3D Print Preparation

Note: This guide refers to the z450 3D Printer and its specific software Printer but the general techniques and ideas are appropriate to both machines.

Before models can be printed on the z450 3d Printer they need to be converted to “.zbd” files.  This file type is used by the 3d Printer’s “zPrint” software.  zPrint can import a wide range of 3d file formats, but the following three are common and recommended:

  • STL – Stereolithographic
  • 3DS – Autodesk 3ds
  • VRML – Virtual Reality Modelling Language

All 3d software can export with at least one of these file types as an option; in fact some software includes a “publish to 3d printer” option.  Here are some examples of generating zPrint friendly files:

Sketchup Pro:

File – Export – 3D Model [Export Type: 3DS File]


File – Print 3d – Z Corp ZPrint

If Rhino detects zPrint software is installed then it exports the model as a vrml file and opens straight into zPrint


Select the object then choose

File – Export Selected – [STL/VRML/3DS]


File – Publish – Send to 3D Print Service – Continue – [select model]

Saves as STL file and tries to connect you to online 3d printing service which you can cancel; the STL file is saved and importable into zPrint


File – Export – Other Formats – [choose Lithographic STL] – [select model]

3D Studio Max

File – Export – [STL or 3DS or VRML]

The zPrint software is installed on all machines in the digital studio; it is also available to students who want to install it on their own machines.

Bring the Model into zPrint

When you have your STL/3DS/VRML file you can bring it into zPrint. In zPrint select

File – Open – [select the file]

zPrint shows you details of the model you are importing

If the model comes in at a size that will fit into the 3d printer then the file opens straight away, otherwise you get an extra dialogue box prompting you for resize options.

If you know the actual dimension you want the model to print out at, you can enter them here – note these are dimensions of the overall extent of the model; the total height, width or length that the model reaches.

Alternatively you can just put in a percentage figure – this is useful for making the model to scale; i.e if you modelled correctly in Autocad then you can bring in a 1:100 version by setting the scale at 1%

Don’t worry about getting your figures exactly right here – it is still possible to rescale the model after it has been brought into zPrint by right clicking on the model and selecting scale. 

You can swap between the units of inches or mm by selecting

Settings – General Preferences

Checking the 3D Model for Errors

By far the most common problem with preparing 3d models for printing is flipped normals, also referred to as reversed faces.  This is when one or more surfaces of the model is “inside-out”.  Even though a model with flipped normal may still render properly it will cause problems when 3d printing.  A flipped normal in zPrint is indicated by a dark area: Here’s a correct and incorrect model brought in from Sketchup

Correct and Printable
Incorrect and won’t print Properly

An additional tool in zPrint allows you to view the cross section of the model – you can slide a section line up and down to view how that layer of the model will appear to the printer.  This should show solid black areas where there is something to print.  Viewing in this mode is very useful as it can really highlight problem areas – the 3d imports don’t always work and using the section view lets you view and check exactly what the printer will send at each layer.

Select this viewing mode by selecting the 2D button to the right of the tool bar

In the screenshot above you can see that the software is misinterpreting the model at that section point – there are two white voids running through the model, which should not be there; the presence of a flipped normal elsewhere has thrown out another part of the model. If this model were to be sent to print it would print wrong.

Fixing Flipped Normals

Simply put, it is a lot easier if there are no flipped normals present in the first place.  There are tools in 3D software to reverse faces but unless they are simple it can be time consuming and frustrating to attempt a repair – it may work out easier to remodel the incorrect part.

Here are some pointers to repair options [Note: often fixing one face results in another face somewhere else in the model that was correct then becoming incorrect]

  • Sketchup:
    change View – Face Style to monochrome, and look for blueish grey faces. You can right click on these faces and choose Reverse Faces.
  • 3D Studio:
    select the part and choose the normalise modifier and Unifiy Normals
  • Rhino 3d
    type “flip” and select the surface

Pricing the Model

Cost of the final model depends on what volume of powder is used in making it. At time of writing [autumn 2010] the price is £2.50 per cubic inch.

In zPrint you can find out the volume of your model [after setting the units to inches] by selecting

View – Calculate Part Statistics

In the example above the total volume of parts is 8.38 cubic inches;

8.38 x 2.5 = £20.95

You can reduce the cost of your model by:

  • Scaling down the size of it: right click the model, select scale and put it at 75% will bring the volume / price down considerably (though be sensible about how useful a much smaller model would be)
  • Add voids: a solid box will be a large volume and cost a lot but if you subtract a block out of the bottom of it then that is that much space that you are not printing. Two important notes here:
    • Don’t void it so much that the walls are all wafer thin as it will break
    • Don’t void the inside of a shape without leaving a weephole for the loose powder to get out – the 3D printer will re-use any loose powder left over from a build, but if the powder is sealed inside a box then it can’t be extracted.
  • Shell it: the 3DS Shell modifier can sometimes help by allowing you to thin (and thicken) walls, though again be careful not to trap the loose powder inside walls.

After the Model has Printed

Typically a model is sent in the late afternoon to run overnight.  3D prints can’t be queued so they all go one after the other, but it is possible to put a number of models into one build so they can be sent altogether.

The next morning the model will be sitting in the printer build tray inside a cube of loose powder.  That loose powder then has to be manually vacuumed away leaving the solid model.

Next, the model is moved to the air brush area where remaining powder is blown away.

The final – though not always necessary – step is to apply a hardening solution (which is essentially superglue).  This is either administered with a brush or by dipping the model into a small trough filled with the solution.



FoACH :: SwS :: UoG :: Faculty TechSupport

Information, technical support, guides and news for students using facilities in the University of Greenwich Stockwell Street S11 Building.  This site is primarily for students in the departments of Architecture & Landscape and CPDA



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