Re: Rugged CoreXY June 07, 2016 07:23AM |
Registered: 8 years ago Posts: 168 |
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lkcl
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hobbymods
Yep I'm feeling this one too.
I'm really leaning towards using 2x 10mm ground rods across the center (X) axis, there's just so many reasons.
Of course there's the fact that it'll cost 10% of what my precision rail setup would, but then there's probably half the weight, 2 less major machining/tool making steps, the ability to slide the rods out and change carriages (CNC/laser engraver attachment) and the fact that it'll probably work just as well using proper ground/hardened rod and 4x brand name LM10U bearings.
I think I'll go this way and see if it all works out.
talked this one through with realthor just over a week ago, we figured that if you use linear bearings, as long as you keep the linear bearings as far apart as you dare, any "play" in them will not result in significant rotation of the carriage. if there _is_ any play, gravity shouuuld keep it down, but even if there is, the further apart the bearings are the less effect any up/down will have... as long as the hotend is as close to the dead-centre-point of the carriage bearings as you dare. having the bearings so close to the printbed that they knock bits of plastic off is clearly bad...
Re: Rugged CoreXY June 07, 2016 07:32AM |
Registered: 9 years ago Posts: 776 |
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hobbymods
One of my filament suppliers told me that he had a machine come through new that had too much play, and when he changed the brand new 8mm linear bearings with good name brand from the bearing supplier the difference was night and day.
I'm also talking 10 mm hardened rod over a 400mm max span.
Not sure yet, but being able to remove the carriage without upsetting everything and more room to see/reach into the top would be appealing.
Re: Rugged CoreXY June 07, 2016 08:36AM |
Registered: 8 years ago Posts: 168 |
Re: Rugged CoreXY June 07, 2016 01:31PM |
Registered: 10 years ago Posts: 346 |
Re: Rugged CoreXY June 07, 2016 09:00PM |
Registered: 8 years ago Posts: 168 |
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LarsK
@ Ikcl - I like your focus on reducing the length from center of X rods to edge of out nozzle. I have never understood that it was not given more attention. Mine is 33mm from center of rods to nozzle edge, I wish it was less, but it is hard to design something printable and something that won't melt and then I wanted the dual nozzles...
But sometimes I see some designs that makes me confused... Like this Kickstarter campaign: [www.kickstarter.com] - How does that nozzle not go 1-2 mm from side to side?
@ Hobbymods - Personally, if I was making a new printer, I would use linear rails. Not smooth rods. Especially if you can design it with only one rail for the X axis. Makes so many things so much easier I think.
Mine I posted pictures of earlier (the one with crossed belts) was my attempt at making my own linear rails, it has some ball bearings rolling on the 2020 profile with springs applying pressure - It prints and have been working reliably, all the orange parts in pictures are printed with it, but the quality is just not good enough... I purchased a "real" linear rail some time ago, just to get a feel for it, and it is a different world, so compact yet so exact and smooth. And the ease for mounting on a linear rail compared to having to clamp a smooth rod bearing... mmmhm. But it is costly.
Re: Rugged CoreXY June 07, 2016 10:20PM |
Registered: 14 years ago Posts: 268 |
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hobbymods
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LarsK
@ Ikcl - I like your focus on reducing the length from center of X rods to edge of out nozzle. I have never understood that it was not given more attention. Mine is 33mm from center of rods to nozzle edge, I wish it was less, but it is hard to design something printable and something that won't melt and then I wanted the dual nozzles...
But sometimes I see some designs that makes me confused... Like this Kickstarter campaign: [www.kickstarter.com] - How does that nozzle not go 1-2 mm from side to side?
@ Hobbymods - Personally, if I was making a new printer, I would use linear rails. Not smooth rods. Especially if you can design it with only one rail for the X axis. Makes so many things so much easier I think.
Mine I posted pictures of earlier (the one with crossed belts) was my attempt at making my own linear rails, it has some ball bearings rolling on the 2020 profile with springs applying pressure - It prints and have been working reliably, all the orange parts in pictures are printed with it, but the quality is just not good enough... I purchased a "real" linear rail some time ago, just to get a feel for it, and it is a different world, so compact yet so exact and smooth. And the ease for mounting on a linear rail compared to having to clamp a smooth rod bearing... mmmhm. But it is costly.
Yes, might have had a lapse of reason there...
Problem is that I don't agree with a single rail (especially unsupported) on the X axis, as they are designed to generally be run as 2 parallel rails. I feel I've stretched the rules a bit just using one carriage on each rail, but will use the longer carriage on the X axis.
What I'm looking at here is a pretty heavy X axis, but I did say I wasn't going for speed I guess. I'll keep going with the rails and see how it plays out.
