Laser cutting question..

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CorvusCorvus Frets: 2924

I'm wanting to get some templates laser cut, got a few control cavity type things to do. Reckon it'll save time etc.

With a DXF, is there a standard/accepted way of showing what's a 'hole' and what's a 'solid piece' - like what is the cover ("male"), and what's the cavity template ("female" )..?

Maybe just add a rectangle outline around the 'female' part?

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  • Modulus_AmpsModulus_Amps Frets: 2569
    tFB Trader
    it should be self explanatory if all you are doing is cut outs, the laser will cut along your line, simple as that.

    Presumably you are drawing closed loops, so a loop inside another loop will be a hole, if you draw a loop inside a loop inside a loop though then ... you are too loopy.

    Can you share a picture to show what you are concerned about
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  • CorvusCorvus Frets: 2924
    tFB Trader

    It's for guitar control cavities, so there's three templates; one for the cover plate itself. One for the recessed ledge it sits in. One for the deep cavity itself.

    Basically if they cut out the cover plate from a sheet of plastic, how do they know whether I want the sheet, or the cutout part:

    The plate and recess templates are very similar; plate template would be a fraction smaller all round, but superficially they look the same. But for one I want the plate, the other I want the sheet with bit cut out.

    So I was wondering if there's a std way to denote which is which.

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  • NomadNomad Frets: 549
    edited August 2017

    I might be missing something, but laser cutters don't mill out bulk, they make lines. Whether or not something is a hole should be a logical consequence of the arrangement of lines.

    If you have a sheet of template material in a guitar body shape, and cut out a cover-sized piece, you'll have a hole in the body template that's the size and shape of the cover, and a separate piece that's the size and shape of the cover that fits into the hole. The sizes will be slightly different, depending on how thin the machine can make its cuts. The bit from the middle could be used as a template for making the cover.

    If you want a template to use for routing out the actual cavity, then you'd need to make the outline that size (ie, smaller than the cover), and the bit in the middle would be waste because it's too small. If you wanted a cover template as well, that would need to be made separately. If you wanted to have both a cavity template, and one for the rebate around the cavity that a recessed cover goes into, you'd need to make two templates.

    DXFs know nothing about holes - all they do is define basic drawing elements like lines, circles, curves, etc. In more conventional machining, you would provide a drawing showing the parts to be made, with dimensions and annotations describing the features you want, like holes, pockets, rebates, etc. The DXF could be provided in addition to that to make things quicker for the machinist (CNC programming software can read a DXF, but the operator has to tell it what the basic elements represent, which is info that he gets from the drawing).


    Nomad
    Nobody loves me but my mother... and she could be jivin' too...

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  • CorvusCorvus Frets: 2924
    tFB Trader

    DXF is just lines sure, but what I wanted is to tell the person doing the cutting which pieces are wanted and which are waste. The cover & recess example; in 'raw' DXF they look exactly the same, apart from a size difference. But for one I want the cover plate, the cutout part. For the other, I want a sheet with a cutout in it.

    The equiv of the old annotated drawing might just to send JPG versions with colour fills. Or for the 'sheet with cutout' I make a rectangle around the cutout. Or I could just add DXF "text" to each part wanted. I just wondered if there was a standard way.

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  • NomadNomad Frets: 549
    The standard way is to provide a drawing of each part, although not necessarily with all dimensions if it includes a note with an unambiguous reference to a DXF. The customer shouldn't need to worry about waste - that' the fabricator's job.

    2D drawings aren't old in the sense of no longer being in wide use.- they are as current now as they have always been. PDF format is fine these days.

    Nomad
    Nobody loves me but my mother... and she could be jivin' too...

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  • BigMonkaBigMonka Frets: 1763
    Unless you're using a big online-only type place then you can normally just speak to them and ask, or give an annotated drawing which explains it. Or get someone you can have a conversation with to do it for you, didn't the @TheGuitarWeasel buy a "laser"? (Dr Evil style)

    Always be yourself! Unless you can be Batman, in which case always be Batman.
    My boss told me "dress for the job you want, not the job you have"... now I'm sat in a disciplinary meeting dressed as Batman.
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  • Jimbro66Jimbro66 Frets: 2418
    If the dxf file is prepared in a CAD package can't you use hatching to show what is solid or vice versa?
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  • SporkySporky Frets: 27585
    Given that the laser cut has a thickness to it, you could probably just use two sheets. One has the main cavity (and the middle bit gets thrown away), one has the larger cutout and the plate. The plate bit will naturally be a bit smaller than the cutout.
    "[Sporky] brings a certain vibe and dignity to the forum."
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  • CorvusCorvus Frets: 2924
    tFB Trader

    Cheers all. I'm using Inkscape, I can ask matey about hatching or can spit out colour-fill PNG or JPGs to pair up so he can see what's what.

    Sporky that's true but how much smaller the cutout is I don't know, I'll ask him. Thought I may as well decide that with a separate file as there's no extra cost in it. Then I can buzz the plates on the router table to a good-fit size, hopefully no edge sanding to fit.
    So I'm going to knock up a pile of DXFs, get a few build's worth done together.

    Thanks all. Simple thing but I'm a fish out of water with it.

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  • SporkySporky Frets: 27585
    Corvus said:

    Sporky that's true but how much smaller the cutout is I don't know, I'll ask him.

