Curved rack gears

Question

Curved rack gears

alikureishy opened this issue 3 years ago · comments

Ali Safdar Kureishy commented 3 years ago

In the gears API, do you envision being able to make curved racks (with teeth along the side or along the curve)?

Teeth along the side:

Teeth along the curve:

My use case for having rack teeth along the side (the first image) would be for a motor shaft (whose axis of rotation was the X axis) to be able to drive/rotate a revolute joint along the Y or Z axes.

Ali Safdar Kureishy · Answer 1 · Wed Sep 29 2021 10:55:17 GMT+0800 (China Standard Time)

Will try that using a beveled gear in your openscad tool and update this thread if that works.

Ali Safdar Kureishy · Answer 2 · Wed Sep 29 2021 14:10:10 GMT+0800 (China Standard Time)

Looks like a bevel gear system gets me closer to my goal, with one being attached to the motor shaft, and the other, illustrated below, driving the rotating part. But, aside from being secured to a shaft, I also need to be able to screw that second gear onto the subsequent link's surface, so that that section rotates along with the bevel gear (i.e, around the same axis/shaft). So, I'd like to include flange-like screw holes (illustrated in red color below), that I could use to attach the gear firmly to the subsequent section:

I generated the image above for the second beveled gear using the tool you have on thingiverse, but since it is STL I can't import it into cadquery for adding the holes. One option would be to print and then drill out the holes for the time being. But, if there is another (more straightforward) option you know of, I'd love to get your thoughts.

Sorry if this seems like a silly or obvious question. I just started reading up about gears a week ago and am still a little lost. I'm trying to build a robot arm with 3DOF. I've already implemented one revolute joint (with axis along the motor shaft), but the other two joints (for pitch/yaw motion) are what I'm stuck on. I understand there are multiple ways of achieving rotational motion that is perpendicular to the axis of the motor shaft -- using beveled gears, or worm gears, but in either case, I need some way of attaching the final gear firmly onto the next body part (link) that's being rotated. One option would be to secure both the gear and the next part together indirectly by securing each to the common shaft using their respective setscrews, but it feels like much smpler/better design to attach the gear to the part directly first (like using a flanged coupler), and then have that combined apparatus rotate freely on the shaft. Hope I explained that well...

Roger Maitland · Answer 3 · Thu Sep 30 2021 22:58:22 GMT+0800 (China Standard Time)

Curved rack gears could be miter gears or spiral gears with the center section removed from the larger gear. Teeth along the curve gear pair could be spur gears with the large gear center removed (i.e. a very large bore dimension).

…

On Tue, Sep 28, 2021 at 10:45 PM Ali Safdar Kureishy < ***@***.***> wrote: In the gears API, do you envision being able to make curved racks (with teeth along the side as well as along the curve)? Teeth along the side: [image: curved_rack] <https://user-images.githubusercontent.com/1193219/135193757-0a03b0c7-decf-42d7-a928-93ca4a0f12c4.png> Teeth along the curve: [image: curved_rack] <https://user-images.githubusercontent.com/1193219/135193841-7f715d7a-fff1-4a77-9334-8f15be2b5c2e.jpeg> My use case would be for a motor shaft (whose axis of rotation was the X axis) to be able to drive/rotate a revolute joint along the Y or Z axes. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#4>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AUNL25RKGIIEONOHYH6ZCF3UEJ4TFANCNFSM5E6ZEVNA> .

Roger Maitland · Answer 4 · Thu Sep 30 2021 23:47:10 GMT+0800 (China Standard Time)

I designed the gear_warehouse (which inspired cq_warehouse) to be easy for OpenSCAD developers to create the base shape and then manipulate further with simple OpenSCAD facilities. Here is a example of how to add holes to a gear (make sure gearWarehouseV1.0.scad is in the same directory as your design): use <gearWarehouseV1.0.scad> mm = 1; difference() { involuteGear(gearType="spiral",gearModule=3,totalNumTeeth=20,faceWidth=15*mm,pitchAngle=55,spiralTwist=30,bottomHub=false,hubDiameter=20*mm,setscrew="3",keyway="3x3"); for (angle=[45:90:360]) rotate([0,0,angle]) translate([13*mm,0,0]) cylinder(h=50*mm,r=2*mm,center=true,$fn=32); } which results in this: [image: image.png] (It has been a long time since I've done anything with OpenSCAD and I've realized I'm very rusty!) The more securely you can attach your gears the better. You could do the same thing by importing a STEP model (from McMaster) and adding holes in cadquery. By the way, there are some excellent YouTube channels on robot design. I've seen some good ones on joint design, motor placement and selection, etc. Cheers, Roger