Re: Rugged CoreXY June 07, 2016 10:51PM |
Registered: 8 years ago Posts: 168 |
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Koko76
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hobbymods
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LarsK
@ Ikcl - I like your focus on reducing the length from center of X rods to edge of out nozzle. I have never understood that it was not given more attention. Mine is 33mm from center of rods to nozzle edge, I wish it was less, but it is hard to design something printable and something that won't melt and then I wanted the dual nozzles...
But sometimes I see some designs that makes me confused... Like this Kickstarter campaign: [www.kickstarter.com] - How does that nozzle not go 1-2 mm from side to side?
@ Hobbymods - Personally, if I was making a new printer, I would use linear rails. Not smooth rods. Especially if you can design it with only one rail for the X axis. Makes so many things so much easier I think.
Mine I posted pictures of earlier (the one with crossed belts) was my attempt at making my own linear rails, it has some ball bearings rolling on the 2020 profile with springs applying pressure - It prints and have been working reliably, all the orange parts in pictures are printed with it, but the quality is just not good enough... I purchased a "real" linear rail some time ago, just to get a feel for it, and it is a different world, so compact yet so exact and smooth. And the ease for mounting on a linear rail compared to having to clamp a smooth rod bearing... mmmhm. But it is costly.
Yes, might have had a lapse of reason there...
Problem is that I don't agree with a single rail (especially unsupported) on the X axis, as they are designed to generally be run as 2 parallel rails. I feel I've stretched the rules a bit just using one carriage on each rail, but will use the longer carriage on the X axis.
What I'm looking at here is a pretty heavy X axis, but I did say I wasn't going for speed I guess. I'll keep going with the rails and see how it plays out.
There are very specific types of rails "designed" to be used in pairs. Typically these have unequal load capacities in all directions and are set up in opposing pairs. These are not the styles you are talking about. More typical "equal load" rails are designed to run singly just fine, they have listed moment loads singly for a good reason.
Re: Rugged CoreXY June 08, 2016 12:11AM |
Registered: 14 years ago Posts: 268 |
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hobbymods
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Koko76
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hobbymods
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LarsK
@ Ikcl - I like your focus on reducing the length from center of X rods to edge of out nozzle. I have never understood that it was not given more attention. Mine is 33mm from center of rods to nozzle edge, I wish it was less, but it is hard to design something printable and something that won't melt and then I wanted the dual nozzles...
But sometimes I see some designs that makes me confused... Like this Kickstarter campaign: [www.kickstarter.com] - How does that nozzle not go 1-2 mm from side to side?
@ Hobbymods - Personally, if I was making a new printer, I would use linear rails. Not smooth rods. Especially if you can design it with only one rail for the X axis. Makes so many things so much easier I think.
Mine I posted pictures of earlier (the one with crossed belts) was my attempt at making my own linear rails, it has some ball bearings rolling on the 2020 profile with springs applying pressure - It prints and have been working reliably, all the orange parts in pictures are printed with it, but the quality is just not good enough... I purchased a "real" linear rail some time ago, just to get a feel for it, and it is a different world, so compact yet so exact and smooth. And the ease for mounting on a linear rail compared to having to clamp a smooth rod bearing... mmmhm. But it is costly.
Yes, might have had a lapse of reason there...
Problem is that I don't agree with a single rail (especially unsupported) on the X axis, as they are designed to generally be run as 2 parallel rails. I feel I've stretched the rules a bit just using one carriage on each rail, but will use the longer carriage on the X axis.
What I'm looking at here is a pretty heavy X axis, but I did say I wasn't going for speed I guess. I'll keep going with the rails and see how it plays out.
There are very specific types of rails "designed" to be used in pairs. Typically these have unequal load capacities in all directions and are set up in opposing pairs. These are not the styles you are talking about. More typical "equal load" rails are designed to run singly just fine, they have listed moment loads singly for a good reason.
Yes and that's all well and good, but I am assured by my contact at Hiwin that these specific rails that I'm talking about will give best results installed in parallel on a horizontal surface. I am well aware of the moment loads as well, and most if not all printers wouldn't come close to them, but I'm chasing long term continuous duty operation in a workshop environment as well as quiet as possible operation.
But I do appreciate what you are explaining to me and the reasons behind the explanation (saving money and weight).
Is there any reason I see the XY steppers installed on peoples corexy builds at 45 deg?
That would actually be quite good for me design wise, but I'd only want to do it if there was a solid reason to do so.
