Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread May 25, 2015 11:01PM |
Registered: 9 years ago Posts: 57 |
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AndrewBCN
First, I congratulate you for coming up with your own original design, and both the CAD design work and the impressive assembly work on your printer. The whole venture is admirable and you really have earned everybody's respect.
There are a few points that I would have done differently (e.g. I wouldn't use printed profiles, I honestly prefer them in aluminum), because I feel you have in some cases gone to great lengths to "reinvent the wheel", on the other hand, there are so many brilliant ideas in your printer that this does not in any way tarnish my general impression about it: it's awesome!
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gmh39
Impressive!
Definitely stealing that CoreXY chart for my current build.
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grat
One thing to be aware of, based on personal experience: Looking at your RAMPS board, there are two things you might want to change... First, the right-angle terminal block for the power supply inputs is rated at 10A, and with ABS printing, you'll be pulling 11A+ through it. I'd look for the upgraded 15A connectors (It's a 2 x2 connectors, rather than 1 x4 connector). Sooner or later, the connector will probably start melting. You don't need to change the terminal block mounts on the PCB, just the connector itself.
Secondly, get a heatsink for the Q3 mosfet, and attach it with some heatsink compound. Also make sure it isn't touching the mosfet output terminal block, as it can get hot enough to melt it.
Otherwise, looks good!
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread May 26, 2015 01:13AM |
Registered: 9 years ago Posts: 57 |
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread May 26, 2015 07:41AM |
Registered: 9 years ago Posts: 977 |
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 10, 2015 03:14AM |
Registered: 9 years ago Posts: 57 |
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 10, 2015 06:27AM |
Registered: 8 years ago Posts: 93 |
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 10, 2015 10:46PM |
Registered: 8 years ago Posts: 6 |
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 11, 2015 10:55PM |
Registered: 9 years ago Posts: 57 |
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asbo
It looks like some sort of counterweight to me, perhaps to offset the weight of the bed?
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 12, 2015 06:19AM |
Registered: 8 years ago Posts: 93 |
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 12, 2015 09:42AM |
Registered: 9 years ago Posts: 346 |
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redhatman
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asbo
It looks like some sort of counterweight to me, perhaps to offset the weight of the bed?
Ding ding ding! I have modified it already since posting that picture, however the idea remains the same. Hopefully this will eliminate the z-wobble condition.
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 13, 2015 06:49PM |
Registered: 9 years ago Posts: 57 |
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asbo
I'm in the process of building a CoreXY myself and I'm now thinking a counterweight might be a good idea, may have to pinch your design
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LarsK
I am curious where you plan to install that, will you change to using belts instead of screws? Or will you remove one of the two trapezoidal screws and make that side of the system passive with the counterweight?
I am myself fighting with z-wobble these days. Last night I abandoned my trapezoidal screw and installed belts, but I am concerned for power cuts that will make the build platform drop the 300 mm. On the other hand, in mechanical engineering we have mostly abandoned counterweight systems in favor of stronger electronics and structures and control systems. Hmm
I will sure keep an eye on your experiences with this counterweight. Interesting.
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 13, 2015 07:02PM |
Registered: 9 years ago Posts: 57 |
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 13, 2015 07:02PM |
Registered: 9 years ago Posts: 57 |
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 14, 2015 11:02AM |
Registered: 9 years ago Posts: 346 |
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 14, 2015 12:04PM |
Registered: 9 years ago Posts: 1,159 |
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LarsK
It is an interesting design but I am not clear why you think this will help wobble? Wobble is the lag of centricity of you screw. When it rotates it pushes your carriage from side to side. For this reason you should see that the wobble in your printed pieces is exactly with the distance of the pitch on your screw.
The system you have made will only help if you have the problem with your linear rods binding the carriage so that it gets stuck in one side when moving up or down. But the root cause for that happening is your screw pushing the carriage to a side and increasing friction in that side and reducing the other.
Again, that is my point of view with my limited knowledge.
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 14, 2015 01:29PM |
Registered: 9 years ago Posts: 346 |
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dougal1957
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LarsK
It is an interesting design but I am not clear why you think this will help wobble? Wobble is the lag of centricity of you screw. When it rotates it pushes your carriage from side to side. For this reason you should see that the wobble in your printed pieces is exactly with the distance of the pitch on your screw.
The system you have made will only help if you have the problem with your linear rods binding the carriage so that it gets stuck in one side when moving up or down. But the root cause for that happening is your screw pushing the carriage to a side and increasing friction in that side and reducing the other.
Again, that is my point of view with my limited knowledge.
It is also more pronounced if the lead screws are constrained at both ends which is why the Std Prusa style machine have the screw mounted only at the motor ends and left to move at the upper end in a larger than required hole for it.
If they are constrained at both top and bottom then any out of true will be transmitted into the Bed as Z Wobble.
