Riding the Rhino
Aug. 4th, 2014 09:55 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
calzephyrOne of the deceptive things about 3D printing and laser cutting is that they are seemingly magical - watch this spool of plastic turn into a piece of cruft line by line, watch this metal box light up because lasers. The viewer only sees the product being made, not the behind the scenes part of wrestling with software and models. While you can sit down with your 3D printer or laser cutter and start making stuff from free online models, most likely you will start with a sketch, then plot it all in a program like Rhino (or Sketch Up, Blender, Inkscape or Illustrator). Some of the software that comes with machines are downright clunky! It's definitely this learning curve that I think will hold up 3D printing for most folks.
The very first thing to start out with is a sketch. For my Klutz wheel, I simply traced it and drew in the shapes that I wanted to have on the wheel. I carefully counted the number of teeth (34). Then I got out a ruler and found a second ruler because I didn't quite trust the first metal one. My measuring caliper is kicking around here somewhere, and that would have been idea, but a transparent plastic ruler worked out best. I noted the width of the wheel (100 mm), the width of the gears at the narrowest part (1.5 mm, later determined by Rhino to be 1.4 mm) and the distance between the midpoint of two gears (8 mm). I almost forgot to measure the thicknews (2 mm). Can I say, at this point, how thankful I am for the metric system!
By the way, afterwards I found out that there are all these names for the parts of a gear and I realize that in this entry, I'm not using any of them :-D Also, when I talk about curves, a curve is any line in Rhino, not necessarily one that is curved.
My first idea at creating the wheel was to simply create a boundary circle with a width of 100 mm, then another 8mm wide. I would create all 33 gaps with the circle by using polar array, which is a fancy way of saying rotate X number of objects around a centre point. Using the boundary circle as the trim guide, I would have the dip between the teeth. Then I would use blend curves to create the gear tooth, polar array that, and, as Cam liked to say, BOOM! DONE! It was a fine plan, except...I couldn't blend a curve between the two half circles. Just not happening. When I look at a screencap of my idea, it seems like a reasonable way of solving the problem:
So I gamely tried to create half a curve with half a tooth on either side. I would run another polar array and the wheel would be instantly created. Haha! No. I was left with teeny gaps between each copy that couldn't be blended into one continuous curve. Fine.
Now, when educators talk about STEM crises, I don't blame them. If I was only better at math, Rhino would be so much easier. But I'm not. It's been 19 years since I graduated from high school and almost failed Grade 12 math. My attempts at polar array was not without happy accidents though. I have no idea how this happened:
Finally, after realizing that all the scaling in the world was not going to get me my wheel, I remembered another handy Rhino command, Flow. All I needed to do was create the shape I wanted to flow around (a circle), the shape I wanted to end up with (a gear) and a baseline that was the length of the shape.
I made two boundary circles, one 100 mm and one 96 mm. The distance between the two would house the gear teeth. On another layer, I started building the teeth in one straight line that would equal the circumference of the inner circle. To get the gear shape, I made two 8 mm circles side by side, with a 1.5 mm circle between them. A little trimming later, I had my gear shape. I copied it across until I had a shape that was 4 mm high.
I joined the gear curves together - and - and made a seperate baseline, which was just a straight line. Here is a part of the gear teeth and the baseline:
The nice thing about Rhino is that it often patiently waits for you to enter a command, especially when you angrily click the mouse and wonder why nothing's happening ;-) In the case of Flow, first you select the shape to be flowed. Then you select the baseline near one end. Then you select the target curve - and see what happens.
It was tricky. I don't remember exactly what kind of tricky it was - but it took some experimenting to get the height of the gears right. The baseline had to be closer to the bottom of the gear shape, I think. When I had a completed gear, I exported it as an Illustrator file which I imported into my Pazzles and had a sip of tea while it cut the gear. There was something a little funny about the paper prototype though. It didn't quite match the plastic wheel. A little more boring futzing around and the size matched up. Taking the tip of the gear tooth down to 1.4 mm from 1.5 made all the difference. However...it took two more tries to get a paper prototype to match the wheel. Sometimes when cutting materials, you'll lose a tiny bit of material each time. I scaled the final exported Illustrator drawing up to 101 mm and that seemed to work best for the third paper prototype. It could be a quirk of the Pazzles software too.
