Experimental 3D Printable Nema 17 Stepper Motor
Description
Stepper Motor: This Experimental Build Is My First Attempt At Making A Practical 3D Printable Stepper Motor. The Goal Was To Create A 3D Printable Stepper Motor That Could Directly Replace A Nema 17 Stepper Motor In A Reprap Style 3D Printer. This Motor Has Been Demonstrated To Work Directly With A Standard Allegro 4988 Bipolar Stepper Driver In The 12 Volt Range, And Has A Native Resolution Of 240 Steps/Revolution In The Full-Step Mode. It Runs Best, However, In The Half-Step Mode, With An Effective Resolution Of 480 Steps/Revolution. It Has The Standard Nema 17 Hole Pattern For M3 Machine Screws. It Cost Around $5Usd In Parts And Took 3.25 Hours To Print. Motor Designed By David Hartkop For The Pueblo City-County Library District'S *Idea Factory* Makerspace Programming. The Approach: Rather Than Designing A Rotor With High Angular Resolution, This Motor Uses A Single Magnet And Four Electromagnets. The Electromagnets Are Arranged In Diagonal Pairs, Which Are Wired In Series To Provide A Total Of Two Coil Circuits For The Motor. The Motor Has A Native Resolution Of 4 Steps Per Revolution In The Full-Step Mode. This Low Resolution Stepper Motor Then Drives The Input Of A Split-Annulus Orbital Gearbox, Which Provides A 60:1 Gear Reduction. Effort Was Made To Match The Impedance Of A 0.6W Bipolar Stepper Motor Using 33 Gage Magnet Wire. Each Of Four Electromagnets Was Wound With 75 Feet Of Wire, Though Exact Turns Were Not Considered. Results: This Motor Works, But Is Mostly A Curiosity At This Point. The Torque Is Suitable For Driving A Reprap Printer'S X Or Y Stages But The Coils Were Found To Easily Overheat. I Recommend Attaching A Heat Sink To The Exposed Ends Of The Four Electromagnets. Ideas For Improvement: 1. Use Steel Nuts For Iron Pole Pieces Placed Around The Rotor, Gets Coils Closer To Magnet 2. Use Large Washer Or Steel Square As Flux-Return Over Open Ends Of Electromagnets 3. Place Heat Sink On Electromagnets 4. Use Looser, Lower-Friction Bearings 5. Use Silicone Based Lubrication Vs. Petroleum Grease Which Will Degrade The Abs. 6. Use A Higher-Diameter Diametrically Polarized Magnet For A Rotor For Better Torque.
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