Curved paths May 27, 2015 07:27PM |
Registered: 9 years ago Posts: 978 |
Re: Curved paths May 27, 2015 07:39PM |
Registered: 10 years ago Posts: 14,685 |
Re: Curved paths May 27, 2015 11:04PM |
Registered: 9 years ago Posts: 978 |
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dc42
What alternatives to STL representation do you have in mind?
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Instead of using Bresenham, which sends stepper motor pulses at irregular intervals, why not calculate the times when the next steps are due based on distance travelled along the curve? I do a similar thing to generate the motor movements on a delta printer without using segmentation, in RepRapFirmware.
X Y slope Pulse X Pulse Y 50 50 1.98 x y 51 51 1.94 y 51 52 1.94 x y 52 53 1.9 y 52 54 1.9 x y 53 55 1.86 y 53 56 1.86 x y 54 57 1.82 y 54 58 1.82 x y 55 59 1.78 y 55 60 1.78 x y 56 61 1.74 y 56 62 1.74 x y 57 63 1.7 x y 58 64 1.66 y 58 65 1.66 x y 59 66 1.62 y 59 67 1.62 x y 60 68 1.58 x y 61 69 1.54 y 61 70 1.54 x y 62 71 1.5 x y 63 72 1.46 y 63 73 1.46 x y 64 74 1.42 x y 65 75 1.38 y 65 76 1.38 x y 66 77 1.34 x y 67 78 1.3 x y 68 79 1.26 y 68 80 1.26 x y 69 81 1.22 x y 70 82 1.18 x y 71 83 1.14 x y 72 84 1.1 x y 73 85 1.06 x y 74 86 1.02 x y 75 87 0.98 x y 76 88 0.94 x y 77 89 0.9 x y 78 90 0.86 x y 79 91 0.82 x y 80 92 0.78 x y 81 93 0.74 x y 82 94 0.7 x y 83 95 0.66 x 84 95 0.62 x y 85 96 0.58 x y 86 97 0.54 x 87 97 0.5 x y 88 98 0.46 x 89 98 0.42 x 90 98 0.38 x y 91 99 0.34 x 92 99 0.3 x y 93 100 0.26 x 94 100 0.22 x 95 100 0.18 x 96 100 0.14 x 97 100 0.1 x 98 100 0.06 x 99 100 0.02 x
Re: Curved paths May 28, 2015 03:40AM |
Registered: 10 years ago Posts: 14,685 |
Re: Curved paths May 28, 2015 05:55AM |
Registered: 9 years ago Posts: 977 |
Re: Curved paths May 28, 2015 06:18AM |
Registered: 10 years ago Posts: 14,685 |
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AndrewBCN
In practical terms, what exactly would anyone gain with moving away from STL and any of the standard firmwares? I can print curves just fine on my Prusa i3, including very small radius circles.
Re: Curved paths May 28, 2015 06:48AM |
Registered: 9 years ago Posts: 977 |
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dc42
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AndrewBCN
In practical terms, what exactly would anyone gain with moving away from STL and any of the standard firmwares? I can print curves just fine on my Prusa i3, including very small radius circles.
For a start, the slicing programs would have a better chance of getting the inner diameter of circular holes right.
Re: Curved paths May 28, 2015 08:08AM |
Registered: 10 years ago Posts: 14,685 |
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AndrewBCN
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dc42
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AndrewBCN
In practical terms, what exactly would anyone gain with moving away from STL and any of the standard firmwares? I can print curves just fine on my Prusa i3, including very small radius circles.
For a start, the slicing programs would have a better chance of getting the inner diameter of circular holes right.
@ dc42
Have you ever printed the very same g-code on two different printers and noticed that the inner diameter of circular holes was not the same? I have. Even changing the filament on the very same printer will sometimes result in variations in the inner diameter of circular holes.
"Getting the inner diameter of circular holes right" to use your expression, is more a matter of empirical experimentation and calibration on a particular printer, than the use of pure curved paths vs. approximating straight segments.
