Full Spectrum Laser Focus Ruler

[Brian Kauke]

Hi All,

I was working with the laser tonight and was struggling to get the detail I wanted for my application. According to the FS 24x18 users manual, the autofocus function is not recommended for precision work, and one should instead use the included focus ruler to manually adjust the Z axis. Does anyone know where this ruler is?

If it can't be found, cutting a new one doesn't seem like a big deal. In another post here, Andrew from FSLaser mentioned the possibility of measuring the focal length, so I can look into how to do that.

As an aside, I was trying out a method of PCB etch resist printing by melting a layer of acrylic powder with the laser. I had some limited success with it. However, Bill mentioned that someone had just recently been experimenting at the shop with a method of engraving through acrylic paint. If whoever was doing that is on the list, I'm curious about how well it worked. Is the method capable of creating solder pads for a typical surface-mount IC?

[Nathan Bryant]

There is a translucent white plastic bin about 5"x4"x6" with blue latches at the top that should have that in it. It might be under the laser cutter itself or on the shelves above the workbench with the shapeoko (closest to the craft section).

There is also a 5" focus length lens and associated focal length ruler in there. Please don't confuse them. Also, please make sure anything that gets removed finds its way back.

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[Nathan Bryant]

Also, remember that there is an air compressor that shots air at the laser target. That probably won't work well for powder. You may be able to unplug it (in the danger room) if you're careful with the settings and clean the lens (and plug the compressor back in) when you're done. Do we have those wipes yet Aakin?

[Nathan Bryant]

At this point, I'm probably telling you things you already know but...

The reason the air jet is there is to put out any little fires and to keep vaporized target material away from the lens. I'm not sure if it's important for cooling the lens as well. If you're only melting stuff rather than vaporizing it, some of those problems go away. Just be careful and start conservatively. You should probably still clean the lens when you're done because it is likely there is some volatilization of whatever you're lasing.

OK, I'm really done now. :-)

Nathan

[Andrew Morrow]

Ill just jump in to say that I've seen several articles about laying down a couple layers of black spray paint, then lasering away the areas you want to etch.  

As an aside that doesn't sound relevant to THIS project, but might for others, I've been using a silhouette vinyl cutter identical to the one in the shop to create etch resist for larger designs for some time.    Just cut out your traces, stick the vinyl on the board and go nuts.  It's not great with very small traces or drill holes, but it works very well for a lot of designs.    A trick is to leave smaller pads out of your design, get a good MG chemicals etch resist pen - looks like a sharpie but resists MUCH better - and draw the pads in after the vinyl is down.   You can lift the vinyl SLIGHTLY and make sure your resist goes all the way before etching.   I find that my most RELIABLE results come from this technique.  

Andrew

[Brian Kauke]

Thanks, Nathan. I'll try the focus ruler next time I'm at the shop, and hopefully also find someone to guide me through cleaning the lens and mirrors.

Currently, I think the air jet is not causing problems with my method. I slightly wet the board with some monomer liquid on a paper towel, then pour the powder over the board, recovering the excess. It's like flouring a cutting board, and the stuff that sticks seems to remain still throughout the lasering process. Unfortunately the powder I have contains a benzoyl peroxide activator, so the un-melted regions will eventually harden if I don't complete the process quickly enough. I'll need to either find a different liquid binder (water doesn't work) or separate out the activator by washing the powder through a filter and re-drying.

I was also looking to try a conventional electrostatic powder coat system, thereby completing the process of slowly re-inventing the laser printer. In this case, the air jet certainly would interfere.

I'll certainly write all this up if anything comes of it, but the subtractive process is probably better anyway.

[Andrew Morrow]

Copper clad CAN be powder coated if it's coated completely.   A group you should take some time to look through (if not already a member) is:
http://tech.groups.yahoo.com/group/Homebrew_PCBs/

There are some really brilliant folks in there, and they've tried just about everything possible.   A popular one is the inkjet conversion to direct-print resist on.  This is possibly with some people having much more success than others.

[Bill Tomiyasu]

Here's another option… laser printing toner directly on the copper clad board.

http://www.youtube.com/watch?feature=player_detailpage&v=WQ0QPcXfuPo

--BillT

bi...@synshop.org

[Andrew Morrow]

I'm very surprised to see this working!  All attempts I've seen before to try this technique have failed due to the inherent issues with the laser printing technology not printing on to a conductive surface.   Attempts at creating a brush-ground have added SOME success, but not to the level I'm seeing here. I'd be interested to learn more!

[Andrew Morrow]

That said, if anyone wants to try something like this, I have several Laserjet 4000's sitting in my garage that all work (to varying levels) and take cheap toner.  I also have a couple of the network cards for them, so we can skip the usb->parallel step.

