Probe_basic Toolchanger

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06 Apr 2023 04:29 #268377 by CNC_ANDI
Replied by CNC_ANDI on topic Probe_basic Toolchanger
Thank you so much looks very nice. at this time i print my version. but please you can give me your version too. so i will lookout what version is better for my machine.

[quote} add a spring-loaded hinge on the carousel mount. [/quote]
yes i´m thinking about that. i will see it. let me check the height with tools to the gantry height.

yes using a nema23 Motor...
rotatet wheel 200mm without the toolholders.

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06 Apr 2023 10:11 #268400 by tommylight
Replied by tommylight on topic Probe_basic Toolchanger
@Spumco,
No locking ?
See the gif, it locks in place.

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06 Apr 2023 11:42 #268415 by spumco
Replied by spumco on topic Probe_basic Toolchanger
Tommy,

It locks.  The driving wheel outer rim is tangent to the inner OD of the driven wheel pins.  Since they are two different diameters the outer pins get captured just as the main indexing pin exits the slot.

The two issues with geneva mechanisms (that I've read about, no expert here) are friction and a wonky accel/decel profile.  There are two versions I found online (and copied) which eliminate the friction problem if you use rolling elements instead of pins.

 
Same channel has another, similar one that's even simpler... but that one is strange as it moves two pins per driving wheel rotation.
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06 Apr 2023 12:50 #268422 by tommylight
Replied by tommylight on topic Probe_basic Toolchanger
Need to clean glasses, or get new eyes as i could not see how it locks! :(

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06 Apr 2023 13:33 #268428 by Lcvette
Replied by Lcvette on topic Probe_basic Toolchanger
I have found that it is better to utilize a small pin for smoother motion.  if you want to add a bearing, add it to the rotor body and use a press fit pin that rotates inside the bearing rather than fitting a bearing to an existing pin which increases the diameter.  I have built a few of these over the years and initially tried the proposed methods but it had a jerky motion that was eliminated with a smaller drive pin.  Just some food for thought.

 
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06 Apr 2023 13:58 #268434 by spumco
Replied by spumco on topic Probe_basic Toolchanger

Need to clean glasses, or get new eyes as i could not see how it locks! :(

2nd basic design I mentioned.  Two indexing pins per pocket, no sliding motion.  Same concept in that the drive wheel is tangent to the driven wheel pins and locks them in place (red dashed line to help visualize).

It's a little fussy to model, but that's likely due to my lack of CAD and math skills.  I did get it working in F360.

 

Could still use small-diameter needle roller bearings on the pins to achieve what Lcvette suggests.  I suspect that relatively large-diameter bearings in typical geneva slots may have the effect of changing moment arm lengths significantly - maybe leading to the jerky motion.
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06 Apr 2023 17:00 #268442 by CNC_ANDI
Replied by CNC_ANDI on topic Probe_basic Toolchanger
today i got my doughter mesacard 7i78.

so now i have to change the bitfile of my mesa 7i76e...

when i do that, do i lost any configurations?

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06 Apr 2023 23:08 #268461 by spumco
Replied by spumco on topic Probe_basic Toolchanger
Internal drive model attached as requested.

Keep in mind that it's basically an electronic napkin sketch and not a ready-to-manufacture assembly.  I'll probably keep working on it and maybe print a prototype to see if my theory about rolling elements makes this a better option than traditional geneva configs.
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07 Apr 2023 00:34 #268470 by spumco
Replied by spumco on topic Probe_basic Toolchanger
I couldn't help myself.

 

This one is nicer on the CAD side. More constraints, less specific dimensions so should be easier to modify for different pocket counts and units.
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07 Apr 2023 01:29 #268474 by tommylight
Replied by tommylight on topic Probe_basic Toolchanger
Very nice, indeed.
Thank you.

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