Machsupport Forum

General CNC Chat => Show"N"Tell ( What you have made with your CNC machine.) => Topic started by: Glad on November 13, 2010, 01:10:36 PM

Title: Very small parts, smallest possible engravings.
Post by: Glad on November 13, 2010, 01:10:36 PM
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.
Title: Re: Very small parts, smallest possible engravings.
Post by: budman68 on November 13, 2010, 01:46:03 PM
Looking good, Glad, how deep are they and what will you use for color "fill"?

Dave
Title: Re: Very small parts, smallest possible engravings.
Post by: RICH on November 13, 2010, 01:51:55 PM
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
Title: Re: Very small parts, smallest possible engravings.
Post by: Glad on November 13, 2010, 01:55:22 PM
Thanks Dave.
Forgot an important part; depth is 0.25mm and I'm using Testers paint.
Title: Re: Very small parts, smallest possible engravings.
Post by: Glad on November 13, 2010, 02:11:17 PM
Hi RICH,
Interesting project, cool engravings. I like the binoculars, good idea.
Title: Re: Very small parts, smallest possible engravings.
Post by: Tweakie.CNC on November 15, 2010, 05:10:22 AM
Quote
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  ;D

Tweakie.

Title: Re: Very small parts, smallest possible engravings.
Post by: RICH on November 15, 2010, 06:25:12 AM
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
Title: Re: Very small parts, smallest possible engravings.
Post by: Tweakie.CNC on November 15, 2010, 06:44:19 AM
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.
Title: Re: Very small parts, smallest possible engravings.
Post by: Glad on November 15, 2010, 10:21:02 AM
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.
Title: Re: Very small parts, smallest possible engravings.
Post by: Tweakie.CNC on November 15, 2010, 11:44:52 AM
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.
Title: Re: Very small parts, smallest possible engravings.
Post by: Jammerm on November 16, 2010, 03:25:49 PM
How small could you go if you cut away the background and left the letters stand out? Small stuff like this would be great for some decorative scrollwork on pocket watch cases and guns, etc.

Tweakie, that a nice nickle you have, those usually don't have the date on then anymore. Where are you going to get any checkers that small? :D
Title: Re: Very small parts, smallest possible engravings.
Post by: RICH on November 16, 2010, 05:29:24 PM
Tweakie, in case you need some any extra checkers, here are a few:

.   .   .   .   

RICH ;D
Title: Re: Very small parts, smallest possible engravings.
Post by: Tweakie.CNC on November 17, 2010, 02:07:35 AM
Come on Rich, there is only eight there and you know I need sixteen.  ;D

Tweakie.
Title: Re: Very small parts, smallest possible engravings.
Post by: Sam on November 17, 2010, 11:58:32 PM
LOL @ Rich. Don't forget the red ones.
. . . .
Title: Re: Very small parts, smallest possible engravings.
Post by: rcaffin on September 30, 2011, 08:56:30 PM
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.

No, that is normal for a stock laser beam. It's called a Gaussian distribution. Commercial laser-cutting machines often have some expensive beam-shaping optics to convert that into a flat-topped distribution, which makes for better cutting in heavy metal at a commercial scale.

cheers
Title: Re: Very small parts, smallest possible engravings.
Post by: kregan on October 29, 2011, 09:30:28 PM
Here are some tests I did engraving HO scale bricks in plastic sheet.

Title: Re: Very small parts, smallest possible engravings.
Post by: Tweakie.CNC on October 30, 2011, 02:37:43 AM
Hi kregan

Looking good.  ;)

You seem to be getting a turn-on (or turn-off) delay looking at the dots on those short lines ??

Tweakie.
Title: Re: Very small parts, smallest possible engravings.
Post by: kregan on November 07, 2011, 08:15:44 PM
I think it is a limitation with my machine accuracy.  That was done with the spindle
off and just dragging a sharp point across the plastic sheet.