Re: Development corexy September 30, 2017 02:54AM |
Registered: 8 years ago Posts: 5,232 |
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MKSA
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the_digital_dentist
.....
Your CAD model looks like you have put bearings on the ends of the screws, but if I understand what you're doing correctly, the screws aren't going to rotate, so bearings won't be needed.
Congratulation doc, you are the only one who spotted the obvious fault ! In fact, the screw WILL rotate at an unpredictable speed depending on nut friction and counter motor torque. Imagine the result !
As for the rest, indeed plenty of question marks.The three ball supports, wrong, and more complicated to make/align than the correct solution !
Re: Development corexy September 30, 2017 04:58AM |
Registered: 10 years ago Posts: 97 |
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MKSA
Quote
the_digital_dentist
.....
Your CAD model looks like you have put bearings on the ends of the screws, but if I understand what you're doing correctly, the screws aren't going to rotate, so bearings won't be needed.
Congratulation doc, you are the only one who spotted the obvious fault ! In fact, the screw WILL rotate at an unpredictable speed depending on nut friction and counter motor torque. Imagine the result !
As for the rest, indeed plenty of question marks.The three ball supports, wrong, and more complicated to make/align than the correct solution !
Re: Development corexy September 30, 2017 05:11AM |
Registered: 10 years ago Posts: 97 |
Re: Development corexy September 30, 2017 07:10AM |
Registered: 10 years ago Posts: 14,672 |
Re: Development corexy September 30, 2017 04:07PM |
Registered: 7 years ago Posts: 249 |
Re: Development corexy September 30, 2017 05:01PM |
Registered: 11 years ago Posts: 5,780 |
Re: Development corexy October 01, 2017 03:20AM |
Registered: 7 years ago Posts: 249 |
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the_digital_dentist
The concept is pretty simple- instead of turning a massive screw, you fix the screw and drive the nut. This is usually used in high speed machines where turning a long screw fast results in "whipping". It's a lot easier to control a small, low mass nut than a long, flexible, heavy screw.
Re: Development corexy October 02, 2017 11:13PM |
Registered: 8 years ago Posts: 1,671 |
Re: Development corexy October 03, 2017 04:07AM |
Registered: 6 years ago Posts: 1,007 |
So please explain the Z movement with both the screw and the nut rotating (the nut is part of the stepper rotor) !Quote
o_lampe
Quote
MKSA
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the_digital_dentist
.....
Your CAD model looks like you have put bearings on the ends of the screws, but if I understand what you're doing correctly, the screws aren't going to rotate, so bearings won't be needed.
Congratulation doc, you are the only one who spotted the obvious fault ! In fact, the screw WILL rotate at an unpredictable speed depending on nut friction and counter motor torque. Imagine the result !
As for the rest, indeed plenty of question marks.The three ball supports, wrong, and more complicated to make/align than the correct solution !
Of course, the screws will rotate. They have to !
Where have you two been at physics classes?
Re: Development corexy October 03, 2017 06:58AM |
Registered: 10 years ago Posts: 97 |
Quote
MKSA
So please explain the Z movement with both the screw and the nut rotating (the nut is part of the stepper rotor) !Quote
o_lampe
Quote
MKSA
Quote
the_digital_dentist
.....
Your CAD model looks like you have put bearings on the ends of the screws, but if I understand what you're doing correctly, the screws aren't going to rotate, so bearings won't be needed.
Congratulation doc, you are the only one who spotted the obvious fault ! In fact, the screw WILL rotate at an unpredictable speed depending on nut friction and counter motor torque. Imagine the result !
As for the rest, indeed plenty of question marks.The three ball supports, wrong, and more complicated to make/align than the correct solution !
Of course, the screws will rotate. They have to !
Where have you two been at physics classes?
Re: Development corexy October 03, 2017 07:12AM |
Registered: 11 years ago Posts: 5,780 |
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MechaBits
I would like to see a Z moving by spinning the nuts via pulleys & belt been thinking about it for some time, just not got around to doing it.
Re: Development corexy October 03, 2017 01:59PM |
Registered: 10 years ago Posts: 97 |
Re: Development corexy October 03, 2017 04:16PM |
Registered: 11 years ago Posts: 5,780 |
Re: Development corexy October 04, 2017 01:31AM |
Registered: 8 years ago Posts: 5,232 |
Quote
MKSA
Quote
o_lampe
Of course, the screws will rotate. They have to !
Where have you two been at physics classes?
So please explain the Z movement with both the screw and the nut rotating (the nut is part of the stepper rotor) !
