Design Guide for 3D Printing with Composites

Quick Reference Sheet

These guides serve as recommendations and may not reflect all implementations, as 3D printing is a geometry-dependent process. Unless otherwise specified, data is based on parts printed on Markforged composite printers at 100 micron layer height in Onyx with default print settings.


Maximum part size

Desktop Series

X: 320 mm (12.60”)
Y: 132 mm (5.20”)
Z: 154 mm (6.06”)

Industrial Series

X: 330mm (13.00”)
Y1: 270 mm (10.63”) Y2: 250 mm (9.84”) with fiber
Z: 200 mm (7.87”)

These build volumes reference the maximum bounding box your part must fit in
to print on either a Desktop or Industrial Series Markforged composite printer.
Industrial Series printers have a deeper print area when printing with only plastic.


Minimum part dimensions
X: 1.6 mm (0.063”)
Y: 1.6 mm (0.063”)
Z: 0.8 mm (0.031”)
Minimum part size is limited to the extrusion width and height of each bead. The dimensions are derived from the minimum number of roof layers, floor layers, and
shells needed to print a part successfully.
Minimum unsupported overhang angle
θ: 40o
This is the minimum angle to the horizontal at which a feature of a part can print
without needing supports to hold it up. Eiger will generate supports for angles
below 45o, but may not be needed in all cases.
Minimum hole diameter
XY: 1.5 mm (0.059”)
Z: 1.0 mm (0.039”)
Holes with too small a diameter may close off during printing or print inaccurately.
Horizontal surface holes (Z) print more precisely than vertical surface holes (XY).
Minimum post diameter
XY: 1.6 mm (0.063”)
Z: 2.0 mm (0.079”)
Posts with too small a diameter may not print precisely. Consider adding dowels
or pins to your part for strong vertical posts to avoid shear along layer lines
Minimum engraved feature size
Z Layer features
H: 0.10 mm (0.004”)
W: 0.50 mm (0.020”)
Horizontal XY features
D: 0.20 mm (0.008”)
H: 0.80 mm (0.031”)
Vertical XY features
D: 0.20 mm (0.008”)
W: 0.50 mm (0.020”)
An engraved feature is one that is recessed below the surface of the model.
Common examples include lettering and texture. Engraved features may blend
into the rest of the model if they are too small.
Minimum embossed feature size
Z Layer features
H: 0.10 mm (0.004”)
W: 0.80 mm (0.031”)
Horizontal XY features
D: 0.20 mm (0.008”)
H: 0.80 mm (0.031”)
Vertical XY features
D: 0.20 mm (0.008”)
W: 0.80 mm (0.031”)
An embossed feature is one that is raised above the surface of the model.
Common examples include lettering and texture. Embossed features may blend
into the rest of the model if they are too small.

Identifying 3D Printing Opportunities

3D printers vary widely in size, material, and method — simply put, they are just tools to help you create specific parts. Just as you wouldn’t use a screwdriver on a nail, a 3D printer is well-suited for certain types of parts and ineffective for others. The key to determining whether to 3D print a part stems from its material properties and return on investment (ROI).

Calculate ROI

Use ROI calculations to justify which parts or subassemblies will benefit from 3D printing. Upload your parts to Markforged’s Eiger software to get the material cost and print time, and compare this to estimates from other manufacturing platforms. This should give you a sense for the time and cost savings involved in creating your part.

Time analysis

3D printing allows for rapid iteration so you can test out many different designs early and often to refine your models. Continuous fiber reinforcement facilitates strong parts for workslike prototypes and end-use that you can improve print-by-print and implement in a matter of days. Look for opportunities to cut down on lengthy lead times with additive manufacturing.

Cost considerations

Turn to 3D printing when the costs of traditional manufacturing are prohibitively expensive for your needs. 3D printing is often appropriate for low- to mid-volume applications, but for a given part there is always an inflection point at which other manufacturing methods become more cost-effective. Compare cost-per-quantity values to discover this tipping point.

Determine material needs and behaviors

Consider the material requirements of your part.

  • How strong or stiff does it need to be?
  • What environment will your part be in?
  • How many cycles does it need to last?
  • How much can it weigh?

Use these considerations to select a material that suits the part.

When should you print with continuous fiber?

Continuous Fiber Fabrication (CFF) serves as the backbone for strong 3D printed parts. Inlaid fibers within a printed plastic matrix form a composite part in which the properties of the fiber provide high stiffness, toughness, strength, or heat deflection.

Metal strength

The strength of a fiber reinforced part comes from the combined strength of the plastic and the continuous fiber strands woven throughout the part. This can make parts comparable to aluminum in strength and stiffness.


Reinforcing fibers can vastly increase the lifetime of a part. Fibers strengthen the part far beyond traditional plastics, meaning a reinforced part can hold up much better over an extended period of time than a standard plastic part.

Optimized properties

Continuous Fiber Fabrication is unique in that you can selectively reinforce a part for its use-case. Tailor a part’s strength profile exactly for its application by adding continuous fibers where strength is needed most.

What to Consider When Printing

As you design your part, consider how it can be optimized for the layer-by-layer printing process. Below are six considerations to keep in mind when designing your parts:

1. Determine loading conditions

Composite 3D printed parts are stronger on planes parallel to the print bed, especially if you are reinforcing with continuous fiber. Analyze how your part will be loaded and design the part such that the largest forces traverse the XY plane. Some parts may need to be split into multiple printed pieces to optimize for strength.

2. Identify critical dimensions

3D printers have higher precision in planes parallel to the build plate. What are your critical dimensions or features? Critical features print optimally when in plane with the print bed.

3. Maximize bed contact

Greater surface area on the print bed minimizes supports and improves bed adhesion. Which face of your part contacts the bed? Try to orient the part so that the largest face lies on the print bed, unless strength or geometry needs dictate otherwise.

4. Reduce supports and improve overhangs

Fewer supports reduce printing and processing time. How can you design to minimize supports? Are the supports in your part accessible? Use angled overhangs to reduce supports and improve support removal.

5. Fillet or chamfer edges

Adding fillets ensures smooth edge transitions and reduces stress concentrations at corners. Filleting edges normal to the print bed reduces the potential for warping, while chamfering edges flush with the build plate makes part removal easier and prevents edges from splaying on the first layer. Chamfers on interface edges like holes will help line up fits more easily.

6. Consider printer bandwidth

Consider when you use your printer and how to make efficient use of its bandwidth. Print longer jobs overnight and shorter jobs during the day. You can also create builds by printing multiple parts together that start and end during a workday. Here is a table of guidelines and four example days of prints to help you: