Laser cutting

[John Stevenson]

One of the reasons for buying the laser cutter was from a post I saw on this forum where some guy [ only posted once and never returned or answered PM's or email ] mocked a cylinder head up for a model Subaru out of 1.5mm card.

Can't show some of the work as it's proprietary and the customer doesn't like work splashed round t'internet so did this instead.



Five layers cut out of 3.2mm thick MDF to replicate a timing cover or similar.

The holes are needed to accept wooden dowels to line up whist the glue is drying under clamping pressure.



Assembled with M5 screws holding it together for the photo shoot, as an idea of size the small inner diameter is 20mm and the larger inner diameter is 40mm, bosses are 10mm.



Angled shot of the same showing a bit of scrubbing with a strip of emery. If this was a genuine pattern each layer would be slightly larger than it's predecessor to give a draft angle.
It's a doddle to do this and also allow for shrinkage as it's all a question of scale in simple 2D CAD.

Simple job and not using draft angle it took 20 minutes from off the top of the head drawing to bolting the cut parts for the photo shoot.

Local foundry has seen the prototype patterns [ with draft angle ] and have OK them, they are also very, very interested in the process as this can knock literally days off conventional pattern making.

Roll on retirement < BG >

[Brass_Machine]

That is a cool way to make a pattern. Almost takes a 3D printer aspect to it...

Eric

[PekkaNF]

Very nice idea to have draft factored into all layers and to have holes to locate all layers together.

MDF is very porous to vacum forming and  vacum bagging to composite items. Takes a lot epoxy and other stuf under pressure to have surface reasonably impermeable.

Are these going to be more of a one-off type patterns? How are you going to coat these?

Pekka

[Jasonb]

One of the guys I know who is making a 6" traction engine has used the same method on several patterns but at his scale most was cut from 18mm and then thinner where there were more detailed features. Stick them together, bit of body filler, paint and its good to go.

J

[vtsteam]

Seems very useful for small intricate patterns in thin or fragile sheet material.

Where a part of some thickness is required, however I think a CNC router would have some advantages for automated pattern making. The part does not have to be aligned and glue laminated out of small pieces, though  draft can be cut  in a similar way -- by progressive layering. In fact, the intervals can vary with a CNC router and this is a particular advantage where not only straight line draft is required, but complex curves in the Z direction are needed. Where the curve changes rapidly the intervals of the "lifts" can be made smaller programatically. The same physical thing can be done with a laser, but not without changing the material thickness on the table and running program modules for each thickness.

Another advantage for a router is that the tool bit can be varied in shape, -- a ball end tool can be used, etc, so it is possible to easily internal radius protrusions like bosses and pockets that way, if it is an advantage to. A laser cuts in a straight line. In fact it would be possible to make a tool bit that has, say a 2 degree taper, and to use that to cut a non-stepped automatic draft in all cuts on a pattern.

It is great to see the laser capabilities above illustrated so well on the MDF and I sure wouldn't mind owning both tools, to take advantage of the particular strengths of each. I imagine in some home built machines, it might be possible to have a single machine that does both.

[John Stevenson]

Job I'm doing at the moment is a sump for a racing bike.
Got a choice use the laser and do it in layers or use the router.

With using the router I have to draw this up in 3D because of the shape, then program it in a 3D package, then cut it.
Because I'm not that good at 3D this is going to take me a while, possibly a few nights but it's not wasted as it's a learning curve.

Where the waste comes in is the cutting, because it's a sump there is a lot of material to remove inside, a quick guestimate puts the cutting at about 4 hours machine time.

Because the laser is faster, non contact so no fancy jigs needed to allow it to machine inside and out and the fact it doesn't have to pocket the inner but instead it can profile the inner shape the cutting time is under 20 minutes allowing for changing sheets etc.

Any errors or mistakes like the pattern splitting can easily be rectified with the laser by cutting a new sheet. With the router it's start again time.

[Monkey with a mill]

I was wondering what brand your laser cutter is as well as what drew you to that model? How many watts does it it put out and how thick of various material can it cut? I would like to buy one in the near future, so would appreciate any advise on what to look for and what to avoid.

[sparky961]

The possibilities are endless when you start adding layers of profile cut parts.  We make short run press brake dies for odd stuff this way at work.  It's a pretty common practice in the metal working industry.

-Sparky

[AussieJimG]

Sounds like thre is a case for roughing with the laser then finishing with the router if filleted corners are needed.

Jim

[Alan Haisley]

John,
Is there any good reason that the laser head couldn't be set up with programmable pivot in two directions? It would complicate programming but would allow the laser to produce the draft angle.
Alan