I need to get some small prototype casings made up (for little keyfob-
sized bit of electronics) - and we're looking at having the bits laser-
cut out of neoprene.

First round would be just irregular-outline shapes cut from something
like 8mm thick neoprene (ideally printed as well).

(later 3 thinner layers glued together, with the centre layer cut out
to form a pocket).

Has anyone experience of a laser-cutting service, willing to take on
small-scale jobs like this? (probably 50 parts on the first round,
100's later).

And - does anyone have experience of buying/owning/using entry-level
laser-cutters that can do this kind of work (or whatever sub-1000-quid
laser-cutters can do?)

wrote:
I need to get some small prototype casings made up (for little keyfob-
sized bit of electronics) - and we're looking at having the bits laser-
cut out of neoprene.

First round would be just irregular-outline shapes cut from something
like 8mm thick neoprene (ideally printed as well).

(later 3 thinner layers glued together, with the centre layer cut out
to form a pocket).

Has anyone experience of a laser-cutting service, willing to take on
small-scale jobs like this? (probably 50 parts on the first round,
100's later).

And - does anyone have experience of buying/owning/using entry-level
laser-cutters that can do this kind of work (or whatever sub-1000-quid
laser-cutters can do?)

multiply that by ten for 8mm neoprene.

On Apr 15, 7:27 pm, " wrote:
I need to get some small prototype casings made up (for little keyfob-
sized bit of electronics) - and we're looking at having the bits laser-
cut out of neoprene.

First round would be just irregular-outline shapes cut from something
like 8mm thick neoprene (ideally printed as well).

(later 3 thinner layers glued together, with the centre layer cut out
to form a pocket).

Has anyone experience of a laser-cutting service, willing to take on
small-scale jobs like this? (probably 50 parts on the first round,
100's later).

And - does anyone have experience of buying/owning/using entry-level
laser-cutters that can do this kind of work (or whatever sub-1000-quid
laser-cutters can do?)

ebay has "adverts" for these services on steel anyway - try searching
for "custom pc case* panel* " or therabouts

Jim K

On 15/04/2011 19:27, wrote:
I need to get some small prototype casings made up (for little keyfob-
sized bit of electronics) - and we're looking at having the bits laser-
cut out of neoprene.

First round would be just irregular-outline shapes cut from something
like 8mm thick neoprene (ideally printed as well).

(later 3 thinner layers glued together, with the centre layer cut out
to form a pocket).

Has anyone experience of a laser-cutting service, willing to take on
small-scale jobs like this? (probably 50 parts on the first round,
100's later).

And - does anyone have experience of buying/owning/using entry-level
laser-cutters that can do this kind of work (or whatever sub-1000-quid
laser-cutters can do?)

Have you looked at water jet cutting? I would have thought it a better
technology for cutting neoprene.

Colin Bignell

On Apr 16, 11:26*am, "Nightjar \"cpb\"@" "insertmysurnamehere
wrote:

Have you looked at water jet cutting? I would have thought it a better
technology for cutting neoprene.

It is, but water jet cutters are more expensive than lasers.

The Natural Philosopher wrote:
wrote:
And - does anyone have experience of buying/owning/using entry-level
laser-cutters that can do this kind of work (or whatever sub-1000-quid
laser-cutters can do?)

multiply that by ten for 8mm neoprene.

Yup. Ours (fairly high end, 40W Spirit GX) just about manages 6mm (ply,
acrylic), but anything thicker requires multiple goes. The results for ply
at least aren't that great (heat just gets absorbed into the body material).
I haven't tried this that much though, so I could just be lacking in
technique.

Theo

On Apr 16, 10:06*pm, Theo Markettos theom
wrote:

Yup. *Ours (fairly high end, 40W Spirit GX) just about manages 6mm (ply,
acrylic), but anything thicker requires multiple goes.

I've found that I can cut ply by cranking the power up and lowering
the feed rate. However MDF (quite a bit denser than my ply) doesn't
like this and it's better if I do it with two faster passes instead,
even if the total energy per cut length remains the same.

The problem is that too much power (per volume) means too much rise in
temperature alongside the cut, so I see a lot more charring. Even
though the plywood is easier to light (less energy needed per volume),
the ratio between energy to cut and energy to ignite is much closer
for MDF.

I have no problem at all multi-passing on wood. Thick Perspex leaves a
certain visible ridging at the two or three cuts, but for wood the
variation due to machine repeatability is less than the variation due
to the wood fibres.