Re: Rugged CoreXY June 08, 2016 12:52AM |
Registered: 8 years ago Posts: 168 |
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Koko76
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hobbymods
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Koko76
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hobbymods
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LarsK
@ Ikcl - I like your focus on reducing the length from center of X rods to edge of out nozzle. I have never understood that it was not given more attention. Mine is 33mm from center of rods to nozzle edge, I wish it was less, but it is hard to design something printable and something that won't melt and then I wanted the dual nozzles...
But sometimes I see some designs that makes me confused... Like this Kickstarter campaign: [www.kickstarter.com] - How does that nozzle not go 1-2 mm from side to side?
@ Hobbymods - Personally, if I was making a new printer, I would use linear rails. Not smooth rods. Especially if you can design it with only one rail for the X axis. Makes so many things so much easier I think.
Mine I posted pictures of earlier (the one with crossed belts) was my attempt at making my own linear rails, it has some ball bearings rolling on the 2020 profile with springs applying pressure - It prints and have been working reliably, all the orange parts in pictures are printed with it, but the quality is just not good enough... I purchased a "real" linear rail some time ago, just to get a feel for it, and it is a different world, so compact yet so exact and smooth. And the ease for mounting on a linear rail compared to having to clamp a smooth rod bearing... mmmhm. But it is costly.
Yes, might have had a lapse of reason there...
Problem is that I don't agree with a single rail (especially unsupported) on the X axis, as they are designed to generally be run as 2 parallel rails. I feel I've stretched the rules a bit just using one carriage on each rail, but will use the longer carriage on the X axis.
What I'm looking at here is a pretty heavy X axis, but I did say I wasn't going for speed I guess. I'll keep going with the rails and see how it plays out.
There are very specific types of rails "designed" to be used in pairs. Typically these have unequal load capacities in all directions and are set up in opposing pairs. These are not the styles you are talking about. More typical "equal load" rails are designed to run singly just fine, they have listed moment loads singly for a good reason.
Yes and that's all well and good, but I am assured by my contact at Hiwin that these specific rails that I'm talking about will give best results installed in parallel on a horizontal surface. I am well aware of the moment loads as well, and most if not all printers wouldn't come close to them, but I'm chasing long term continuous duty operation in a workshop environment as well as quiet as possible operation.
But I do appreciate what you are explaining to me and the reasons behind the explanation (saving money and weight).
Is there any reason I see the XY steppers installed on peoples corexy builds at 45 deg?
That would actually be quite good for me design wise, but I'd only want to do it if there was a solid reason to do so.
You've been talking about pairs of 15mm rails. I designed and built built a drill rig recently for a customer that used a pair of 15mm rails to drill into a hardened bearing race to pin a >1meter diameter bearing. Those rails were able to keep the carbide tipped drills pretty stable too. There's simply no need to have the weight and space for all that hardware in your application. Weight adds wear to components too.
Re: Rugged CoreXY June 08, 2016 05:24AM |
Registered: 8 years ago Posts: 168 |
Re: Rugged CoreXY June 08, 2016 06:11AM |
Registered: 14 years ago Posts: 268 |
Machinist/Toolmaker is pretty close. I'm not one to cut corners either, the rails in my delta cost more than what most people spend on a whole printer (they are used singly and are of the single bearing race variety). That's why I keep talking about the rated load and moments. If you stay within those, then you get the rated service life as well, and typically even those are rated moving the rails at speeds you won't see while printing. There are also options for lubrication for smaller series rails. The THK rails I use in my machines can be supplied with lubrication ports, but I usually just oil the rails. They also are of a slightly different design which separate the balls with a cage that keeps them quieter and traps lubrication.Quote
hobbymods
Well I'm already printing a housing to run 2, but I will take your advice and also make a single rail version.
It certainly would make life easier.
I take it you're a machinist/toolmaker of some sort?
What I don't want to use is the MG rails, as they only have one bearing race as opposed to the EG series which has 2, and can be supplied with a grease nipple (I build everything to be serviced).
Please don't think I'm not one to listen, I'm just so used to hearing "naaahhhh....you don't worry about that shit, just use this paddle pop stick and a rubber band", which is just not how I roll.
I'd still use the single X carriage horizontally mounted, because it would be easier to marry up to my Y axis, with a machined L bracket dropping down into the build area.
Lots of advantages this way in addition to weight/cost....access to the extruder, ability to mount some sort of engraver for a different application, as well as simply looking better.
So cheers for that.
