Laser cutter / engraver

[SMIDSY]

Hi,

Okay I'm not new to electronics, however I am new to lasers.

I appreciate that my questions have probably been asked many times before, but there's so much information out there that it can take a life time to read through. I have tried my best at researching but sometimes it's best just to ask.

I am wanting to build a 2 axis CNC laser cutter and engraver. I will be engraving plastic and I will be cutting upto aprox 1cm of neoprene, aka rubber foam.

I have read that a CD writer's laser can engrave plastic and I assume it will be able to cut through neoprene.
I have been looking at getting the following drive to source the laser diode: Pioneer 112D (Was going to put a link to it but it wouldn't let me.)

I would like some advice on my project:
1) Would this laser be able to do the task ?
2) What kind of power do these lasers output ?
3) What kind of safety glasses / screen (I.e. Sheet that I can put up around the CNC so that people outside of the screen don't have to ware anything.) can be used ? (Links to UK suppliers would be REALLY helpful.)
4) What can I use for the optics ? I'll presume that I can't just use the diode on it's own, or can I ? Can optics be borrowed from the drive ?
5) I've heard about "wire cutters" being used to remove the laser diodes from CD drives. What are these ?
6) How much focal control is needed ? Do I need a third axis or not ? Can I just adjust the laser power instead ?
7) What can I use as a table that won't be cut / damaged by the laser when cutting neoprene ?
8) What current should I be using for the laser from the drive mentioned above, for each task ?
9) Anything else that I need to know ?

Thank you for any help,
-Andrew.

IDK if this is helpful but I knwo from experience that if you want to cut through ~5cm of acrylic at a reasonable speed then you need 40W of IR power.

The machine I've used has adjustable focus so it automatically focuses for a hairline beam it can also set the focus inside the clear acrylic and engrave letters inside the block which looks really nice as well as engraving on the surface...

to 20W version takes much longer to cut but can easily cut 2cm acrylic and etch and engrave.

neither laser can cut metal except the 40W one which can just about cut 1mm aluminium (never tried larger)

 

[yngndrw]

Thanks for your reply.

From what I can see, there seems to be a nice correlation between thickness and power. 10Watts per 1cm of acrylic. For my usage, 1cm of neoprene, seems as neoprene is so soft and dark I would guess that 5Watts should be used which is useful because it means I was right not to get the 2Watt laser diode.

Interesting point about the optics, the machine you've used focuses to a point and not to a parallel beam - Does it take multiple passes to cut, taking thin layers off at a time ? I never would have thought about using focus to etch into the middle of a piece.

That gives me quite a good heads up for if (When I can afford to) build a laser head for this machine, thanks again.

 

[SMIDSY]

Thanks for your reply.

From what I can see, there seems to be a nice correlation between thickness and power. 10Watts per 1cm of acrylic. For my usage, 1cm of neoprene, seems as neoprene is so soft and dark I would guess that 5Watts should be used which is useful because it means I was right not to get the 2Watt laser diode.

Interesting point about the optics, the machine you've used focuses to a point and not to a parallel beam - Does it take multiple passes to cut, taking thin layers off at a time ? I never would have thought about using focus to etch into the middle of a piece.

That gives me quite a good heads up for if (When I can afford to) build a laser head for this machine, thanks again.

no problem-

no its cuts straight through with a parallel beam but I notice that with especially large pieces there is a slight taper. It does the cuts in one pass.

for etching/ engraving it focuses onto a point- obviously it focuses the point inside the acrylic when engraving in the middle.

i know there is an upgrade kit for this machine that allows a second laser to work on a piece thus allowing it to cut and engrave in 3D but as the machine cost in excess of $34000 I doubt my college is willing to pay for the upgrade!

About power Id imagine 5W would be enough but it may take quite a long time to cut through the material so multiple passes could be necessary and if your computer is off on alignment on the second pass itll ruin what you are making...

bear in mind the focus needs to be so precise as otherwise you wont get a clean cut at all.

