Cylindrical Positioning Speculation
Posted by ZachHoeken
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Cylindrical Positioning Speculation April 10, 2007 05:16PM |
Admin Registered: 16 years ago Posts: 1,487 |
A bit 'o speculation is fun right? Well, heres my two cents:
a cylindrical positioning system could easily be achieved by building on the darwin system. if we added a turntable module that could be attached to the Z build platform, we could then be able to make things with vertical radial symmetry.
basically, we would get really easy cylinders, hopefully better gears, possibly primitive plastic threads, belts?
also, its possible that we could also attach some sort of horizontal wire feed and have it do automated wire wrapping. the feed attachment could be pretty simple... just a spindle holder (which would be eminently reprappable...) the wrapping would be around the vertical axis, and the Z motion of the table would control where it wrapped as the turntable spun. being able to produce our own motors would be a huge future step.
some day. =)
a cylindrical positioning system could easily be achieved by building on the darwin system. if we added a turntable module that could be attached to the Z build platform, we could then be able to make things with vertical radial symmetry.
basically, we would get really easy cylinders, hopefully better gears, possibly primitive plastic threads, belts?
also, its possible that we could also attach some sort of horizontal wire feed and have it do automated wire wrapping. the feed attachment could be pretty simple... just a spindle holder (which would be eminently reprappable...) the wrapping would be around the vertical axis, and the Z motion of the table would control where it wrapped as the turntable spun. being able to produce our own motors would be a huge future step.
some day. =)
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Re: Cylindrical Positioning Speculation April 10, 2007 05:31PM |
Admin Registered: 16 years ago Posts: 1,915 |
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Re: Cylindrical Positioning Speculation April 10, 2007 05:49PM |
Admin Registered: 16 years ago Posts: 1,487 |
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Re: Cylindrical Positioning Speculation April 10, 2007 06:25PM |
Admin Registered: 16 years ago Posts: 7,871 |
You can express a circle in Cartesian coordinates to 0.1mm accuracy with Darwin. That is the same as the thickness of a piece of paper. With the current filament size and accuaracy of deposition are you really going to notice the difference going to a turntable?
My point was that when making a tube it would be better to lay down a coil rather than a stack or circles, but that does not fit in with slice and dice.
My point was that when making a tube it would be better to lay down a coil rather than a stack or circles, but that does not fit in with slice and dice.
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Re: Cylindrical Positioning Speculation April 10, 2007 06:29PM |
Registered: 16 years ago Posts: 304 |
hmm... am i right to believe that the device shwon there is able to print concentric cylindric shapes only? i mean, imagine a shape that has 2 or more cylindric off-axis features. that rig wouldn't be able to do it, right?
Only if we design a table that moves in the x,y plane and that carries a rotating disk, able to spin 360
Only if we design a table that moves in the x,y plane and that carries a rotating disk, able to spin 360
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Re: Cylindrical Positioning Speculation April 10, 2007 06:34PM |
Registered: 16 years ago Posts: 304 |
To nophead:
0.1 mm??? that's pretty good!!
Do we really need the turntable? i know that it would make cylindical symetry printing faster, but the precision seems to be OK allready, not?
Switching between cylindrical coordinates and cartesian coordinates could introduce error margins that would make awaye with the advantages of the change in coordinates system, don't you people think?
0.1 mm??? that's pretty good!!
Do we really need the turntable? i know that it would make cylindical symetry printing faster, but the precision seems to be OK allready, not?
Switching between cylindrical coordinates and cartesian coordinates could introduce error margins that would make awaye with the advantages of the change in coordinates system, don't you people think?
