Aligning the laser cutter to existing art

[Patrick Barnes]

I want to print out a set of the 'Cards Against Humanity' game onto
300gsm cardstock (Thank you Officeworks), and use the laser cutter to
cut the cards from the sheets and give them nice rounded corners.

The source file is:
http://www.cardsagainsthumanity.com/pdf/CAH_MainGame.pdf
(Don't open if you are a nice person or easily offended. ^_^ The cards
are set on each sheet in a grid with lines between)

Issues;
- The source file is Letter, not A4.
I guess the print process will just warp the cards a bit, and I'll have
to take the measurements from the printed page rather than the file.

- There are black/white lines separating the cards already.
Not too much of an issue, I'll make the cutting shape a little bit smaller.

- Alignment!
So, once I've printed my card sheets and made a cutting file, how do I
ensure that the laser cutter is properly aligned with the paper? Last
time I used the laser cutter, the jog buttons seemed to make very large
movements.

Cheers,
-Patrick

[Rebecca]

I would begin by affixing in place a sheet of acrylic with plenty of tape then laser cutting a hole in it which provides a nice snug fit for the card sheets.

Remove the cut out using bluetac.

Then you'll have a nice starting point to begin alignment.

Using callipers accurately measure where you desire the laser cuts on the printed cards.

With the initial jig cut already stored in the computer for reference you should be able to line up your individual rounded card cuts to the card stock pretty easily.

Just expect a bunch of tweaking/calibration cuts will be required and have duplicates made to avoid undue stress.

Bec

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[Patrick Barnes]

On 11/09/2012 3:35 PM, Rebecca wrote:
> I would begin by affixing in place a sheet of acrylic with plenty of
> tape then laser cutting a hole in it which provides a nice snug fit for
> the card sheets.
> Remove the cut out using bluetac.

The sheets will be A4. Do you think it would be sufficient to fix an
engineer's square on the laser bed and just press the card into the corner?

> Then you'll have a nice starting point to begin alignment.
> Using callipers accurately measure where you desire the laser cuts on
> the printed cards.
> With the initial jig cut already stored in the computer for reference
> you should be able to line up your individual rounded card cuts to the
> card stock pretty easily.
> Just expect a bunch of tweaking/calibration cuts will be required and
> have duplicates made to avoid undue stress.

Good idea. Without the alignment though from having cut the acrylic out,
what about:
1. Place a scrap piece of paper in there with the printed tiles on it
2. Jog the laser to somewhere close to the top-left corner of the sheet
3. Do a test fire.
4. Measure the offset from the hole in the paper to where the first cut
needs to be, and use that for every sheet.

Is there a way to jog the laser more finely? That way I could fire the
laser at the scrap piece repeatedly until I got the origin in the right
place.

-Patrick

[Rebecca]

Hi Patrick,

On Tue, Sep 11, 2012 at 3:51 PM, Patrick Barnes <mrt...@gmail.com> wrote:

On 11/09/2012 3:35 PM, Rebecca wrote:

I would begin by affixing in place a sheet of acrylic with plenty of
tape then laser cutting a hole in it which provides a nice snug fit for
the card sheets.
Remove the cut out using bluetac.

The sheets will be A4. Do you think it would be sufficient to fix an engineer's square on the laser bed and just press the card into the corner?

While this might work you can't assume the laser bed will be square with the laser beam axis. It might work but I suspect it will not be easily repeatable and be dogged by being almost but not quite square/aligned. Laser cutting a jig avoids this problem because it will be correctly square by default.

Also note that the bed is also not completely immobile.

Even when using a jig firmly affixed to the bed there may be some tiny but unavoidable drift each time a piece is placed and removed from the jig.

If instead of using a jig you are aligning the card by pushing it against a corner of the bed you will likely experience more bed drift than would be experienced using a jig.

IMHO a snug but not tight jig cut in 3mm acrylic is the way to go. Will give you the best alignment outcome possible with the machine.

Then you'll have a nice starting point to begin alignment.
Using callipers accurately measure where you desire the laser cuts on
the printed cards.
With the initial jig cut already stored in the computer for reference
you should be able to line up your individual rounded card cuts to the
card stock pretty easily.
Just expect a bunch of tweaking/calibration cuts will be required and
have duplicates made to avoid undue stress.

Good idea. Without the alignment though from having cut the acrylic out, what about:
1. Place a scrap piece of paper in there with the printed tiles on it
2. Jog the laser to somewhere close to the top-left corner of the sheet
3. Do a test fire.
4. Measure the offset from the hole in the paper to where the first cut needs to be, and use that for every sheet.

Is there a way to jog the laser more finely? That way I could fire the laser at the scrap piece repeatedly until I got the origin in the right place.

