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9g Servo arms, different couplers to 5mm threaded rod WIP

by Schorhr, published

9g Servo arms, different couplers to 5mm threaded rod WIP by Schorhr Jan 4, 2013

Description

Thingiverse is great. With flouSH's part I did not have to start from scratch. Unfortunately the PP3DP UP has different tolerances and print properties, the first ones where to loose and the teeth did not turn out well.
There you have a great example for reprap/slic3r VS closed source: While the later will usually produce great and repeatable results, there's just not much you can do when something just won't work with the limited settings available.

By the way, in the Sketchup SKP file is a (rough but close enough) 3D model of the servo and the inner gear setup, as I could not find something similar. I did not have the digital caliper handy, so it's not very precise, but good enough if you plan on tinkering with a servo and (like me) do not want to take it apart twenty times for your sketches.

###UPDATE 1 #### JAN 5 2013
I modeled the servo arm (File "servoarm.skp"/"Servoarms.stl", if you want to print one, you may want to try the great thing thingiverse.com/thing:28566 if you are looking for printed servo arms)

###UPDATE 2 #### JAN 5 2013
I added the servo topper coupling, which will sit ontop of the four-arm and does not require aditional screws (perhaps a longer one though!)

Recent Comments

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Works well! Just need to get the fit a little tighter and modify it for either a different screw or make the walls thinner so the short one will fit. Other then that, seems good.

Yes, that idea came to me too :-)
I just don't know if it will be stable / wobble free and if I have enough clearance for it to rotate.
I was thinking about using the four-sided arm even (it has two little flaps more then the two-arm part).
Do you think self tapping screws will do? I was kind of affraid it would either split the layers or wiggle it's way out after moving a lot under force.

One Idea I just had typing this and looking at the part: I could make two segments enclosing the four arms, and two bolt with nuts tightening it arround both servo-arm and the 5mm threaded rod...
(rough sketch: http://thingiverse-production.... )

Apart from the nice design, and the challenge involved in printing the fine details.
Why not create an adapter for using the existing servo arm?

Using a double arm and two small self tapping screws.
Perhaps even cutting down the servo arm length.
Won't be as pretty as this design, but much easier :)

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Instructions

I have not finished the part, as you can see I printed it many, many times to both fit the 5 mm threaded rod and the tg9e 9g micro servo. The main problem: I only have one of these servos here at the moment, and the many trial&error tests ruined the top gear's hole which holds the screw.

If you want to print it, try the plate of 6 (2x3 test pieces).
I basically re-created most of the original part to tinker with it. I made both holes shorter for my setup, and in the latest files tried a squeeze-fit. With the UP I have a great deal of trouble with printing little teeth to secure the servo knob, so I experimented.
Last resort: Super glue ;-)

ToDo: Create a drop-in nut slot to secure the M5 threaded rod
Figure out how to print little teeth with the UP that secure the servo
Build the rest... Amazing how one part can hold up a whole project, even with thingiverse providing rtr models!

I made the hole for the threaded rod tighter, with the UP the 5mm rods will be tight to screw in but held in place even without glue or a locking screw/bolt.
As you can see the WIP files are quick & dirty, you may need to clean up the files before printing (so far I just cleaned the servo arm models)

Comments

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Schorhr on Jan 6, 2013 said:

Works well! Just need to get the fit a little tighter and modify it for either a different screw or make the walls thinner so the short one will fit. Other then that, seems good.

talpa on Jan 5, 2013 said:

Apart from the nice design, and the challenge involved in printing the fine details.
Why not create an adapter for using the existing servo arm?

Using a double arm and two small self tapping screws.
Perhaps even cutting down the servo arm length.
Won't be as pretty as this design, but much easier :)

Schorhr on Jan 5, 2013 said:

Yes, that idea came to me too :-)
I just don't know if it will be stable / wobble free and if I have enough clearance for it to rotate.
I was thinking about using the four-sided arm even (it has two little flaps more then the two-arm part).
Do you think self tapping screws will do? I was kind of affraid it would either split the layers or wiggle it's way out after moving a lot under force.

One Idea I just had typing this and looking at the part: I could make two segments enclosing the four arms, and two bolt with nuts tightening it arround both servo-arm and the 5mm threaded rod...
(rough sketch: http://thingiverse-production.... )

Jason-wratten on Jan 4, 2013 said:

Could you print the coupler slightly smaller then heat the part and force it onto the splines ?

I also have a UP! :-)

Schorhr on Jan 4, 2013 said:

No need to print it smaller, I created a tight-fit version with a gap in the tube, you could just heat the top ... great idea! I'll just create a nëw version with bigger teeth or perhaps a screw to dig into the servo knob :-)

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