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Re: Cylindrical Positioning Speculation April 10, 2007 07:01PM |
Admin Registered: 16 years ago Posts: 1,487 |
i dont claim that it will work, but it would be an interesting thing to attempt. especially for things that circular styles work well for, it would be a very elegant solution... and the results may be better.
plus, if you want to do normal cartesian print either:
1. dont run the table and print to its build surface
or
2. remove the turntable entirely.
what is better? an XYZ system, or an XYZ + theta system. =)
hell, once you got the rest of the thing setup, you might as well go the whole way!
plus, if you want to do normal cartesian print either:
1. dont run the table and print to its build surface
or
2. remove the turntable entirely.
what is better? an XYZ system, or an XYZ + theta system. =)
hell, once you got the rest of the thing setup, you might as well go the whole way!
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Re: Cylindrical Positioning Speculation April 10, 2007 07:28PM |
Admin Registered: 16 years ago Posts: 7,871 |
Well I might be biased because my machine has a six micron step size but I think you are better off putting effort in to increase the accuracy of the XYZ system than adding a fourth redundant axis. That way all shapes benefit rather than just circles which are a special case of an ellipse which is special case of a curve.
It may be worth adding a curve drawing function to the firmware rather than expressing curves with a large number of straight lines, but I can't see the point of a turntable.
Currently the filament deposition system seems to be the limiting factor when it comes to accuracy and surface smoothness rather than the axes.
It may be worth adding a curve drawing function to the firmware rather than expressing curves with a large number of straight lines, but I can't see the point of a turntable.
Currently the filament deposition system seems to be the limiting factor when it comes to accuracy and surface smoothness rather than the axes.
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Re: Cylindrical Positioning Speculation April 10, 2007 11:09PM |
Admin Registered: 16 years ago Posts: 1,487 |
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Re: Cylindrical Positioning Speculation April 11, 2007 04:34AM |
Registered: 16 years ago Posts: 304 |
I think the cylindrical positioning system might have some usefull applications.
Nevertheless, i think the cartesian one with good precision has one advantage that the cylindrical can't beat:
For non circular shapes, given an arbitrary stepper precision, incremental error margins simply add (or substract) up in the cartesian system, whereas in the cylindrical, error margins are proportional to the radius distance between the turntable origin point and the point where you are printing and add up (or substract) proportionally. In other words, having a 0,1
Edited 1 time(s). Last edit at 04/11/2007 04:59AM by Fernando.
Nevertheless, i think the cartesian one with good precision has one advantage that the cylindrical can't beat:
For non circular shapes, given an arbitrary stepper precision, incremental error margins simply add (or substract) up in the cartesian system, whereas in the cylindrical, error margins are proportional to the radius distance between the turntable origin point and the point where you are printing and add up (or substract) proportionally. In other words, having a 0,1
Edited 1 time(s). Last edit at 04/11/2007 04:59AM by Fernando.
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Re: Cylindrical Positioning Speculation April 12, 2007 06:22PM |
Registered: 16 years ago Posts: 304 |
I've been thinking a lot about how to get the best of the two reference systems, to achieve the best precision and efficiency. I can see how having a cylindrical positioning system could become an advantage if you want massively print some types of shapes.
Like i mentioned above, error margins will propagate a lot more in each system when you are trying to do something which it's not good at:
Drawing a circle in a cartesian system involves a lot of steps, each step adding up a new error source.
Drawing straight lines in a cylindrical system adds radial errors that can become significant very fast.
What about building the rig in a way that the x,y positioning pane is contained inside a large toothed disc, with the axis of the disc, it's radius=0,alpha=0
Like i mentioned above, error margins will propagate a lot more in each system when you are trying to do something which it's not good at:
Drawing a circle in a cartesian system involves a lot of steps, each step adding up a new error source.
Drawing straight lines in a cylindrical system adds radial errors that can become significant very fast.
What about building the rig in a way that the x,y positioning pane is contained inside a large toothed disc, with the axis of the disc, it's radius=0,alpha=0
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Re: Cylindrical Positioning Speculation April 12, 2007 07:04PM |
Admin Registered: 16 years ago Posts: 7,871 |
Having a Cartesian system doesn't mean you can only draw straight lines. Its just a matter of the firmware controlling the motors. You should be able to draw a circle with all the points on its circumference accurate to within half the step size, i.e. 0.05mm. Since the filament is going to be at least 0.5mm I don't think you are really going to notice the X,Y quantisation. If you did it is probably easier to make the existing axes more accurate than it is to introduce a new one.
