finding perfect focus

Discussions on optics for laser cutter/engravers

finding perfect focus

Postby J45on » Tue Aug 16, 2011 2:24 pm

How I the perfect focal point for my laser ?
I have a 55mm focal point lens which gives me a rough idea.
I presume for engraving I would want to be focused on the surface
And for cutting focused half way through the material being cut ?

What is the easiest way to measure focus ?
J45on
 
Posts: 258
Joined: Thu Mar 31, 2011 11:30 am
Location: Kent,united kingdom

Re: finding perfect focus

Postby edmond22 » Tue Aug 16, 2011 7:17 pm

Our Trotec lasers at work use a little tool you hang on the side of the laser head on a specially machine step and then raise the table till the bottom of the tool just touches the top of the material.

I plan on doing something similar on my machine, just need to find the correct tool length once the right focal length has been established.

You can also set it with a vernier just mesure 55mm from the lens to the top of the material so you would need to mark where the lens is situated
edmond22
 
Posts: 127
Joined: Sat Oct 09, 2010 7:55 pm
Location: Sunny South Africa

Re: finding perfect focus

Postby BenJackson » Tue Aug 16, 2011 7:55 pm

What I did was prop a bit of cardboard on a block so it was slanted across the build area. Then I cut a series of stripes in it all at the same power/settings. When it was done I picked the finest cut and moved the carriage over it and measured from the bottom of the carriage to the cardboard.

With the measurement in hand I then cut a few spacers out of various materials (I had to compensate for the kerf by hand because I was writing gcode manually).
BenJackson
 
Posts: 522
Joined: Fri Apr 15, 2011 6:13 pm

Re: finding perfect focus

Postby naPS » Tue Aug 16, 2011 8:28 pm

I believe the distance from the bottom of the lens to the bottom of the carriage is about 15mm. So you should be able to set your material at 70mm below the bottom of the carriage. I've just been using a metric ruler to do this, and my cuts have been coming out amazing.
naPS
 
Posts: 202
Joined: Sat Apr 09, 2011 1:53 am


Return to Optics and Lasers

Who is online

Users browsing this forum: No registered users and 9 guests

cron