…

On Wed, Sep 29, 2021 at 2:10 AM Ali Safdar Kureishy < ***@***.***> wrote: Looks like a bevel gear gets me closer to my goal, but aside from being secured to a shaft, I also need to be able to screw the gear onto another flat surface (i.e, the subsequent link's surface), so that that section rotates along with the bevel gear (i.e, around the same axis/shaft). So, I'd like to include screw holes (illustrated in red color below), that I could use to attach the gear firmly to the subsequent section: [image: marked] <https://user-images.githubusercontent.com/1193219/135210509-7c657ee1-b6bd-4e9f-bd05-48e6dc905100.png> I generated the image above using the tool you have on thingiverse, but since it is STL I can't import it into cadquery for adding the holes. One option would be to print and then drill out the holes for the time being. But, if there is another (more straightforward) option you know of, I'd love to get your thoughts. Sorry if this seems like a silly or obvious question. I just started reading up about gears a week ago and am still a little lost. I'm trying to build a robot arm with 3DOF. I've already implemented one revolute joint (with axis along the motor shaft), but the other two axes (for pitch and yaw) are what I'm stuck on. I understand there are multiple ways of achieving rotational motion that is perpendicular to the axis of the motor shaft -- using beveled gears, or worm gears, but in either case, I need some way of attaching the final gear firmly onto the body (link) that's being rotated. One option would be to secure both the gear and the next section together indirectly by securing each to the common shaft using their respective setscrews, but it feels like better design to attach the gear to the part directly first, and then attach that apparatus onto the shaft in just one place. Hope I explained that well... — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AUNL25RNA6QTUJONKRSY4PTUEKUU3ANCNFSM5E6ZEVNA> .

Ali Safdar Kureishy · Answer 5 · Sat Oct 02 2021 07:24:41 GMT+0800 (China Standard Time)

Thanks a million, Roger!
Your code suggestion above worked perfectly. I need to start learning OpenSCAD, to round out my CAD skills ;).
As for step files from McMaster ... thx for the tip... I've added that to my todo list.
Many thanks again for the help.

[It'd be awesome to stay connected via linkedin, if that's something you'd be open to. If yes, please feel free to add me].

Roger Maitland · Answer 6 · Sun Oct 10 2021 04:34:37 GMT+0800 (China Standard Time)

Ali, I discovered that there already is a cadquery gear library here: https://github.com/meadiode/cq_gears Although I haven't used it yet, it looks like most of what I was going to create so I expect to just use cq_gears instead of creating my own. Cheers, Roger

…

On Fri, Oct 1, 2021 at 7:24 PM Ali Safdar Kureishy ***@***.***> wrote: Closed #4 <#4>. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AUNL25V5HQNKMESDAPWENYDUEY7MHANCNFSM5E6ZEVNA> .

Ali Safdar Kureishy · Answer 7 · Thu Oct 14 2021 09:06:39 GMT+0800 (China Standard Time)

Thanks for the note, Roger! I will check it out this weekend. From the looks of it, it seems pretty straightforward. Makes sense to use that instead of rewriting it. Thanks again for the update. Cheers, Ali

…

On Sat, Oct 9, 2021, 1:34 PM gumyr ***@***.***> wrote: Ali, I discovered that there already is a cadquery gear library here: https://github.com/meadiode/cq_gears Although I haven't used it yet, it looks like most of what I was going to create so I expect to just use cq_gears instead of creating my own. Cheers, Roger On Fri, Oct 1, 2021 at 7:24 PM Ali Safdar Kureishy ***@***.***> wrote: > Closed #4 <#4>. > > — > You are receiving this because you commented. > Reply to this email directly, view it on GitHub > <#4 (comment)>, or > unsubscribe > < https://github.com/notifications/unsubscribe-auth/AUNL25V5HQNKMESDAPWENYDUEY7MHANCNFSM5E6ZEVNA > > . > — You are receiving this because you modified the open/close state. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAJDKAZYWDIQL2STU7HM5FLUGCROPANCNFSM5E6ZEVNA> .