stereolithography

Warning, might contain newb-questions :

Is anyone making headway in DIY stereolithography laser sintering? the resin/DLP craze is not for me, since it's limited in application (unless someone has made a resin that does not cure in sunlight? maybe i missed that post, but i was under the impression all laser cured resins would continue to cure when exposed to sunlight and become brittle)

Is there a power loss when using the laser with stereolithography mirror? I am only asking because most of the DIY SLS i've seen built is on a X & Y platform, and it looks slow to be honest. And when i look at the expensive commercial machines, most of the time they are stereolithography. and i figured since i haven't come across any diy attempt, it must be because either the equipment is too expensive, or there are some drawbacks I am failing to see.

Been watching a friend of mine build a rostock delta the past week, and it's defiantly the platform i would try to combine with laser sintering if stereolihography was not an option,

... it's mostly lack of really high energy lasers, that were needed for Stereolithography-type of 'scanning' SLS, what's the biggest hurdle for DIY.

While a laser with <1W of power is enough to melt powder when (slow) moved in a XY-plotter, for scanning SLS you'll see lasers with some hundred Watts to Kilowatts in comercial systems.

Simply calculate for yourself, how much energy per spotsize and time you'll need for melting a voxel of let's say 0.1mm in size and 0.05mm high ... and then multiply this for your building volume and fabbing time ...

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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]

Quote

Is anyone making headway in DIY stereolithography laser sintering?

Uhm, are you talking about stereolithography, the process to harden UV sensible resins, or about sintering, the process to melt powder? They're quite different, especially in what wattage the laser requires and in which materials can be processed.

Quote

i was under the impression all laser cured resins would continue to cure when exposed to sunlight and become brittle

Yes, the part of the process using the laser hardens resins some 80% only and the hardening will continue after this part is done. That's why 3D Systems stereolithography machines usually are sold together with an UV "oven" (made for exposing parts to lots of UV light at room temperature).

That doesn't mean parts have to become brittle or have to curl, though. It's a matter of selecting proper materials. The better ones are filled with glass spheres, hollow glass spheres or similar powders.

It's also a matter of a good laser beam exposure strategy. A problem of the upside-down stereolithography machines is undoubtly there is only one such strategy: expose the whole surface evenly.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Traumflug Wrote:
-------------------------------------------------------
> Is anyone making headway in DIY stereolithography
> laser sintering?
>
> Uhm, are you talking about stereolithography, the
> process to harden UV sensible resins, or about
> sintering, the process to melt powder? They're
> quite different, especially in what wattage the
> laser requires and in which materials can be
> processed.
>
> i was under the impression all laser cured resins
> would continue to cure when exposed to sunlight
> and become brittle
>
> Yes, the part of the process using the laser
> hardens resins some 80% only and the hardening
> will continue after this part is done. That's why
> 3D Systems stereolithography machines usually are
> sold together with an UV "oven" (made for exposing
> parts to lots of UV light at room temperature).
>
> That doesn't mean parts have to become brittle or
> have to curl, though. It's a matter of selecting
> proper materials. The better ones are filled with
> glass spheres, hollow glass spheres or similar
> powders.
>
> It's also a matter of a good laser beam exposure
> strategy. A problem of the upside-down
> stereolithography machines is undoubtly there is
> only one such strategy: expose the whole surface
> evenly.

Quote
the resin/DLP craze is not for me,

powders, not resins

... I have all the relevant parts of a 20 years old Stereolitho-printer from 3DSystems here, that was aimed for a powder-SLS by replacing the original HeCd-UV-laser with a 50Watts IR-fiberlaser for melting the powder - but actually busy with some other projects around 3D-scanning with structured light and an old CO2-laser-engraver.

You can use XY-galvo-scanners with drivers for show-laser applications, that can costs from 100-200USD and up - the scanning quality and applicable scanning area is depending on the price of the modules, so for SLS comparable to comercial systems you'll have to pay a lot more

Fiberlasers aren't so common in the DIY-scene (and really pricey too), so you should look for used NdYAG-lasers or try with collimated IR-diodelasers.

A possible 'hack' around XY-scanning is salvaging the optical setup of an old laser-printer - the polygon-mirror with the two lens-slides for focussing a line will be the X-axis and when tilting the complete X-module you'll get Y ... but while the X-line will be on a plane, the Y-dimension will be on a cylinder-surface - so only usable for short Y-ranges or for very long focussing distances, what will reduce the usable focus quality ...

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

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

Lithography is a technique which is made from an image which is applied to a flat surface. It is a very much versatile printing technique. It mainly depends upon oil and water. It is mainly discovered in late 1970's. Coloured lithographs are produced by taking impressions from several stones in succession, each adding a different colour to selected parts of the print. There are more and more stereo lithography company in India. Hongyijig is one of them.