(This is 100% a function of nozzle diameter and X-Y resolution of the printer. Tiny teeth are weaker and more difficult to print accurately.ģD printing a tiny gear is like trying to use a thick sharpie to color inside the lines of an itty bitty coloring book. But adding more teeth requires that each tooth get smaller to fit on the same diameter of gear. More teeth per gear increases the contact ratio (average number of teeth in contact at any time) and provides smoother rotary motion. Think about this: If you wanted a 2:1 gear ratio for that linear actuator pictured earlier, how many teeth would you put on each gear? Are you better off with 30 & 60 teeth, 15 & 30, or 8 & 16?Įach of those ratios would have the same mechanical advantage but each would produce a very different set of gears if printed. Modelling involute gear teeth from scratch is tedious as hell so before taking the time to do it, first check if you can get by with one of the gear design templates I link to at the end of this article. A well designed set of gears should transfer motion almost exclusively through a rolling action, with very little sliding involved. This is done in such a way that ensures the rotational speed and angle of contact of the gears stays constant throughout their rotation. Involute (spur) gear teeth are called such because the contour of gear teeth has a special curve inward. The difference is subtle to the untrained eye, but doing it the right way will be more accurate and have better properties in the end.
Tempting as it may be, poorly designed gears don’t mesh properly and suffer from excessive friction, stress, backlash, and jerky uneven rotational velocity. It’s really common to see gears improperly designed by the hobbyist community online because doing it the right way is hard.
Richrap did a great job documenting the problem and various solutions on his 3d printing blog here.
Some software is better than others at automatically fixing this, but one way to manually solve is to increase the layer overlap. Gaps inside tiny teeth are common even when the slicer is set to 100% infill. To combat this it can help to oversize holes in the model by ~.005” across the diameter, or plan to ream them out.Īnother common challenge is getting a solid infill can be difficult on small gear features. So a slicer designer may choose to intentionally make holes tighter.Īlso, any misalignment between layers and any discrepancy between the actual and intended extrusion width can have a measurable hole tightening effect. If you consider the absolute innermost edge of the extruded plastic to be the inside edge of the hole and shoot to make that the desired hole size, then the hole diameter is easy to stretch out of tolerance when you press something inside. Slicing software can also have an effect as different programs may choose different spots for the hole to actually start. ( Export gear STLs with higher segment counts to avoid this.)
Some to thermal contraction of cooling plastic and some is because the holes are modeled as polygons that have lots of segments cutting short around the perimeter of the hole. Expect to have to bore holes to the right size & clean up teeth with a blade.Ĭenter hole shrinkage is a very common issue that occurs even on expensive printers. Printed gears usually require a little post processing prior to use. This Nema 17 Stepper Motor Planetary Gear Reducer.The ubiquitous 3D printer extruder gear drive.The majority of functional applications take the form of a speed reducer, usually for a small electric motor or hand crank. But when designed correctly, printed gears can provide efficient and reasonably high load transfer and are an ideal solution for some applications. Of course printing gears using the commonly available plastics is a sacrifice in surface finish and durability compared to injection molded or machined plastic parts. Best of all, 3D Printers are common enough that a set of STL files can be shared with tons of people eager to use them online. The prototyping & creation process is quick & clean. Printed plastic gears are a cheap, quick, and customizable motion transfer solution compared to alternative ways to make gears. So why choose to 3D print gears over alternative manufacturing methods, and what strengths does 3D printing offer?
Geared Light Switch Cover: Device For Sale Here and Free Printable STL Files Here.įDM Printing Specific Benefits & Examples of Gear Use: