Laser cutter / engraver

[yngndrw]

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.

 

[woop]

answer to Q1 and 2- the IR out of the 115 is only about 160mW (at 250mA)... the red out of the same drive is at least 270mW at 450mA. (got this info by SEARCHING) you will probably need a bit more power than that to cut anything
3 - don't know about glasses, i don't have any (i will probably go blind )
4 - the optics in the drive are no good for collimating the beam as far as i know. and you will need some type of heat sinking, so maybe get an aixiz module to put the diode in (comes with a collimating lens to focus the beam)
buy from here: http://www.aixiz.com/shop/product_info.php?cPath=1_26&products_id=33
or here http://www.sureelectronics.net/goods.php?id=194
5 - removing the diodes from the 115 is not very easy. i used a dremel with a cutoff wheel to carefully cut the metal off. before that i killed 2 trying to push them out
6 - to cut with such a low power diode, the beam will need to be focused to a tiny dot, so you will either have to constantly adjust the focus or somehow achieve a tiny beam (the aixiz module has a huge beam when focused to infinity)
7 - anything white won't get cut by a diode around 200mW, or you could use metal
9 - i don't think you will be cutting anything using the diode you suggest. you might be able to engrave (black) stuff really slowly

 

[Zom-B]

From what I know, the optics in any drive are VERY good. They are designed to focus the laser at the smallest spot possible, after all. The only modification that might increase the usefulness is removing the beam splitter just in front of the diodes. These are only used for tracking (following the groves on the disc)

For cutting things with thickness (even beyond 0.1mm) a parallel beam is required rather than a collimated beam. This would require a far more powerful laser and a very narrow beam

 

[woop]

ok i take back what i said about the optics being useless, i just tried using the objective lens (the one mounted on a servo with magnets and coils) and it works really good, parallel beam width is less than 1mm... (awesome) i mounted it in an aixiz module

what you could do, is reuse the servo that holds the lens, and mount the laser directly under it somehow, then use the servo to focus the laser however you want (you would need to work on a electronic controller to do this)
the laser should be mounted a mm or so from the lens (it has a really short focal length, thats what allows the beam to be so thin)

Zom-b, not removing the laser from the original case would result in a lot of loss, there would be a lot more power mounting the laser directly under the objective lens

 

[yngndrw]

Thanks for the replies guys. I'm sorry my questions were quite broard but I didn't have much of a starting point for my research, not knowing much about lasers.

Are you saying that using the writer's own lense would be better than using an Aixiz module / lense, and that I should use the writer's own lense servoto control the focal length hence change the cut height in order to cut through the neoprene ?

Neoprene is rubberised foam and is thankfully black. (At least the stuff that I'll be using is.) Would I be right in saying that I could cut slowly and vary the focus in order to cut through it ?

Also, I have a vague idea of how a CD drive is put together as I took one apart a long time ago. From what I remember, the servo is just a very simple magnet and coil moving the lense sideways. I'll assume the feedback part of the loop is through what the laser reads. Would I be wise is saying that I should scrap that servo and just add a third (Very small) axis driven by a stepper motor and a very fine leadscrew ?

If the writer's optics have two lasers and a combiner, can I not use both the IR laser and the red laser combined to increase the cutting power ? Will this make the focus control too hard, or does it not work like this ?

On the electronics side of things, I've always known lasers to have the laser diode and a photo diode, where the photo diode is a feedback system to control the power of the laser diode. However, looking around here most people seem to just use a current controlled system, leaving out the feedback photo diode. Why is this ? I'll admit that I havn't searched for this and I will do now - See if I can answer my own question. :-[

Finally, if this kind of laser is too weak to use for these applications - What would you suggest to use instead ? (Maybe use a better laser with the same optics from the drive ?) I don't have a lot of money for this project so it would have to be as cheap as possible.

 

[phenol]

If the writer's optics have two lasers and a combiner, can I not use both the IR laser and the red laser combined to increase the cutting power ? Will this make the focus control too hard, or does it not work like this ?

both red and IR have their own beam paths and a common focusing assembly, which means that its focal length would be different for both wavelengths - if one is properly focused, the other would be out of focus. It could pe possible to swap the IR one with another red because reds are normally more powerful, the wavelength is the same, so it the focal length.

On the electronics side of things, I've always known lasers to have the laser diode and a photo diode, where the photo diode is a feedback system to control the power of the laser diode. However, looking around here most people seem to just use a current controlled system, leaving out the feedback photo diode. Why is this ? I'll admit that I havn't searched for this and I will do now - See if I can answer my own question.

cd/dvd writer LDs are typically not equipped with feedback PDs. Besides, constant current drivers are much more accessible to laymen that optical feedback drivers . I wouldnt mess with such a circuit powering a strong /and expensive/ LD for hobby purposes- spurious retroreflections from shiny objects could upset the optical feedback thus blowing the LD.

Finally, if this kind of laser is too weak to use for these applications - What would you suggest to use instead ? (Maybe use a better laser with the same optics from the drive ?) I don't have a lot of money for this project so it would have to be as cheap as possible.

Frankly speaking, those LDs are best suited for showing off to friends and inducing an occasional 'wow' effect in ladies.
There are more suitable lasers for material processing -CO2 and high power IR semiconductor emitter arrays being among the most popular. You can get single emitter 808nm LDs up to 3-5W. I think those would readily cut thru neoprene and even set it on flames for that matter.