Andy Dingley wrote:

I have no problem at all multi-passing on wood. Thick Perspex leaves a
certain visible ridging at the two or three cuts, but for wood the
variation due to machine repeatability is less than the variation due
to the wood fibres.

Is this all NC stuff? So, the ridges are due to tolerances in the arm
holding the laser/moving the work? Or is there something inherent in the
process that produces a ridge?




--
Murphy's ultimate law is that if something that could go wrong doesn't,
it turns out that it would have been better if it had gone wrong.

On Apr 17, 1:49*pm, "GB" wrote:

Is this all NC stuff? So, the ridges are due to tolerances in the arm
holding the laser/moving the work? Or is there something inherent in the
process that produces a ridge?

Yes and no. Laser cutters don't produce sideforces like milling
machines, so they're quite lightly constructed (belt drives, akin to a
decent printer mechanism). There can be some variation here, but it's
very minor. The laser beam isn't straight either (mostly a problem
when drilling long narrow holes) as it makes smoke, then is steered
off-axis by refraction due to varying smoke density.

With wood, there's no variation in the edge, by layer. The variation
in the wood's ease of cutting, or the depth of charring in MDF, is
sufficient to hide this completely. In Perspex, which laser cuts to a
beautiful glassy surface, you can feel it as a slight step every 1/4"
or so (if that's your one-pass cut depth). It comes out with fine wet
& dry.

Andy Dingley wrote:
The problem is that too much power (per volume) means too much rise in
temperature alongside the cut, so I see a lot more charring. Even
though the plywood is easier to light (less energy needed per volume),
the ratio between energy to cut and energy to ignite is much closer
for MDF.

I think we might also be having issues with the laser losing focus if the cut
is too deep, at which point it just gets to heat up the surrounding wood.

I have no problem at all multi-passing on wood. Thick Perspex leaves a
certain visible ridging at the two or three cuts, but for wood the
variation due to machine repeatability is less than the variation due
to the wood fibres.

I'll give plain wood a try. Polycarbonate cuts, but with a rough carbonised
edge which isn't too pretty. Perspex is great - you don't even need to
polish the edge.

Theo

Theo Markettos wrote:
Andy Dingley wrote:
The problem is that too much power (per volume) means too much rise in
temperature alongside the cut, so I see a lot more charring. Even
though the plywood is easier to light (less energy needed per volume),
the ratio between energy to cut and energy to ignite is much closer
for MDF.

I think we might also be having issues with the laser losing focus if the cut
is too deep, at which point it just gets to heat up the surrounding wood.


yes. Use longer focus lenses for thicker wood.

I have no problem at all multi-passing on wood. Thick Perspex leaves a
certain visible ridging at the two or three cuts, but for wood the
variation due to machine repeatability is less than the variation due
to the wood fibres.

I'll give plain wood a try. Polycarbonate cuts, but with a rough carbonised
edge which isn't too pretty. Perspex is great - you don't even need to
polish the edge.

Theo

Andy Dingley wrote:
The laser beam isn't straight either (mostly a problem
when drilling long narrow holes) as it makes smoke, then is steered
off-axis by refraction due to varying smoke density.

Blimey, I hadn't thought of that. Would the air temperature also provide a
gradient?

On 17/04/2011 16:05, Andy Dingley wrote:
... The laser beam isn't straight either (mostly a problem
when drilling long narrow holes) as it makes smoke, then is steered
off-axis by refraction due to varying smoke density....

I used to make beam deflectors for laser surgery - effectively 45 degree
stainless steel mirrors at the end of a long tube. They were made as two
concentric tubes with the beam going down the middle and the smoke being
extracted up between the two tubes.

Colin Bignell

On Apr 17, 4:32*pm, Theo Markettos
wrote:
Andy Dingley wrote:

I think we might also be having issues with the laser losing focus if the cut
is too deep, at which point it just gets to heat up the surrounding wood.

Most of them have a fairly easy focus height adjustment, which you
have to adjust between thin sheet stock or working on the top of thick
planks (laser cutters have a metal mesh bedplate that the stock sits
on, but the useful focus is only a centimetre-ish). A few cutters also
have a 3rd axis here, which can switch the focus to "high" or "low"
positions (it doesn't really change the optics, just moves the
objective up & down) under machine control.