Nothing to be gained here by moving away from STL, sorry.
Re: Curved paths May 28, 2015 08:58AM |
Registered: 9 years ago Posts: 977 |
Re: Curved paths May 28, 2015 01:51PM |
Registered: 10 years ago Posts: 14,685 |
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AndrewBCN
There is no such thing as a "true circle" or a "true cylinder" or a "true sphere" in the digital world, we are always dealing with approximations, as you are fully aware of.
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AndrewBCN
Again, in practical terms there is strictly nothing to be gained, and much to be lost, by moving away from STL and standard firmware that approximates curves using short straight segments.
Re: Curved paths May 28, 2015 03:52PM |
Registered: 9 years ago Posts: 978 |
Re: Curved paths May 28, 2015 04:21PM |
Registered: 10 years ago Posts: 119 |
Re: Curved paths May 28, 2015 05:50PM |
Registered: 9 years ago Posts: 978 |
Re: Curved paths May 28, 2015 05:51PM |
Registered: 9 years ago Posts: 977 |
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frankvdh
I see some direct benefits in moving to curves:
1. Better quality of output due to smaller approximations, more accurate placement of the head, no jerking acceleration between segments, more consistent thickness of deposited filament due to more consistent speed of the nozzle.
2. Probably faster printing since higher speeds will be able to be maintained.
3. Maybe also less vibration, consequently better quality and machine life.
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frankvdh
There's also the indirect benefit of better models being shared. This is particularly true of shared files on (e.g.) Thingverse, where you're limited to the quality of the STL generated by the originator. (I know this doesn't apply to OpenSCAD source files, but the vast majority of shared files are currently STL).
Whether these benefits are practical depends on how much the end user values quality and print speed and durability
Bear in mind that this is a software change, so it's a one-off development effort that could be retrofitted to all? Cartesian printers.
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frankvdh
3D printing is in a development/growth phase which I think is approaching an explosion of use... each improvement that moves it forward will make it a more widely useable, more widely used technology and closer to that consumer-use threshold.
Whilst there is a downside of potentially wasted time, that's the nature of research and development. Worst case, this is consigned to the scrapheap of 3D TVs and Betamax and bubble memory and everyone carries on with the inferior technology.
Re: Curved paths May 28, 2015 06:13PM |
Registered: 9 years ago Posts: 978 |
Thank you for telling me what I am trying to do.Your ESP ability is exceeded only by your rudeness.Quote
AndrewBCN
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frankvdh
I see some direct benefits in moving to curves:
1. Better quality of output due to smaller approximations, more accurate placement of the head, no jerking acceleration between segments, more consistent thickness of deposited filament due to more consistent speed of the nozzle.
2. Probably faster printing since higher speeds will be able to be maintained.
3. Maybe also less vibration, consequently better quality and machine life.
LOL!
You are trying to make this into a panacea for all printing woes, which is quite absurd, since there is no direct causal link between the file format being able to convey circular paths, and any of the things you have listed above!
Re: Curved paths May 28, 2015 06:24PM |
Registered: 9 years ago Posts: 977 |
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dc42
Andrew, I don't understand why you are being so negative.
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AndrewBCN
There is no such thing as a "true circle" or a "true cylinder" or a "true sphere" in the digital world, we are always dealing with approximations, as you are fully aware of.
The approximations we have to accept in STL files and in our slicer output are much courser than our printers can handle - and printers are getting better all the time.
...
Re: Curved paths May 28, 2015 06:32PM |
Registered: 9 years ago Posts: 977 |
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frankvdh
Thank you for telling me what I am trying to do.Your ESP ability is exceeded only by your rudeness.
...
Re: Curved paths May 28, 2015 07:29PM |
Registered: 9 years ago Posts: 978 |
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LOL!
You are trying to make this into a panacea for all printing woes, which is quite absurd,
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Thank you for making this into an ad hominem argument, it allows me to disregard any of your further arguments