| Rack and Pinion Linear Actuator [message #31107] Mon, 18 July 2011 22:01 UTC |
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I'm really happy with my rack and pinion linear actuator.
You can see a video of it in action here-
http://www.youtube.com/watch?v=KRZ9TLhD0i4
You can see how I packaged the pieces here-
http://www.shapeways.com/model/293549/randp.html?gid=ug (I'm having trouble uploading other pictures for some reason- it claims they aren't jpegs. Any suggestions on that?)
I was worried at first because the racks wouldn't fit in the holes at first but after some cleaning and cramming, the excess powder came out and everything fit like a glove. I designed it around a cheap Chinese stepper motor I bought on ebay and it fit just as designed.
I hope you like it and feel free to ask any questions.
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| Re: Rack and Pinion Linear Actuator [message #31131 is a reply to message #31107 ] Tue, 19 July 2011 12:55 UTC |
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Hey this is great, Very nicely done.
Leigh
http://www.shapeways.com/shops/most
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| Re: Rack and Pinion Linear Actuator [message #31173 is a reply to message #31107 ] Tue, 19 July 2011 23:09 UTC |
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Thanks for your comments.
Also thank you for the tip about the size of the photos- I shrunk them a bit and they uploaded fine. Now there are some still photos on the design page.
As to what it's for...linear actuators can be used for tons of things- they convert the precise rotational movement from a stepper motor to precise linear motion. One thing I'm going to try soon is to use three of them together to make a tripod plotter/robot/pick-and-place machine. I have other ideas and I'll post videos if they ever come to fruition.
Thanks again.
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| Re: Rack and Pinion Linear Actuator [message #32973 is a reply to message #31173 ] Fri, 19 August 2011 18:52 UTC |
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Good stuff, I've been looking around and not many people on SW are making functional components, It's seems mainly(understandably) art and asthetic parts. I'm interested in putting RP to "work" like this and it's encouraging to see efforts like yours.
Thanks for sharing that.
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| Re: Rack and Pinion Linear Actuator [message #34242 is a reply to message #31107 ] Wed, 14 September 2011 16:51 UTC |
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Can the gear system be designed to accomplish exact 0.01mm steps/movement?
Also, did you try it with a load? - how did WSF work out for you with a load? (thou i see its thick , still it tends to bend no?)
http://www.3Dizingof.com
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| Re: Rack and Pinion Linear Actuator [message #34246 is a reply to message #34242 ] Wed, 14 September 2011 17:16 UTC |
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Exact 0.01mm steps? That's asking alot- 0.01mm is pretty fine. As it is now, no. I designed in a little backlash so it would fit together well. I think the cheap motors have some backlash to them too. They are steppers but are geared as well. So between the motors and the design, this isn't terribly accurate but with some tweaking on the gears and a different motor I think you could get decent accuracy. If you had a motor with 200 steps per rotation and did eighth steps so you had 1600 steps per rotation and with a small gear (2cm diam) with a really tight fit maybe you could get 0.04mm but I'm not sure this would be the solution for that.
I was thinking you could attach a variable resistor to it to figure out it's position that way like a servo.
As far as strength goes- again I haven't done tests on it. The motor can't tolerate a ton of stress but WSF is pretty strong. For like, hobby robots or something I think this would be plenty strong. But it is plastic after all. Would you want a plastic rack and pinion in your application?
Do you have an application in mind? I can try to design something for you.
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| Re: Rack and Pinion Linear Actuator [message #34249 is a reply to message #31107 ] Wed, 14 September 2011 17:38 UTC |
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Well as crazy as it may sound i want to explore a mini Z axis-only 3d printer with UV curable resin.
I have a different approach in mind - so far could not find ready-made mini linear actuators/sliders with a stepper that can move a plate on the Z axis with such precision of 0.01mm
Saw few youtube of some guys staring this kind of project , here is one:
http://projectguru.org/3dprinter-articles/3dprinter-blog
http://www.3Dizingof.com
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| Re: Rack and Pinion Linear Actuator [message #34251 is a reply to message #34249 ] Wed, 14 September 2011 17:51 UTC |
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You can get this accuracy by having a stepper turn a threaded rod. 32 threads per inch = 1/32 inches per rotation. If you have a stepper that has 200 steps per rotation,a nut on the rod moves 1/(32*200) inches per step which is 0.004mm per step if I'm not mistaken. Having a stepper turn a threaded rod to get linear motion is how many cnc type machines work.
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| Re: Rack and Pinion Linear Actuator [message #34252 is a reply to message #34251 ] Wed, 14 September 2011 17:57 UTC |
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Here's a video of a cnc machine working with threaded rods that shows what I tried to explain above. (I just picked the video at random- thanks to whoever posted it.)
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| Re: Rack and Pinion Linear Actuator [message #34253 is a reply to message #31107 ] Wed, 14 September 2011 17:59 UTC |
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Thanks , any idea where i can buy those parts?
http://www.3Dizingof.com
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| Re: Rack and Pinion Linear Actuator [message #34254 is a reply to message #34253 ] Wed, 14 September 2011 18:08 UTC |
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McMaster Carr has lots of parts like this. I would suggest you look at some CNC machine plans online. You only really need the z-axis but you can get an idea of what you need to do. You need a track that your tray slides on and a threaded rod and correponding nut (attached to the moving part) to drive it.
This is doable and would be a great project.
It doesn't seem like it would have to withstand too much stress. You could probably design most of it in WSF if you are good at CAD design and just mount the motors, nut, and threaded rod (and all the other stuff that can't be 3d printed.)
