Design Tips

When designing for prototyping, there are many variables to take into consideration to get the optimum part for your needs. Some of these variables are wall thickness, feature orientation, feature function, environment the parts will be used in, material, and process that will be used. Please refer to our Process Specification Chart for detailed information on your preferred process.

The minimum feature size varies across the different prototyping processes. Both our plaster Zcorp parts and standard resolution SLA parts are printed with 0.1mm (0.004″) layers. We recommend a minimum 2mm wall thickness for part strength and to reduce warping. Features less than 0.5mm (0.020″) can be lost or not properly bond to the rest of the part. With some High-Res-SLA and Polyjet parts, much finer detail can be achieved with layers down to 0.015mm (0.0006″).

Stair Stepping

Stair stepping happens on every additive prototyping process. This occurs because all 3D printed parts are grown in layers. The result is a wood-grain like effect, especially across curved surfaces. As mentioned above, the layer thickness can depend on the process used. The thicker the layer, the greater the visible effect.

Faceting is controlled by the surface output settings in your 3D CAD software. If you export a coarse (low-polygon) part, it will appear to have many triangles over the surface , however if you export a part with fine faceting (high-polygon) you won’t notice the triangles but the file may be too large and unmanageable. The trick is to find the balance that takes into consideration features and part size to give you the best possible surface finish and file size combination.

Hinges

3D printed parts tend not to work well with living hinges. A simple way around this problem would be to use tape on both parts to simulate a living hinge. Some processes offer the ability to simulate actual living hinges including polymer casting and some SLS materials.

Mechanical hinges should be well supported in 3D printed parts. Since the fine details tend to be brittle, a metal or plastic pin should be used as the axle and the parts should be handled with care. To prototype functional hinges, it is best to use a process such as CNC or SLS due to their mechanical stability.

Hollowing-out or shelling solid parts is a good technique to cut down the volume of your 3D printed parts. This is helpful because volume (which equates to machine time and amount of material used) is one of the main factors that drives up the price of 3D Printing. Don’t forget to leave a hole for the excess powder or resin to escape from. The inverse is true with CNC Machining, as in that case, you start with a block of solid material and the more material you remove the more time (therefore money) is required to make your part.

Points, Knife, Edge, and Thread Design

Many parts are designed with points or knife-edges in them. Typical 3D printing technology cannot produce these parts well. CNC Machining is generally used for this type of part and some high-resolution SLA/Polyjet parts can get within the tolerances required for Validation prototypes. 3D Printing will round-off sharp features and they may be brittle or look jagged. The most commonplace use for this type of feature is in thread design. If 3D printing is what you would like to use, we advise that you do not include threads in the design unless they are course and on large diameters. It is advisable to use taps or dies to create smaller thread features. Our prototype experts can help you make an appropriate decision for your specific needs.

Text & Logos

Text and logos follow the same rules as small features do. If your text and/or logo is a important part of the prototype please let our prototype experts know. The reason is that sometimes the best prototype process for the part is not the best for the logo. When possible keep spacing between letter around .020″ and try to use common fonts such as “arial” “tahoma” or “veranda” because these are designed to print clearly even at smaller sizes.