I saw this build today and was wondering why its not more popular. Is there any reason why everyone went with the 2020 rails when this was always available?
http://www.thingiverse.com/thing:102972
for one h-bots hav racking problems… a corexy is much better
means twist of the frame as the print head moves the frame can twist. this is why most have moved to corexy
IMHO id just pick a corexy build and go that route. 2020 extrusions are cheap enough. i am sitting under 400 USD for the fuse box. could have got it for allot less but went with better motors. better brackets. better belts
this is made with 1515 but others have modified it to work with 2020. i went with 1515 just to keep it original. above is my bom with links to misumi and folgertech and makerfarm with what i bought
@Mark_Ellison @Nathan_Walkner , Racking is due to a lack of rigidity in the linear guide system and is inherent to H-bot style kinematics. If you look at how forces are balanced in an H-bot when the print head travels along the x-axis, you will notice a torque created across the gantry, causing the gantry to twist–coreXY solves this problem by using a different belt configuration, negating the torsional moment on the gantry
All hail Hydra
I thinl the question here is tubes vs 2020 extrusion profiles. Not h-bot vs core-xy
@Ishaan_Gov I am no fan of the H-Bot but if the issue was the lack of rigidity in the linear guide (linear rods were all the rage when H-Bot was in style) then maybe linear rails can solve that issue… just a thought.
@Florian_Ford there is never any scenario where HBot is better than CoreXY. It’s pointless to build an HBot printer when you can make a tweak to the belt routing and get a superior-performing CoreXY printer with nearly identical parts and design.
Most people use 2020 instead of conduit because 2020 is straighter, much easier to mount hardware on, and still cheap enough that there isn’t much price increase.
I agree with the first part :). 2020 gets pricey when you factor in all the T-nuts and corner brackets, plus maybe the cube connectors …
You can use printed brackets with extrusions just like this conduit design. And there are extrusion profiles that accept regular metric nuts. The expensive metal stuff is optional (although I always use it because it’s just so much stiffer than plastic).
If plastic brackets are used it’s pointless to use alu extrusions because the weakest link in the chain has already been defined. At that point conduit makes more economic sense and alu extrusions would only offer the slot for easy attachments. I agree that if you use extrusions you’d better go with the metal brackets too.
Extrusions are superior for wheels-on-frame drivetrains like V-wheels, and arguably better for hiding belt and wiring runs. Plus you can order an extrusion cut to length +/-0.1mm or better with a perfectly square end… That’s very valuable for frame alignment.
It’s a few dollars difference per frame member, if you’re hurting for $50 on the printer build then you should be buying a cheap i3 instead of building a custom CoreXY. And wheels-on-frame designs can actually be CHEAPER than conduit when you factor in linear rods.
I’d have to disagree on the cost issue…Conduit (HomeDepot) is nearly 1/10 of the price of extrusion (mcmaster), this is comparing 3/4" to the 20x20 at 10’ lenghts. Modifying the design to change to a CoreXY belt run wouldn’t be that hard either. So this is a pretty decent alternative for someone strapped for cash.
I don’t see this as a solution for strapped-on-cash folks but a solution for what they would get out of the printer. It makes no economic sense whatsoever to reach for such expensive gadgets as those using extruded aluminum with laser cut tooling plates and linear guides if all you do with it is print trinkets. And even if i’d print something useful that actually holds together in real world situations, when would I get out of it the value I put in it?
Thanks for explaining. So what about if someone were to create lets say a large 1 meter square core xy printer, which frame would make more sense in that case. stability and cost
secondly why did the MPCNC design choose to go conduit. was it not feasible with rails?
I would go for some kind of extrusion rail. 2020, makerbeam or makerslide or something like that. The small amount of added costs will offset the ease of attaching stuff and keeping everything straight. Tubes are simply not designed for something like this.
1m is long, you will need quite a bit of stiffness.
I doubt stiffness would be a problem, http://www.thingiverse.com/thing:724999, if a CNC machine is possible with conduit, I don’t see a reason why a printer wouldn’t be also. As a matter a fact the MPCNC can be converted to a 3D printer with a change of the toolhead. I understand that a lot of people here probably have printers made of nice aluminum extrusion but for someone like me who stills runs a printer made out of threaded rod and mostly printed parts this is a very interesting idea.
Don’t get me wrong I definitely would love an all metal printer. This is just another option available.
Just to be completely clear, the MPCNC is a miserably bad milling device. The milling tolerances you’ll get out of conduit “rails” and printed structural parts are crap, and the surface finish and tool life you’ll get at such low feedrates are also crap. (Read up on “feeds and speeds” and learn why cutting slower to make up for floppy mechanics is a bad approach.)
BUT, it’s a cool build that is just barely, barely, barely adequate for cutting aluminum, and that’s valuable to people who have a minimal amount of milling to do and thus don’t want to shell out for a Shapeoko or X-carve or whatever.