Yup. From memory it's:

ESC

MENU

scroll up/down until you highlight something like "JOG DISTANCE".

ENTER

then use the direction pad to select select and change digits which vary the jog amount. 

ENTER

ESC

or something like that.

[Max Nippard]

The jog distance (Move distance in the menu) can be set to 1mm or maybe less via the menu on the laser cutter controller. 

Hit Menu- v(down arrow) until Move distance is selected - Enter - then > to highlight the 5  - then v to lower the value. 

You may also want to test how well the card stock cuts. Should be fine but some card gets a bit chared on the cut edge. 

On Tuesday, September 11, 2012, Patrick Barnes wrote:

On 11/09/2012 3:35 PM, Rebecca wrote:

I would begin by affixing in place a sheet of acrylic with plenty of
tape then laser cutting a hole in it which provides a nice snug fit for
the card sheets.
Remove the cut out using bluetac.

The sheets will be A4. Do you think it would be sufficient to fix an engineer's square on the laser bed and just press the card into the corner?

This depends on how well the printing is alined to the paper.  

Then you'll have a nice starting point to begin alignment.
Using callipers accurately measure where you desire the laser cuts on
the printed cards.
With the initial jig cut already stored in the computer for reference
you should be able to line up your individual rounded card cuts to the
card stock pretty easily.
Just expect a bunch of tweaking/calibration cuts will be required and
have duplicates made to avoid undue stress.

Good idea. Without the alignment though from having cut the acrylic out, what about:
1. Place a scrap piece of paper in there with the printed tiles on it
2. Jog the laser to somewhere close to the top-left corner of the sheet
3. Do a test fire.
4. Measure the offset from the hole in the paper to where the first cut needs to be, and use that for every sheet.

Is there a way to jog the laser more finely? That way I could fire the laser at the scrap piece repeatedly until I got the origin in the right place.

-Patrick

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[Patrick Barnes]

On 11/09/2012 4:14 PM, Rebecca wrote:
> While this might work you can't assume the laser bed will be square with
> the laser beam axis. It might work but I suspect it will not be easily
> repeatable and be dogged by being almost but not quite
> square/aligned. Laser cutting a jig avoids this problem because it will
> be correctly square by default.

Ah yes, I should have spotted that.
Good thing there are plenty of clever people around on this list. ^_^

-Patrick

[Rebecca]

Just realised I didn't answer this clearly:

"- Alignment!

So, once I've printed my card sheets and made a cutting file, how do I ensure that the laser cutter is properly aligned with the paper? Last time I used the laser cutter, the jog buttons seemed to make very large movements."

It is possible to adjust the jog distance of the laser cutter but I would avoid this approach.

Calibrate the fine location of the laser cuts in software/cad rather than by jogging the laser cutter by hand.

Doing it in software is much more civilised and repeatable.. Just make sure you have plenty of 'test' cards.

Also wouldn't hurt to have test cards which include some printed indication of where the laser cuts should be.

This would allow you to quickly measure up the offset and nudge the vectors in software as required.

Bec

[Dr Ada Not-a-fruit]

On Sep 11, 4:14 pm, Rebecca <r3be...@gmail.com> wrote:
> Also note that the bed is also not completely immobile.
> Even when using a jig firmly affixed to the bed there may be some tiny but
> unavoidable drift each time a piece is placed and removed from the jig.
> If instead of using a jig you are aligning the card by pushing it against a
> corner of the bed you will likely experience more bed drift than would be
> experienced using a jig.
> IMHO a snug but not tight jig cut in 3mm acrylic is the way to go. Will
> give you the best alignment outcome possible with the machine.

I haven't tried this, but:

is there a problem using a jig referenced to the corner of the
machine, and absolute positioning of the origin?

Process:

- take a 300x350 piece of acrylic. cut out sufficiently sized cutouts
that you can jam it into the corner of the bed mechanism, with
alignment against two edges of the bed.
- switch the laser cutter to absolute position mode
- cut out a 297x210mm hole
- insert piece of paper in this hole

In fact, such a jig would be a useful shared object.

[Ray]

Hi Patrick,

 

I had a look at the Cards Against Humanity game, it looks awesome to me. 

 

Did you have any luck with your plans to print onto card and then laser cut? I would love to make my own set!

 

Cheers

Ray

[Patrick Barnes]

I ended up just using a guillotine.
The printer curled all the pages, so they wouldn't sit flat on the laser
cutter. You might be able to get the laser cutter to etch the design
*and* cut each page out, that's probably worth trying.

-Patrick

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[Ray Pace]

Yeah fair enough, I guess using the laser sounds good, but some times the old ways are easiest.  Especially as we aren't trying to produce hundreds of sets.

 

Thanks

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