My 150x100x130 h-bot design

Hello, gentlemen, thanks for letting me in.

This is my h-bot design (yes, I know what you're going to say about racking, but so far this has been a non-issue). I could turn it into a CoreXY with a few extra bearings, but at the moment I would rather not. Components are mostly china-made or chinese clones (Rumba, E3D, MK8 extruder). The design was inspired by several other printers (leapfrog creatr, 3dprintedlife's Eclips3d, ultimaker 2, 5th gen replicator mini, hypercube, hypercube evo, etc), which you can tell by looking at certain details.

Linear rails are taiwanese Hiwin (kind of overkill now that I have tested both Hiwin and some chinese clones), Z-rods are 12mm, build platform is 4.7mm aluminum.

It has an acrylic build platform as a practical placeholder, but I have a 150x100mm heated bed designed for it which I will eventualy have made out of 1.6 or 2mm MCPCB, which is supposed to use Ultimaker 2-style clips to hold the glass plate in place. Printing to bare acrylic or bluetap I have no issue with adhesion. In fact, PLA sticks a bit too well to both, but I think it's just a matter of finding the right z-offset. It has no z-probe, but since the z-endstop is optical the bed can travel some mm up after it's triggered, that way I can use the manual-probing automatic bed levelling function in Marlin.

Printed parts are made of ABS because I had a roll lying around. The extruder holder is the same part as Hypercube Evolution's Z-motor holder. In fact, I started with a Hypercube Evolution frame and designed my own to fit it.

It's not intended to be used enclosed with a heated chamber, as the aluminum gantry plate bolted to the x-axis linear rail would work as a bimetal, that wouldn't be good at all. It originally had an extrusion on the top-front part, but I had to remove it because it would cause the rails to bind, since the frame is not exactly square, but it looks way cooler like this. Maybe I'll eventually bolt the XY stage to a milled or laser-cut aluminum plate and ditch several other portions of the frame as well, but that will require quite a bit of redesign.

I still need to design/print a few accessories, but it prints really, really well, but then again so do 199$ chinese printers nowadays.

IMGUR album here: [imgur.com]

I like it!
Personally, I think H-bot gets a bad rap from people using 8mm smooth rods and printed axis parts, throwing rigidity out the window (for any printer design, really).

Curious as to what you've found with the Chinese clone rails. I've not tried them for all the horror stories..

Quote
Diggrr
I like it!
Personally, I think H-bot gets a bad rap from people using 8mm smooth rods and printed axis parts, throwing rigidity out the window (for any printer design, really).

Curious as to what you've found with the Chinese clone rails. I've not tried them for all the horror stories..

I'm glad you liked it. The h-bot design is used in a lot of industrial pick and place machines that work nonstop, so it can't be all that bad. I think if you move the carriage by hand the motors will be resisting your movement, which will cause the gantry/frame to twist, but when the machine itself is moving the racking will be much less severe, and it may be not noticeable at all (such as in my case). The twisting motion is proportional to the length of the gantry and to the tension, so a longer gantry and a high X acceleration + heavy carriage will rack more than if you make a transversal carriage (if it's a retangular machine) with a light head. You end up spending more on rails/rods if you go that way, but it might be worth it.

It seems there are a lot of chinese manufacturers that make the rails without any brand, and using the same coloring. Some of them will be a bit sticky, some will be really smooth. Some will be sticky, but because of imperfections in the plastic parts not on the balls or the rails. The carriages are not exactly interchangeable. Sometimes a carriage from one manufacturer will slide super smoothly on the rail of another manufacturer, but if you do it the other way round, then the carriage of that second manufacturer will stick if you apply just a bit of twisting load, and if you actually run that carriage on that rail, you'll wear out the rail, and when you try the original block on it it will be super-loose, but it will still be much more rigid and solid feeling than the usual LM8UU bearings and 8mm rods.

I bought some MGN12 linear guides and carriages. There are Hiwin compatible ones with ball diameter of 2.381 (1/8 inch) mm, and the other ones with 2.5 mm. You can see the difference at the form of the guide also. Putting one type of carriage on the guide is much too loose and otther round too solid.

I have bought some used Hiwin guides now, and I am a bit disappointed, as they have imperfections also. So I will use the other ones in the future also.

Edited 1 time(s). Last edit at 08/01/2018 02:15AM by JoergS5.

The whole point of using linear guides is that they eliminate a lot of the quality issues with end supported round rails. If you only want the look of linear guides without their performance (or cost), keep buying the crappy hiwin knockoffs. If you want the performance, too, look for real, high quality linear guides.

If you are able to purchase things via ebay where you live, you can buy very high quality Japanese made industrial surplus linear guides, usually for just a little more $ than the crappy hiwin knockoffs. No, you may not be able to buy a part that fits a specific BOM. You might have to use your brain a little and modify the design to accommodate whatever guide rails you are able to get a good deal on, but you won't have to screw around trying to find replacement balls and hoping that they turn a POS into a good linear guide. If the manufacturer couldn't be bothered to use the right size/quality/quantity of balls, what else did they skimp on?

Check for brands like IKO:
[www.ebay.com]
[www.ebay.com]
[www.ebay.com]

THK:
[www.ebay.com]
[www.ebay.com]
[www.ebay.com]

NSK:
[www.ebay.com]
[www.ebay.com]
[www.ebay.com]

It took 5 minutes to find those. If you dig a little you may find NOS guides still in their boxes for similar prices - I have on several occasions. If I even think I'm going to build another printer, I start shopping for the linear guides that will be long enough and come with enough bearing blocks to do the job. If I find a deal I buy, if I don't, I don't.

Don't worry if the rails are too long- you can cut them down to the length you need with a cut off wheel on a grinder.

Hiwin makes good linear guides, but if you search for those on ebay you get 99.9% knockoff crap. If you want Hiwin linear guides, buy them from a Hiwin dealer.

Edited 1 time(s). Last edit at 08/01/2018 03:53PM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

JoergS5, you need to take into account that these guides are not really intended for precision sub-microscopic work. We're using a component that is just as likely to be employed in a insole-making machine. They're also supposed to be mounted to flat-milled surfaces (i.e: for example the E3D's toolchanger demo machine), and a lot of people are bolting them to aluminum extrusions (like I am), which I'm not sure would match their intended flatness tolerances.

the_digital_dentist, there are some legit Hiwin dealers that sell on Aliexpress, and some also have THK and other brands, which is good when the ebay sellers don't ship to your country (my case). I think most of them are interchangeable, maybe not on rail/block level, but if you design the machine for hiwin MGN12 you could use iko LWL 12.

I can echo the digital_dentist's comments. I have had good experience/luck buying both THK and IKO guides. Also, do not be afraid of contacting the seller and asking for a modification. I was looking for a set of 3 500+ mm guides for a delta printer and a seller had 2 875 mm IKO rails with 4 blocks on them for a good price. I asked if I could get 3 with 1 block on each and he created a custom item for me. I believe I only paid $60 per rail with free shipping.

@Kewtdz that's how I got my 200/150mm rails. I asked two aliexpress sellers for custom lengths and they did it for me.

The Hiwin guides I bought: I suspect the seller combined block and guides not fitting, i. e. the
preloads are incorrect. I bought 3, one is ok, one high preload and one very high. I will try buying fitting block+guide in the future.

In the meanwhile I bought THK and I am very satisfied with them.

When I have time (when it is winter...) I will try recombine blocks and rails and exchange balls with G10 balls to rescue some if the linear guides.