Re: Rugged CoreXY June 08, 2016 06:43AM |
Registered: 8 years ago Posts: 168 |
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Koko76
Machinist/Toolmaker is pretty close. I'm not one to cut corners either, the rails in my delta cost more than what most people spend on a whole printer (they are used singly and are of the single bearing race variety). That's why I keep talking about the rated load and moments. If you stay within those, then you get the rated service life as well, and typically even those are rated moving the rails at speeds you won't see while printing. There are also options for lubrication for smaller series rails. The THK rails I use in my machines can be supplied with lubrication ports, but I usually just oil the rails. They also are of a slightly different design which separate the balls with a cage that keeps them quieter and traps lubrication.Quote
hobbymods
Well I'm already printing a housing to run 2, but I will take your advice and also make a single rail version.
It certainly would make life easier.
I take it you're a machinist/toolmaker of some sort?
What I don't want to use is the MG rails, as they only have one bearing race as opposed to the EG series which has 2, and can be supplied with a grease nipple (I build everything to be serviced).
Please don't think I'm not one to listen, I'm just so used to hearing "naaahhhh....you don't worry about that shit, just use this paddle pop stick and a rubber band", which is just not how I roll.
I'd still use the single X carriage horizontally mounted, because it would be easier to marry up to my Y axis, with a machined L bracket dropping down into the build area.
Lots of advantages this way in addition to weight/cost....access to the extruder, ability to mount some sort of engraver for a different application, as well as simply looking better.
So cheers for that.
I get wanting to do it right, but again in this case it's really not needed for this application.
Re: Rugged CoreXY June 08, 2016 07:13AM |
Registered: 10 years ago Posts: 1,873 |
Re: Rugged CoreXY June 08, 2016 07:42AM |
Registered: 14 years ago Posts: 268 |
Lots of feels. You certainly try to minimize unwanted forces acting in ways you don't want, but you use a bearing to provide lower friction while resisting load of some kind while not wearing "too much*". Otherwise you could use a few flat pieces of closely sized material, slap some lube on it and call it a day. Small stuff costs more to make and hold tolerance on.Quote
JamesK
I always find it difficult to think in terms of single linear rails. Even if the turning moments are well within spec it feels more natural to design so that as much of the force as possible falls on the primary load bearing axis. Typically that would allow sizing for much smaller rails as the primary axis will typically take a load orders of magnitude above the torque load, but things start getting odd when the smaller parts cost more than the big ones. I'm still not sure I could ever bring myself to hang things off the side of a single rail though - it just feels like an unnatural act dammit!
Re: Rugged CoreXY June 08, 2016 08:22AM |
Registered: 10 years ago Posts: 1,873 |
Re: Rugged CoreXY June 08, 2016 08:53AM |
Registered: 10 years ago Posts: 346 |
Re: Rugged CoreXY June 08, 2016 08:58AM |
Registered: 10 years ago Posts: 346 |
Re: Rugged CoreXY June 08, 2016 09:06AM |
Registered: 10 years ago Posts: 1,873 |
Re: Rugged CoreXY June 08, 2016 09:57AM |
Registered: 8 years ago Posts: 168 |
Re: Rugged CoreXY June 08, 2016 10:23AM |
Registered: 10 years ago Posts: 1,873 |
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The point Koko is making I feel is that our pissy little extruders weigh and exert forces MILES under the extremes these precision rails are made to take continuously
Re: Rugged CoreXY June 08, 2016 10:39AM |
Registered: 8 years ago Posts: 168 |
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JamesK
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The point Koko is making I feel is that our pissy little extruders weigh and exert forces MILES under the extremes these precision rails are made to take continuously
Yes, looks like you are right. A quick back of the envelope calculation suggests that the static rated moment specs for mgn 15 in all 3 axis are ~2 orders of magnitude over anything the print-head is likely to experience during normal operation, even making fairly wild assumptions about head weight and CoG position. No question these are pretty impressive parts.
Re: Rugged CoreXY June 08, 2016 11:19AM |
Registered: 14 years ago Posts: 268 |
I dare say that 20 or 25mm rails would be better still in performance. But "better" is application dependent. If you can fit them and don't mind the penalties you pay for moving more mass then great!Quote
hobbymods
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JamesK
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The point Koko is making I feel is that our pissy little extruders weigh and exert forces MILES under the extremes these precision rails are made to take continuously
Yes, looks like you are right. A quick back of the envelope calculation suggests that the static rated moment specs for mgn 15 in all 3 axis are ~2 orders of magnitude over anything the print-head is likely to experience during normal operation, even making fairly wild assumptions about head weight and CoG position. No question these are pretty impressive parts.
Yes.
And if you check out the specs on the EG15's, which is the precision rail I'm referring to, you'll find several more orders of magnitude again over the MG15's, due to the second race of bearings and tighter tolerances.
Point of interest was that the Hiwin guys I spoke to told me that if I could fit it the EG's were a much better rail and cheaper than the MG's.
