Re: Rugged CoreXY May 30, 2016 09:23AM |
Registered: 12 years ago Posts: 5,796 |
Re: Rugged CoreXY May 30, 2016 09:25AM |
Registered: 8 years ago Posts: 776 |
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hobbymods
Yeah....I'm getting all the emotion.
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Back on track....did a little research and my contacts assure me that 15mm EG/HG rails not only have better features than the miniature rails, but he can do them cheaper.
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Yes I will have a 3 point spring loaded manual bed leveling system, and yes I agree that springs on the build plate are a necessary insurance policy against busting something really expensive. I just plan to do something better than chinese spec wing nuts and soggy mismatched springs.
[/quote}
haha yeah. do consider that 2-extra-fixed-rods-not-dissimilar-to-tiny-3mm-ID-linear-bearings idea. in fact if you _can_ find tiny linear bearings...
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I think I've been misunderstood about my Z axis plans....I'm hoping to do something like this monstrosity (check the PRICE!!):
[3dprintersuperstore.com.au]
yeaaaoowwwww check out the length of those linear bearings, one at each corner. my guess is that those are so over-spec'd that they would prevent exactly the kind of rotation i was talking about if you had only 2 ball / lead screws.
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Only with rails instead of rods, and the 2 ball screws driven by the same motor/belt/pulley system.
even with rails you have an axis of rotation about the 2 ball screw mount-points onto the print-bed any rotation about that axis will be transferred into rotation of the rails, but with a lever-effect that dramatically increases the amount of force being applied. so if the rail carriages are say 50mm long, and the distance to the edge of the printbed is 150mm (a 300mm bed, 1/2 the distance), you have a THREE to one increase in any rotation (see-sawing) around the 2 ball screws.
so when you get the datasheet on those rails, you'll need to check the carriage length, check the expected amount of weight deflection that you're happy to tolerate, check the amount of rotation that they'll withstand, check the amount of force that they can tolerate before they'll go out of specs (BUT remember to multiply it by the calculated lever effect!), check that the anticipated wear and tear due to potential rotational side-loading is acceptable during their projected lifetime....
... beginning to sound like a f****g pain in the ass, isn't it?in my mind, all that checking i just to be absolutely honest i could not be bothered when by simply adding one extra ball screw the need for all that checking... simply disappears.
the rest i don't have the experience or expertise to comment so i'll leave it there, hth hobbymods.
l.
Edited 1 time(s). Last edit at 05/30/2016 09:26AM by lkcl.
Re: Rugged CoreXY May 30, 2016 09:35AM |
Registered: 9 years ago Posts: 1,873 |
Re: Rugged CoreXY May 30, 2016 09:43AM |
Registered: 8 years ago Posts: 168 |
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lkcl
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hobbymods
Yeah....I'm getting all the emotion.
and now for something completely different [www.youtube.com]
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Back on track....did a little research and my contacts assure me that 15mm EG/HG rails not only have better features than the miniature rails, but he can do them cheaper.
got any photos / specs / links to datasheets?
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Yes I will have a 3 point spring loaded manual bed leveling system, and yes I agree that springs on the build plate are a necessary insurance policy against busting something really expensive. I just plan to do something better than chinese spec wing nuts and soggy mismatched springs.
[/quote}
haha yeah. do consider that 2-extra-fixed-rods-not-dissimilar-to-tiny-3mm-ID-linear-bearings idea. in fact if you _can_ find tiny linear bearings...
Quote
I think I've been misunderstood about my Z axis plans....I'm hoping to do something like this monstrosity (check the PRICE!!):
[3dprintersuperstore.com.au]
yeaaaoowwwww check out the length of those linear bearings, one at each corner. my guess is that those are so over-spec'd that they would prevent exactly the kind of rotation i was talking about if you had only 2 ball / lead screws.
Quote
Only with rails instead of rods, and the 2 ball screws driven by the same motor/belt/pulley system.
even with rails you have an axis of rotation about the 2 ball screw mount-points onto the print-bed any rotation about that axis will be transferred into rotation of the rails, but with a lever-effect that dramatically increases the amount of force being applied. so if the rail carriages are say 50mm long, and the distance to the edge of the printbed is 150mm (a 300mm bed, 1/2 the distance), you have a THREE to one increase in any rotation (see-sawing) around the 2 ball screws.
so when you get the datasheet on those rails, you'll need to check the carriage length, check the expected amount of weight deflection that you're happy to tolerate, check the amount of rotation that they'll withstand, check the amount of force that they can tolerate before they'll go out of specs (BUT remember to multiply it by the calculated lever effect!), check that the anticipated wear and tear due to potential rotational side-loading is acceptable during their projected lifetime....