If you want to spend less money you could 'Tape' a 5W laser onto a computer controlled sowing machine (lol) then program that to do the etching/engraving... so just use the machine to position the laser and the other signals to switch on the laser....

just a thought...

 

[yngndrw]

Ah I see, thanks for clearing that up.

I will be making a 3axis CNC base anyway so that part isn't the problem. (Although I do have a computer controlled sowing machine here if all else fails, never thought of that idea. ) The cost problem is more with the laser diode and the optics.

2Watt is all I could reasonably afford, so I think that a hot wire cutter would be much faster and cheaper for my application. I guess it could also do engraving to some extent, although I may aswell just do that with a router.

Thanks for your help, it's cleared up quite a bit as well as adding numbers to it all.

 

[SMIDSY]

thats ok Im happy to help

if you want to use a router that sound like a good idea to me! You can engrave and cut with the router its the engraving inside the acrylic that wont happen...

use the 3 axis (which would go to waste on the laser as it only needs 2 axis) with the router! That would give you 3D cutting ability and you coudl easily change the head to different sizes depending on what you wanted to do...

Ive used one of those too! you use a spinning router computer controlled by the same method as the laser to make the cuts- not as clean but it'd do it chepaer than the laser and would still give great results!

In fact I have in front of me something I made with that machine (and with the laser cutter) do you want pics? I will admit it was made a very long time ago (when I was 12!) so what you could do now would be better!

I have serious doubts that 2W of laser will do much- sorry... possibly for engraving but not cutting

5W maybe but not 2

also how do you intend to protect your eyes. The cutter I used had a shield OD of 10 at the wavelength...

 

[yngndrw]

There was some safety goggles from OEMLaserSystems which has an OD of "7+" for IR. I was just going to use them. (It's in a room of it's own, so I don't need to shield the whole lot off.)

The 3Axis base that I'm going to use will probably have interchangable "heads" anyway, so I can always mess around with other tooling later on. I think router and hot wire cutter will be all I'll need at this stage.

Yes I'd like to see the pictures. Infact if you have a comparison of milled cuts and laser cuts, that would be great.

 

[SMIDSY]

of course I do!

this is a set of helping hands I made on a milling machine when I was 11 (i still use them as they are brilliant!)

made from lathed brass crok clips and thumb screws.

Base is 2 layers of 6mm acrylic which I used the milling machine on- so it cut through the first layer to bring out the second if that makes sense.

If you look you can see that the edges need to be polished to a finish as they are quite rough and that on the letters you can see the many passes made by the tool:

 

[SMIDSY]

this was made by the laser cutter. It was a bit of fun with the machine tech demo!

It unlike the other one was cut entirely by the laser cutter and is much larger. It is only 3mm acrylic BUT unlike the other one this was cut from 2 pieces of acrylic one red one black an the 'feet' swapped round in each one (so you get one with a black background one with a red background one with black feet one with red feet) so the feet are the same thickness as the background...

That is how precise the machine is! each repetition is exactly the same

also the edges are shiny and smooth so no further work is needed on them they are an excellent finish!

I have more pics if needed....

 

[yngndrw]

Ah I see, that's quite a big difference then. I will see about a more powerful laser one day. Thanks for posting the comparison !

 

[SMIDSY]

Ah I see, that's quite a big difference then. I will see about a more powerful laser one day. Thanks for posting the comparison !

the difference really is in application

if you want to fit a jigsaw puzzle together then laser is the way to go

if you are engraving or cutting and you want to save some $$ and done mind finishing then router all the way!
and you're welcome Im happy to help

 

[yngndrw]

Aye, I'll have to see if the setup I'm designing now is good enough.

I've purchased a ballscrew (Converts rotational motion into linear motion) for the Z axis (Up and down) which will give me a Z resolution of 0.0005mm. I thought that I should splash out on a better one for the Z seems as I'll also be milling PCBs and need to be able to take thin layers off.