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| Re: Rack and Pinion Linear Actuator [message #34274 is a reply to message #34255 ] Thu, 15 September 2011 10:18 UTC |
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By the way, Instructables.com has a whole section devoted to CNC with tons of plans and designs for free.
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| Re: Rack and Pinion Linear Actuator [message #34281 is a reply to message #34277 ] Thu, 15 September 2011 16:33 UTC |
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LEGO NXT with some custom WSF gears would work for that 
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| Re: Rack and Pinion Linear Actuator [message #34285 is a reply to message #34284 ] Thu, 15 September 2011 17:27 UTC |
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I knew it was only a matter of time before this know-it-all chimed in.
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| Re: Rack and Pinion Linear Actuator [message #34286 is a reply to message #34285 ] Thu, 15 September 2011 17:31 UTC |
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| CristobalGordo wrote on Thu, 15 September 2011 17:27 |
I knew it was only a matter of time before this know-it-all chimed in.
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Is that underhand comment directed at me?
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| Re: Rack and Pinion Linear Actuator [message #34287 is a reply to message #34277 ] Thu, 15 September 2011 17:33 UTC |
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Driving two stepper motors with an arduino is definitely doable but is kind of involved- too much to explain here. I'd look at some examples on the arduino forums to start. Different motors require different setups etc but there are tons of tutorials online.
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| Re: Rack and Pinion Linear Actuator [message #34289 is a reply to message #31107 ] Thu, 15 September 2011 17:46 UTC |
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Let's keep this productive discussion civil please.
The Mad Moder
michael@shapeways.com
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| Re: Rack and Pinion Linear Actuator [message #34290 is a reply to message #34289 ] Thu, 15 September 2011 17:50 UTC |
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| Youknowwho4eva wrote on Thu, 15 September 2011 17:46 |
Let's keep this productive discussion civil please.
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fine with me 
more brain food to do with LEGO gearing - a bit off topic, but demonstrates what can be done (by me)
http://www.youtube.com/watch?v=ShuKDU_FG-4
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| Re: Rack and Pinion Linear Actuator [message #34294 is a reply to message #34293 ] Thu, 15 September 2011 18:31 UTC |
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No worries Dizingof, though LEGO is an easy and cheap way of bashing out prototypes expecially with the three stepper motors in the NXT kit... best I've got with a native LEGO double worm gear setup is 0.38mm steps per 360 degree revolution, but the gear slop is a bit bad. (that setup was built into a diamagnetic levitation rig capable of floating 10mm cube magnets)
Have fun with your printer steppers and if they don't work out, slap a set of blades on them and turn them into wind generators.
[Updated on: Thu, 15 September 2011 18:31 UTC]
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| Re: Rack and Pinion Linear Actuator [message #34295 is a reply to message #34293 ] Thu, 15 September 2011 18:37 UTC |
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I would think a threaded rod would be better for you than a belt driven system. I think (not certain) that belts are used to speed things up but in your case I don't think speed will be an issue- you need to move 0.01mm then, pause, then move 0.01mm then pause etc correct? Check out some cnc designs on instructables- you only really care about the z-axis, they are usually pretty in depth, and some may even go into the software to drive the motors.
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| Re: Rack and Pinion Linear Actuator [message #34590 is a reply to message #31107 ] Mon, 19 September 2011 16:06 UTC |
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I think this is the stuff i was looking for - parts from a CD-ROM..
http://www.youtube.com/watch?v=EqNyUIJKM5g&feature=relat ed
- a VERY precise threaded rod , a stepper motor (steps must be extremely precise - to move the laser eye on a CD.. in micro increments) + 2 small shaft rods easily unscrewed and screwed back to any other design
http://www.3Dizingof.com
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| Re: Rack and Pinion Linear Actuator [message #34592 is a reply to message #34590 ] Mon, 19 September 2011 16:21 UTC |
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I used two of those to make a little laser cutter (it cut black paper only) which you can see here
(Ok so now I'm the know-it-all guilty as charged)
Cons for you- small range of motion maybe too small for you,
maybe too weak to lift what you need to lift but maybe not
Pros- easily available, maybe good place to start, probably lots of good instructions online to teach you how to use it. I used EasyDriver stepper drivers driven by an arduino. Check out Sparkfun for those. There are probably other ways to do it including using their built in drivers but I don't know about that.
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| Re: Rack and Pinion Linear Actuator [message #34594 is a reply to message #31107 ] Mon, 19 September 2011 16:30 UTC |
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Nice.... well if it can pull your laser with all its weight and wires i guess it can easily pull thin layers of polymer.
I am looking to design a small unit, so it should be a good start.
(i can see you know your stuff! http://www.flickr.com/photos/87592791@N00/401251067/in/photo stream/ , how many cnc versions you've made so far?)
[Updated on: Mon, 19 September 2011 16:42 UTC]
http://www.3Dizingof.com
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| Re: Rack and Pinion Linear Actuator [message #34608 is a reply to message #34594 ] Mon, 19 September 2011 19:50 UTC |
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I've made a few cnc type machines over the years. I don't know about "know my stuff" but I can say that I'm proof that you can start from next to zero electronics-wise and learn what you need to know just from tutorials/videos/forum posts. If I can do it you can do it. If arduino is your thing search "driving stepper motors with arduino" or something along those lines and you'll find tutorials that are better than I could explain.
In looking at your (very cool) mathematical sculptures, it seems like most of them would be well suited to this UV cured plastic technique- being connected. You can't have layers with "islands" in that technique but seems like your wouldn't (if I'm understanding the technique and your sculptures correctly.)
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