New 24 x 48 laser project log

[CNCadmin]

OK I have started to design my new laser, so far this is what I'm going with-

1) 5/8" feather shafting mounted on end supports

2) cutting area of 24" x 48"

3) nema 23 frame stepper motors

4) belt driven X and Y

5) simplicity linear bearing with my own billow blocks

6) 20w RF co2 laser w/ 80 volt power supply

[buscht]

Paul, I'm not the expert on this, but I think that there are a few more things you need for a working system.

1. The Z axis must float over the material. Its very important the the laser beam is focused exactly at the right point. Its kind of like holding a magnifying lense over a piece of paper. You have to move it up and down to get the proper pin point of light to burn the paper. Your 5/8" rails will sag. The material will warp and bow. You have to make up the difference with the Z axis.

Maybe someone else can chime in with some real life experience. You must not be cutting much with only a 20 watt laser. Balsa wood?

2. You will need some kind of baffle to sit your parts on. Honeycomb plastic should work well.

3. A fume extraction under the table would be helpful so you don't smoke up the place.

Good luck and keep us informed

Trent

[CNCadmin]

Originally Posted by buscht Paul, I'm not the expert on this, but I think that there are a few more things you need for a working system. 1. The Z axis must float over the material. Its very important the the laser beam is focused exactly at the right point. Its kind of like holding a magnifying lense over a piece of paper. You have to move it up and down to get the proper pin point of light to burn the paper. Your 5/8" rails will sag. The material will warp and bow. You have to make up the difference with the Z axis.

1) I think 5/8" would be more than enough, the carnage that will be holding the lens should be less than 5lbs, so the amount of sag will be less than +/-.001 ? I do need to play with some numbers.

Maybe someone else can chime in with some real life experience. You must not be cutting much with only a 20 watt laser. Balsa wood? 2. You will need some kind of baffle to sit your parts on. Honeycomb plastic should work well. 3. A fume extraction under the table would be helpful so you don't smoke up the place.

1)with 20w I will be cutting balsa, ply, foam as well as engraving, and vinyl cutting.

2,3) I plan on using alum honeycomb material with a pan on the bottom for vacume and to terminate the laser beam.


BTW here is the laser I bought- http://cgi.ebay.com/ws/eBayISAPI.dll...e=STRK:MEDW:IT

[CNCadmin]

Does anyone have some experience with feather shafts and bearings?

[ViperTX]

Regarding the sag....I put those numbers on the other thread....so with a 5/8 inch end supported rail the deflection at the center with 10 lbs is 0.100 inches....the 0.001 is the straightness of the Thomson shafting per 12 inch length.

[CNCadmin]

Originally Posted by ViperTX Regarding the sag....I put those numbers on the other thread....so with a 5/8 inch end supported rail the deflection at the center with 10 lbs is 0.100 inches....the 0.001 is the straightness of the Thomson shafting per 12 inch length.

That's a solid shaft right? .100 should be acceptable I would think, I could always add a support in the middle?

[fyffe555]

The 5/8" Feather shafting is the Pacific bearing CC10 stuff? Then I've used it on a sliding table for my table saw which isn't very relevant. Surplus stuff but its works well for that.

Note it's 6061-T6 so has a modulus of 10,000kpsi. 48" of 5/8" feather shafting with ends simply supported with a central 5lb load will deflect 0.1538". Fixed ends drop that to 0.0385"

24" shaft will deflect 0.0192 and 0.0048 respectively.

If you use the Pacific End support blocks I'd suggest you'd be more towards the fixed end figure.

nice buy on the laser !

Andrew

[ger21]

Next time I decide to dig out my bearing catalog and do some deflection calculations, I'll just wait 20 minutes for you guys to do it.

[fyffe555]

Ah, I cheated -- I still had the spreadsheet from when I was working out the tablesaw.... Used the same 5/8" stuff...

Only problem with it was cutting it to length by hand. The coating is RC70 which is harder than SS or drill rod.. Took a bit of effort to get the hacksaw started without it skating all over the place...

besides, you have to keep the moderator happy!

[CNCadmin]

Well after much designing I have started over, I found a cheap more accurate way of getting this thing moving. I won't go into it yet, but I have ordered some material for testing, but I think I really found a great solution to using thk or linear bearings.

[Mr.Chips]

Oh come on give us a hint.

Is it cheaper?

Stronger?

More precision?

Lasts longer?

Or all of the above????

[CNCadmin]

Here is a first look at my design.........