I’m not sure the terms “straight Loft” and “compound curvature”, as I used them above, are accurate or helpful. As this image shows, these teeth “valleys” are wider at the bottom at one end and narrower at the top at the other.
So I created a model that lofts these two yellow lines from the raw cut and compares the results, first by volume:
But volume doesn’t really measure surface differences, so I created a second model that measures the distance between the raw and lofted (not smoothed) polysurfaces at random points. The ‘amplify’ slider (blue group) moves the points away in proportion to their actual distance. And indeed, when multiplied by 12, there appears to be a slight bump toward the bottom of the valley:
I have imported the files into Solidworks and it all runs smoothly!
I have adjusted the addendum shape in Solidworks to create space for the tops of crown teeth and added a “humongous” 0.18mm fillet in to the base. Very happy with that!
As for the fillet on top of the tooth. Literature says that fillets are not recommendable on top of gear teeth. I suspect that this is because a fillet will increase the contact surface area between the crown and pinion and result in increase friction.
@maje90 and @Joseph_Oster
I will print the crown and pinion using a microprototyping proces https://www.mareco-prototyping.com/micro-prototyping-details.html
The layer thickness of this method is 16 micron and with this new surface that will print smooth as butter. It will still remain a massive surprise if the whole thing will work. During my day job I design baby strollers, so working on this miniature scale is quite alien to me. I still have a lot of work to do on the watch casing itself before I can print. If you guys are interested I will let you know if it the gear works when I have it in my hands.
cheers,
michel
Hi Joseph,
That is some pretty impressive stuff. As to your question about whether I will notice a difference in through my print resolution: I honestly don’t know. I’ll let you know when I can physically feel it in my hands.
I can however proudly say that the three of us (to be honest, you guys did way more work these last few days) cracked this little thing. If my watch doesn’t work it will surely not be because of the mathematics behind it.
Thanks again!
michel
@Joseph_Oster and @maje90
Hi guys,
In case you are interested I thought I’d update you on my progress. I have 3D printed the parts and I am super excited because the gears are working as intended.
The pinion (orange in the photo) I have printed using RCP material and microprinting. This one turned out immaculate. The crow I have printed on a Statasys Objet printer because of different requirements. This printer was not as good as I had hoped as it still looks pretty rough but still everything worked as intended. Albeit not as smooth as I had hoped. Still for a first prototype is was really good.
Right now I am working on a second revision of the prototype and I need to adjust the gear ratio and modulus slightly, but this is a piece of cake with Riccardo’s code. I remain even more hopeful that one day this mechanism might make it into a real watch!
I still have a lot of work to do on the watch casing itself before I can print. If you guys are interested I will let you know if it the gear works when I have it in my hands.
