What's Wrong With This Picture... August 07, 2017 01:28PM |
Registered: 6 years ago Posts: 90 |
Re: What's Wrong With This Picture... August 07, 2017 04:41PM |
Registered: 10 years ago Posts: 293 |
Re: What's Wrong With This Picture... August 07, 2017 06:26PM |
Registered: 6 years ago Posts: 90 |
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WZ9V
1) Extra weight due to having to haul the X or Y stepper with the moving platform. With COREXY both X and Y stepper are fixed.
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WZ9V
2) Equal tension as you move in any direction which should help keep both X and Y axis in alignment as they move.
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WZ9V
That said there is nothing inherently wrong with a decently designed X/Y setup as long as you are not going for the latest in cool or trying to make a speed demon.
Re: What's Wrong With This Picture... August 08, 2017 02:17AM |
Registered: 8 years ago Posts: 5,232 |
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The cross assemblies will be driven on both ends by the same dual-shaft stepper, 1 for each axis of course, fixed to the frame. 4 belts, each 1m in circumference driving each end of each axis.
Re: What's Wrong With This Picture... August 08, 2017 08:34AM |
Registered: 6 years ago Posts: 90 |
Re: What's Wrong With This Picture... August 08, 2017 09:14AM |
Registered: 11 years ago Posts: 5,780 |
Re: What's Wrong With This Picture... August 08, 2017 09:30AM |
Registered: 12 years ago Posts: 2,470 |
Re: What's Wrong With This Picture... August 08, 2017 10:00AM |
Registered: 6 years ago Posts: 90 |
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the_digital_dentist
It looks interesting, and if you can make it work, it will be great. What jumps out at me is using CF tubes and bushings in lieu of linear motion components. The tubes aren't made with the sort of surface finish/tolerance of a guide rail for linear motion- motion could be rough. CF is abrasive stuff, and plastic bushings sliding on CF probably won't last long. Also, plastic bushings are made to slide on steel. Friction sliding on CF/epoxy will probably be much higher. Then there's the diameter. The CF tubes have some nominal, poorly controlled diameter. Chances of getting bushings made to fit a very specific size steel rail to fit on a CF tube without any slop or being too tight seem unlikely. Finally, is the CF going to be rigid or behave like a bunch of springs?
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the_digital_dentist
You are going to learn a lot developing this mechanism.
Re: What's Wrong With This Picture... August 08, 2017 10:58AM |
Registered: 11 years ago Posts: 5,780 |
Re: What's Wrong With This Picture... August 08, 2017 05:21PM |
Registered: 9 years ago Posts: 135 |
Re: What's Wrong With This Picture... August 09, 2017 03:04AM |
Registered: 8 years ago Posts: 5,232 |
Re: What's Wrong With This Picture... August 09, 2017 09:38AM |
Registered: 6 years ago Posts: 90 |
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Feign
This is commonly known as an "Ultimaker Style" Cartesian. Named for the company that first commercialized it. The general concept is open source, and pretty solid, but people want to be unique and make something new rather than use what's been proven to work.
Re: What's Wrong With This Picture... August 09, 2017 09:48AM |
Registered: 6 years ago Posts: 90 |
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o_lampe
You're planning to use carbon rods for the stepper shaft extensions too?
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o_lampe
BTW, before you start a build blog, this baby needs a name
As mentioned before the gantry style isn't new, but using carbon rods and suited plastic bearings is.
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o_lampe
All you need is an extruder that can deal with the potentially high speed.
Re: What's Wrong With This Picture... August 09, 2017 09:55AM |
Registered: 6 years ago Posts: 90 |
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Srek
Igus is offering CF tubes for use with their Drylin bushings
[www.igus.de]
Not a cheap option though, but definitly one with very little moving mass
Re: What's Wrong With This Picture... August 09, 2017 11:03AM |
Registered: 6 years ago Posts: 50 |
Re: What's Wrong With This Picture... August 09, 2017 12:00PM |
Registered: 11 years ago Posts: 5,780 |
Re: What's Wrong With This Picture... August 09, 2017 12:08PM |
Registered: 6 years ago Posts: 90 |
Re: What's Wrong With This Picture... August 12, 2017 07:01PM |
Registered: 6 years ago Posts: 90 |
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gtj
Oh yeah. I really need to go through all the forum sections.
Lotsa belts though.
Re: What's Wrong With This Picture... August 13, 2017 09:29AM |
Registered: 8 years ago Posts: 776 |
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Srek
Igus is offering CF tubes for use with their Drylin bushings
[www.igus.de]
Not a cheap option though, but definitly one with very little moving mass
Re: What's Wrong With This Picture... August 13, 2017 09:35AM |
Registered: 8 years ago Posts: 776 |
Re: What's Wrong With This Picture... August 13, 2017 03:16PM |
Registered: 8 years ago Posts: 776 |
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gtj
*] The center of gravity for the hotend (bowden setup) will be right in the center of the tool platform.
What am I missing?