 

[rog8811]

inducing an occasional 'wow' effect in ladies.

***must resist the temptation****must resist the temptation*****quick, put in something on topic******

Having been donated an NIR LD I thought I would have a go at some kind of engraver.....I am having a play with the idea of using an electric car mirror and joy stick to steer the beam..... I throw it in as an idea that may or may not work.... True XY CNC would be nicer though...how are you thinking of doing that bit yngndrw?

Regards rog8811

 

[yngndrw]

The restriction of not posting links is god damn annoying, I just lost my post.

I initially got the idea for this project from a post on CNC Zone forums about someone who was engraving black plastic with a DVD writer laser. It seemed to be going pretty well so I assumed that the same setup would be able to cut through neoprene. (Remember, it's just rubberised foam.)

I want a nice neat cut and engraved lines, so no need for 100Watt lasers that can set the bed on fire. On the other hand I don't want it to cut so slow that I'd be better off using a knife and doing it by hand.

I don't mind using watercooling and/or peltiers to get a bit more out of the laser, if required. As long as the life of the unit and the weight of the laser head isn't too much for the stepper motors. I wanted to keep the laser diode as cheap as possible. I was thinking about upto £40 for the laser diode, although it seems that is unrealistic. I think I will have to re-think my plans.

For the CNC part, I have ordered some stepper motors: 36Ncm, 380g, 42x42x48mm.
I will only be controlling the X and Y with these, as it's a laser. I may add another small stepper for focal control.
The main movement will be using proper leadscrews or maybe belt drive. It will be a "real" CNC machine either way. The bed will be fixed, so that the part does not need to be clamped much, if at all.
There will be about 60cm of travel on both the X and Y.

I'm starting to think I've bitten off more than I can chew, well afford.

 

[rog8811]

I'm starting to think I've bitten off more than I can chew, well afford.

LOL, that is this hobby I am afraid........... I have got an XY drive unit from an autosampler but have no idea how to drive the stepper motors :-[

Regards rog8811

 

[yngndrw]

Here's a heads up on stepper motor control:
hades.mech.northwestern.edu <slash> wiki <slash> index.php <slash> Stepper_Motor_Circuits

I would be using the software Mach3 to allow computer control over the machine. I would have the computer drive a home-made stepper motor controller in order to power the motors.

I might just get one of the Pioneer 112D drives just to see if the laser would be powerful enough. (You never know ?) As I said, I don't mind using stupid amounts of cooling, Although I would probably end up using 200x more power cooling the laser than actually powering the laser. -40C laser anyone ?

 

[rog8811]

http://hades.mech.northwestern.edu/wiki/index.php/Stepper_Motor_Circuits

Fixed that in case someone else wants it, in the google search there was a photo of a breadboard drive circuit that looked quite simple...I may have to give it a go sometime...
I had a quick look at the bit of kit I have, it turns out to be XYZ, 3 stepper motors 2 with toothed belts,X&Y, the Z axis has a lead screw.

Regards rog8811

 

[yngndrw]

Thanks for sorting out the link.

Your kit seems exactly what I was thinking of doing, only (Probably) which different sized parts.

When my steppers arrive, I was going to design and build some microstepping controllers. The controllers will be designed to be controlled by Mach3 via a parallel port. They will be controlled by a PIC micro controller. I guess I could produce kits, although I don't know what shipping would cost from here. (The UK.)

Electronics is my most familiar subject, closly followed by programming. Shame these two parts are the most well documented and that the mechanics aren't as documented.

 

[rog8811]

I may be interested if you do make a kit....
No problem for me with delivery as I am also in the UK
I will try to get a photo of the assembly I have in the next couple of days and post it here.

Regards rog8811

 

[yngndrw]

Well I should be getting the steppers pretty soon, then I can start playing about with some designs. I will probably then have to order in some power transistors but I should have all of the other components lying around.

I'll be interested in seeing your gear, I may just adapt that design for my needs. (I need about 60cm of travel in each axis.)

I will try design a laser head when I can with two 112D laser diodes. They will be at 90degrees from each other and will feed into a combiner which will then feed into a lense. The lense will move on a tiny leadscrew for focal adjustment and then whole assembly will be cooled by a peltier and a waterblock. (I have a 266Watt peltier around here, that is 266Watts of cooling power for 320Watts of electrical power, so to run it at 100% I would need to design a water block which can cool 580Watts of power. This is of course assuming I can find the peltier.)

I'm hoping that the "super cooling" will allow me to run the laser pair high enough to cut the neoprene as well as to engrave / mark aluminium. I'm guessing 2x 500mW ? If I was to do this (Let's say the laser cans are at -40C each.), what could I expect the life of the laser diodes to be ?

The internals would be sealed from the air in order to stop condensation. I hope that the laser passing through the lense will clear any condensation from the lense. This is all just thoughts because as I said before, I have no real experiance of lasers.

Does my plan sound solid ? What do you think I should change ?

 

[rog8811]

I think what I could build would be considered a toy compared to your spec

The XY on mine is around 15cm each way from memory.

Regards rog8811

 

[woop]

as far as i know (although i am not an expert on lasers) the main limitation you will face will be the lasing cavities not being able to handle that much light... so cooling it to -40C will not really change that.
you would probably get just as much power running the pelter at 2W as at 200W because the lasers will produce around 1W of heat