... beginning to sound like a f****g pain in the ass, isn't it?in my mind, all that checking i just to be absolutely honest i could not be bothered when by simply adding one extra ball screw the need for all that checking... simply disappears.
the rest i don't have the experience or expertise to comment so i'll leave it there, hth hobbymods.
l.
Clearly I'm missing something here....
It seems that you've said that the linear bearing rods on the printer I've linked to are good enough to work with the 2 ball screws configured as shown, but go on to say that supported rails in their place won't work with the same 2 ball screws. Unless of course I've misunderstood you.
And then there's the fact that I've never seen a printer sold with 3 ball screws on the Z axis, including the one I've linked to, can you please link me to an actual picture of the setup you're describing?
I'm certainly not saying you're wrong, but I've never seen it done that way.
The bed size I'm going for is 300x300mm, half the size of the printer shown.
Re: Rugged CoreXY May 30, 2016 09:47AM |
Registered: 8 years ago Posts: 168 |
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JamesK
I suspect you may be overthinking it a little Ikcl. While you're right that some degree of turning moment around the line joining the two lead screw nuts will exist, it's likely to be very small. The two screw design with the screws in the mid-points of opposing edges is relatively well balanced, and remember that there are plenty of printers with fully cantilevered beds supported from a single edge. It seems the bigger problem people have with 4 guide systems is getting them well enough aligned to avoid binding.
Re: Rugged CoreXY May 30, 2016 09:58AM |
Registered: 8 years ago Posts: 168 |
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the_digital_dentist
My printer uses NEMA-23 motors in all three axes (only really necessary in the Y axis, but I had the other motors so I used them). While they can be driven directly by the smoothieboard, I used external DSP based drivers for the X and Y axes because the Y axis motor required more current than the smoothieboard drivers could deliver and I wanted to experiment with microstepping in X and Y to make the machine quieter (it didn't help the Y axis, but the X axis just hisses quietly as it moves). As long as the motors need 2A or less you can drive them with the smoothieboard. NEMA-23 motors tend to vibrate more than NEMA-17 motors, so if you can use the smaller motors, do it, unless you don't mind a noisy printer.
It is very easy to connect external drivers to the smoothieboard, if you need to.
Re: Rugged CoreXY May 30, 2016 10:08AM |
Registered: 8 years ago Posts: 776 |
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JamesK
I suspect you may be overthinking it a little Ikcl. While you're right that some degree of turning moment around the line joining the two lead screw nuts will exist, it's likely to be very small.
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The two screw design with the screws in the mid-points of opposing edges is relatively well balanced,
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and remember that there are plenty of printers with fully cantilevered beds supported from a single edge.
Re: Rugged CoreXY May 30, 2016 10:17AM |
Registered: 8 years ago Posts: 168 |
Re: Rugged CoreXY May 30, 2016 10:18AM |
Registered: 8 years ago Posts: 776 |
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hobbymods
That's kind of what I was thinking.
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And yes, the possibility of binding would be very real, if not difficult to avoid. There would need to be some careful jiggery there for sure.
Re: Rugged CoreXY May 30, 2016 10:34AM |
Registered: 8 years ago Posts: 776 |
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hobbymods
To be honest it'll be forever until I get to that.
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I'm sure the gantry will keep me busy for a while.
I actually don't have a subjective assessment at this stage, just asking for clarification, but I do see the Makerbot Z18 uses the same configuration as well.
Mind you, I've heard they are shit.......
Re: Rugged CoreXY May 30, 2016 10:50AM |
Registered: 12 years ago Posts: 5,796 |
Re: Rugged CoreXY May 30, 2016 11:25AM |
Registered: 8 years ago Posts: 776 |
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the_digital_dentist
Yes, smoothieboard and AFAIK, most other 32 bit controllers, set motor current with a line of text in the config file. No little pots to break!
For me the best thing about the smoothieboard is that configuration changes and firmware updates don't involve compiling the firmware. There's a single config.txt file located on a uSD card that contains all the variables including motor currents. You edit it with any text editor then reboot the board and you're done. Firmware updates are just as easy- copy the new firmware to the uSD card and reboot. Done.
