Concavities

[bovalis2037]

Hello everyone. The only 3d printer I have been able to use is the one in my highschool. It is a stralasys printer with 2 extruder heads and it is amazing because it prints plastic and with the second head it prints dissolvable material. After a part is done printing we throw it into a vat of NaOH and the support material dissolves away. This gives us the ability to create amazingly complicated and hole-y prints with alot of overhangs. I was wondering what you all think the peachy printer will be able to do? I have doubts about starting an entire new layer on top of nothing no matter how few and small the forces are acting on the print but I would like feed back from you! Also it begs the question how does a print start? How do they get the print to attach to a base if there is a layer of resin inbetween?

[masterada]

Hello!

You can make support structures with under cured resin, that you can easily remove after the print is done (dont know if the software will support this, but it should be possible with the printer). For the "how the print starts" question i recommend watching some of their videos where they print. For a full picture on that subject, watch this video at 2:45: http://www.peachyprinter.com/#!Our-M...0-2C7F1C26381F

[Slatye]

Quick comparison:

• Supported FDM (Stratasys) - can print overhangs to any angle, although keeping it under 45 degrees saves time because it doesn't bother with support material. Can print an object inside another (hollow) object, provided that the outside object has a tiny hole for the support material to dissolve through.
• Unsupported FDM (every cheap printer) - can print overhangs to around 45 degrees nicely, getting much further tends to require lots of tweaking and produces lower quality. Can print bigger overhangs with support structures that hold the weight of the new part.
• SLS (Peachy) - can print overhangs approaching 90 degres nicely. Might be able to do 90 degrees too. Can print bigger overhangs with support structures, and support structures can be thin because they are only for positioning. The weight of the overhang is supported by the water bath.

On the other hand, the Stratasys printer at my university was about $15K, filament for it costs a fortune and it can only print one model material (ABS) in one colour (white).

Here's an object that the Stratasys printer can (ideally) do but the Peachy can't do nicely.

sixballs.jpg

It's a buckyball (red) inside a buckyball (yellow) inside a buckyball (green) inside a buckyball (cyan) inside a buckyball (purple) inside a buckyball (blue). Colours are just to make it easier to see; it all prints in one colour. I did a three-layer one on the Stratasys printer and that worked beautifully, although it took days to run and a vast amount of support material. This one can't actually be printed because the STL file is massive (over 50MB even with Coarse export settings) and it causes the Catalyst EX print software to crash during slicing. Hopefully the Peachy software can handle it...

You could do it on a Peachy, but it'd have support struts going all over the place and getting them out without damaging the (thin) inner shells would be very difficult. Not as difficult as getting the support structure out if it was done with an unsupported FDM printer, however.

[mike_biddell]

Quick comparison:

• Supported FDM (Stratasys) - can print overhangs to any angle, although keeping it under 45 degrees saves time because it doesn't bother with support material. Can print an object inside another (hollow) object, provided that the outside object has a tiny hole for the support material to dissolve through.
• Unsupported FDM (every cheap printer) - can print overhangs to around 45 degrees nicely, getting much further tends to require lots of tweaking and produces lower quality. Can print bigger overhangs with support structures that hold the weight of the new part.
• SLS (Peachy) - can print overhangs approaching 90 degres nicely. Might be able to do 90 degrees too. Can print bigger overhangs with support structures, and support structures can be thin because they are only for positioning. The weight of the overhang is supported by the water bath.

On the other hand, the Stratasys printer at my university was about $15K, filament for it costs a fortune and it can only print one model material (ABS) in one colour (white).

Here's an object that the Stratasys printer can (ideally) do but the Peachy can't do nicely.

sixballs.jpg

It's a buckyball (red) inside a buckyball (yellow) inside a buckyball (green) inside a buckyball (cyan) inside a buckyball (purple) inside a buckyball (blue). Colours are just to make it easier to see; it all prints in one colour. I did a three-layer one on the Stratasys printer and that worked beautifully, although it took days to run and a vast amount of support material. This one can't actually be printed because the STL file is massive (over 50MB even with Coarse export settings) and it causes the Catalyst EX print software to crash during slicing. Hopefully the Peachy software can handle it...

You could do it on a Peachy, but it'd have support struts going all over the place and getting them out without damaging the (thin) inner shells would be very difficult. Not as difficult as getting the support structure out if it was done with an unsupported FDM printer, however.

