[Swansea Hackspace] Laser cutter kerf

[Justin Mitchell]

The simplest one someone can do in an evening, 
use a scrap of wood or plastic, cut into an elongated L shape, so it
has a little lip that can be hung on the top of the rail or lens
holder. 

put a piece of scrap wood or card in the machine with one end propped
up, making a gradual slope.

engrave or cut a straight line up the slop.

without disturbing it, look where the cut is at its narrowest

shorten the L shape until it is at that height when resting on the
chosen guide point.

and there you have it, you can now quickly check the height of the bed
for your chosen material, have it touch the surface for engraving, have
it midway through for cutting.


I have been meaning to make one myself for a long time, but always seem
to get distracted when i'm actually in the space.



On Thu, 2018-03-01 at 11:41 +0000, Andy Rush wrote:
> Right. I think it's probably better to try the simpler approaches and
> seeing if/how they improve things before moving onto more complex
> solutions. I say we should get a proper bed and level it as a first
> step. Once we have a level cutting surface, we can work on
> improvements from there.    
> 
> From: hackspace-bounces at swansea.hackspace.org.uk <hackspace-bounces at s
> wansea.hackspace.org.uk> on behalf of Justin Mitchell <justin at swansea
> .hackspace.org.uk>
> Sent: 01 March 2018 11:18
> To: hackspace at swansea.hackspace.org.uk
> Subject: Re: [Swansea Hackspace] Laser cutter kerf
>  
> On Thu, 2018-03-01 at 11:00 +0000, Andy Rush wrote:
> > I've made a few laser cut pieces recently, and as far as I can
> tell,
> > the beam's kerf is near 0.3mm at its thinnest, 0.6 at the widest.
> All
> > the dimensions are 0.6-1.2mm off what they should be on paper. I've
> > had a quick google around, and most places suggest that a laser
> > cutter kerf should be within 0.18-0.22mm at the thinnest part of
> the
> > cut. Are there steps that we can take to improve how accurately the
> > laser cutter cuts, beyond trying to to account for the kerf within
> > the original design by padding out all dimensions in the original
> > file?
> 
> The bed is very likely not perfectly level, the main bedding sheet
> tends to get propped by pieces of scrap to an appropriate height for
> the material being cut, and may not even be at the optimal focal
> depth
> for you, depening what your doing.
> 
> there are things we can improve that cost varying amount of time,
> effort, or money.
> 
> 1) Someone can measure and build a focussing aid
> 
> this could be as simple as a cut/3dprinted depth gauge that you hang
> off the top of the laser head to physically see where the focal depth
> si supposed to be.
> 
> or as complex as finishing fitting the alignment head we 3d printed,
> which has two line projecting laser to make a cross hair for lining
> up
> jobs, add a 3rd spot laser at an angle and it could indicate depth as
> well.
> 
> 2) replace the current bed with one thats actually level, perhaps a
> honeycomb type. There are lots of designs floating around for
> adjustable (either mechanically or electrically) ones that would let
> you easily change the focal point.
> 
> 3) improved optics, i have read claims that you can buy replacement
> focal lens that has a sharper kerf, but i dont know what the costs
> are
> like on that.
> 
> 
> 4) if you care about accuracy of cut then you do always have to
> account
> for the kerf in your design, at least once you have a stable idea of
> what that value is.
> 
> 
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