Engineering the Perfect 3D Printed Gears – Material Selection, Design Tips, and Printing Techniques

Gears are a crucial component in many engineering and robotics projects. With 3D printing, we can now easily prototype and produce custom gears rather than rely on off-the-shelf parts. However, not all materials and printing methods are ideal for gears. In this guide, we’ll explore how to design and 3D print durable, high-performance gears for your projects.

What Makes a Good 3D Printed Gears?

When designing gears for 3D printing, there are several key factors to consider:

Strength – The material needs to be rigid and strong enough to transmit torque and forces without bending, stripping or cracking teeth.

Wear Resistance – The gear teeth need to withstand friction and wear over time without significant deformation. The material should have low friction and abrasion properties.

Dimensional Accuracy – Precise dimensions, tooth profiles and alignments are required for smooth meshing and operation. The printing process must have good resolution and low shrinkage.

Temperature Resistance – Many applications require gears to withstand high temperatures. The material should resist creep and maintain integrity under thermal loads.

The optimal material and printing method depends on the specific application and operating conditions for the gears. Let’s look at the pros and cons of different plastics for 3D printed gears.

Best Materials for 3D Printed Gears

ABS

ABS (acrylonitrile butadiene styrene) is a common material for general 3D printing. It’s relatively strong, affordable and easy to print. However, ABS has some downsides for gears:

Pros:

• Good tensile strength and impact resistance
• Higher temperature resistance up to 80°C

Cons:

• Prone to bending and stripping under high torque loads
• Teeth wear quicker than other materials
• Medium dimensional accuracy and layer adhesion

ABS is acceptable for prototypes and light-duty applications, but not optimal for final parts. The temperature resistance limits usage in hot environments.

PLA

PLA (polylactic acid) is another very popular 3D printing filament, known for good printability. But PLA has some issues for gears:

Pros:

• Easy to print with good layer adhesion
• Low friction/wear properties

Cons:

• Much lower strength than ABS
• More prone to bending, stripping and cracking
• Low temperature resistance (50-60°C)

For PLA gears, lightweight applications and lower speeds are recommended to prevent premature failure. The low melting point also restricts use in hot conditions.

Nylon

Nylon filaments are a good upgrade from ABS/PLA for gear printing. Benefits include:

Pros:

• Excellent tensile strength and wear resistance
• Low friction properties, resilience to abrasion
• Higher temperature resistance up to 80-100°C

Cons:

• More difficult to print, prone to warping
• Moderate dimensional accuracy and layer adhesion

Nylon is suitable for small-medium sized gears seeing moderate loads and speeds. The excellent wear properties provide longer lifetimes.

PETG

PETG (polyethylene terephthalate glycol-modified) offers a unique balance of properties:

Pros:

• Very high impact strength and flexibility
• Maintains dimensions extremely well
• Easy to print with good layer adhesion

Cons:

• Not as stiff as ABS, more prone to bending under high loads
• Lower temperature resistance (~70°C)

PETG can make strong, long-lasting gears for low-medium torque applications. The excellent dimensional stability helps achieve smooth meshing and motion.

Polycarbonate

Polycarbonate (PC) is an engineering-grade filament suitable for demanding applications:

Pros:

• Extremely high strength and temperature resistance (110°C+)
• Good wear resistance and dimensional stability
• Low friction properties

Cons:

• Difficult to print, requires high temps and enclosed printer
• More expensive filament

Polycarbonate gears can handle very high loads and speeds suitable for remote controlled vehicles, robotics, and mechanical devices. The high heat resistance enables use in hot environments.

Key Design Considerations for 3D Printed Gears

To maximize the performance of your 3D printed gears, follow these design guidelines:

• Gear profiles – Use standard involute, spur or helical profiles for proper meshing. Avoid exotic shapes.
• Wall thickness – Make sure teeth and walls are thick enough to prevent bending and breaking. For small gears consider 1.5-2mm minimum thickness.
• Tooth count – Limit tooth counts to avoid excessive thinness and undersized profiles. Around 10-30 teeth often works well.
• Unsupported walls – Minimize thin unsupported sections that can droop during printing.
• Fillets and chamfers – Add in fillets and chamfers around gear teeth to increase strength and prevent cracking.
• Clearances – Have some clearance between meshing gears to prevent binding. Around 0.1-0.2mm is usually sufficient.
• Holes – Reinforce holes with extra perimeters and avoid overhangs. Holes stress concentrations can lead to cracks.

Following established gear design principles tailored for 3D printing will ensure your gears print successfully and function reliably.

Optimizing Print Settings for Strong, Precise Gears

Dialing in the right print settings is crucial for high-quality gears. Here are some key recommendations:

• Nozzles – For small, high precision gears, use smaller nozzles around 0.25-0.4mm for improved resolution. Larger nozzles speed up bigger gears.
• Thin layers – Print with thin layers from 0.10-0.15mm for smooth surfaces and accurate tooth profiles. Slow down for the best results.
• Infill – Use 100% infill for maximum strength. Lower infills around 30% can be OK for prototyping. Solid infill prevents internal voids.
• Perimeters – Add extra perimeters (at least 4-6) around gear teeth and holes for reinforcement. This removes weak points.
• Supports – Well-placed supports prevent overhangs and maintain accuracy on downward facing teeth.
• Slower speeds – Reduce print speeds to around 30-40mm/s. This gives time for layers to bond together and prevents skips/oozing.

Dialing in temperatures, cooling, retraction and other settings specific to your printer and filament type also helps. Take the time to optimize your profile!

Advanced Printing Tips

Beyond basic settings, there are some additional tricks to boost your 3D printed gears:

• Annealing – With ABS and Nylon, annealing can increase strength and wear resistance. Just beware of shrinkage.
• Carbon fiber – Reinforced carbon fiber filaments improve stiffness and longevity for gears seeing high loads.
• Lubricants – Applying dry lubricants like PTFE or graphite powders reduces friction and wear on gear teeth.
• Print orientation – Laying gears flat instead of vertically removes layer lines from the tooth faces and minimizes flexing.
• Post-processing – Smoothing gear faces with vapor treatment, acetone or tumbles removes surface defects.

Combining the right material, design, print settings, and post-processing allows even hobbyist 3D printers to create quality gears for low-load mechanisms and robots.

For high-performance industrial applications, consider SLS 3D printing with flexible resin for extremely strong and durable end-use gears.

Conclusion

This guide provides a snapshot of how to optimize your 3D printed gears. Follow these best practices:

• Choose materials with good strength, wear and temperature properties for your specific loads and operating environment. Engineering grades like nylon and polycarbonate excel here.
• Design robust, thick gears with proper mechanical profiles. Reinforce weak points and minimize unsupported sections prone to drooping and cracking.
• Dial in your slicer with small layers, extra perimeters, dense infills and slower print speeds. Well-placed supports also improve quality on downward facing gears.
• Consider post-processing like annealing, lubricants and smoothing. Advanced methods like carbon fiber reinforcement and SLS take results to the next level.

With some experimentation and fine-tuning, you can 3D print great quality custom gears for all your projects. Just match the material and printing technique to the mechanical design requirements. Let us know if you have any other tips for designing and producing gears with 3D printing!