3D Printing and inverted surfaces

[mrabercrombie]

Hello all,

Over the last few days I have sent 4x 3D prints of sections taken from an Archicad model into both HP and Makerbot 3D Printers.

The HP was having issues with inverted surfaces created by the integration of elements in composite walls, window frames and so on. Whilst the Makerbot was struggling with any elements that required any form of support material.

The long and short of this is, it would be really useful if there was (or is) a way to export the model as a shell with only the outer most surface included. Alternatively if there was a way to unify the model so that building becomes a solid block.

This would also be useful for preparing files for 3D milling and routing too.

Any tips for how to do this either direct from Archicad or in third party software would be great, as well as any for improving the output.

Cheers,

Scott

[Barry Kelly]

Are you saving from Archicad as an STL file?
The reference guide say that an STL file contains only the surface geometry with the following limitations.

Limitations
1.ArchiCAD does not check the exported STL file for errors, e.g. in terms of solidity. These are usually done by the 3D printer.
2.STL file does not store the scale and unit of the model, these have to be set in the viewer/printer. ArchiCAD always exports 1 m as 1 STL unit.

Barry.

[Link]

Have you tried setting your model view options and partial display options up prior to exporting?

We have a client who uses a makerbot very successfully to print out high end custom homes. I do recall him saying that for large expanses like a roof, he will print separately and place on the model manually. And any large openings that tend to sag when printed, he'll put a struct in the model then cut it out later.

I'm sure the technology will progress quickly. In fact he mentioned one 3D printer that produced a model that could dissolve in water, so you just wet the parts you don't want to include. And some use powders instead of filaments, etc.

Cheers,
Link.

[mrabercrombie]

@BarryKelly Yeah, saving direct to STL from Archicad. Also analysed the model using Meshlab, Netfabb and SketchUP to look at the surfaces. These applications allow you to see the surface conflicts that Archicad generates where something that is an outside face can be located within another object which confuses the print software etc.

It seems that it exports the surface geometry of each element, even where this intersects or is within another component.

The second limitation also seems incorrect as Archicad allows you to choose the scale when you are exporting the model (which is particularly useful!)

@Link Only briefly, will investigate that further now that there is no deadline. Keen to get the Makerbot working well in particular as we can print from it for approx £20 per 10x10x10cm model, whilst the HP is around £150-200.

Yes, I think printing elements separately is the way forward with the Makerbot as the soluble support material tends to clog the head apparently and the ABS supports are a nightmare to remove cleanly. The HP uses a soluble support filament which is why it can produce such fine surfaces.

Hope so regarding the technology. It seems counterintuitive to produce a highly detailed BIM model and then want to unify it down to a simple block, but it would almost definitely make the printing process faster and produce higher quality results.

Scott

[Haneef Tayob]

We've also just started experimenting with the Makerbot by exporting to .STL from ArchiCad.
At small scales (under 1:300), the walls, columns and roofs tend to collapse as they are too thin at that scale. We've been thickening up certain elements.

Also then noticed that elements do not seem to be solid. There are features on the 3d printing software that one is able to tweak to help (rafts and supports)

At present the printing time is very long and the 'bombing out' rate is high. We've resorted to splitting up the model and printing in sections, even if it is able to fit on the printers base plate.

Still early days.