Building a laser cutter. any tips?

Hi, I just finished building a 3d printer and want to take on the laser cutter challenge. it will be completely my own design so I have to buy parts since it wont be a kit. I was just curious as to what I am missing on my list. I have a spare Arduino + ramps 1.4 laying around with 3 extra stepper drivers luckily enough for me. so far ive compiled a list and looked at tons of of guides but what I don't understand completely is the concept of focal length and depth of focus. I took a cinematography class that focused massively on that so I am somewhat familiar but not sure if the same applies, and even if it did I didn't really understand it all to well either way since that is not what I am studying for anyways.

so this is the list.
1- co2 laser head [www.ebay.com]
1- 40w co2 tube
1- 40w psu for laser cutter(has the needed functions specifically for laser cutter use)
1- 20mm mirror + lense(s)
1- Some sort of base for the material to be cut to be laid on.
1- some form of curly/straight cable for fumes to be absorbed through from laser head? I still don't understand the use of the malleable tube I see coming out of every laser head)

(most of the materials I already have are extras from the 3d printer I built. like end stops, linear shafts, gt2 belts+pulleys, t-slots etc).
I still need to decide on a cooling unit(probably water pump)

since I am designing the enclosure then it shouldn't be an issue for size. but I'm thinking something along the lines of 24x24 if possible(for future size upgrades)


I want to cut acrylic less than 6mm thickness. more than likely ill be mainly cutting 3 mil on average.

if anyone knows what I am missing it would be great to know. I am on a budget of about ~400. but would like to keep spending to a minimum as this is only a small hobby to keep me distracted and maybe make a few cool acrylic designs for my room.

I kjnow that I just need the main components that get the laser working and a bit of understanding (mainly how to set up the lenses according to the sizes I get) ive seen 1.5", 2", 2.5" 3" etc. yet I am not sure what differences the gaps do)

my apologies for the long winded novel in advance.

You might want to add some mechanics to the list...
Motors, rails, bearings and such.
Same for mounts.
If you have enough material for frame and mechanics then you will sure find bits and pieces on the way you might need, srews, washers and so on - always good to have a small box of them at hand.
You can find complete optics sets incl. mounts on Ebay if there is no local store around.

It might help to do the mechanical design on the computer, that way you can make changes without wasting material.
Often people forget to consider cables, hoses and other things in the design stages and have to substitute a workaround for the connections.
Simple fishtank water pump is sufficient for a small laser, cooling only required for small reservoirs or if the usage is really heavy and with hogh power.
If your main aim is to cut thicker materialy you might want to use a lens with a longer focal lenght to avoid the slopes on the cutting edges.
Although properly focussed shorter focal lengths work fine too, just make sure the focal point is in the center of the material.
And since you design from scratch consider a work table that is adjustable in the height - it really helps a lot for thicker materials that you want to engrave.

Wil keep all that in mind thabks for the heads up. I have a few quick questions.

I was looking into the small fish pump as acooling unit, does the hose go attached to the laser head?

Also the laser heads ive seen on ebay come with mirror mounts and mounts, can i just buy the head without mount and 3d print my own. Or are the mirror mount and mount the same?

You mentioned longer focal length, so gettin g a 2.5"/3" wpuld be gpod right?

Thanks for your time man it really helps!

The tube to the head nozzle is for blowing air to keep the beam free from smoke, cool the lens and maybe also aid in the cutting of the material. So you need an air pump for that, a compressor works of course but is not really needed since it is not very high pressure. A 12v pneumatic valve can be nice to operate as part of the cutting, air on , cut, air off.
Water goes to the lasertube, it needs to circulate with a small pump. Some cooling is needed, it dépends on the climate where you live. When you start to think why isnst ir cutting so go good, is it broken? the first thing to check is the cooling water temperature.
Exhausts, you absolutely must take care of the fumes. For the environment to be politically correct but more importantly for youself. Cutting wood or plastic generates a lof of smelly smoke. The first cut maybe one can stand it, but absolutely not in the long run. It smells a lot.. It causes your eyes to tear. You will start to caugh. The whole room will smell for days.
A nice cutting table can cost a lot to buy. You are thinking of an area of meter x meter? A table that size will cost a bit over 100$, I paid 300$ for a table 0,8 x 0,8 meter but most was for shipping.
One thing that still bothers me is the case. Aluminium profile frame, ok. And then sheet metal, but I have not been able to find a good source for the sheet metal, it is maybe 20 sheets of digferent sizes, so a lot of cutting. The case is still going through reiterations of the design, when working with the mavhine and see how things work in practise. For now i cut out sheets of masonite in the laser cutter, including scew holes and monting holes etc. Quite fun and they fit wonderful.
Your question of printed holders for the mirrors - I would say that the mirror holder including the adjustments screws and that is best in metal. For stability and there is some heat generated in the mirrors. The metal holder can then be mounted in a printed holder to the frame, rail, or wherever they will go.
It is pretty important to have the beam focussed on the material, so you need a way to set focus. Table that can move up and down if ou have really large variation pf thickness of the objects you will cut, or a laser head where the lense can be moved up and down.