Re: Development corexy October 04, 2017 01:34AM |
Registered: 8 years ago Posts: 5,232 |
Re: Development corexy October 04, 2017 12:37PM |
Registered: 6 years ago Posts: 1,007 |
Quote
o_lampe
Quote
MKSA
Quote
o_lampe
Of course, the screws will rotate. They have to !
Where have you two been at physics classes?
So please explain the Z movement with both the screw and the nut rotating (the nut is part of the stepper rotor) !
Sorry, I have to apologize. I fooled myself, because I knew the leadscrew does rotate. But you have to keep it from spinning to get axial movement.
Next time, I keep my big mouth shut...
O_Lampe
Re: Development corexy October 04, 2017 05:51PM |
Registered: 8 years ago Posts: 1,671 |
Quote
the_digital_dentist
Quote
MechaBits
I would like to see a Z moving by spinning the nuts via pulleys & belt been thinking about it for some time, just not got around to doing it.
It's usually done the other way because it's pretty easy to couple a screw to a motor, pulley, or bearing, and a lot harder to add bearings and pulley teeth to typical lead nuts. What would would be the advantage of driving the nuts in a printer's very slow Z axis that would make it worth the trouble (!) and expense (?) to do it?
Re: Development corexy October 04, 2017 06:42PM |
Registered: 11 years ago Posts: 1,049 |
Re: Development corexy October 04, 2017 09:19PM |
Registered: 8 years ago Posts: 1,671 |
Re: Development corexy October 07, 2017 05:12AM |
Registered: 6 years ago Posts: 1,007 |
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andornot
The lead screw is fixed
Re: Development corexy October 20, 2017 04:02PM |
Registered: 10 years ago Posts: 97 |
Re: Development corexy October 20, 2017 05:52PM |
Registered: 8 years ago Posts: 601 |
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andornot
i have decided to build a d-bot, its for son's christmas present and i will get a better understanding of corexy machines. Does anybody have experience of building such a machine and any improvements to it?
Re: Development corexy October 21, 2017 03:07AM |
Registered: 8 years ago Posts: 5,232 |
Re: Development corexy October 21, 2017 04:32AM |
Registered: 10 years ago Posts: 97 |
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Origamib
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andornot
i have decided to build a d-bot, its for son's christmas present and i will get a better understanding of corexy machines. Does anybody have experience of building such a machine and any improvements to it?
That's a shame... your machine looked better then a Dbot.
V slot wheels and printed plates are not a great combination in my opinion. The heavy pre load you must place on the wheels with the eccentric nuts tends to bow the plastic mounts. The other downside is that you must tighten the wheels to the plates, and if you use cheap bearings they bind... Loosen the nuts, and the wheels are sloppy though. Buy good bearings, and make sure to use metal plates as much as possible. The 3mm plates offered by openbuilds are good but not brilliant. In the end you will want custom plates to fit your own needs.
You can get delrin wheels from china that are considerably cheaper, and quality is not hugely important on these. I have used both openbuilds delrin wheels and chinese ones... The chinese ones have a tight fit on the bearings and they are tough to get out, but once you make the wheel it doesn't need to come apart. The delrin is 'tougher' from china, but wear over time seems equal. My printer has been in constant use for at least a year now.
Re: Development corexy October 24, 2017 01:12PM |
Registered: 8 years ago Posts: 601 |
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andornot
Quote
Origamib
Quote
andornot
i have decided to build a d-bot, its for son's christmas present and i will get a better understanding of corexy machines. Does anybody have experience of building such a machine and any improvements to it?
That's a shame... your machine looked better then a Dbot.
V slot wheels and printed plates are not a great combination in my opinion. The heavy pre load you must place on the wheels with the eccentric nuts tends to bow the plastic mounts. The other downside is that you must tighten the wheels to the plates, and if you use cheap bearings they bind... Loosen the nuts, and the wheels are sloppy though. Buy good bearings, and make sure to use metal plates as much as possible. The 3mm plates offered by openbuilds are good but not brilliant. In the end you will want custom plates to fit your own needs.
You can get delrin wheels from china that are considerably cheaper, and quality is not hugely important on these. I have used both openbuilds delrin wheels and chinese ones... The chinese ones have a tight fit on the bearings and they are tough to get out, but once you make the wheel it doesn't need to come apart. The delrin is 'tougher' from china, but wear over time seems equal. My printer has been in constant use for at least a year now.
So i would really be better carrying on the design of my corexy and buy my son a cheap printer to learn 3d printing. Any recommendations on a cheap printer to learn how to print?
Re: Development corexy October 25, 2017 02:59AM |
Registered: 8 years ago Posts: 5,232 |
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Sure, why not just make this printer with your son? Enjoy the learning curve together, with input from both of you.