- July 8, 2017 at 4:48 pm #37788
I have been doing some crude prototyping with the core xy geometry for a few reasons but I could use some feedback.
1)Anyone interested in a corexy style printer, or laser etching/cutter base?
2)The HiWin style import rails, or smooth rods? Price is very similar now for a set but I have no idea how long the “hiwin” style bearings last but they are easier to use.
1 user thanked author for this post.July 9, 2017 at 1:43 am #37798
I think it depends on the design of the frame. I am definitely interested in the corexy. it looks like a really cool platform for a printer. I am wonder how large it can scale for very large format printers.
GaryJuly 9, 2017 at 5:22 am #37801
We saw a core xy at mrrf that had something like a 4 foot cubed build area. There was also a taller one, but I can’t remember if it was a core, or standard gantry style printer.July 9, 2017 at 5:27 am #37803
BTParticipantJuly 9, 2017 at 7:43 am #37812
Wood for sure, or I should say sheet material extrusions are expensive, sexy but expensive. The odd thing about core xy is it cuts resolution in half, both steppers have to move to move x or Y so in the firmware the steps get cut in half. Not sure if this has an effect but When I print with one I will find out.
I ran it yesterday at 150mm/s to watch the belts and things, it looks comical that fast. I am finding no one prints faster than about 50mm/s, 60 for the quick and dirty prints. So speed isn’t really a big deal. It just comes down to making a printer with a Z axis mounted bed. The top gantry isn’t all that important, the CoreXY is just pretty fun to build and watch and only has disadvantages when you get really big from belt tension.
I saw that smartrap core last night. When I tried that with mine the belt could actually catch on itself in the extreme position shown in the main pic on that link. That design is killer though, simplistic and gets two thumbs up from me. I want to do the Z axis differently though. This one has the longest stretch of belt at an angle directly off the empty side of the pulley which is okay but on mine caught with the gantry and could only be solved by moving the corner further away.
The smartcore from the github link has bad belt geometry. That is how I originally made mine and I know it isn’t right. There is an angle at the far side of the gantry to the corner blocks. It is not a lot but is not correct.July 9, 2017 at 12:28 pm #37843
I am already missing my ability to print stuff, so I am interested in a corexy printer. I was thinking of making a mp3dp but the corexy stuff has me really interested. I had this idea to once modify the z axis of the mp3dp and have a z axis that is a bed that descends like you would normally expect, but it just doesn’t seem worth it. For printing there are much more agile options. Printing big for me didn’t end up working out like I thought because at such big prints, the layers cool (even without a fan) too quick for the next sequential layer to bond. Probably could of been solved with an e3d volcano…whatevs
If you make a mostly milled or printed version, I would try it out.
After you print above 60mm/s ish, does the arduino 8bit become a bottleneck? I saw a video here https://www.youtube.com/watch?v=ySqj3gPqfrs where the ramps/arduino we use eventually become too slow to keep up. Not that big of a concern but just something I sawJuly 9, 2017 at 12:42 pm #37847
Interesting video, I think he is making or missing some huge points.
Acceleration, jerk, arcs.
A circle small enough can trigger acceleration slowing, not processor limits. You would need to monitor the processor load to know for sure.
Similar with the box, and you can tell by his corners he had some wonky settings. This might be where volumetric extrusion comes into play.
At the same time a fast printer isn’t going to excel at small prints anyway.July 9, 2017 at 4:49 pm #37864
I’d be interested in building a larger one, say 500mm cube or perhaps gated by a heat bed. The largest bed heater I have is 400mm x 500mm. I haven’t had any luck finding borosilicate glass large enough and have been thinking of using either aluminum or steel plate as the print surface. With a corexy I think aluminum would be the better choice due to weight.July 9, 2017 at 4:57 pm #37865
I’ve been printing parts all day, on the 4th revision. we’ll see how it comes out.July 9, 2017 at 5:05 pm #37866
Dang Bill I didn’t put much thought into my reply. For something that big, the “hiwin” rails or the smooth rods will be hard to find. You would probably have to go to extrusions and there are a bunch of printers made out of those already in the coreXY.July 9, 2017 at 5:13 pm #37867
What are the reasonable limits to smooth rods or hiwin? I haven’t dug into it much but don’t remember the rods being an issue when I sourced them for the MP3DPXL…July 9, 2017 at 5:16 pm #37868
Well if you can find the rods then it should be fine, I didn’t think they were easily sourced that long. Maybe McMaster but those are so expensive.
If this works out I do want to make the sand table using conduit and corexy. Who knows how that will work, but it could be good?July 9, 2017 at 5:21 pm #37869
So a quick look on Aliexpress finds me 8mm or 10mm rods at 500mm length for about $6.00 each shipped. I’m thinking with that length I might be better off with the larger diameter? How well do you think they would work for the sand table in lieu of conduit?July 9, 2017 at 5:26 pm #37871
Im making the current parts for 8mm rods, but im not sure 100mm extra is enough, maybe.
