Optimizing Part Design for Speed and Material Savings With High Speed Additive Manufacturing—Part 1

Fused Filament Fabrication (FFF) can unlock the potential for additive manufacturing in many different applications including jigs and fixtures, casting, and end-use part production. While some believe additive manufacturing can be used as an alternative to recreate almost any part designed using traditional methods, the truth is not all manufacturing processes translate. Engineers cannot simply cut and paste design guidelines developed for CNC machined, injection molded, or vacuum formed products into 3D printing workflows.

Additive manufacturing is different; if large speed increases and time savings are to be found, products have to be designed specifically for the 3D printing process.

And since high speed extrusion is a unique implementation of additive manufacturing technology, there are specific design techniques to increase print speed and material throughput using high speed extrusion that are different from other forms of 3D printing such as selective laser sintering (SLS) or stereolithography (SLA).

High speed extrusion allows for faster print times without sacrificing quality, thus reducing cost and time to part. As a result, engineering designers need to adopt new design principles to optimize a part’s functionality for the additive manufacturing process.

The Essentium HSE 3D Printing Platform is 5-to-15 times faster than any other extrusion printer on the market (up to 500 mm/second), so there will naturally be time savings over other 3D printing methods.

But what if you could shave two hours off a 12-hour high speed extrusion build time, or compress a 90-minute print time down to 60 minutes through some simple design changes? That may not sound significant on a per-piece basis, but think about the savings that can be achieved when printing hundreds or thousands of parts per year.

With that thought in mind, here are some design tips for users to achieve faster print times with maximum quality and repeatability:

• Print chamfers (if you have to) and fillets in the Z direction to create gradual overhangs to minimize the need for support material. Benefit: Reduced Cost
• Optimize the print orientation. During the design phase, keep in mind the printing process and include a face that makes printing orientation clear and reliable. Print in proper layering directions to maximize the strength of the part. Orient the part in the bed in such a way that the expected loads are running perpendicular to the print layer direction, if possible. Benefit: Strength
• Substitute fillets for corners. One of the keys to successful high speed extrusion printing is optimizing part design for even material extrusion rates at a steady temperature for consistent results and better bonding between layers. Sharp vertexes and chamfers force the print head to decelerate or even come to a full stop when approaching the edge of a straight segment, and to re-accelerate after turning a corner. This occurs for all acute turns and even some more open turning angles on every layer. This not only affects print speed, but the temperature of the filament as well, as it is held in the nozzle while the printhead negotiates each corner. By rounding corners to a minimum of 5mm or greater, the print head does not have to decelerate or stop when printing the fillet. Maximum print speed and consistent filament temperature is maintained for the best quality parts. Benefit: Speed and Quality
• Combine multiple assemblies into fewer printed parts. 3D printing allows for geometries that cannot be created as a single part using traditional methods, reducing post-printing assembly time and labor. Benefit: Speed
• Optimize travel movements. Travel movements are like jumps in the middle of the build space. In areas where no material is required, the print head stops, ceases extrusion, moves to the start position of the next block of material, and resumes extruding. These extra starts and stops occur at every layer in the X/Y planes, extending print time. Meanwhile, material held in the nozzle during travel movements continues to heat while pressure continues to build up behind it, causing stringing and blobbing. The solution? Minimize the number of islands (cross-sectional areas of a part that are not connected). Link mergeable bodies wherever possible. Or, redesign the part with a thicker base plate and sink the control surfaces into the part rather than build up. (The extra material used to join islands or build a thicker base will be offset by the speed and quality gains from eliminating travel movements.) This reduces the number of starts and stops to ensure a more consistent extrusion rate, which in turn improves quality, reduces print time, and helps avoid defects such as stringing. Benefit: Speed and Quality
• Use ribs to add strength. Minimal use of additional materials to increase rigidity and strength in areas the will be exposed to stress. Benefit: Reduced Cost
• Plan toolpaths for thin walls and infill paths. When making parts or tools that have thin walls, holes, or gaps close to the edge of a part, design the thickness of the space in multiples equal to the aperture of the nozzle diameter. For instance, using a 0.8 millimeter nozzle it is easy to build a high quality wall that is 2.4 mm thick with three equal passes. Designing the wall to be 3 mm, on the other hand, exposes the part to possible over- or under-extrusion and poorly printed walls. Further, to achieve maximum speed and eliminate unnecessary accelerations and decelerations during infill, move a hole or window slightly to allow for longer toolpaths. Benefit: Speed and Quality

These and other design practices can help make your high speed extrusion 3D printed jigs and fixtures and parts the best they can be while saving time and materials in the process.

In Part 2, we will examine several more advanced techniques for creating parts with odd shapes, overhangs, and cutouts using additive manufacturing. We invite you to learn more about best practices optimized for high speed extrusion additive manufacturing by watching our webinars, Designing for High Speed Extrusion, Parts I and II.