三颗夹爪装置带螺旋齿轮

Three Jaw Chuck with Spiral Gearing

2024-03-18 00:33:02

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Summary

This design mounts to the top of a nema 17 motor to be used as a vertical chuck for my vertical rotary laser engraver: https://www.thingiverse.com/thing:5296551

After redrawing the following design: https://www.thingiverse.com/thing:5171097 in fusion 360, I realized using a spur gear tooth profile instead of the rectangle profile for the spiral path might have a smoother movement. I wanted to use as small a pitch as I could & still have descent size tooth engagement. Since the python script spur gear gives a Pitch diameter based on the input variables, I worked backwards using a spreadsheet to get the module needed for whatever spiral pitch I needed. I used the standard of Metric, Pressure Angle of 20 Deg, Number of Teeth 24, backlash 0.2mm, root Fillet of 0.5mm, Gear Thickness of 3 & Hole diameter of 3. The only variable I changed between the various spiral pitch distances was Module. The spiral pitch relative to the spur gear is the same distance as the arc length between 2 teeth. So to get the Pitch diameter needed, I used the formula:
(Pitch / Teeth) / pi() or (3.5 / 24) / pi() = 22.91831181
Changing the Module size by trial & error in fusion 360, I can get closer than I need to for the spiral pitch desired with vary little effort. A 3mm spiral pitch gave a tooth size of about 1.63mm width which is probably too small to use. I attached a spreadsheet of my calcs for 3mm, 3.5mm, 4mm, 5mm & 6mm spiral pitches in case someone wants to play with this further.

Instead of a clip to hold the scroll plate in place, I use a threaded thumb nut. I think this works better than the clip. Fusion 360 does not make it easy to add tolerances to threads or use non standard threads, so I used openscad to create the threading & added several thumb nuts with different tolerance fit. The thumbnuts are named ThumbNut_xx_Rev5.stl where xx is the the tolerance fit. _10 = 0.10 clearance all the way around to 0_50 clearance all the way around.

I used a tolerance fit of 0.15mm between the jaw sliders & the 62mm_ChuckHousing. The tighter fit & still give you a smooth movement the better. I added versions for 0.15mm & 0.10mm tolerance.
Jaw_A_3_5P_Wid_15.stl & Jaw_A_3_5P_Wid_10.stl, plus the B & C Jaws.
The Jaw_A should be opposite the side where the M3 screws mount to the Nema 17 motor. You can also refer to the attached fusion 360 model or step file to make this more clear.

The scroll plate I made in 3 different tolerance fits of 0.10mm, 0.20mm & 0.30mm. That is a simple inner cylinder fit, so is easy to adjust. This part & where it connected to the Chuck housing is the only part I really needed to file or sand for best fit. I did not print any of these with supports, but 62mm_ChuckHousing_Wid.stl might do better with supports. In 2nd attached photo there is a closeup of the print around where the openings of the jaws come thru. That is the only part of any of the prints that came out rough for me. I was able to improve that by slowing the print down to 30mm/sec during those layers of the print. I used adaptive heights for all the prints varying between .12mm & .24mm.

I also included Jaw_A_3_5P_Wid_BK_15.stl , B & C if you want to insert the jaws backwards.

There is also an optional Scroll_Wrench.stl to use instead of using your fingers to turn the scroll plate. Tightening with my fingers worked better for me though.

If you want to modify the openscad source files used for the threads, you will need to download the threads module from: https://dkprojects.net/openscad-threads/

This design still has a little play in it, but might be useful. I certainly learned a lot by working through this design.