[Krux]

As a fyi, with the laser I noticed that the accuracy is not very good at times when you run it at full speed, so you'll want to run it slower (like 80%) at less power if precision is important.  

Though this sounds like one of those things that takes some playing with anyway.

perl -e 's==UBER?=+y[:-o]}(;->\n{q-yp-y+k}?print:??;-p#)'

[Bill Tomiyasu]

Eli has been to the shop before. He's got a bunch of other cool videos on his channel too. Worth checking out. 

-BillT

bi...@synshop.org

Sent from my iPhone

[Eric McFall]

I wish I knew we had a 5” focal length lens.  I spend the better part of an evening trying to get decent cuts through some thick ¼” acrylic.  Heavy bevel and not even close to straight.  Do you happen to know what the focal length is of the lens we currently have installed?

 

- Eric McFall

 

email) Er...@LVMcFall.com & Er...@AudioForceDesigns.com

web) SmokingCircuits.com

cell) 702-379-9033, home) 702-987-0323

snail mail) 7480 Emerald Glow St, Las Vegas, NV 89123

[Nathan Bryant]

I think it's 2.5". If we install the 5" one, we need to go through and reconfigure the autofocus to the right height. We do a lot more cutting than engraving and it would be good to get it installed.

[Aakin Patel]

I should be at the shop tomorrow night, I'm willing to work with someone to get the lens swapped out. We need to do a thorough cleaning of the laser anyways.

- Aakin

[Chance c]

 And I was in the Danger Room yesterday on the receiving end of all the fumes that were coming out of the laser cutters.  Had to prop open the back door or pass out, it was so bad.  I know there's a venting system in place, but I'm here to tell you it's got some leaks!

[Brian Kauke]

Hi,

The smell in the danger room had nothing to do with the laser cutter, but instead with the monomer liquid I was using, which smells like superglue. I didn't expect the smell to get invasively bad, and I didn't notice that it was bothering people. For that I apologize, and I'll do any further experimentation outdoors.

[Bill Tomiyasu]

Found the box under the laser cutter and put it on top of the machine.  Labeled it "Laser Cutter".  There is a lens, some tools, some papers (manual?) and various micro switches -- also a couple of lens wipes that are unused.

--BillT

bi...@synshop.org

[Nathan Bryant]

The rulers are laser cut pieces of acrylic with the size etched into them. I think there's a little "tooth" that sticks off of one corner.

[Bill Tomiyasu]

There's a long one marked 5.0 and a short one etched with "57".

[Nathan Bryant]

Cool. The short one is for the lens that's in there. 57mm is about 2.25". :-)

[Andrew Morrow]

Where can we find the process for focusing using the ruler? I read the manual that I was able to find online and didn't find reference to it.  

Thanks!

Andrew

[Nathan Bryant]

I think they used the slow jog on the laser (and then checked using the gauge) when they came out to set it up. Both sides of the z axis have threaded rod, but I don't remember if there are 2 steppers (that can get out of sync if manually adjusted ) or there is a belt system that links them.

[Brian Kauke]

Hi Andrew,

The manual can be found here: http://fslaser.com/files/2418pro_manual.pdf

The instructions for using the focus ruler are on page 30.

[Andrew Morrow]

Thanks!

Were we able to get the lens cloths that FSE recommended?   I MIGHT have some unexpected time at the shop tomorrow, and if so, I can go and change out the lens, adjust the autofocus and make sure it's all good.

[Bill Tomiyasu]

There are lens wipes in the box with the 5.0 lens.  I would assume that they are the recommended ones since they came with the machine from FSL.

--BillT
bi...@synshop.org

[Andrew Morrow]

I'll take a look if I can indeed make it down there tomorrow.  The only thing I'd wonder is if they'd be any good anymore.  I used to buy and use a fair number of the Zeiss lens wipes that AndrewFSE was recommending, and they went bad and dried out after about 6-8 months.

[Aakin Patel]

I was planning on trying to swap it out tonight. I haven't ordered the wipes yet, but I can grab some from walgreens if the ones in the box are dried out.

- Aakin

[Andrew Morrow]

If you're going tonight, I WOULD plan on getting some in advance.  They're not terribly expensive, though I haven't seen them at Walgreens.  I do remember buying some from Sams Club long ago, but you know how the big club stores are, they have no consistency from week to week, much less over a decade.

[Andrew Morrow]

oh! And as I'm learning more about the laser and trying to get myself up to speed, do we have 4th gen or 5th gen electronics in it?

[Aakin Patel]

K, I'll head out and grab some.

- Aakin

- Aakin

[Nathan Bryant]

I suspect the Zeiss lens wipes are made from only the fluffiest baby bunny tears and I'd hate to scratch the mirrors with anything else. :-) Better to go with what's recommended or something well researched.

[Aakin Patel]

The photo sections of most drug stores tend to have wipes for photography lenses, which I suspect are the same grade; I know they work well on my camera lenses, and I suspect that will be no different for the laser.

