have Fun,
RICH

[Glad]

Thanks Dave.
Forgot an important part; depth is 0.25mm and I'm using Testers paint.

[Glad]

Hi RICH,
Interesting project, cool engravings. I like the binoculars, good idea.

[Tweakie.CNC]

If any of you had any experience with small scale engraving please respond.

Excellent work Glad. Real neat job.

Although not really relevant to rotary engraving I am trying to produce a small checkers board. I am cheating a bit by using a laser but so far with an 8 x 8 matrix I am down to 0.5mm x 0.5mm. These were the initial tests with a 14 x 14 matrix and the smallest here is 1.25mm x 1.25mm. The problem is photographing the result, looks like I will have to invest in one of those USB microscopes 

Tweakie.

[RICH]

Tweakie,
So 1.25 x .0394=.04925"
     .0490/14=.0035" is the individual square

If you want send me an email and i'll give you my address. Then if you wish, you can send me a sample and i will measure them
and give you a picture / info. I would be interested in the results.

RICH

[Tweakie.CNC]

Sorry Glad we are hijacking your thread here.

Rich,

There is an interesting abnormally with the 0.5mm x 0.5mm matrix in so far as the dot size is smaller than I can cut a hole in a piece of kapton. It would appear that as the center of the beam contains more energy if you fire it quick enough you can get a smaller dot size. Strange.
The 0.5mm x 0.5mm tests have been done on anodized ally these photos are of traffolite engraving laminate.
Here is a slightly closer shot of the previous pic.

Tweakie.

[Glad]

Tweakie,
as long as hijacking is informative, I’m glad you did that.
Can you do engravings like that on a brass? If not: what would it take in terms of laser power and investment to get these results?
Glad.

[Tweakie.CNC]

Hi Glad,

I can't engrave brass, to be able to do it would cost mega bucks I am afraid. 
Small CO2 lasers, like mine, see all metals as being reflectors and the only chance you have is to change the appearance of a surface coating. Their saving grace is that they are extremely good with acrylics and can cut up to 10mm thickness.

Tweakie.