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?
If so
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.
Ryan
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.
Gary
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.
I like the idea of a corexy and have been thinking about trying one - I’ve been studying the SmartCore version on github. There’s also another version I just found on thingiverse. There both based on a wooden frame rather than an aluminum extrusion frame.
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 That is how I originally made mine and I know it isn’t right.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.
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 saw
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.
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.
I’ve been printing parts all day, on the 4th revision. we’ll see how it comes out.
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.
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…
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?
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?
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.
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.
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.
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.
The Z?
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.
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”
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.