From CAD to 3D Printer (Slicing)

No matter which technology is utilised by you the designer in the output of a CAD design to a 3D Printer, the process is the same.

A virtual model is sliced into layers and these layers are then built by the 3D Printer, and that building process is why 3D Printing is more accurately called Additive Manufacture (AM)

There are many different technologies now including but not exclusively:

• Stereolithography (SLA)
• Digital Light Processing (DLP)
• Fused deposition modelling (FDM)
• Selective Laser Sintering (SLS)
• Selective laser melting (SLM)
• Electronic Beam Melting (EBM)
• Laminated object manufacturing (LOM)
• Diode Area Melting (DAM)

Shropshire 3D Print specialises in desktop FDM technology and provides high quality machines from the best manufacturers around the world.

If you are a CAD Designer who is  new to the 3d Printing technology you do have some considerations, and these include:

• Application
• Interior of the object
• Geometry of the object
• Orientation of the object in-build
• Finish of the object

Application

Affecting other considerations, application is key to on which technology the object should be made; in what orientation; how dense it should be; and what finish is required.

For instance, it is quite normal for you as a designer to iterate first designs on an FDM machine, which is low-cost in terms of output. Indeed, many manufacturers, like MishiMoto, iterate on a MakerBot and move to other technologies or traditional manufacturing to make the final product.

An FDM machine can make products in PLA, ABS, PETG, FLEX, Wood, Glass and PVA. (Water-soluble) in the main these are forms of plastics and whilst ideal for some applications, might not suit BAE for final output when the item to be 3D Printed is a Jet Fighter part, and needs to withstand very high pressures, temperature changes and stresses.

Interior of the object

You as a CAD designers might normally only consider the design the exterior of the object, their further considerations being the materials used and the process. If a CAD designed product is designed to be output on a lathe, then there is no need to think about what is inside the model as it is the same material and density as the exterior design.

Geometry of the object

A key advantage of AM is the fact that geometries can be very complex as manufacturing constraints are not the same as with traditional manufacture.

Similarly, AM can provide massive material and weight savings, as items can be re-designed with skeletal facades, retaining strength and integrity of the object and providing massive cost savings not only in production, but also payload.  See Lockheed Martin’s use of MakerBot 3D Printers as they design parts smaller, lighter and more fitted to satellite launch.

Orientation of the object in-build

In considering the geometry, you as a designer then has to consider in what orientation the object will be made.

Understanding that in 3D Printing a layer cannot be made unless laid upon an existing layer (or initially the bed of the 3D printer) is vital to you in this respect.

This leads to further considerations:

Will the item need support material to be made in the layering process?

What is the best orientation to give maximum strength?

Orientation is essential in 3D Printing from designing the part to output of the part on a 3D Printer. Understanding orientation enables better success with 3D printed.

The best orientation in is surprisingly 45 degrees

In FDM 3D Prints the main area of weakness is between the layers. If you were 3D printing a slender cylinder that needed to have strength it would not be wise to print the cylinder vertically. Instead it would be better for you to print the cylinder lying flat on the print bed. This also depends on the forces which will be applied to the 3D model (application).

Finish of the object

It is a common misconception for designers new to the technology that a 3D Printer outputs the finished article 100% of the time.

Manufacturers are well used to fettling a product after initial production. Most items built with 3D Printing will require some finishing, and this is called Post Processing. Finishing can be:

• Removing Support Material
• Glueing (your object may be an assembly and have been printed in parts)
• Sanding
• Priming / Painting

The finer the layers the item is built in the finer the finish before post-processing.

How can all this be achieved.

The good news is that all CAD output files are processed by software called slicing software prior to print.

It is advisable for you to check using either the slicing software or other software that the file is actually 3D Printable. These software packages can check that the object is meshed (that is has no holes in it) and a models polygon count (all CAD objects are made from a number of polygons – the greater the finer the model – and larger the file size). You can do this online at MakePrintable.com

Therefore all models can be virtually oriented and manipulated prior to additive manufacture.

Slicer Settings

Even scaling of the original dimensions (uniformly or independently in the X, Y or Z axis) is possible for you, together with:

• Adding Rafts – to make the model adhere to the build plate in FDM technology
• Orientation for best build, best output application

• Adding supports for challenging geometries
• Maximising / Minimising infill (the interior of the object)
• Increasing Shell / Roof and Floor Thickness (shells are the walls of the model, while roof and floor depend on orientation and are top and bottom of the object)
• Layer Height – the lower the height the finer the output – however, the longer it will take to build.

There are more settings within the slicing software and seasoned 3D Printer users will tinker with these for even better output.

The great news is that MakerBot and Stratasys use GRABCAD based slicing software to maximise workflow and iteration time.

MakerBot Print for instance will accept native CAD files, so there is no need to convert to a readable format from CAD for the slicing software. Common readable files formats are .stl , .obj , .prt. This software also allows 1 click changes for important settings like infill and MakerBot have introduced a great feature called Minfill

Finally it is now easy for you as the designer to slice the object/ model prior to build, see how much material will be used, where supports will be, how long the build will take, and whether further setting alterations are advisable before 3D Printing.