Now to see if the paper prototype would work! The largest shape on one of the wheels is a pointy circle, so I traced a few of those and used small paper punches to make some shapes. I took some Zots, an aggressive paper crafting adhesive, and stuck the paper protoype to the plastic wheel and drew away. Conclusion - yes! This can work.
From there, it was just a matter of building simple shapes to put on the wheel. Now I just sit and wait and hope for the best when my wheel arrives in the mail.
The very first thing to start out with is a sketch. For my Klutz wheel, I simply traced it and drew in the shapes that I wanted to have on the wheel. I carefully counted the number of teeth (34). Then I got out a ruler and found a second ruler because I didn't quite trust the first metal one. My measuring caliper is kicking around here somewhere, and that would have been idea, but a transparent plastic ruler worked out best. I noted the width of the wheel (100 mm), the width of the gears at the narrowest part (1.5 mm, later determined by Rhino to be 1.4 mm) and the distance between the midpoint of two gears (8 mm). I almost forgot to measure the thicknews (2 mm). Can I say, at this point, how thankful I am for the metric system!
By the way, afterwards I found out that there are all these names for the parts of a gear and I realize that in this entry, I'm not using any of them :-D Also, when I talk about curves, a curve is any line in Rhino, not necessarily one that is curved.
My first idea at creating the wheel was to simply create a boundary circle with a width of 100 mm, then another 8mm wide. I would create all 33 gaps with the circle by using polar array, which is a fancy way of saying rotate X number of objects around a centre point. Using the boundary circle as the trim guide, I would have the dip between the teeth. Then I would use blend curves to create the gear tooth, polar array that, and, as Cam liked to say, BOOM! DONE! It was a fine plan, except...I couldn't blend a curve between the two half circles. Just not happening. When I look at a screencap of my idea, it seems like a reasonable way of solving the problem:
So I gamely tried to create half a curve with half a tooth on either side. I would run another polar array and the wheel would be instantly created. Haha! No. I was left with teeny gaps between each copy that couldn't be blended into one continuous curve. Fine.
Now, when educators talk about STEM crises, I don't blame them. If I was only better at math, Rhino would be so much easier. But I'm not. It's been 19 years since I graduated from high school and almost failed Grade 12 math. My attempts at polar array was not without happy accidents though. I have no idea how this happened:
Finally, after realizing that all the scaling in the world was not going to get me my wheel, I remembered another handy Rhino command, Flow. All I needed to do was create the shape I wanted to flow around (a circle), the shape I wanted to end up with (a gear) and a baseline that was the length of the shape.
I made two boundary circles, one 100 mm and one 96 mm. The distance between the two would house the gear teeth. On another layer, I started building the teeth in one straight line that would equal the circumference of the inner circle. To get the gear shape, I made two 8 mm circles side by side, with a 1.5 mm circle between them. A little trimming later, I had my gear shape. I copied it across until I had a shape that was 4 mm high.
I joined the gear curves together - and - and made a seperate baseline, which was just a straight line. Here is a part of the gear teeth and the baseline:
The nice thing about Rhino is that it often patiently waits for you to enter a command, especially when you angrily click the mouse and wonder why nothing's happening ;-) In the case of Flow, first you select the shape to be flowed. Then you select the baseline near one end. Then you select the target curve - and see what happens.
It was tricky. I don't remember exactly what kind of tricky it was - but it took some experimenting to get the height of the gears right. The baseline had to be closer to the bottom of the gear shape, I think. When I had a completed gear, I exported it as an Illustrator file which I imported into my Pazzles and had a sip of tea while it cut the gear. There was something a little funny about the paper prototype though. It didn't quite match the plastic wheel. A little more boring futzing around and the size matched up. Taking the tip of the gear tooth down to 1.4 mm from 1.5 made all the difference. However...it took two more tries to get a paper prototype to match the wheel. Sometimes when cutting materials, you'll lose a tiny bit of material each time. I scaled the final exported Illustrator drawing up to 101 mm and that seemed to work best for the third paper prototype. It could be a quirk of the Pazzles software too.
Now to see if the paper prototype would work! The largest shape on one of the wheels is a pointy circle, so I traced a few of those and used small paper punches to make some shapes. I took some Zots, an aggressive paper crafting adhesive, and stuck the paper protoype to the plastic wheel and drew away. Conclusion - yes! This can work.
From there, it was just a matter of building simple shapes to put on the wheel. Now I just sit and wait and hope for the best when my wheel arrives in the mail.