Re: Rugged CoreXY May 30, 2016 11:37AM |
Registered: 12 years ago Posts: 5,796 |
Re: Rugged CoreXY May 30, 2016 11:52AM |
Registered: 11 years ago Posts: 14,685 |
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the_digital_dentist
Smoothie has a web server too. I don't know about editing the config file and rebooting via the web interface- I've never tried it (I'm not sure why you'd want to do it remotely, but then I don't get the point of trying to remote control a printer at all- too old, I guess). You can edit the config file via the USB port or pull the uSD card and sneakernet it.
Re: Rugged CoreXY May 30, 2016 11:53AM |
Registered: 8 years ago Posts: 776 |
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the_digital_dentist
Smoothie has a web server too. I don't know about editing the config file and rebooting via the web interface- I've never tried it (I'm not sure why you'd want to do it remotely, but then I don't get the point of trying to remote control a printer at all- too old, I guess). You can edit the config file via the USB port or pull the uSD card and sneakernet it.
Re: Rugged CoreXY May 30, 2016 12:04PM |
Registered: 12 years ago Posts: 5,796 |
Re: Rugged CoreXY May 30, 2016 04:17PM |
Registered: 8 years ago Posts: 776 |
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the_digital_dentist
Maybe the new printer will get a Duet...
Re: Rugged CoreXY May 30, 2016 08:51PM |
Registered: 12 years ago Posts: 1,049 |
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ikcl
so let's imagine that someone has done that, but they are experimenting, so they have some firmware where the hotend hasn't quite been set up properly, or the slicing software hasn't been set up properly yet, and it heats up the hotend and a lot of plastic oozes out. let's imagine then that there is a huge blob of plastic on the hotend which they don't notice is there (or don't realise what's coming next). during the print, that blob then goes onto the printbed (they don't notice it because it's at the back of the hotend, out of their line of sight). that blob ends up on the printbed, and the hotend runs over it.
Re: Rugged CoreXY May 30, 2016 09:26PM |
Registered: 8 years ago Posts: 168 |
Re: Rugged CoreXY May 30, 2016 09:50PM |
Registered: 12 years ago Posts: 1,049 |
Re: Rugged CoreXY May 30, 2016 11:40PM |
Registered: 8 years ago Posts: 168 |
Re: Rugged CoreXY May 31, 2016 12:08AM |
Registered: 12 years ago Posts: 5,796 |
Re: Rugged CoreXY May 31, 2016 01:04AM |
Registered: 8 years ago Posts: 168 |
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the_digital_dentist
Mount one rail then slide the undercarriage back and forth and tighten down the second rail is how I did it and it has worked fine for a year and a half, in spite of hundreds of heating cycles and being transported in my car on multiple occasions.
I did not grind a reference shoulder into the base plate, though it would probably provide some extra stability.
Re: Rugged CoreXY May 31, 2016 02:49AM |
Registered: 9 years ago Posts: 622 |
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hobbymods
Seriously, does it take the new guy to say "C'mon kids, play nice with each other. Don't make me come back there"?
Re: Rugged CoreXY May 31, 2016 04:21AM |
Registered: 8 years ago Posts: 776 |
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cozmicray
You forgot:
that the outside of the hotend (the place that just melted the plastic)
is very cold and the blob is not very soft, and hotend does not just plow thru the blob
and the blob is so well adhered to the bed it can't be knocked off.
Re: Rugged CoreXY May 31, 2016 04:49AM |
Registered: 8 years ago Posts: 776 |
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deckingman
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hobbymods
Seriously, does it take the new guy to say "C'mon kids, play nice with each other. Don't make me come back there"?
I think the problem stems from the fact that we have 2 different schools of thought. On the one hand, there are those that build, or attempt to build rugged, reliable printers based on sound engineering principles. Of course there is nothing wrong with that if you have the budget and/or access to machining and fabricating facilities. On the other hand, these are after all the RepRap forums so such a printer will be a "Rap", but certainly not a "Rep". That is to say, that it cannot reproduce the parts that it was made from. Until these forums get renamed to "Build the best printer you can" or some such, there is bound to be conflict.
Re: Rugged CoreXY May 31, 2016 09:15AM |
Registered: 8 years ago Posts: 168 |
Re: Rugged CoreXY May 31, 2016 09:18AM |
Registered: 8 years ago Posts: 168 |
Re: Rugged CoreXY May 31, 2016 09:24AM |
Registered: 9 years ago Posts: 1,873 |
Re: Rugged CoreXY May 31, 2016 09:27AM |
Registered: 8 years ago Posts: 776 |
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hobbymods
Sorry....Australian middle aged male....can't help you with deep and meaningful philosophy, but can I interest you in a sarcastic comment?