Doug
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 14, 2015 01:51PM |
Registered: 9 years ago Posts: 1,159 |
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LarsK
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dougal1957
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LarsK
It is an interesting design but I am not clear why you think this will help wobble? Wobble is the lag of centricity of you screw. When it rotates it pushes your carriage from side to side. For this reason you should see that the wobble in your printed pieces is exactly with the distance of the pitch on your screw.
The system you have made will only help if you have the problem with your linear rods binding the carriage so that it gets stuck in one side when moving up or down. But the root cause for that happening is your screw pushing the carriage to a side and increasing friction in that side and reducing the other.
Again, that is my point of view with my limited knowledge.
It is also more pronounced if the lead screws are constrained at both ends which is why the Std Prusa style machine have the screw mounted only at the motor ends and left to move at the upper end in a larger than required hole for it.
If they are constrained at both top and bottom then any out of true will be transmitted into the Bed as Z Wobble.
Doug
I have seen that and I don't think it is a concept that will make it into the " best practices" book. You are putting all the axial load on the small stepper bearings and they are not designed for that. I see that it works on prusa but on a big coreXY with a huge bed I don't think that is the solution - unless you make a counterweight system like redhatman is doing so that the bed Weight is reduced. Then it is feasible.
A picture example for those who wants to see what it looks like
[lh6.googleusercontent.com]
Wobble is easily solved by putting a motor and coupling at the end of this:
But when you go that route you quickly need special parts or machining on a lathe. That is why I have for now abandoned it.
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 14, 2015 04:37PM |
Registered: 9 years ago Posts: 57 |
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LarsK
It is an interesting design but I am not clear why you think this will help wobble? Wobble is the lag of centricity of you screw. When it rotates it pushes your carriage from side to side. For this reason you should see that the wobble in your printed pieces is exactly with the distance of the pitch on your screw.
The system you have made will only help if you have the problem with your linear rods binding the carriage so that it gets stuck in one side when moving up or down. But the root cause for that happening is your screw pushing the carriage to a side and increasing friction in that side and reducing the other.
Again, that is my point of view with my limited knowledge.
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 24, 2015 10:29AM |
Registered: 9 years ago Posts: 977 |
@ redhatmanQuote
dougal1957
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LarsK
It is an interesting design but I am not clear why you think this will help wobble? Wobble is the lag of centricity of you screw. When it rotates it pushes your carriage from side to side. For this reason you should see that the wobble in your printed pieces is exactly with the distance of the pitch on your screw.
The system you have made will only help if you have the problem with your linear rods binding the carriage so that it gets stuck in one side when moving up or down. But the root cause for that happening is your screw pushing the carriage to a side and increasing friction in that side and reducing the other.
Again, that is my point of view with my limited knowledge.
It is also more pronounced if the lead screws are constrained at both ends which is why the Std Prusa style machine have the screw mounted only at the motor ends and left to move at the upper end in a larger than required hole for it.
If they are constrained at both top and bottom then any out of true will be transmitted into the Bed as Z Wobble.
Doug
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 26, 2015 01:04AM |
Registered: 9 years ago Posts: 57 |
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AndrewBCN
@ redhatmanQuote
dougal1957
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LarsK
It is an interesting design but I am not clear why you think this will help wobble? Wobble is the lag of centricity of you screw. When it rotates it pushes your carriage from side to side. For this reason you should see that the wobble in your printed pieces is exactly with the distance of the pitch on your screw.
The system you have made will only help if you have the problem with your linear rods binding the carriage so that it gets stuck in one side when moving up or down. But the root cause for that happening is your screw pushing the carriage to a side and increasing friction in that side and reducing the other.
Again, that is my point of view with my limited knowledge.
It is also more pronounced if the lead screws are constrained at both ends which is why the Std Prusa style machine have the screw mounted only at the motor ends and left to move at the upper end in a larger than required hole for it.
If they are constrained at both top and bottom then any out of true will be transmitted into the Bed as Z Wobble.
Doug
Hmmm, I agree 100% with both LarsK and Doug, and I am not sure that removing the 2.5kg weight on the 8mm rods (using a complex counterweight system) and straightening them will solve your Z-wobble problem. But that is from my limited knowledge and experience: I have only used rather soft (easy to bend) 5mm galvanized carbon steel rods on my various Prusa i3 and P3Steel printers and not once I saw Z-wobble as bad as you have shown in your pictures above. In fact I never detected any significant Z-wobble distortion in any of my prints up until now on any of my printers, even though some of the 5mm rods I am using are clearly not straight! So I guess Josef Prusa's solution has some merit to it: simple, inexpensive and does the job!
Based on the above I would suggest you think about and try to design a K.I.S.S. solution to your Z-wobble problem.
Just my $0.02.
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 26, 2015 01:09AM |
Registered: 9 years ago Posts: 57 |
Re: "Project Locus" - *gasp* My Plastic Frame - CoreXY Build Thread June 26, 2015 01:10AM |
Registered: 9 years ago Posts: 57 |