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Re: Cylindrical Positioning Speculation April 12, 2007 07:46PM |
Admin Registered: 16 years ago Posts: 1,487 |
true, but note the title of the thread... 'Speculation' its obvious that a top notch 3d positioning system is the biggest priority... but i'm waiting on parts and full of ideas =)
like fernando said, the value of an added axis would be able to adapt the technique to the problem at hand. of course you can program a cartesian axis to do circles. we're just saying that the circles produced might be of higher quality with cylindrical.
like fernando said, the value of an added axis would be able to adapt the technique to the problem at hand. of course you can program a cartesian axis to do circles. we're just saying that the circles produced might be of higher quality with cylindrical.
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Re: Cylindrical Positioning Speculation April 16, 2007 08:30AM |
I've been following your project for a while, and I do see advantages to the turntable (if all you're making is watertight vessels, do them like a coiled clay pot). All you have to coordinate is the rate of rotation and a x/z slope.
Another thing, since the extruder seems to be nailed down, the transport system (or extrusion bed) seems to be the next "evolution". When I first started reading about this system, I envisioned the same type of system used in the amusment park "claw machine". In theory, this would allow the system to be scaled up to room size. Then the transport head (extruder) could move from table to table, reading a sensor on each one to "zero" the X/Y/Z, and start extruding.
This would allow workers to remove the part, reset the table and move on to the next.
Another thing, since the extruder seems to be nailed down, the transport system (or extrusion bed) seems to be the next "evolution". When I first started reading about this system, I envisioned the same type of system used in the amusment park "claw machine". In theory, this would allow the system to be scaled up to room size. Then the transport head (extruder) could move from table to table, reading a sensor on each one to "zero" the X/Y/Z, and start extruding.
This would allow workers to remove the part, reset the table and move on to the next.
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Re: Cylindrical Positioning Speculation April 16, 2007 09:21AM |
Admin Registered: 16 years ago Posts: 1,487 |
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Re: Cylindrical Positioning Speculation April 16, 2007 02:49PM |
Well, since we're building watertight, then small boat parts could be done in a room-size reprap.
The opensource robot the size of a room allows parts larger than the standard reprap bed.
Also, the coils of material can be carried like a cartridge on the extrusion head assembly.
But the main flexibility would be loading up several diagrams, then moving from table to table.
The opensource robot the size of a room allows parts larger than the standard reprap bed.
Also, the coils of material can be carried like a cartridge on the extrusion head assembly.
But the main flexibility would be loading up several diagrams, then moving from table to table.
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Re: Cylindrical Positioning Speculation May 21, 2007 04:54PM |
Registered: 15 years ago Posts: 17 |
OK, I'm very new, and don't really know much about reprap's design yet. But..
If we're talking about adding turntables for flexibility (which I also don't really see a need for, if print/filament/movement resolution is good)... wouldn't it make more sense to have the print head able to rotate around the print "arm"'s position, wherever that is, rather than to have a single, fixed-center turntable?
If we're talking about adding turntables for flexibility (which I also don't really see a need for, if print/filament/movement resolution is good)... wouldn't it make more sense to have the print head able to rotate around the print "arm"'s position, wherever that is, rather than to have a single, fixed-center turntable?
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Re: Cylindrical Positioning Speculation May 21, 2007 09:09PM |
Registered: 15 years ago Posts: 246 |
Personally, I think it'd be just as easy to program the existing motors to draw a circle, or a hill, as it'd be to add another motor specifically to draw circles.
Decoding that a circle needs to be drawn would be the big thing, then the existing motors, and control boards, could be coached through drawing it using basic geometry.
