Ah, I've never heard that. Thanks!

 

Are you switching DC? A MOSFET or array of MOSFETS will probably do better at those temps and cost considerably less.

 

Well, for the layman, a MOSFET is a switch (transistor) that is operated with the presence or absence of a voltage at an electrical "gate" connection. In this case, you would switch the transistor on and off with your regular heated bed power output.

MOSFETs can be bought already mounted to a circuit board with the relevant connections available on connectors and are available in a massive amount of voltage and current capacities/ratings.

I purposely left this a bit open-ended as it does require a bit of prior experience to implement as they're significantly less fault-tolerant in numerous ways than a solid state (or mechanical for that matter) relay.

As a guide; an ~80A MOSFET of suitable voltage rating can be bought from RS/Farnell for <£2 in as low as single digit quantities.

 

Looking good! Are you planning on wrapping the hot-block with some kapton?

 

After converting my bot to direct drive (using the STLs from the C-Bot page), I had a number of issues (not related to direct drive, though).

Over the past few days I've been on a mission to stiffen up my printer's frame. Almost completely dismantled the electronics and most of the lower frame and moving Z-stage. I've added some long (~330mm) 45 degree brackets (printed out in PLA before the dismantling began) to the frame and early indications are that it will help stiffen the frame. I also un-twisted all the stepper motor cables and re-twisted the pairs, rather than twisting all four wires together.

Anyone have thoughts on going to larger-diameter idler bearings? The artifacts I saw in my prints (before dismantling) led me to think the diameter of the idlers I have was too small.

 

Whoa, that is an accident waiting to happen if I ever saw one. Do i remember you saying somewhere that you bought your SSR from eBay or AliExpress? They're generally junk. Just buy a genuine one from Mouser or Digikey. They're rated for the max stated current if you bolt them to a heatsink

I'm aware Jetguy is a highly regarded 3Dprinter, but come on... As a minimum, a schematic drawn in MS paint should be a gigantic red flag

Extruder bracket looks very familiar! I have a wanhao i3

 

Adam,

I've tried to find an answer on the forums to my questions but had no luck so hopefully you could help us or point us in the right direction. We really like the design of your printer and are wondering about its abilities.

Though we have been having some good success with a printrbot simple metal, We thought it would be a good project to build a machine with a larger build area and hopefully better resolution and print quality.. We would like to be able to make some really fine, accurate, prints. After looking at the corexy system we thought it would be a great system, until we came upon your cbot style. My son and I are looking into building a c-bot with the 3 (xy) linear actuators on top like yours, possibly with the gantry made of c-beam using a belt system (gt2 or gt3) . We are thinking a build area of 14x18in. so the unsupported length of the gantry might be somewhere near 20"-24" . What kind of resolution do you think we could get using a head like the e3d-v6? is the v-slot concept the right one for accuracy and precision?

Are we better off with ball screws vs a belt system? your thoughts and those of the others would be appreciated. I expect to return to this thread a great many times during our build.

 

Hi Alar,

Having just completed(?) a 18x18x18 Triple-C-Bot, I can give you a few things to watch out for

1) Keep in mind that along with a larger build area, you're going to experience GREATLY increased print times. I used to think that 8 to 10 hour prints on my Rep1 clone were long... Unless you go with a bigger nozzle, you'll be in for a bit of a shock
2) My build actually came out closer to 14 inches in the Z axis, mostly due to a larger Z stepper motor and a taller build plate mounting setup. Be sure to model it all before cutting your extrusion.
3) For anything larger than, say, 12" squared, don't try bowden, go direct-drive. I could have spent many many more hours tweaking my bowden setup and might eventually get to somewhat satisfactory results, but still wouldn't compare to what I'm getting with direct drive.
4) Add in extra braces and cross-supports where possible. Make the frame as stiff as possible. I put the question mark on the "completed", because I'm still working on making my bot's frame as stiff as possible.
5) Your "resolution" largely depends on your nozzle diameter. I started out with 16T pulleys on my X and Y steppers, which worked out to be 100 steps/mm (with 1/16th microstepping). I switched to 20T pulleys, dropping it down to 80 steps/mm, and I cannot tell the difference (output is similar in "resolution" to my Rep 1 clone). I did this mainly to make things easier on the printer board (Azteeg X3 with a 2560). If you go with a 32 bit controller, that may become a moot point.

My only regret with this build was cutting the vertical legs too short. I really should have triple-checked the modeled build height before cutting. It is, however, fairly straightforward to extend the printer in the Z axis, if I ever decide to do that

-Joe

 

Thank you for all your answers, It's a lot to take in. work got in the way this week so i'm trying to get some free time to think about more questions, after reading more posts and learning some more.