Slayte ....This whole question of support is an annoying and vexing problem, which affects all current methods. I've been on some of the stuff Rylan's on (LOL) and doing thought experiments. How about a tank full of resin which is like a thick jelly. The resin remains in its jelly-like state unless exposed to a certain intensity of laser light. So you have three lasers such that the jelly only hardens where the three lasers focus (transparent jelly obviously) and not along the axis of a single laser. In this way, you could print any object and it would remain supported in the jelly, without the need for any support struts. The object would be printed in situ and nothing would move (only the lasers). Meanwhile..... back in the real world !!!!

[Feign]

The Peachy can probably print that nested Buckyball, it would just take a nightmare maze of support structure. Effectively a system of sprues that connect all the lowest points of each separate piece. The main difference between how the Peachy has to make supports and how other SLA printers like the Form 1 do them is that the conventional printers need enough grip on the part in order to separate each layer from the glass plate. With the Peachy, there's effectively no force requirement on the supports, since each layer only has to break away from the resin's surface tension, meaning you can have diagonal or even horizontal support structure on the parts to make removal easier.

[Slatye]

Mike - I've seen something like this in laser cutters, where they can cut something out of the middle of a block of plastic by having two lasers focus on the same point. Since the two lasers only meet at one point (and one laser doesn't cause any damage to the block) you don't get any lines from the edges, just a design that exists right in the middle of the block. It's a cool technology, and with the price of the Peachy having a couple of them working together might be practical. However, for the stock Peachy it's not really an option.

Feign - as you've said, there's no force requirements on the supports. Combining that with what Mike's suggested (a thick-jelly resin) might result in something that works very nicely. Suppose that you do the supports very fast, too fast to properly cure the resin. Then they'll have a jelly-like consistency. That should be enough to keep the parts positioned, but weak enough that if you hit it with reasonably high-pressure water afterwards it'll just wash away.

It's still not quite as nice as the Stratasys system, because you need space to get high-pressure water into there (so a cube within a cube, where the outer cube only has a 1mm hole to let the support material out, probably won't work). However, for something like the buckyballs it should be fine. It has an advantage over the Stratasys system because you don't need two materials, and also because you can get rid of the support material quickly with plain water - no need to leave it for a week in an extremely toxic heated bath.

[mike_biddell]

Mike - I've seen something like this in laser cutters, where they can cut something out of the middle of a block of plastic by having two lasers focus on the same point. Since the two lasers only meet at one point (and one laser doesn't cause any damage to the block) you don't get any lines from the edges, just a design that exists right in the middle of the block. It's a cool technology, and with the price of the Peachy having a couple of them working together might be practical. However, for the stock Peachy it's not really an option.

Feign - as you've said, there's no force requirements on the supports. Combining that with what Mike's suggested (a thick-jelly resin) might result in something that works very nicely. Suppose that you do the supports very fast, too fast to properly cure the resin. Then they'll have a jelly-like consistency. That should be enough to keep the parts positioned, but weak enough that if you hit it with reasonably high-pressure water afterwards it'll just wash away.

It's still not quite as nice as the Stratasys system, because you need space to get high-pressure water into there (so a cube within a cube, where the outer cube only has a 1mm hole to let the support material out, probably won't work). However, for something like the buckyballs it should be fine. It has an advantage over the Stratasys system because you don't need two materials, and also because you can get rid of the support material quickly with plain water - no need to leave it for a week in an extremely toxic heated bath.

Slatye.... interesting stuff..... that would be the ultimate 3d printer, where the object just appears in a vat of jelly.... and from what you say, it probably would work.

[mike_biddell]

Slatye.... interesting stuff..... that would be the ultimate 3d printer, where the object just appears in a vat of jelly.... and from what you say, it probably would work.

It also occurs to me that we could accomplish this in opaque material using focussed microwaves, which would generate heat at the focal point, and the jelly would be heat curable.

[mike_biddell]

It also occurs to me that we could accomplish this in opaque material using focussed microwaves, which would generate heat at the focal point, and the jelly would be heat curable.

Slayte..... you are right the technology to do what I am suggesting (i.e. object is printed in situ, with no movement) already exists.... the technique for producing 3d images in glass is know as a bubble gram....... this would be the dream ticket for a 3D machine..... it would scoop the market. http://en.wikipedia.org/wiki/Bubblegram