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Author Topic: Modelling with a laser  (Read 6764 times)

mermod

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Modelling with a laser
« on: March 11, 2015, 08:50:04 am »

I have noticed a few questions on here in the past on how to get boat plans lasercut and whats involved, as I'm about to start a new model I thought I might show step by step how I go about it, I'm sure others have their own ideas but the basic principles are the same.


First step is to get the plans scanned, sometimes I get it done on a large format scanner but mostly I use my A3 document scanner, I can usually fit all the rib lines on in one hit but sometimes I have to scan larger pictures in pieces making sure they overlap for later when they are put together in the design software, unfortunately they will be in JPEG or similar which is a single entity with no individual lines so I trace over the lines with CorelDraw (design software)


So here is a plan that has been scanned, then imported as a jpeg into CorelDraw then I have traced the lines over the top of the scanned image.
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mermod

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Re: Modelling with a laser
« Reply #1 on: March 11, 2015, 08:53:49 am »

This photo shows the ribs that have been traced over the plans then copied and placed next to the original, the small black rectangles become my locating holes for lining the whole thing up later, kinda like the old method of drilling holes in the ribs then racking them up onto dowels


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mermod

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Re: Modelling with a laser
« Reply #2 on: March 11, 2015, 09:02:33 am »

After that I take each rib, add the cutouts for stringers, keel, rubrails and such then mirror the image.
Keep in mind that this all takes quite a bit of time even with the best of software and computer, the ribs alone take about a full day to do right, quite often when you zoom in to the original image it will pixelate badly so often it can take ages to get the curves just right.


So this picture shows the cleaned up ribs layed out ready for the laser, my bed size is 610mm x 457mm so it's a case of fitting them on the best you can, there are programs that will optimize the arrangement for best use of materials (the proper name is "nesting") but I do just fine without it.


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mermod

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Re: Modelling with a laser
« Reply #3 on: March 11, 2015, 09:16:29 am »

About now I send the parts to the machine to be cut while I work out other bits I need, my machine is 50watt so the ribs cut from 3mm MDF  take about 20mins to cut, with a laser the three settings I work with are speed, so how fast the head moves, power and frequency which is how quickly the laser pulses out its beam so 3mm MDF would be about 15% speed 100% power and 2500 frequency.
When I cut the 6mm MDF for the locating strips and spacers the only ting that changes is the speed which I drop back to 7%
It takes a bit of practice to get the hang of speed v power depending on the material to be cut, something like 3mm acrylic runs at about 25% speed 100% power but I up the frequency to 5000 so I get a near flame polished edge, kinda cool really:)
If I'm cutting 1mm ABS I will drop the power right down to 10% but run it at max speed so it doesn't create to much heat and melt the piece or distort the edge


Here's the parts showing how they locate onto those strips.



By the way the thickest I have cut is 25mm acrylic which I ran at 2%speed 100% power, it actually came out well but the laser beam tends to bend when it goes too deep.
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mermod

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Re: Modelling with a laser
« Reply #4 on: March 11, 2015, 09:22:26 am »

This picture shows the keel traced and ready to be cut, as this piece is longer then the size of my table I have put a jigsaw type join in it, drawn in green on the left side of the part about 100mm from the side, I then seperate it into two individual parts.


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mermod

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Re: Modelling with a laser
« Reply #5 on: March 11, 2015, 09:27:47 am »

So this is all the parts put together so far, the spacers between the ribs can be seen in the very first photo with A,B,C and so on,that way there can be no chance of incorrect spacing plus by running then past the top of the hull they are used to line it up and off the bench, any spacers that run past into places they shouldn't will be trimmed off later.
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mermod

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Re: Modelling with a laser
« Reply #6 on: March 11, 2015, 09:29:52 am »

I also cut a little centreline just so any twisting is easily visible.


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mermod

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Re: Modelling with a laser
« Reply #7 on: March 11, 2015, 09:31:33 am »




I will put up some more pics as I progress.


Phill
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Re: Modelling with a laser
« Reply #8 on: March 11, 2015, 10:08:55 am »

An excellent topic Mermod.  I found it very interesting, especially as I'm drawing up plans of my own at the present.

You mentioned copying and overlaying two copies which is something I have spent two days getting right.  Did you find that when adjoining sections are lined up on the computer and then printed out on paper that they come out slightly misaligned and apparently showing a small difference in scale  ? I rotated some of these  copies to get it a particular part on the A4 sheet copy and the problem became worse ?
Sorry but not in the world of CAD, just my paint program.