- Aakin

- Aakin

[Andrew Morrow]

Actually, Nathan, you're wrong.  They're made with the wishes of happy children going to Disneyland for the first time.   Eisner started collecting them in a failed attempt at immortality, then realized he'd rather die young, but more rich.   They're even more expensive than ink jet ink.

On Thu, Aug 29, 2013 at 1:54 PM, Nathan Bryant <nathan....@gmail.com> wrote:

[Nathan Bryant]

Sounds good.

[Aakin Patel]

We cleaned it up, swapped out to the 5" lens, and are realigning now.

- Aakin

[Nathan Bryant]

Great work! We need to figure out how to reset the autofocus distance.

[Krux]

I would think that would be in the pc software I believe... perhaps the FSL guys can give a better answer.


perl -e 's==UBER?=+y[:-o]}(;->\n{q-yp-y+k}?print:??;-p#)'

[Aakin Patel]

Hopefully. There's nothing in the manual or any settings. 

We tried one of my standard test files using the manual focus ruler, and it works great at 5". We just can't figure out how to set the autofocus to the new height. Any help would be welcome. 

- Aakin

[Andrew Morrow]

All I could fins was this:
http://fullspectrumengineering.com/forums/viewtopic.php?f=3&t=1202&sid=1ce380549b396c67a963009a48fd9fad

A bit cryptic to be sure!

[Andrew Morrow]

I take it back.  This looks better:
http://fullspectrumengineering.com/forums/viewtopic.php?f=3&t=27615&p=32694&hilit=auto+focus#p32694

[kr...@thcnet.net]

> I take it back. This looks better:
> http://fullspectrumengineering.com/forums/viewtopic.php?f=3&t=27615&p=32694&hilit=auto+focus#p32694

There you go.

[Aakin Patel]

Cool. Can one of you handle this tomorrow? I'm about to head out of here...

I'll leave a sign saying to focus manually on the laser...

- Aakin

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- Aakin

[Andrew Morrow]

Roger.  Not sure if I'm going to be able to make it, but I'm sure going to try.

[kr...@thcnet.net]

> Roger. Not sure if I'm going to be able to make it, but I'm sure going to
> try.

I won't be there tomorrow. But if it's not done before Saturday, I'll take a
look

[Nathan Bryant]

I would, but I'm not going to be able to make it in either. Good job getting the lens in though. That should have been on our list for a while.

[Aakin Patel]

It was a team effort... there were four of us involved. We formed all the parts of Voltron minus the black lion.

Which worked out pretty well, actually. We skipped the random bits and went straight to the blazing sword.

- Aakin

[Andrew Morrow]

I've set up the autofocus.  I also did a firmware upgrade, re-aligned the laser and secured a bolt that was loose on the tube.  

Three  things:

It fires better now, and the red dot is more accurately placed.  

The auto focus is more accurate now than it was before (by 30%)

The IP address of the laser changed when the firmware update hit.   I changed it in the software and updated all.  It worked from 3 reboots of testing and appears solid, but if it doesn't connect for some reason remember to turn the laser off and on and note the IP.   In one of the top menus in the software, there's a place to set the IP to connect to.   Let me know if there is any issue and I'll come running!

I did not unfortunately notice a real increase in slicing power from the new lens.   Tests at similar settings showed a SLIGHT improvement, but the bevel was as significant.   What DOES make a BIG difference is putting a damp paper towel on top of the work piece before cutting.    The scorch and bevel drops by 50% at least!

Something to think about!

Andrew

[Andrew Morrow]

One more thing I neglected to mention.  I tested out the raster abilities of the laser with the new lens by trying out the black spray paint on copper clad technique I was referring to earlier in the email chain.  Note that this is very high quality paint, but sprayed from a cold bottle with too-little shaking in a humid back yard.   That explains the awful coverage.   I suspect that I'd have gotten even better results if the paint covered more evenly.   That said, even though I was only working at 150 DPI, the result was pretty darn great.   (see attached)

I can absolutely see this as a technique for doing etch resist on PCBs, and I believe with a very low raster speed (this was 5%) and high power, very thin traces can be achieved.  At least as good, and likely much better than the toner transfer methods I've used.

An important thing to note is that I did use the wet paper towel method where a slightly damp paper towel is placed over the piece to be cut and left in place as the cutting takes place.  In experiments with wood, cardboard, this board and even acrylic yesterday, I saw reduced beveling of the cut and scortching of the surface in all cases.  The only issue I'd suspect might be a problem, and I didn't see this first hand, but I can picture, would be warping of the material being cut if it's prone to that sort of thing VERY QUICKLY when exposed to moisture.