 

I started out looking to build a c-bot, but at a 12" cubed size it seems better to go with the triple leadscrew design you have. Your BOM's second tab has a form for the extrusion cut lengths which doesn't seem to have formulas embedded. Is it the same as the c-bot's?

 

Are you using a closed loop belt for the z axes? The reason I ask is that in the photos the belt is not a closed loop.

 

I noticed in earlier posts that you modeled everything in fusion 360. Is that publicly available?

 

Thanks, Adam. I asked because I may make a few small tweaks to use materials I have on-hand and also to reduce the number of places I'll need to order parts from. Hopefully the step files will import into OnShape, but I've been meaning to spend time to learn Fusion 360 for some time now as well.

Is the 200mm^3 printer you're building for your friend going to be mostly the same or an entirely different design from this one?

 

I'd like to get some input / suggestions for a new build. I currently own 6 delta printers and a Taz 4 Cartesian built from a kit. I've built several dozen printers over the years but this is my first venture into Core X-Y.

My plan is to build a Core X-Y printer with a 12" x 24" x 12" work envelope. The Triple C Bot seems like a good compromise for Z motion. One question I've pondered is should X (carriage) be 12" or 24"? I can make arguments to support each, what do others think or know?

In this configuration, 2 of the screws would be at the corners of the long edge and the other at the middle of the long edge opposite. That should allow reasonable clear access into the printer and the long edge will be the front of the printer - I really don't care if this long dimension is labeled X or Y.

For the table I'm thinking 1/4" MIC 6 with two 12"x12" silicone heaters underneath. A piece of PEI adhered to the top. This should be light, rigid and flat. I primarily print PLA but would use this for occasional ABS, Nylon and maybe NinjaFlex.

Thanks in advance,
Michael

 

I think it's based on what you want to build vs the strength of those objects: Mine is 12x12x24-ish(tall), so it's great for printing tall things. But not wide things. If I wanted to build a table-leg, I could print it straight up, but since the layer-lines are perpendicular to its height, it would more easily snap if bent. However, if it was printed laying on its side, the layer-lines would run down the length making it much stronger.

In my magical shop of the future I'll have both

 

Sorry, perhaps I wasn't clear - I'm talking about 24" wide by 12" deep x 12" tall. I have a delta with a 22" Z so I don't need tall, I need wiiiiide! I'm working on a 3D printed fishing rod (shhh!) and I just need something a little wider than I have to make longer sections. So the question, should I align X with the short 12" dimension so I have a short carriage travel or with the 24" long dimension so I have a long carriage travel. I'm leaning towards 12" X travel as I think that might lead to a more rigid mechanism.

 

Gotcha! I guess you totally could have a 'deep' printer, that would have a short X travel, but long Y: That would cut down on the overall mass of the top gantry, which is probably a good thing. You'd just have to workout the leadscrews to make sure they lift that oblong bed correctly. Maybe one in the front, and one in the back, like I'm doing?

Or how about you just go 24x24?

 

That's what I was thinking - short X travel/carriage travel would reduce the overall moving mass. It also leads to a more rigid assembly with lighter materials (by this I mean one could make a more rigid assembly by using beefier frame extrusions, bracing, etc that all increase mass and especially moving mass).

The reason I posted in this thread is the triple screw design. My thinking was as stated in my first post, that two screws would be at the corners of the long edge and the third in the center of the opposite long edge. Like this ("O" is a screw):

-O-----------------------O-
| |
| |
| |
| |
-------------O-------------

Does this make sense? What about arrangement of the guides (not sure about whether I'd use OpenBuilds wheeled carriages on all 4 corners, or two in the middle of the short edges or some other arrangement. Perhaps linear guides?

I don't want to take on the expense, table mass, and footprint of 24x24. Heating a 12x24 bed with a PEI surface is going to be a large enough expense and challenge. My target parts are long and skinny so I really don't need a bed that large. Not to mention not having enough bench space for a beast that large! I am going to increase the Z though to at least a working 18".

 

I was completely joking about 24x24 btw
The screw design you posted above is basically what others have done for smaller, wider beds. I'm no leadscrew expert though, but it seems like it should work.

 

It wasn't a *bad* suggestion Eric! But that would be a monster printer. Maybe next time!

I posted on the google group asking for recommendations for the Z for this printer. So far, the triple c-bot seems to be the best option and it makes sense to me.