    Probably depends a bit on the cutter. When I had a big laser job done a year or three ago it was about 0.25mm cut width, which is more slack than it sounds.
    "[Sporky] brings a certain vibe and dignity to the forum."
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  • GSPBASSESGSPBASSES Frets: 2335
    edited August 2017 tFB Trader
    If you're determined to write the code yourself, you may find that the company is going to do the laser work or CNC router will charge more to interpret your code, then do the job there self. I occasionally have back plate jigs made, the company that makes them for me, prefer me to take just a pen and ink drawing (or computer generated image) of the back plate. They will scan this into their system that will generate the tool paths for back plate. This can then be used for the female version of it, simply by telling the the system to cut inside the line. The difference in size between inner and outer tool paths will only be a fraction of a millimetre. The the jig for the main cavity is normally 2 - 3 mm smaller than the backplate itself, plus four or five bulges for want of a better word, with the backplate is screwed on. This is the way I go about it, I also know quite a few custom builders do exactly the same. Interestingly, if I'm having these jigs made from a MDF type material they are laser cut, but the actual backplate itself, which is normally made from scratch plate material (plastic) they are CNC routed. It might also be worth looking around to see if you can find a premade set jigs that will suit your purpose, there are several companies who make all different sorts of jigs for back plates and cavities.


    These are very good.    https://guitarsandwoods.com/templates

    I purchased a set of acrylic jigs from the above company, I do not use these in production, but I made MDF copies of them them. I use the MDF jigs for the production work. The photo below shows the acrylic jigs and the MDF ones I made from them. I believe the acrylic jigs were CNC routed. In the photo you can see the headstock jig of the telecaster that was clearly CNC routed.

        





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  • CorvusCorvus Frets: 2924
    tFB Trader
    Cheers chaps. 0.25mm might be fine Sporky, I made one a half mil inset.
    Hi Graham, interesting about the plates being routed, these guys do CNC milling & routing too. The inside/outside the line sounds like a fine plan and saves some faff, cheers, didn't know that was do-able.
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  • GSPBASSESGSPBASSES Frets: 2335
    tFB Trader
    Making a male-female jig set is fairly straightforward on a CNC. When the shape has been established, when the software asked you what size tool you using for the inside cut you tell it your using a 12.7mm tool. This will make the female part of the jig exactly the right size. When you program for the male part of the jig you tell the software you're using a 12.8mm tool but actually still use the 12.7mm tool. This will give you a fairly tight fit, if you needed to be slightly looser you tell the software you're using a slightly bigger tool , but still use the 12.7mm tool for the cut.

    Your life will improve when you realise it’s better to be alone than chase people who do not really care about you. Saying YES to happiness means learning to say NO to things and people that stress you out.

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  • SteveRobinsonSteveRobinson Frets: 6914
    edited August 2017 tFB Trader
    With the laser cutter I use, I set the vector-based shapes (in Inkscape) to be zero fill and lines to have width 0.03mm.

    I then export as PDF which I "print" to the laser whose driver turns the lines into cuts.

    Other cutters may of course require different input.

    I made a load of acrylic templates late last year.
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  • 4string4string Frets: 33
    tFB Trader
    BigMonka said:
    Unless you're using a big online-only type place then you can normally just speak to them and ask, or give an annotated drawing which explains it. Or get someone you can have a conversation with to do it for you, didn't the @TheGuitarWeasel buy a "laser"? (Dr Evil style)

    We bought a laser cutter a little while back and very useful it has been too. Ash is on his much deserved hols now, but if you still need a chat in a couple of weeks, feel free to drop us a line. I am not allowed to play with the sharp edged tools or the laser cutter :-(
    Chief Bottle Washer @ Oil City Pickups.
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  • SporkySporky Frets: 27585
    You can do very fine cuts on a CNC mill if you've set up right. I have 0.5mm and 0.6mm bits which will cut the cavity and cover at the same time in thin ply or MDF. You've got to get the feed rates right if you want them to last but it's doable.

    Laser is the better choice for this though. I send out for my laser work, I don't have room for three machines at the mo.
    "[Sporky] brings a certain vibe and dignity to the forum."
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  • CorvusCorvus Frets: 2924
    tFB Trader

    Thanks guys, all great info and much appreciated.

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  • WezVWezV Frets: 16546
    Sporky said:
    I send out for my laser work, I don't have room for three machines at the mo.
    Have you considered buiding a bigger workshop ;)
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  • GSPBASSESGSPBASSES Frets: 2335
    tFB Trader
    Sporky said:
    You can do very fine cuts on a CNC mill if you've set up right. I have 0.5mm and 0.6mm bits which will cut the cavity and cover at the same time in thin ply or MDF. You've got to get the feed rates right if you want them to last but it's doable.

    Laser is the better choice for this though. I send out for my laser work, I don't have room for three machines at the mo.
    Can't you fit a Laser head  onto your existing CNC, after all the mechanics are just same  basically might need different software driving it, plus something to protect the bed.

    Your life will improve when you realise it’s better to be alone than chase people who do not really care about you. Saying YES to happiness means learning to say NO to things and people that stress you out.

    https://www.facebook.com/grahame.pollard.39/

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  • SporkySporky Frets: 27585
    GSPBASSES said:
    Sporky said:
    You can do very fine cuts on a CNC mill if you've set up right. I have 0.5mm and 0.6mm bits which will cut the cavity and cover at the same time in thin ply or MDF. You've got to get the feed rates right if you want them to last but it's doable.

    Laser is the better choice for this though. I send out for my laser work, I don't have room for three machines at the mo.
    Can't you fit a Laser head  onto your existing CNC, after all the mechanics are just same  basically might need different software driving it, plus something to protect the bed.
    Possibly - that's  a good idea and worth investigating.

    The laser machines I'd looked at (for future planning) are built quite differently though - the laser tube usually sits at the side, and the beam goes via mirrors to a focusing head. For light cuts I could probably do something with an overdriven blu-ray laser...
    "[Sporky] brings a certain vibe and dignity to the forum."
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