[Andrew Morrow]

The settings I used to get through THAT paint (you can see my test cuts) were 5 speed and 90 power at 100% current.   Immediately after making the cut, the result looks similar to the top right most curve where there is brown material left in the etch.   One side effect of using the damp paper towel method, however, is that it gives you a handy cloth to clean up with.  

Quantifying the actual amount of water to leave in the towel is difficult without you being able to feel it, but I can say that once the paper towel has been COMPLETELY soaked, wring it out to the stage where if you were to unfold it and shake it, not one drop of water would fly off, but it still feels damp when you touch it.

[Nathan Bryant]

Just for general information, here's what Full Spectrum says about the difference between the 2.5" and 5" lenses:

2.5"

This ProLF laser includes a 2.5" lens which is a good combination of cutting up to 1/4" and engraving details down to around 8pt fonts.  If you cutting constantly at thicker materials, a longer focus lens will give you straighter cut. A long focus lens keeps the focus longer allowing for straighter edges but does not focus down to as small a minimum spot.

5"

This ProLF laser includes a 2.5" lens which is a good combination of cutting up to 1/4" and engraving details down to around 8pt fonts.  If you cutting constantly at thicker materials, a longer focus lens will give you straighter cut.  A 5" lens is useful when engraving into objects where you need more working distance like engraving bowls or boxes with hide sides. In addition, on this machine the doors swing open and in order to reach down to the level of the open doors, you need a 5" lens.

[Brian Kauke]

Hey Andrew,

This looks fantastic. I'll give it a try with some test PCB patterns when I get a chance. What kind of paint are you using?

I might also try a polyester clear-coat and see how that stacks up in terms of detail and board adhesion.

[Bill Tomiyasu]

FYI, in another thread it was mentioned that the laser bed needs to be leveled again...

-BillT

bi...@synshop.org

Sent from my iPhone

[Brian Kauke]

I don't know anything about leveling the bed, and I can't find it in the manual, but it seems like the adjustment of the optics should be able to account for small tilts in the bed.

Andrew, when you did the re-alignment after tightening the tube, did you follow the procedure on pages 26-29 on the manual? On Thursday we found that it was easy to get the laser dialed in on one corner of the workspace, but trickier to align both corners simultaneously.

[kr...@thcnet.net]

> I don't know anything about leveling the bed, and I can't find it in the
> manual, but it seems like the adjustment of the optics should be able to
> account for small tilts in the bed.

No, it seems one side of the bed is lower than the other.. it's over a wide
area, not minor variations. I'm thinking since Nathan leveled the bed without
the the honeycomb on it, there might be some variations there, that is causing
the issue. Another possibility is someone may have raised the bed and had
gotten it stuck under the lip at the top.. another advantage of the 5" focal
length is this isn't really a possibility anymore.

[Aakin Patel]

If you use the autofocus, it still has to raise the bed until the brass plunger hits the cut material; it will just drop down further afterwards. So it could still skew the bed if it catches on the lip.

- Aakin

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- Aakin

[Andrew Morrow]

I did indeed follow that procedure.   I went through it 3 times using a piece of Mylar film instead of thermal paper because it tends to show the center point more clearly.  It also stays perfectly flat and each point can be labeled with a dry erase marker for reference.   

I got it so that the difference in points was reduced by about 3mm on the lower right side.   

I also haven't seen anything about leveling the platform.  

Andrew

[kr...@thcnet.net]

> If you use the autofocus, it still has to raise the bed until the brass
> plunger hits the cut material; it will just drop down further afterwards.
> So it could still skew the bed if it catches on the lip.

Ahh.. yea, it would.

[Andrew Morrow]

Brian,

In this instance, I used Liquitex Professional in the Carbon Black color. 
http://www.liquitex.com/spraypaint/

I think it's reasonably important to use black paint as opposed to clear because the black absorbs more of the laser energy and burns off faster.   I think clear might give unpredictable results.   If you wanted to use exactly the same paint because we know it works at least THAT well, you can get it at Michaels.  It's not with the main spray paints, but is in the fine art section near the oil paints and canvases.

[Brian Kauke]

Thanks, I'll pick some up. 

It sounds intuitive that we should use black paints, but the CO2 laser emits in the far infrared (10 um), and many materials that are transparent in visible light are opaque to the laser (such as glass and most plastics). I'm thinking that simple polyester may burn off more cleanly than paints with various colorants, etc, although your results look pristine compared to the pictures I saw on Instructables.

Also, I see the error in my thinking with respect to the laser optics. The adjustment of the mirrors will put the optical path of the laser in the plane of the XY gantry, which is not necessarily the same plane as that of the platform. So the platform does need to be leveled by measuring the distance from the lens to the platform at all the corners.

It occurs to me that the total length of the optical path will get longer as you move towards the lower right of the machine, so if there is any beam divergence then the effective focal length will be increasing. This might be something to check out if the flat leveling doesn't produce adequate results.