Depth behind panel

Discussions and help on this commercial controller.

Moderator: twehr

Depth behind panel

Postby generalsocial » Sun Oct 16, 2011 10:37 pm

On those DSP thingys, how much room must there be under the panel?

On my laser there isn't much room and I need to make some room but I don't know how much.

http://mambohead.com/category/cnc/cnc-laser-cnc/

I'd make a 2x but I wanted a considerably larger cutting area and I can get extruded aluminum angle locally. My machine needs about 80 feet of it.
generalsocial
 
Posts: 37
Joined: Thu Jun 02, 2011 12:04 pm
Location: Ottawa, Ontario, Canada

Re: Depth behind panel

Postby bdring » Sun Oct 16, 2011 10:48 pm

Don't under estimate the difficulty of making a larger machine. Twice as big might need to be 4 times more accurate. Most of the big DIY lasers I know have failed completely to ever to be usable.
Bart
"If you didn't build it, you will never own it."
bdring
Site Admin
 
Posts: 2966
Joined: Sun Nov 22, 2009 7:33 pm
Location: Chicago, IL, USA

Re: Depth behind panel

Postby generalsocial » Sun Oct 16, 2011 10:55 pm

My cutting area is 46×26″.

It's not that much bigger but I need to fit a 40" roll of material into it. I also need to accept balsa up to 36".

But how much room is needed behind the panel?

Which part of the machine contributes to inaccuracy?
generalsocial
 
Posts: 37
Joined: Thu Jun 02, 2011 12:04 pm
Location: Ottawa, Ontario, Canada

Re: Depth behind panel

Postby andrewblanejr » Sun Oct 16, 2011 11:56 pm

the 2020 extrusions will bend after a while if not supported. I'm not sure the limit, there are some real technical measuresments of stiffness, they are usually published and available for any type of extruion. I just don't know how to make sense of the formula yet. you should look into this, you dont want your gantry sagging.

also my understanding is that the mirrors tend to get harder and harder to align the larger you go. They must all be on the same plane, which if your frame sags or is misaligned even a little bit makes a larger difference over a longer length. Also the angle of the mirrors becomes mroe important, an minute adjustment in angle may not be noticed in a smaller system but it could amplify over distance and be critical in a larger system.

good luck!
andrewblanejr
 
Posts: 59
Joined: Sun Jul 31, 2011 9:16 am

Re: Depth behind panel

Postby r691175002 » Mon Oct 17, 2011 12:27 am

The longer your distances the more accurate the laser has to be since the error is proportional to the distance.
It is also becomes far far more difficult and expensive to align surfaces over large distances. So you have a situation where you need to be more accurate while at the same time it is harder to get that accuracy.

I'm not willing to do the math but I suspect thermal expansion of the extrusion on the laser side will actually come into play when the total laser travel is 70"+. A few thou of expansion suddenly moves the laser a few hundredths of an inch. Either way I suspect the relationship will be at least squared or cubed to the length of the extrusions.

Unfortunately I don't have a DSP so I can't help you there.
r691175002
 
Posts: 242
Joined: Mon Dec 13, 2010 5:05 pm

Re: Depth behind panel

Postby generalsocial » Mon Oct 17, 2011 2:24 am

So what's the space needed to accommodate one of those panels?
generalsocial
 
Posts: 37
Joined: Thu Jun 02, 2011 12:04 pm
Location: Ottawa, Ontario, Canada

Re: Depth behind panel

Postby generalsocial » Mon Oct 17, 2011 2:35 am

The 2x is 12" x 20" right?

So mine is about twice that on both Axis.

If it does prove to be impossible I will buy one from China and change the electronics (I did that for my CNC mill and it worked great).

But I'm not sure if changing the length and width by 2 is enough to poo-poo the project.

Besides, when the gantry is close to (zero, zero) it will be more accurate than (Xmax, Ymax). I mean when the mirrors are closest to the laser it should still be accurate even if it isn't at (Xmax, Ymax).
generalsocial
 
Posts: 37
Joined: Thu Jun 02, 2011 12:04 pm
Location: Ottawa, Ontario, Canada

Re: Depth behind panel

Postby bdring » Mon Oct 17, 2011 2:49 am

The Thunder Laser DSP is in two part. The panel is about 43mm deep from from to back. There is some detail in the TL documentation on the Wiki. Here is a STEP file if anyone is interested.
Attachments
dsp_lcd.zip
Thunder Laser LCD STEP File
(7.17 KiB) Downloaded 759 times
Bart
"If you didn't build it, you will never own it."
bdring
Site Admin
 
Posts: 2966
Joined: Sun Nov 22, 2009 7:33 pm
Location: Chicago, IL, USA

Re: Depth behind panel

Postby generalsocial » Mon Oct 17, 2011 3:09 am

okay thanks, I guess I need to make sure there is 5cm behind the panel then (If I get one of those).
generalsocial
 
Posts: 37
Joined: Thu Jun 02, 2011 12:04 pm
Location: Ottawa, Ontario, Canada

Re: Depth behind panel

Postby generalsocial » Mon Oct 17, 2011 3:12 am

The lasersaur project is 1.2x0.7m.

That comes out to 47x27" That's almost identical to mine.

I'll have a look and see how they get around the issue that was brought forward that the larger format may be too hard to make.
generalsocial
 
Posts: 37
Joined: Thu Jun 02, 2011 12:04 pm
Location: Ottawa, Ontario, Canada

Next

Return to Commercial DSP CO2 Laser Engraving/ Cutter Controller

Who is online

Users browsing this forum: No registered users and 1 guest

cron