Maximum engrave resolution of the AWC608?

[SWMS]

Hi, I can't seem to figure out what the maximum resolution is. I have looked around and can't seem to find anything. Is it 1000 DPI or 1200 DPI?

Thanks

[Techgraphix]

What kind of Laser do you have? With a normal CO2 glass laser with a dot of ~0.06mm (30mm Lens with beam-expander) every setting above 400dpi won't do anything..
Some RF-lasers have smaller dots but 1200dpi??? I thought there was also an issue with scangaps smaller than 0.03, which comes close to 800dpi only.
Kees

[SWMS]

Thanks for this, I have decided to sit down and learn all bout engraving over the past 24 hours and your response helps

[SWMS]

So after loads of reading... I have a 25.4mm focal length lens which using buildlogs calculations sheet depending on the lasers distance from the lens should give a dot size of between 0.059 and 0.1274 ( the distance between the head and the laser aperture can go from around 100mm to 1800mm when taking into account the x, y and z distance ) These are approximations as close as I can get with a tape measure for the moment.

So I averaged that and the average dot size comes out at 0.0932mm.

I converted this to inches and divided that 1inch by 0.00366929134 to give me....an average 271 DPI but depending on which end of the table we are on that could vary significantly. I've got two ranges of Dpi from that anyway, between 199 and 430 DPI so I can try that range..


Does this sound right?...

[Techgraphix]

Not entirely:
the beam from the tube is roughly 3-8mm (40 - 100W) and it can divert a few radians ... the spread from the tube to the most distant point will be about 1-2mm max.. if it diverts more your tube is not the best or the mirrors are not flat
A wider beam gives you a smaller dot but not that much, So if the beam diverts and your dotsize is 0.05mm near the tube it will be something like 0.06 at the other end..

Kees

[SWMS]

So obviously small divergence is better since that enables a more reliable cut/engrave across the bed? As opposed to small at one end and huge at the other. I noticed that the majority of divergence seems to happen early on. Which if I think about it makes sense.

The closer the beam to the first mirror the less divergence. Then after that the flatter the mirror the less divergence over a long distance since the mirror is just bouncing the beam around. No mirror is completely flat so there will be a tiny bit of divergence.


Is that right? It helps to talk things out
This laser stuff is taking me years to learn. There is no one source for anything!

[Techgraphix]

To give you some idea, i made a small excel-sheet with some optical formula's.
The yellow fields are inputs, you can play around with them and see what it does.
Kees

Lasercalc.zip

(6.31 KiB) Downloaded 337 times

[SWMS]

Oh thanks. I'll have a look at that tomorrow. Bed time at the mo!

[SWMS]

Oh thanks for this,is is a nice alternative to the build log form, less fiddly, much easier to use!

I should explain how I came to be on this forum and why I am still asking questions..! I bought a home made laser from a guy here in the UK and tbh, if he had taught me everything to know about laser cutters I would have had to live with him for two weeks. He bought the AWC608 from light object and I was looking for the upgrade files.

So, off and on its been a bit of a learning curve and there isn't one resource for all your laser cutting needs! I've gone through learning about thermal shock, algae in the coolant, having enough coolant ( he sold it with 5 litres of uncooled water as he only used it for maybe an hour at a time ), learning the black art of lining the mirrors up, connecting the high voltage cable up safely, snapping the end off the coolant inlet stepper motors, the dreaded backlash, PPI, PWR etc etc...

So, question..... If I move the tube aperture closer to the first mirror, will this reduce the divergence?

Of course I am assuming that if a beam hits a mirror with a small divergence it keeps diverging at that angle and diverges more the further away it is from the source.

I'm also considering a beam expander in the future now as I should be able to get a smaller spot size. I think I might be getting a bit geeky though as others manage fine with out that!