Cheers

ken
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mermod

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Re: Modelling with a laser
« Reply #9 on: March 11, 2015, 10:50:49 am »

Hi Ken, I find that small difference can be the scanner, I have an a4 one I threw in the back shed it was so bad, you could scan the same thing twice and it would come out two different scales which meant ages on the computer trying to line things back up, I now use our a3 brother printer scanner and have never again had that problem, CorelDraw is more of a graphic design package than CAD but it has a great little "nudge" feature so you can set how much you want to nudge it by and in which direction.
The other thing is to draw a "datum" line on the bit you scan, that way you can select that part and punch in the length it should be and let the software autoscale or stretch accordingly in the other directions (if paint lets you do that)


Thanks for watching


Phill
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Brian60

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Re: Modelling with a laser
« Reply #10 on: March 11, 2015, 11:48:09 am »

A great article, can't wait to read the next instalment. If nothing else it gives an insight into how to do things correctly!

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Re: Modelling with a laser
« Reply #11 on: March 11, 2015, 02:00:16 pm »


 Me too!  O0
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hama

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Re: Modelling with a laser
« Reply #12 on: March 11, 2015, 06:59:51 pm »

Me too  :-)
Will never have the patience, skills or laser to do this but it's so interesting!!
Go on, give us more. O0
Hama
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TailUK

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Re: Modelling with a laser
« Reply #13 on: March 11, 2015, 07:12:20 pm »

Is that a Smit Nederland?  The shape's familiar.
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Re: Modelling with a laser
« Reply #14 on: March 11, 2015, 07:52:49 pm »

Keep the posts coming please. Fascinating stuff.

Andy
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mermod

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Re: Modelling with a laser
« Reply #15 on: March 11, 2015, 10:07:50 pm »

I hope to get back in the shed this afternoon so I should have more to report soon, as for the model, it's ex navy tug Bronzewing.
https://www.flickr.com/photos/25846046@N03/15018022719/in/pool-drydocksshipsrigs
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mermod

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Re: Modelling with a laser
« Reply #16 on: March 12, 2015, 06:26:46 am »

So the keel with the jigsaw joins has been cut, joined and slid into place, turns out I missed the slot in the front rib but that was an easy fix.
Also any rib spacers that were protruding past the bottom of the hull have been trimmed off keeping in mind this is only a "plug" so doesn't have to be pretty.
The keel isn't super necessary but it gives a great centreline for later when I'm sanding.

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mermod

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Re: Modelling with a laser
« Reply #17 on: March 12, 2015, 06:50:37 am »

Actually missed if the wrong word, the front slot just wasn't long enough.


Phill
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mermod

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Re: Modelling with a laser
« Reply #18 on: March 12, 2015, 07:02:10 am »

Next up is the rubbing strip, this gets cut from 6mm mdf then has a 3mm x 3mm strip glued underneath, the finished part then slots into the 10mm x 3mm slot around the hull, to make it easy I make the part in front and rear sections so one slides on from the front and the other from the stern.


On the screen, ready to cut



The rear part slid into place also showing the 3x3mm strip, this strip gives me a defining point where the hull meets the rub strip.


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mermod

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Re: Modelling with a laser
« Reply #19 on: March 12, 2015, 07:08:57 am »

Next up is what could be called the caprail, once again this defines the curve for this piece.


On the screen.



On the laser.



On the boat.
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mermod

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Re: Modelling with a laser
« Reply #20 on: March 12, 2015, 07:12:01 am »

Nothing too special here, just the 3mm stringers in place, these were machined from some radiata pine I had under the house.


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mermod

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Re: Modelling with a laser
« Reply #21 on: March 12, 2015, 07:16:49 am »

Stringers trimmed off and as I had the lines already on the computer I used them to cut a filler piece to give the correct curves.





The filler pieces in red at the top of the screen.



Fillers in place.
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mermod

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Re: Modelling with a laser
« Reply #22 on: March 12, 2015, 07:22:43 am »

Due to the way the stringers curve as they reach the stern I coloured them red on the face that makes up that panel so I dont forget which way that panel/knuckle should run.






These photos also shows the 3mm strip on the underside of the rubbing strip, the plan is to run a straightedge against it and the first stringer when filling the hull.

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mermod

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Re: Modelling with a laser
« Reply #23 on: March 12, 2015, 07:26:57 am »

She shows her shape nicely here I think.
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