As far as the actual designs are going, I've pretty much finished the design for the spindle it's self and have started on the Z axis. I will show some designs soon, when I have a bit more to show.

I know this thread isn't exactly laser related now, so maybe it should be moved ? (Although I think it has quite a bit of laser related information in it, so I don't know.)

 

[SMIDSY]

Aye, I'll have to see if the setup I'm designing now is good enough.

I've purchased a ballscrew (Converts rotational motion into linear motion) for the Z axis (Up and down) which will give me a Z resolution of 0.0005mm. I thought that I should splash out on a better one for the Z seems as I'll also be milling PCBs and need to be able to take thin layers off.

As far as the actual designs are going, I've pretty much finished the design for the spindle it's self and have started on the Z axis. I will show some designs soon, when I have a bit more to show.

I know this thread isn't exactly laser related now, so maybe it should be moved ? (Although I think it has quite a bit of laser related information in it, so I don't know.)

called a worm screw/ gear where I come from

its like this right? fig 35? with like a connector that will move up and down with the rotation of the spiral shape...

thats enough resolution- worm screws are good as with lots of rotation is limited linear motion so its a cheap way of getting a good resolution

yeah should move it to another off topic section

if you need any help/ diags for a working (will take a wee bit of time to get) for a working milling machine (or if you prefer CAM/ CNC lol) then ask.

general help is always available from others I'm no expert on this!

hope it all goes well....

 

[yngndrw]

It's like that, but not quite.

Instead of having two meshing faces rubbing together, it has a series of ball barings between them. The groves in the ballscrew are actually little channels.

Using ballscrews mean a few things:
1) Because there's less friction, it can use much tighter tolerances - Meaning less backlash. (Movement when the screw is not rotating.)
2) Less friction means less wear and more power transfered to the tool. I'm using very small motors (36Nm) so I need all the power I can get.
3) More accurate, I'm using ground ballscrews which are grade C3. IIRC the tolerance for C3 is 7um.

As far as the design goes, I think I'm alright at the moment - I have a general idea of it all, it's just taking a little while getting each part designed. (I'm using SolidWorks, so each part is designed separatly and then put together in assemblies.)

However, once I've finished my designs I'll be asking for lots of comments, suggestions and criticisms.

 

[SMIDSY]

thats what I thought it was (though my pic is the cheepo one lol)

are you sure you have your motor powers correct?! 36Nm is huge! a 750W motor puts out 11Nm!! and drains 175A!

http://www.technobots.co.uk/acatalog/Online_Catalogue_500W_to_1000W_Motors_77.html

I think you have made a mistake that would shred your entire assembly!

is it not 0.36Nm? if it really is 36Nm show me the site and ill be getting lots XD

I like the tolerances anythign with +/-7 um is good in my book!

 

[yngndrw]

Sorry, my bad - I ment 36Ncm. :-[ They are stepper motors, so that's the holding torque. The torque will decrease with speed, but should be enough. The Z axis is the only one with any real load as it's fighting gravity, however I've chosen a 1mm per turn ballscrew for that axis so that should help the motor out. I may counterbalance the spindle if I can find the space to do so. (Where I've planned to put the motor (For weight balance reasons.) is also where I planned to put the counterbalance - We'll see.)

If you're in the market for stepper motors, Arc Euro Trade have got a sale on:
http://www.arceurotrade.co.uk/Catalogue/Stepper-Motors

I've attached a picture of my current design for the Z axis. I'm a bit limited by the massive linear bearing blocks, but it depends on what I can get from Ebay. There blocks I can always get, but I'm looking to pick up some smaller units in an auction.

For scale, the top plate is 110mm long x 100mm wide. This setup allows for around 108mm of travel, pretty good from a ballscrew which only has 124mm considering that I had to work around the massive linear bearing blocks. I think it's quite cute.

The back 50mm portion of the unit is actually empty, but will either hold: (Or hold all of)
1) The Y linear bearings
2) The Y ballnut
3) The Z motor
4) The Z counterbalance