Re: What's Wrong With This Picture... August 14, 2017 03:27PM |
Registered: 6 years ago Posts: 90 |
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lkcl
however as i was still quite concerned about rod tolerances changing along the length of any one rod i decided instead to go with twin 6mm rods per axis and LM6UU bearings (total QTY 8). strictly speaking it might even be possible to just use 4 LM6UU bearings but i quite like using 8, it's possible to fit fans (and cables) down the gaps
so that's twin 25mm fans above, through the circular holes. the square ones, i use one to get the E3Dv6 cooling fan duct through it, and the other one i use for cables. the carriage is i think 80mm wide or so, but if you look closely you see the corners are truncated.
btw don't make the mistake i did, make sure that the carriage can be placed without disassembly onto the bearings, don't get fancy, use cableties or some screw-based plastic attachment underneath ffor clamping onto the bearings.
i initially made the mistake of designing the bearings to be push-fit into the carriage, asseembled everything, locked the rods down into the x/y-ends (16 35mm M3 screws in total, takes a hell of a long time....) and then realised FRICK!! i have to redesign the carriage to make the fan holes bigger...
... but i couldn't get the damn carriage off without either disassembling the *ENTIRE* top... or *breaking* the damn carriage plastic, destroying it in the process.
so... do consider that ok?
Re: What's Wrong With This Picture... August 14, 2017 03:32PM |
Registered: 6 years ago Posts: 90 |
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lkcl
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gtj
*] The center of gravity for the hotend (bowden setup) will be right in the center of the tool platform.
What am I missing?
please don't make this a bowden. look up the flexx3drive instead: mutley3d does a very small extruder originally designed for a kossel mini which will have a good enough weight for your needs. please don't use the zesty nimble, either.
Re: What's Wrong With This Picture... August 14, 2017 03:42PM |
Registered: 8 years ago Posts: 776 |
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gtj
Over the weekend I did a little test. I took that 1 CF tube that was out of spec and taped it into the groove of a piece of extrusion that I verified was perfectly straight. Then I vacuum sealed the entire thing and baked it at about 120c for a few hours. I then let it cool slowly in the oven without disturbing it. When I took it out, it was near perfect. It was straight and the diameter varied no more than 10 microns across the entire 500mm length.
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The carriage and end sliders are all just proof of concepts really. The concept being that, with the tools I had, I could create parts that were close enough in tolerance that the entire assembly was square and parallel enough that the carriage and sliders wouldn't bind. Mission accomplished. In reality, the carriage itself will be a flat surface with Igus low profile pillow bearings similar to the following...
The printed pillow blocks are just placeholders of the same size as the Igus ones. The hotend assembly will be its own bracket and will secure to the base with locating pins and screws.
Re: What's Wrong With This Picture... August 14, 2017 05:18PM |
Registered: 8 years ago Posts: 776 |
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gtj
I was actually thinking about some sort of remote or split drive.
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I had a crazy idea of some really light piezo driven thing at the hot-end for accuracy while a stepper mounted to the frame handled the heavy lifting. I'll check out the flexx3drive.
Re: What's Wrong With This Picture... August 14, 2017 06:06PM |
Registered: 6 years ago Posts: 90 |
Re: What's Wrong With This Picture... August 14, 2017 06:27PM |
Registered: 6 years ago Posts: 90 |
Re: What's Wrong With This Picture... August 15, 2017 02:45AM |
Registered: 8 years ago Posts: 776 |
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gtj
The Flex3Drive 4th gen XY version looks cool if we can lop off the bearings.
Re: What's Wrong With This Picture... August 15, 2017 01:39PM |
Registered: 8 years ago Posts: 776 |
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gtj
With 250g suspended in the middle of a 500mm span, I could hear the rods laughing at me. The rods I reinforced with an epoxy/balsa slurry were hysterical.
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My caliper displays to only 10 microns and since measuring sag with contact-type tools is kinda risky, I took 10 measurements unloaded then 10 loaded. In both unloaded and loaded I got a swing of about 35 microns and the average loaded was 10 microns more sag than the average unloaded. I then repeated the whole process and this time loaded was 10 microns less sag than unloaded. Given methods and tool precision, I don't see that as statistically significant.
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Also, I've made up my mind to go with the Drylin N17 linear slides for the perimeter since the rails obviously don't move
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and the weight of the slider would balance with the weight I could remove from my printed ones. That leaves only the 4 rods that make up the cross. Making sure that the force is equally distributed across all 4 will be interesting.
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The final pillow blocks would screw to the carriage plate with M3 screws into M3 press-in nuts on the other side of the plate.
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I think the piezo thing would have to be some kind of ratchet and pawl thing. It wouldn't be able to pull the filament all the way from the spool (or push it back), the fixed stepper would handle the bulk of the force needed to pull the filament up from the spool and over the gravity hump. The piezo thing would just be for accurate metering.
Re: What's Wrong With This Picture... August 18, 2017 08:52AM |
Registered: 6 years ago Posts: 90 |
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lkcl
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gtj
I think the piezo thing would have to be some kind of ratchet and pawl thing. It wouldn't be able to pull the filament all the way from the spool (or push it back), the fixed stepper would handle the bulk of the force needed to pull the filament up from the spool and over the gravity hump. The piezo thing would just be for accurate metering.
i did some cautious research, apparently piezo is being researched for nanotech / bio-engineering but nothing stood out in the mainstream 3d printing world. some inkjet stuff as well. don't want to discourage you but it does sound... either highly experimental/risky or insanely expensive or both