Edit: Sorry for my iPad, it really can't spell.

Edited 1 time(s). Last edit at 04/28/2016 02:36AM by falwty99.

Your build sounds like its going to be pretty rad, best of luck with that.

So the only thin i would have left to learn is how to commect the water pump to the tube. Do you have link? Whenever i search google i get other results that dont have anything to do with the cooling method.

The bed will run on ramps in the z axis now that u mention focusing.

I will definately buy the head with the mirror mount.

The thing that confuses me is that some of the ebay listings vary in prices despite the items being really similar. Aside for some small extra items. The price gap is huge too. Some will be listed at $70 whilst the other at 170$. Why is that??

Water goes in where the laser comes out with the tube placed so all air is forces out with the water flow, some people even have the tube at a slight downward angle.
And for the optics ....
You really don't want to take shortcuts here, plastic vibrates so proper mounts in metal are a must have.
Same for the adjustments, you don't just want to be able to tilt the mirror, you also want to be able to move the entire mount to get a perfect alignment.
I have no clue what listings you mean or what parts you mean as you did not include that info.
In general you have different materials for the otics, quality has a price here.
Similar story for the "little" extras, depending on what they are they can be really costly, like coated mirrors, mirco-adjustable mounts...

Oh bo worries the only plastic is the mount where the laser will be placed onto. The laser i am buying will def come with its own metal parts.

So the water goes into the tube itself? If so, then i wonder how the particles are excited in the water and then fed to the laser head. Unless im wrong. And misunderstood.

Also when you say "Same for the adjustments, you don't just want to be able to tilt the mirror, you also want to be able to move the entire mount to get a perfect alignment."

I dont know exactly what you mean

But i assumethat the laswr head is adjustable and will achieve this after distance adjustments?

As for the listing, you can see the ebay listing i posted and if you scroll a bit downwards the "similar items" will jave higher or lower pricings which i find odd since theyre basically the same item unless im missing something. I havent been able to look at the listings due to being at school all day and having worked before that. I will look up a few listongs and place them here for comparisons


Thanks!

I try to have fun when I work with the laser, so I try also to formulate with a bit of humour. But it is all serious, I have just scratch-built a laser, starting in january I have spent almost every free hour on that project. That is one learning as well - it will take a lot of time. And it is no problem to connect all the pieces and get it to work. Get it to work and look nice, professional - that takes a lot of time. The 80/20 rule is valid here. 20% of the time is spent to get it up and running. Then 80% of the time is spent arranging and mounting everything properly, arrange cooling, exhausts, air feed, ventilation of electronics, lcd display and switches and more. Plus the casing. Legs. Power distribution inside. Ligth in the chamber. A lid to access the laser, with acrylic window. All nice. You'll need perhaps 500 screws. It is my experience, you may think I am exaggerating, but try and see.

I use plastic parts (and metal) in all my mirror mounts. No problem at all. It is PLA so not to be used where heat can be an issue. The price diff is with/without mirror and lense. The laser head in your listing can be extended to give the right focus.

Often there is a small sketch in the article description for a laser tube that describes how to connect water. The laser beam is generated in a maybe 10-15 mm tube in the middle of the laser tube. There is the special gas and electrodes and what not. Around that there is water, separated by the inner glass tube, the large outer diameter is to hold the circulating water. All CO2 tubes I know of have it this way. There are prepared glass tubes/connectors to hook on the hose on all CO2 tubes. Typically one would connect with a silicone hose.

I think you have a little lack of understanding how laser tubes with water cooling work, so I suggest to check Wikipedia
Same for working with mirrors and lenses in a laser setup.
It only makes sense to build from scratch if you fully understand how the single components work.
Falwty99 explained the tube quite good but I strongly suggest to get a better understanding of all as otherwise you will run into unforseen problems when you actually get going.

hah yes I am literally spending every minute of free time on my 3d printer. its almost done(just needs calibration). and I will do the same with the laser cutter. I have not bought any parts yet. I want to understand how the laser cutter works before I can buy the things I need. that is how it was for the 3d printer build. so no worries there. I want to get ahead of myself but age has taught me better . I'm excited for the build and will put all the time I can into it. wish I didn't have to work but without a job I cant buy parts

anyway, I will look into how the laser tube of c02 works but as Falwty explained it, kind of gave me a good picture. thank you Falwty!.

thanks to those who replied to my post, I now know way mrore than I knew before this. the semester is almost over and I can finally have some free time that will be well spent on this project. you guys are great and very insightful when it comes to helping out newbies like myself.


@Falwty99 hey so if I were to build a z axis bed instead, the focusable laser wouldn't be needed then I presume. and I can go ahead and buy the lenses separately instead and the head with the mounts included only. that will save me quite some money. what do you think?