Monday, January 20, 2014

A Primer On 3D Production, Part Deux

This is Part Deux of my series of 3D printing pontifications.  Part One is here.



Don't worry, there's more pictures this time...


The File

There are a number of ways that your 3D file is on your computer screen that is just ones and zeros is turned into physical reality by a 3D printer.  Thankfully, there's a format out there that most 3d printers use.

It's called a Stereolithography file, or .STL as its file extension reads, and I've found that it works best when dealing with quotes and printouts from service bureaus.

STL is the lingua franca of 3d printing.

When you are contacting service bureaus you need to send them an STL file, preferably in a zipped format. STL files compact very easily.  

Actually, you need to send them a number of STL files, all bundled in a zipped folder, one for each individual part you want prototyped.

I used to lay out everything in one large layout file, orienting everything for ease of printing, but eventually found out that, while the service bureau guys think the arrangements are cute, they're going to put the parts where they damn well please, since they know their machines better than I do.  ;)



STL files, if you were to view them on your computer screen ( http://www.3deefab.com/en/faq/viewers ) would look like meshes, or nets, like paper mache objects of chicken wire without the newspaper applied.




 If you were to turn the "skins" of these meshes opaque, they would look like your desired object, but with thousands of facets.  Don't be alarmed, because if you do it right, these facets disappear, since they should be rendered at such small detail levels by your high-resolution printers that they don't even show up to the naked eye on the final printout.



(This is a long-term project that's been in the works for a while, so I can't say too much, but it's a great example of pics I had to illustrate the mesh to printout progression.)

These STL meshes need to be "watertight."  No gaps or holes on their surface.  A mesh done right, from the start, will only have small problems that are usually easily fixed digitally by the service bureaus.

If your sculptor knows what he's doing, there are no naked edges, open gaps, fatal fissures, or inverted surfaces in the mesh he sends out, and each piece you want prototyped is a single, healthy, fused mesh.  Meshes within meshes, or intermingled parts, are usually a no-no.

If it's amateur hour, he's sending out fractured, cluttered messes, and that causes your bill to go up when the service bureau guy has to spend time fixing things.

Meshes that are created with the intent of being video games or for graphic arts are usually not watertight, and require a lot of rehabilitation and patching to be made watertight and suitable for prototyping.

 Stuff that is made for pretty pictures or animation hardly ever ports over to 3D printing without major rehabilitation. Sometimes, an entire resculpt is called for.

I've had people send me multi-part gaming or art meshes and ask me to make them printable. It's like handing a mechanic a basket of parts, and asking him to turn it back into a motorcycle.  Most of the time, I just start over, using their meshes as "blockouts" for a resculpt.

I create my STL files in a program called Rhino3d.  www.Rhino3d.com is the manufacturer's website, but I have usually found it cheaper on Novedge.com ( http://www.novedge.com/products/2217 )


A commercial license for Rhino is about $825.


Another alternative is Moment Of Inspiration, or MOI, found at MOI3d.com for about $295.  Again, it's slightly cheaper at Novedge for $279 ( http://www.novedge.com/products/2985 )

These programs don't put out STL files directly.  Rather, they are solid modeling programs.  Your digital sculptor gives you the final shape you want, he scales it to the desired size, and then exports that solid shape as a high-resolution STL mesh.

You then send this STL file to the service bureau, and he quotes you a price to make it.

The settings for these are various, and I'll go into them later, if they're required, but it varies from program to program.

Basically, you want to get your meshes as high-resolution as possible, without bogging down the 3D printer's processing software.

 Consult your service bureau for their preferred settings for meshes. Min/max distance to edge length, refined meshes, simple planes, these are all minor settings that can impact how much detail gets survives from your computer screen to the real world.

This section was supposed to be a single installment, but it's too much for one serving.

Here's part three:  Drinking From The Fire Hose...

Best,
JBR

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