My goal for the sand table is full diner table so that will be conduit.
A big printer right now has never appealed to me the challenge of that is all in the extruder. I’d rather have two small printers and just section the part. Its more versatile for what I do.July 11, 2017 at 2:57 pm #38012
Printing speed can be increased to much more than 50mm/s, the limitation is the hotend. It needs some energy – and means to not overheat the melting chamber after stopping the output – to melt enough material in a start/stop-mode. E3D once had some information about the theory behind it on their pages, but I am not sure if it is still there.
Eperimentally, I could run my seasoned OrdBot Hadron (sp!) @ up to 150mm/s, but then with a 0.3mm nozzle and, most important, in a pretty continuous motion.July 11, 2017 at 3:14 pm #38014
For me it’s a learning experience, not really trying to reinvent the wheel or break any speed records. From my perspective the corexy does seem to be the best design/geometry for a 3D printer. Until I try it though it is just an observation. So I want to try it, if it’s good, make the larger sand table version. Then some revisions and release some parts for other to try.
It could suck though…Can’t wait to find out. I have V5 of the XY axes on the printers now, Might get to actually run it tonight. If it seems okay, I will work on a Zaxis.July 11, 2017 at 6:21 pm #38034
The only thing that always bothers me about corexy is the moving platform. I think that’s a big reason why the prusa is so easy to replicate and make cheaper.July 11, 2017 at 6:29 pm #38036
I have a few ideas I want to try but it is a big concern for me as well.
The other part is I have beefed up the components more than 5 times now because of flex, the belts pull in so many directions. I want to try it out as is but if it seems cool I will have to redo it again to make it better, 5 revisions deep the CAD file is super ugly at this point. I have an idea to make is pretty slick now but I don’t want to start again I want to try it out to see if there are any other hidden ugly secrets.July 11, 2017 at 7:16 pm #38043
Yeah. I’ve never actually maintained or even ran one, but whenever I touch a moving (in the Z direction, Y is obviously fine) build platform, I get anxious about all the flex. Seems very cool otherwise, and it seems excellent/simple for cases where there is no need for the moving build plate, like the laser engraver or the “table from Dune”July 11, 2017 at 10:24 pm #38046
I haven’t delved deep into the Core-XY designs, but it seems to me like the flex issues would be mostly mitigating by some redundancy in the vertical slides the build platform is moving on. Wouldn’t four smooth rods with linear bearings and two lead screws give a very stable surface? With the cube design to keep the X and Y axis’ solid it should end up with better accuracy than the Prusa designs.July 11, 2017 at 11:04 pm #38047
It’s really easy to over constrain something like a moving bed. It’s better to use 2 bearing posts than 4 on it but they have to be the right capacity. Luckily there is not very much force on it at all, just the drag of the molten plastic, and the weight of the print.
I see why all the printers use the rails at the far end (nothing above them) but they would be better off at the sides. Just like a prusa style gantry moves on the z, swap it with the bed….. But all the corexy is in the way. So then it has to get wider, then it gets weaker…. Design choices stack up fast.
I have two Z ideas I have no idea if they will be any better, but I do enjoy the testing and designing.July 11, 2017 at 11:08 pm #38049
I didn’t actually go into it, 4 have a much higher chance of binding. If your standard z axis is too tilted it will bind. That is one of the main reasons I don’t like auto level, people end up using cockeyed axis. The more rails you add the more perfect it has to be or it will just lock up and skip steps or wear ot the bearings or rails.July 12, 2017 at 3:08 pm #38129
Wow, I’m not so sure about this corexy. If anything is even a tiny bit off, the whole thing is way off. Slightly skewed pulleys or idlers and the geometry is far from smooth, the frame needs to be extremely accurate and rigid. Parallelograms and tight belts times two make it even harder to deal with. Quick and dirty does not work for this, so many revisions and just more issues.
I think I might give it one more try but it isn’t looking good for using inexpensive parts. I thought it was just the rails I was using so I switched the 8mm rod and it seems worse.July 12, 2017 at 4:57 pm #38136July 12, 2017 at 6:38 pm #38142
So it seems to be solved by running a single belt not a double, at least both belts are the same tension, the big issue is when one is unbalanced it pulls like crazy on the frame. This means I might need to reroute the belt, or flip the gantry over, maybe not, ahhhh geometry used to be so easy.July 18, 2017 at 9:35 am #38692
Any news? A video or a photo? A 3d CoreXY Style printer would be amazing!July 18, 2017 at 9:40 am #38693
My prototype is embarrassingly rough. I learned a lot for the 5th revision and am working on two different versions now a large one for the Sand table and a printer. I am pretty sure I have most of the XY issues handled, I have not even started on the Z axis but luckily they are completely separate.
Sorry for the slow progress I am a little scatterbrained and working on a few things simultaneously right now that all kind of apply to each other.July 18, 2017 at 9:52 am #38694
Thank you for the update!!
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