Basic considerations about Delta printers January 05, 2016 03:44AM |
Registered: 13 years ago Posts: 300 |
Re: Basic considerations about Delta printers January 05, 2016 04:23AM |
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Re: Basic considerations about Delta printers January 05, 2016 04:40AM |
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Re: Basic considerations about Delta printers January 05, 2016 05:21AM |
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fma
No, the gonio is under the bed, not on the effector... About the spindle, I'm thinking using a little brushless motor, like used in quadcopters...
Anyway, these are possible options only, and I really want to build a Delta
For now, I need to determine the global size, so arms geometry is an important factor.
Re: Basic considerations about Delta printers January 05, 2016 05:28AM |
Registered: 11 years ago Posts: 734 |
Re: Basic considerations about Delta printers January 05, 2016 06:22AM |
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dougal1957
The Arms should not be less than 20 degrees to the bed at the farthest extent of there travel and should be as wide apart as you can get but aim for no less than 45mm (that is around 40 mm wide fixing points on the effector/carriages which is the std for the Kossel if you can go wider then you will have greater rigidity)
Re: Basic considerations about Delta printers January 05, 2016 06:56AM |
Registered: 13 years ago Posts: 300 |
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hercek
In my opinion, the only reason to prefer delta to coreXY is the high printing speed. Otherwise delta has only disadvantages. It needs more powerful/expensive controller, it is harder to calibrate, and it is taller. But if you want a delta for the fun/challenge of it then go on
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Make your design so that you have an option to avoid the long bowden. The bowden is a major hurdle for high quality of prints which need to retract very often (e.g. models which contain a lot of thin towers). If you are after really high quality of prints then you need get rid of bowden. The options are:
- mount motor on the platform just next to hotend (you need stiffer structure and stronger steppers for this since the platform will be heavier)
- use a thin flexible hard steel cardan/shaft and a speed reduction at the platform - you can design your own or buy e.g. flex3drive
- use the flying extruder mod (search this forum if you do not know what it is)
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Place the equidistant diagonal rod as far away from each other as possible. Use high quality angle ball joints.
Re: Basic considerations about Delta printers January 05, 2016 07:52AM |
Registered: 11 years ago Posts: 734 |
Because the equations for delta are not linear. It is pretty obvious what is incorrectly calibrated from a simple printed cube if you use a cartesian printer. But bad calibration in delta leads to some "strange" distortions in the pritned parts. Regardless it is not so bad now as it was in the past since there are some public tools to help you. You need a Z-probe and then use some of these approaches: [github.com] or [forums.reprap.org] or dc42's firmware for Duet board.Quote
fma
Why is it harder to calibrate?
You want as stiff belts as possible. That means belts with steel core and as wide as possible. GT2 profile is better than T2.5 but steel core GT2 is rare. If you are very advantageous then go for about Ø 1.5 mm steel cable. But in this case you need big diameter drums to minimize impact of the errors because of varying position on drum. And that means you probably need a speed reduction from stepper to the drum. Anyway the common Ø 1.5 mm steel cable will be much stiffer than any common belt you can get.Quote
fma
BTW, I will use Nema 23 motors, and I also need to find strong belt, to avoid elongation under tension. Any suggestion? Does GT2 exist in 10mm width?
Plastic is enough, just get ones which are sold already completed and which are tight. For example: [forums.reprap.org]Quote
fma
What ball joints do you suggest? metal ones? Or plastic (IGUS?) ones?
Re: Basic considerations about Delta printers January 06, 2016 03:49AM |
Registered: 13 years ago Posts: 300 |
Re: Basic considerations about Delta printers January 06, 2016 03:58AM |
Registered: 10 years ago Posts: 14,685 |
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fma
What are the feedbacks on the linear systems using plastic wheels on aluminium profiles? I see that on some commercial 3D printers, but I wonder if it provides good long term accuracy...
It is a very simple design, and very cheap compared to rods/ball bushing.
Re: Basic considerations about Delta printers January 06, 2016 04:01AM |
Registered: 9 years ago Posts: 5,232 |
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hercek
Place the equidistant diagonal rod as far away from each other as possible.
Re: Basic considerations about Delta printers January 06, 2016 04:09AM |
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Re: Basic considerations about Delta printers January 06, 2016 04:33AM |
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Re: Basic considerations about Delta printers January 06, 2016 04:37AM |
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o_lampe
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hercek
Place the equidistant diagonal rod as far away from each other as possible.
I don't fully agree with that. Wider rod distance also leads to a longer lever for any play or wobble in the carrier trucks.
-Olaf
Re: Basic considerations about Delta printers January 06, 2016 04:37AM |
Registered: 13 years ago Posts: 300 |
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dc42
I have only even used Delrin wheels on aluminium profiles, and they work well for me.
Re: Basic considerations about Delta printers January 06, 2016 04:45AM |
Registered: 10 years ago Posts: 14,685 |
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fma
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dc42
I have only even used Delrin wheels on aluminium profiles, and they work well for me.
Like these?
[www.think3dprint3d.com]
Re: Basic considerations about Delta printers January 06, 2016 04:54AM |
Registered: 13 years ago Posts: 300 |
Re: Basic considerations about Delta printers January 06, 2016 05:28AM |
Registered: 13 years ago Posts: 300 |
Quote
hercek
[...]If you are very advantageous then go for about Ø 1.5 mm steel cable. But in this case you need big diameter drums to minimize impact of the errors because of varying position on drum. And that means you probably need a speed reduction from stepper to the drum.
Re: Basic considerations about Delta printers January 06, 2016 12:30PM |
Registered: 11 years ago Posts: 734 |
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dc42
Quote
o_lampe
Quote
hercek
Place the equidistant diagonal rod as far away from each other as possible.
I don't fully agree with that. Wider rod distance also leads to a longer lever for any play or wobble in the carrier trucks.
-Olaf
And I don't fully agree with that either. The longer lever at the carriage end is compensated by the longer lever at the effector end. A wobble of a given angle at the carriage will lead to exactly the same angular wobble at the effector, no matter what rod spacing you use. However, I agree that if you do have carriage wobble about a vertical axis when using wheeled carriages, using wider extrusion will reduce it.
Re: Basic considerations about Delta printers January 06, 2016 12:36PM |
Registered: 11 years ago Posts: 734 |
Put it about the same as your desired accuracy at the hotend tip. I would go for step size of 0.02 mm or smaller.Quote
fma
What accuracy do we need on the axis?Quote
hercek
[...]If you are very advantageous then go for about Ø 1.5 mm steel cable. But in this case you need big diameter drums to minimize impact of the errors because of varying position on drum. And that means you probably need a speed reduction from stepper to the drum.
Re: Basic considerations about Delta printers January 07, 2016 04:58AM |
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Re: Basic considerations about Delta printers January 07, 2016 05:25AM |
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Re: Basic considerations about Delta printers January 07, 2016 06:09AM |
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Re: Basic considerations about Delta printers January 07, 2016 10:48AM |
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fma
Compared to the standard profiles, like 2020 Motedis I-profile, is Openbuilds profile better? It has maybe a better contact whith the wheel?
BTW, I also plan to use excentrics...
Re: Basic considerations about Delta printers January 07, 2016 11:11AM |
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Re: Basic considerations about Delta printers January 07, 2016 11:56AM |
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Re: Basic considerations about Delta printers January 07, 2016 12:05PM |
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Re: Basic considerations about Delta printers January 10, 2016 04:12AM |
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Re: Basic considerations about Delta printers January 11, 2016 04:15AM |
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Re: Basic considerations about Delta printers January 11, 2016 04:21AM |
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