I like that design. I may just have to rebuild mine to handle a 12x12 bed and use this mod. Would only have to recut the 4 side bars.

 

@trublu832 Yeah I love it! Now I have a conundrum though because I was planning on building an 8x12 bed and now I've just ordered enough extrusion to go 12x12.

I was planning on using an AC (120V) bed heater connected through an AC solid state relay because 12x12 really needs some juice to get it up to 100C. This 750W silicone heater seems like a little bit of overkill though. I'm going to contact them and see if I can get a little lower watt density. I feel like 400-500W would be a good number based on my current 8x8 bed's 150W (@14VDC). The silicone heater would be stuck to a 1/8" aluminum plate with a piece of glass on top.

 

Mine is printing - currently ABS replacement for the carriage pieces I managed to deform. I am still putting finishing touches other parts but I thought I would post the latest pic. My bed is 12x12x12 but for ABS I only do 8x8. My PLA 1/4" plate glass really doesn't like to be heated to 90°C. I bought a piece of boro on AMZ for $15. Using a std 8x8 MK2A. I have it at 110° - maybe 10-20min to get there. I have created a print fan duct. It works great - u may be able to see the top and bottom of it. I just need to tweak the file so it will print out without holes in it. The fan is mounted on top of the carriage with the duct work going down in front of the hotends. It comes apart in the middle so I can easily access the hotends.
The platform is not cantilevered. Adam has a similar arrangement. I think mine is different in that it is rotated 90° to allow full access to parts from the front. The adjuster/braces u see seem to work well. The previous design I made did not. The X endstop is incorporated into the carriage and the Y and Z are on the frame. The idler side is the front as u see. I managed to get it all in with a width of 60cm and that includes the 2 Bowden extruders hanging off one side. The depth is under 52cm including the X/Y motors.
I saw someone said they were using brass nuts, which I am also using. Do not use the store's screws if u do as they r too crude for the brass nuts. The screws will work fine with the store's Delrin nuts. Either that or plan on spending a day or 2 filing down all the rough spots inside the screws.

 

This company makes different watt densities, but I only saw the 300mm listed in that high watt density, which isn't all that high compared to some silicone pads I see at McMaster.

I was just thinking bang-bang control out of Marlin it would be on for 5 seconds minimum and I wasn't sure how much overshoot that would cause. The PWM I think is too fast to drive an AC SSR, which will wait for a zero crossing before it switches generally. Looking at the Smoothieboard, I see its PWM frequency is adjustable in their config.txt at least down to 20Hz so I'm thinking 750W isn't overkill at all if it can be PWMed (my brewery PMWs 5500W, although at 1Hz). I've got a 1/4" MIC-6 aluminum coming for the bed because supposedly it is pretty flat. Does anyone know where you'd get aluminum plate made flatter? Like what am I looking for in the phone book if I want the plate made flatter than it comes?

 

Where did you order your MIC-6 from?

 

I was from eBay ]MIC-6 CAST TOOLING ALUMINUM PLATE 1/4" x 12" x 12" $41 with shipping, which was better than I could find it anywhere else (even the seller's website has it for a coupe bucks more after shipping). At 1/4" that means it will weigh 3.6lbs, which once you add the silicone heater I''m starting to wonder about the weight. I probably should have gotten 20x60 for the back but we'll see how much it deflects. I'm sure I'll have to place a second order from openbuilds anyway, who ever gets all the parts they need the first time?

 

I'm looking for a 8x12 plate myself. Will have to email them and see if they can do a custom size. I would love to get one with the back cut down so the heater sits flush to the bottom. Also having a cutout for the thermistor is a plus.

 

Has anyone had success with the E3D v6 or E3D v6lite hot end?

 

I'm using an E3D v6 with no problems.

 

Does the performance justify the cost? They also have the v6 lite, which can only do PLA and ABS and has a lower stated printspeed.

 

The only other hotend I have used is the one that came with my Printrbot. Compared to it, the E3D v6 is a lot better. I guess you could get some cheaper Chinese knockoffs, but the hotend is something you really shouldn't cheap out on.

 

Question to the community: I'm building a 12x12x24" version of this bot: Making great progress, all the hardware is built, I'm currently setting up the electronics.
I've been tuning my stepper drivers, got the X/Y & extruder happy. But the z-platform is giving me problems:
I'm using a Rumba board, with the A4988 stepper drivers that came with it: Currently, I can't get the z-platform to raise, only lower: I've been tuning the pot on the stepper, and it feels like there's just not enough power to lift it: If I help lift it (with my hand), it'll raise up. But I can't dial in any more power: It appears to be the max that driver can give. Like the printer build describes, I have both z-steppers plugged into a single stepper driver. If I decouple the the lead-screws from the flexible couplings, I'm able to move it up and down with little resistance. And while decoupled, both z-steppers move just fine. I'm able to raise and lower the z-platform by twisting the leadscrews by hand all the way up and down ( and 24" is a whole lot of twisting) without any issues I can discern.