I'll give plain wood a try. *Polycarbonate cuts, but with a rough carbonised
edge which isn't too pretty. *

Never tried it - I was warned off it early on, for this reason.

Perspex is great - you don't even need to polish the edge.

Polystyrene (I've been cutting mirror tile) isn't as good as Perspex,
but it's pretty good.

One thing that's nice is surface carving on oak. You start with a
smooth planed plank, then burn a bas relief around this to etch out
pale shiny mesas in a dark, charred ground. As oak is somewhat
intumescent when cutting it, you get a really nice control of carving
depth. Takes power and time, mind you, but the effects are good.

On Apr 17, 4:57*pm, The Natural Philosopher
wrote:

yes. Use longer focus lenses for thicker wood.

Not an option. That's like saying that laser beams are parallel and
monochromatic.

The best objective lens you can use is probably the one that came with
the machine. This gives the longest useful focus that can be achieved
for that laser head, and those carriage mirrors. In particular it will
depend on the beam diameter of the expanded beam that runs around the
machine from the fixed laser to the moving cutter lens. The bigger
this beam is, the easier it is to focus it at the objective (and also
the more that bigger lens will cost you). The smaller that beam, the
more trouble you're going to run into with diffraction becoming a
limit whenever you try to focus down at the Bond-slicer. Also the
larger this beam, the bigger mirrors you need, the better quality
mirrors you need and the more fiddly alignment becomes.

Lens focus is sized so that the vertical extent of the useful focus is
big enough to allow a good full-thickness cut with the laser power
available for a single cut on most likely materials. It is not sized
larger than this, just so that you can avoid the inconvenience of re-
adjusting the objective height (and the position of the focus) between
multi-passes. Generally a machine will cut "light" materials in one
pass, according to its focus limit. It will also cut "dense" materials
up to maybe a quarter of this, owing to its power limit. It's thus no
problem to multi-pass the dense material, because the single cut depth
is smaller than the focus and allows multi-passing without re-
adjustment. If you're seriously involved in thick multi-pass cutting
of light materials (i.e. focus is the limit, not power), then that's
when NC focus shifters start to appear.

On Apr 17, 7:49*pm, "GB" wrote:

Blimey, I hadn't thought of that. Would the air temperature also provide a
gradient?

In principle, possibly. However in practice no. Density is a bigger
change, so has a noticeable effect at smaller dimensions. Air
temperature and miraging is for when you're doing long-range LIDAR.

"Nightjar "cpb"@" "insertmysurnamehere wrote in message
...
On 15/04/2011 19:27, wrote:
I need to get some small prototype casings made up (for little keyfob-
sized bit of electronics) - and we're looking at having the bits laser-
cut out of neoprene.

First round would be just irregular-outline shapes cut from something
like 8mm thick neoprene (ideally printed as well).

(later 3 thinner layers glued together, with the centre layer cut out
to form a pocket).

Has anyone experience of a laser-cutting service, willing to take on
small-scale jobs like this? (probably 50 parts on the first round,
100's later).

And - does anyone have experience of buying/owning/using entry-level
laser-cutters that can do this kind of work (or whatever sub-1000-quid
laser-cutters can do?)

Have you looked at water jet cutting? I would have thought it a better
technology for cutting neoprene.

Colin Bignell

As Colin said. Look at Water Jet.

Baz

On Apr 18, 11:49 am, Andy Dingley wrote:

One thing that's nice is surface carving on oak. You start with a
smooth planed plank, then burn a bas relief around this to etch out
pale shiny mesas in a dark, charred ground. As oak is somewhat
intumescent when cutting it, you get a really nice control of carving
depth. Takes power and time, mind you, but the effects are good.


pseuds corner? ;)

Jim K

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "
saying something like:


Somebody here looking for advice.

I need to get some small prototype casings made up (for little keyfob-
sized bit of electronics) - and we're looking at having the bits laser-
cut out of neoprene.

First round would be just irregular-outline shapes cut from something
like 8mm thick neoprene (ideally printed as well).

(later 3 thinner layers glued together, with the centre layer cut out
to form a pocket).

Has anyone experience of a laser-cutting service, willing to take on
small-scale jobs like this? (probably 50 parts on the first round,
100's later).

And - does anyone have experience of buying/owning/using entry-level
laser-cutters that can do this kind of work (or whatever sub-1000-quid
laser-cutters can do?)