Anyone developing a laser welding system?

After seeing a few extrusion-type 3D printers at Techshop (an "Up" and two MakerBots) produce inconsistent results and weak bonds between layers and strands, it strikes me that there's something fundamentally wrong here. This is a welding process. The extruded strand is being welded to the previous layer. Yet only one side of the weld is being heated. That produces bad welds in metal, and cold solder joints in soldering. It doesn't work for thermoplastics, either.

What's needed is a way to heat both sides of the weld point. One way to do this would be to use a laser beam focused on the weld point. This seems hard to do, but it might not be.

The power required to melt ABS isn't that high. People have built laser cutters using laser diodes from DVD burners. 2 watt laser diodes are now available for about $25. What's needed is an extruder business end that has a laser diode and appropriate optics rigidly attached and aligned so that the tiny target spot is right at the weld point. This puts the heat right where it's needed.

There would still be a heater in the extruder, but for the extrusion process, not the welding.

Has anyone been down this road yet?

... I've built and used some welding heads with fibercoupled IR-diodelasers from 5W to 9W power and sold 6 of this high-power diodelasers to other DIY-ers, but hadn't got feedback from them yet, if they managed to use them as wanted

For me its working for different applications since 1994, when I've equipped some XY-plotters with 5W CO2-lasers for cutting/engraving/sintering and since 2005 with high-power IR-diodelasers for wire-bonding and brazing.

I'm using a 50W-fiberlaser and some 5W- and 9W-IR-diodelasers for laser-cutting and powder-sintering, but actually I'm more busy with 3D-scanning and laser-curing UV-resins, so the laser-welding/brazing/bonding is only reactivated, when needed for special problems.

Interestingly enough, I'm meeting tomorrow with a guy from a German CNC-forum, where we exchange some parts for 3D-printing and laser-diodes ... and he'll give me a laser-engraver with a 40Watt-CO2-laser, so I can make some more tests with clear plastic- and glass-powder, that is not usable with the IR-lasers ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

... go to the discussion side here: [reprap.org]

There we had some talk about using (plastic-) wire in a head, equipped with a laser. that will melt and fuse the wire to te surface ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

This is part of the reason that the plastic is extruded at a far higher temperature than the melting point. The idea is that the extruded plastic can heat the previous layer enough for a proper weld. If the average of the temperatures between the previous layer and the extruded plastic is above the melt point of the plastic, in theory it should melt the surface of the previous layer producing a proper weld.

In the majority of my prints the bonding between layers is very strong, and breaks usually do not happen along a layer. De-lamination is not a problem for me at all.

If the printer is having problems producing welded layers, then the print temperature needs turned up.

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Nagle Wrote:
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> After seeing a few extrusion-type 3D printers at
> Techshop (an "Up" and two MakerBots) produce
> inconsistent results and weak bonds between layers
> and strands, it strikes me that there's something
> fundamentally wrong here. This is a welding
> process. The extruded strand is being welded to
> the previous layer. Yet only one side of the weld
> is being heated. That produces bad welds in metal,
> and cold solder joints in soldering. It doesn't
> work for thermoplastics, either.

This isn't really true. The receiving side of the plastic weld is being heated by all of the following: the residual heat from the previously extruded layer, the heat from the heated build platform (and/or heated build chamber) and the radiated heat from the extruder's heater block. This, combined with the high temperature of the extruder makes the weld strong for except when printing too high above the print platform without a heated chamber (limit depending on many variables).