Thanks for any comments

[Techgraphix]

A good cooling is essential for a lasertube.. Invest a few hundred dollars in a good active cooler (one with a kind of refridgerator in it). This will keep the tube cool and it will live much longer/ degrade slower..
Many people still use water with all kinds of additives. Still they have to replace it every few months.. I use the same coolant as i use in my car. The coolant, i use, is already 4 years old and still clean.. But if you insist to use (deluted-)water, it's your decision..

The divergence can be measured. Place a piece of paper near the tube and fire a pulse with low power, just to colorize the paper. Do the same at the most distant point.. This spot may be a bit bigger.. When you enter the sizes in the spreadsheet it will calculate the divergence in milli-radians..

The placing of the mirrors doesn't matter that much..

An Expander doesn't give you what you expect.. I thought that the dotdensity would be higher but in practice i needed more power to get the same black..
Also when your beam has a diameter of, say, 6mm and you use a 1:2 expander, it will get 12mm.. With a bit spread it is likely that quite a part of the energy won't even get to the lens..
Normaly an expander is used to reduce the powerdensity on mirrors and lenses in high-power-lasers (100W is NOT high power!)
To get a smaller dotsize i placed the expander in the tube that holds the focuslens.. But keep in mind: this is only for engraving.. Cutting-ability will be drasticaly reduced.. So .....(i think you should forget about the expander IMHO)

Kees

[SWMS]

Yeah. I learnt that the hard way, steaming coolant! That was based on his 5 litres of water. So, now I have an aquarium chiller and 15 litres of deionised water with 5 litres of anti freeze.

Re the divergence, well, yeah I learned that the hard way too, so drop the laser power down for stuff like that or you end up vaporising the paper!

So it appears there isn't much you can do about divergence. It is what it is. I found myself looking into it purely because I was looking into engraving and then started looking at spot size for various lenses.

Regarding expanders I think I have come full circle. It sounds like for the money and tweaking you don't get much pay off beyond a 25.4mm focal length lens. I'm getting very reasonable results out of 63.5mm lens as it is and that's a bit more like using a sledgehammer to sculpt stone! Thanks for your responses .

Oh and yeah I know 100 watt isn't much. . My 60 Watt Does the job but it borders on marginally under powered. I can't just think yes it will cut through that. I've been eyeing up upgrading the power supply and tube in the future. I'm thinking of about 120 watt as it's the upper end of being able to engrave.

Thanks for your time anyway.

[Tech_Marco]

Correct me if I'm wrong. Laser is doing continuously on both X & Y cutting so resolution is not existing because it is a solid line.
For the engraving, the X movement is continuously as well so there is no 'dot' anywhere on the route. There is only 'gap' between each Y steps. So, if we magnify the engraving area and with larger scan gap, the image should look like this:
_____________
_____________
_____________
_____________

If the gap is small enough like 0.1mm, most likely you won't see the space between lines but ended up a solid box. To me, the term of 'dpi' isn't a good term to be used in laser. A laser dot seems to have diameter like 0.1mm but each X or Y step is smaller than 0.02mm. Plus, it is really hard to justify the laser dot diameter because the burn mark spread out a bit. So, if the scan gap is 0.1mm or smaller, I don't think we need to care much of the 'dpi' at all unless we turned on 'PPI', the pulse mode. That will be a different game mode


Marco

[SWMS]

well I am only going on all the other websites I have read and there can be a lot of mis information out there. I think what they are getting at is if you choose a scan gap less than your dot size then you can technically get over burn. .

[Tech_Marco]

Right but scan gap is usually apply to Y or sometimes to X if you do vertical scanning (engraving). So far, I don't see any software provide scan gap for both X and Y simultaneously. If any I'll be shocked!

By the way, it is hard to do focus on a 25.4mm focus lens. To go around that, I'll consider beam expander but it is a little bit expensive. Beam expander improve beam divergence and reduce 'stress' on mirrors. But you will get sharper angle because the beam is in double size so the engraving image will be sharper, just like using a shorter focus lens

Marco