Re: Rugged CoreXY June 08, 2016 05:39PM |
Registered: 8 years ago Posts: 168 |
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Koko76
I dare say that 20 or 25mm rails would be better still in performance. But "better" is application dependent. If you can fit them and don't mind the penalties you pay for moving more mass then great!Quote
hobbymods
Quote
JamesK
Quote
The point Koko is making I feel is that our pissy little extruders weigh and exert forces MILES under the extremes these precision rails are made to take continuously
Yes, looks like you are right. A quick back of the envelope calculation suggests that the static rated moment specs for mgn 15 in all 3 axis are ~2 orders of magnitude over anything the print-head is likely to experience during normal operation, even making fairly wild assumptions about head weight and CoG position. No question these are pretty impressive parts.
Yes.
And if you check out the specs on the EG15's, which is the precision rail I'm referring to, you'll find several more orders of magnitude again over the MG15's, due to the second race of bearings and tighter tolerances.
Point of interest was that the Hiwin guys I spoke to told me that if I could fit it the EG's were a much better rail and cheaper than the MG's.
My bearing guy is pretty good on rotary stuff but he knows jack about linear. Even still he isn't (and shouldn't) be suggesting applications without understanding the loads involved.
Re: Rugged CoreXY June 08, 2016 06:08PM |
Registered: 8 years ago Posts: 168 |
Re: Rugged CoreXY June 08, 2016 06:18PM |
Registered: 14 years ago Posts: 268 |
Re: Rugged CoreXY June 08, 2016 06:53PM |
Registered: 8 years ago Posts: 168 |
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Koko76
I guess I thought when you said "I'm well aware of moment loads" earlier in the thread that you were familiar with them. It's not "x amount of kilos", it's force at a distance, in SI expressed as newton meter (Nm). You have static moment loads when a torque is exerted in on an axis such as mounting the rail to a vertical surface and hanging the carriage off of that, in that case the force is gravity. Then there is dynamic moment, which happens as the system moves. Now you have mass and therefore inertia of the components, which must be accelerated. The faster you print and the higher your acceleration, the higher the dynamic moment load.
I understand that you have salespeople advising you and that's great. If my comments aren't helpful and you are just gonna do what they say because they said it, that's cool, I'll not bother. I just thought you might like to better understand the how and why of the system you are trying to build.
Re: Rugged CoreXY June 08, 2016 07:19PM |
Registered: 14 years ago Posts: 268 |
Re: Rugged CoreXY June 08, 2016 07:43PM |
Registered: 8 years ago Posts: 168 |
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Koko76
I'm not touchy or annoyed. It's your money, your design, your printer. You asked for help and input, you keep applying value judgements like "better" without being able to quantify them. I've made a couple suggestions to help you be able to better qualify and quantify "better" for yourself. It does not appear to me from your replies that you understand what I'm saying. Perhaps it is a continents difference in the "same" language. I suggested that if you aren't finding what I say helpful, that's fine with me, I'll stop bothering you. If so I apologize, as I'm really not trying to be rude. If someone were to reply to me here IRL "I'm well aware" of something, I would take it to mean that they had working knowledge of the subject, and depending on tone that they were somewhat annoyed that I had raised the issue.
My recommendation is that 15mm guides of either type are un-needed and frankly unhelpful weight. At most I would suggest 12mm miniature type. They might cost more, you did also say several times that cost was not a deterrent (may have different continents words there too sorry). But they will contribute less to system loads, making things quieter and improving print quality. I personally am using 9mm guides for my X and Y in the H bot that I am building. It will have a printable area of just about 165x165 in X and Y. In the dual rail direction I would have used the 7mm rails but they weren't available in the length I needed anything but a custom order that would have taken longer than I'd like. For Z I have a single rail which IS a 15mm miniature type, but it is a wide variant, 30mm wide but the height of a 15mm miniature (similar carriage too, just wider). I know you aren't planning that type of construction, but I wanted to give an example of where I felt the load capacity would be appropriate. That will hold a 200 mm square bed 8mm thick (at least, might go thicker for parts of it).
Again, If I've been rude I apologize, it's not my intent.
Re: Rugged CoreXY June 08, 2016 08:12PM |
Registered: 10 years ago Posts: 1,873 |
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They did ask about the "moment load" and I couldn't give them a figure....what would we be looking at here?
I would imagine I'd be swinging 400-600 grams off that central carriage, certainly not a kilogram, but I'll run it past them again and estimate a kilo load and see what they say.
Re: Rugged CoreXY June 08, 2016 08:42PM |
Registered: 10 years ago Posts: 346 |