3D wood engraving controller

[lasersafe1]

This topic is carried forward from the "Commercially Available Laser Controllers" topic.

http://www.buildlog.net/forum/viewtopic.php?f=6&t=36

The discussion of 3D engraving in wood appears to be beyond what the present commercial controllers can provide. There are commercial controllers, but they aren't sold separatly from their $15,000+ machines as far as I can tell.

[lasersafe1]

We were talking about moving lenses in the previous posts.

A miniature RC servo would probably work for this application. They are very small and light, and probably fast enough. But you would not get a huge range of motion, and they are not very precise.

I agree with Bart that the mechanical system could never match the speed of the electronic, yet there are some limitations to even the best engravers produced today. They are all limited to clean engrave depth without moving Z. A combination of technologies may be necessary to overcome this limitation.

Each one of us who has built a CNC machine has fallen into the trap of wanting more speed. It's all about inches/minute. We try to suck every ounce of energy from our servos or steppers to get them moving without slip or stall. After all is said and done we realize that there are some things that just behave better when we take it slow. My initial 3D raster tests proved that to me. So did my burning up mill bits on my CNC router.

I love the high speed for paper cutting or engraving on granite or a laptop case, but the 3D wood engraving may need a slow and steady approach. Clearly the software is a bear unless we move back to Mach3 or EMC running files that have been properly prepped for engraving.

If you want extreme precision and rapid speed for moving a focus lens, look no further than the mechanism inside your computer hard drive. The arm that holds the read/write head has a typical seek time moving over an inch of travel in <8 milliseconds. It can carry the load and has super high positional control. It uses the voice coil control that I mentioned before.

The ArtCam Pro 2008 software I was testing on my mill has the ability to output code for a laser engraver where it does indeed adjust power and move to different Z heights. It might be worth a further look. The software is $$$$$ but is also available used.

[bdring]

Many laser engravers use Galvo's (basically the same as a hard drive) to aim the beam. These are used primarily on fiber lasers. They are also used for laser shows.

The problem is the distance to the work piece is always changing so you can't use a focusing lens. The actual beam diameter has to be your spot size. You can often buy complete glavo systems off eBay for a decent price.

I get people emailing me all the time asking how to use Galvo systems with a Chinese CO2 laser...sorry can't help you there.

P.S. Look at Vectric Aspire before you commit to ArtCam
P.P.S. Good idea to split off the topic. I can split an existing topic up from a given point next time. Just send me a note.

[lasersafe1]

I wasn't talking about a galvo above the object to raster. Instead I was thinking about the same gantry type system but a lightweight galvo (voice coil) is used to position the focusing lens up and down during the X raster.

Just a pie in the sky idea.

[lasersafe1]

Urgent News alert! See copy below. Price is $1995. He is sending me a pdf with more detail.

They make the original controller for the Universal Laser System ULS-PS series engravers
http://www.testra.com/laser/index.html

Hi John,

Thanks for the inquiry. Here are the answers to your questions:
>> I have tried to do some homework on this and suspect I will need an RF
>> tube as well to get the 8 bit control of power.
>>
The Chinese glass tube lasers with the high voltage power supplies do not control well at low power levels (basically uncontrollable), therefore if you want true 8 bit control you will have to switch to a RF excited laser.
>> Does your software and controller handle 8 bit grayscale images? I want to
>> acheive a final result to the engravings shown on the Gantryco.com
>> website. This can only be acheived with 8bit power control and cannot be
>> achieved by dithering the bitmap.

YES, we have true 8 bit control so you will be fine here.

If you have other questions or need help on anything please feel free to contact me by e-mail or phone.
Have a Great Day!

Thomas W. Hart, Jr.
President

Testra Corporation
1201 N. Stadem Drive
Tempe, AZ 85281
Ph : 480-966-8428
fax : 480-907-2876
Web : http://www.testra.com

[Tweakie]

Hi Guys,

The problem is the distance to the work piece is always changing so you can't use a focusing lens. The actual beam diameter has to be your spot size. You can often buy complete glavo systems off eBay for a decent price.

Just a bit of additional info:- Some of the jeans (denim) marking machines I have looked at recently use galvo scan systems with a focus lens. The lens type is F-Theta Ronar and they will maintain a constant focal length but they cost an arm and a leg. They are available for 1064nm YAG but I have not yet seen one made for the 10600nm CO2 wavelength.
Some details on F-Theta here http://www.linos.com/pages/mediabase/or ... 9_8308.pdf.

Tweakie.

[lasersafe1]

Sometimes it is simply called a scanning lens. They are sweet and would sure make a CNC machine easier. On the other hand, you are limited to the fixed XY scan distance. I think it would be unusual to find one with a larger scan than 12 by 12 inches.