What would be more useful, in my humble opinion, would be the ability to tilt the head relative to the working surface, so as to apply to the side.
It wouldn't do much good, at present, but might be a useful feature later. Say, when we want to reprap painted parts.
Decoding that a circle needs to be drawn would be the big thing, then the existing motors, and control boards, could be coached through drawing it using basic geometry.
What would be more useful, in my humble opinion, would be the ability to tilt the head relative to the working surface, so as to apply to the side.
It wouldn't do much good, at present, but might be a useful feature later. Say, when we want to reprap painted parts.
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Re: Cylindrical Positioning Speculation May 22, 2007 01:35PM |
Registered: 15 years ago Posts: 17 |
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Re: Cylindrical Positioning Speculation May 22, 2007 02:20PM |
Admin Registered: 16 years ago Posts: 1,915 |
"On the reprap microcontrollers understanding things like circles... why is it done this way? Why not just have X,Y,Z, and A (where A = extruder on/off), and put all the smarts in the software (which would be easier to enhance, etc.?"
I think that you will find both Zaphod, Tommelise, and, I believe, Darwin use XY and "A" (extruder on/off) with Z being handled as a separate command.
The point of having another motor to allow for radial translation of a printed object is that it would allow for finer detail when producing things radial objects such as gears and the like. You have to remember that while 0.1 positioning accuracy is pretty much what we do, the extruded thread of molten polymer is close to 0.8 mm in diameter. That makes printing features of ~ 1 mm a rather difficult undertaking.
I think that you will find both Zaphod, Tommelise, and, I believe, Darwin use XY and "A" (extruder on/off) with Z being handled as a separate command.
The point of having another motor to allow for radial translation of a printed object is that it would allow for finer detail when producing things radial objects such as gears and the like. You have to remember that while 0.1 positioning accuracy is pretty much what we do, the extruded thread of molten polymer is close to 0.8 mm in diameter. That makes printing features of ~ 1 mm a rather difficult undertaking.
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Re: Cylindrical Positioning Speculation May 22, 2007 02:50PM |
Registered: 15 years ago Posts: 17 |
Hi Forrest,
"You have to remember that while 0.1 positioning accuracy is pretty much what we do, the extruded thread of molten polymer is close to 0.8 mm in diameter."
Ahh, I thought the thread was 0.5 or smaller now. Is that a limitation of the material, or process, or just where reprap is at the moment? I know there was some talk of 0.5mm nozzles, and even down to 0.1mm nozzles, and talk of different materials, etc.
"You have to remember that while 0.1 positioning accuracy is pretty much what we do, the extruded thread of molten polymer is close to 0.8 mm in diameter."
Ahh, I thought the thread was 0.5 or smaller now. Is that a limitation of the material, or process, or just where reprap is at the moment? I know there was some talk of 0.5mm nozzles, and even down to 0.1mm nozzles, and talk of different materials, etc.
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Re: Cylindrical Positioning Speculation May 22, 2007 04:02PM |
Admin Registered: 16 years ago Posts: 1,487 |
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Re: Cylindrical Positioning Speculation May 22, 2007 04:48PM |
Registered: 15 years ago Posts: 17 |
Is that with Polymorph, or the starch-based stuff? (heh, I'm still drumming the terminology into my head; sorry 
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Re: Cylindrical Positioning Speculation May 22, 2007 10:01PM |
Admin Registered: 16 years ago Posts: 1,487 |
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Re: Cylindrical Positioning Speculation May 23, 2007 12:52AM |
Admin Registered: 16 years ago Posts: 1,915 |
Have you got the polymer pump on your Mk II to apply sufficient pressure to extrude these polymers at useful rates yet? I'm pumping HDPE with a 0.5 orifice that gives me a 0.8 mm thread and have found that that is right at the edge of the torque that the gearmotor can deliver for reasonable extrusion rates. Mind, I'm using long pulse pseudostepping, too, which get you more applied torque at low extrusion rates than the PWM that the Mk II uses.
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