FYI, I currently have some DRV8825's on order: looks like they're 1.5A vs the A4988's 1A, so maybe it'll give me the juice I need? In the meantime I could actually use two stepper drivers instead, but I was concerned about possible sync issues?

Any thoughts appreciated!

ps : On a side note, I've been trying to blog every step I've gone through. If you want to live vicariously...

 

That is probably your issue. When you have both steppers on the one driver, each stepper can only get half the current the driver can provide. So with only have 1A, each motor is getting 500ma, which isn't enough to provide the torque needed. What you need to do is run a second driver as a slave to the first one so each motor can get all the power the driver can provide.

 

That's what I figured was happening too.
"What you need to do is run a second driver as a slave to the first one so each motor can get all the power the driver can provide." :
Can you comment/link on how to do that? This stuff is Greek, and I'm trying to learn fast Thanks!

 

I'll have to do a little research on the Rumba board to describe it better, but you basically take the ENABLE, DIRECTION, and STEP signals going to the driver and connect them to another driver. I am using a Smoothieboard and there are headers available to do that. Not sure about your board.

 

@Carl Feniak : Glad you like the blog Thanks for the info on loosening stuff (and the screws are oiled). I was actually thinking about eventually redesigning that bit to allow for permissible slide. But in the meantime, I'll just loosen stuff and see if that makes it happier. Yah, the new 60mm bolts with nuts on the back feel way more secure As far as the updated printed bit that attaches the nut to the frame, that was a mod done by @sheffdog : I'll talk him into posting that so he can take the glory

@Elmo Clarity : Good starting point, I'll look into what it takes to work that magic on my drivers. Thanks!

 

I like the blog too, thanks for taking the time to document the process and share the gotchas.
Do you think your print bed is just too heavy? I know you scaled up your design a bit from the original.

 

My bed is 12x12, the same as @sheffdog, and he has no issues with this same setup (his printer and mine are the exact same, other than mine is taller). BUT, he's running the DRV8825 drivers. And really, the weight added by a few more inches of extrusion plus the larger build plate (which is pretty light) seems negligible compared to to say, what Carl made. But what do I know? It's all just theory right now

 

@AK Eric I did some quick research on your Rumba board. While it would be possible to modify the board to do the two drivers/two motors by linking the control lines, given that it has 6 drivers, it would probably be possible to link them in firmware. You might want to bring this question up with maker of the board and see if anyone has already done that. Making the changes to the hardware is not something easily described in a forum like this.

 

Thanks guys: I realize this issue is Rumba specific, and not something directly related to this thread. I'll poke around in other forums and if I get a solution I"ll be sure to post it. Or in a month my DRV8825's will show up and hopefully just fix it

 

Just an FYI: I modified Marlin to support the "Z_DUAL_STEPPER_DRIVERS", and plugged my other A4988 driver into the Extruder2 block (Rumba supports three extruders): After tuning the trimpot, I was able to get the bed to lower, but not raise, even when there was no load (leadscrews were decoupled & bed raised out of the way). Come to find out, it looks like there's a bug in Marlin in that block that causes a conflict with "Z_DUAL_ENDSTOPS" being disabled at same time. I noticed this because while browsing the "Marlin Configurator", it's code section for setting up the z-dual-stepper-drivers differed (in the correct way) from the source I just downloaded from GitHub.

Blah blah blah, long story short, I fixed Marlin, and now I can raise and lower my bed, including the glass plate. Yes!
I still want to eventually drive them both off on DRV8825 to resolve any possible sync issues, but in the meantime this will do.
Thanks again for the feedback.

 

Hello all, I wanted to post my improved acme blocks for the Z gantry, they align perfectly with the Z motor mounts of the original C-Bot build from Carl. This version is slightly wider to fit the openbuild acme blocks and extends slightly forward to perfectly align with the Z stepper couplings.

 

Here is the STL for my ATX mounts, the great thing about them is the little bumps that stick up do not interfere with Z height. They do not keep the PSU from sliding left and right, but they are convenient for mounting the psu so you can easily move the bot around.

 

Here are the files for my Heated Bed mounts.

 

Here is the Electronic Box I made for my Rumba board. Excuse the messy wires!

 

Here is the Auto Bed Leveling Sensor mount.

 

Here are my custom Endstops for my bot. The X is placed on the Left hand side of the X gantry. The Y is mounted on the outside left corner of the bot (This is the same file that Carl posted so I am not attaching it). The Z end stop is mounted on the front side of the left rear leg.