feenix, I paid some 20 or so USD for shipping for a large silicone pad worth 370 USD, I don't think that's over priced.
on the other hand, if you buy more stuff, you pay more for shipping, that's pretty much the same everywhere. try looking for companies with free shipping.

 

Okay. Got how the bed leveling work. Been thinking about installing a crossbar between the two arms so I could do the 3 screw setup. Shouldn't be that hard to do.

The video didn't go into setting the Z home position. I'm guessing you set the Z end stop to close, but not touching the nozzle, with plenty of of the bolt sticking out. Then slowly start adjusting the bolt and checking distance until it is correct. This about it? With the Printrbot, you use the M212 command to fine tune how far the Z axis moves after the end stop is triggered. Is that command also used in this type of setup?

 

So this is the procedure I use for adjusting the height of the nozzle to the bed on my Printrbot. I manually lower the hot end until it is about the thickness of a piece of paper from the bed. Like what is done when leveling the bed. I then adjust the height of the sensor to be about 1mm above the bed (have a gauge I use to get that height). Once the sensor is locked in place, I start a print job that will cause the hot end to home. If the print doesn't stick, I use the M212 command to lower the hot end. The command says how much additional movement to add after the sensor is tripped. I repeat this until I got the height right.

What I am guessing is the bolt on the Z axis will act somewhat like the M212 command. I use the course adjustment on the Z axis to get it close, say about 1mm, from the bed. I then slowly adjust the bolt down until I get the right height for the print to stick without the head going through the glass plate. That sounds about right? There are no g-codes to issue. Purely mechanical adjustments.

 

Does anyone here use a Smoothieboard? If so, do you have a case for it? All the ones I have found on Thingiverse seem to be for the original beta version or have other issues. I'm starting to design my own, but if there is already one available, would like to try it.

 

My first print! Still need to do some adjusting though. 25mm test cube. Measured at 24.9 x 25.03 x 24.33 so not bad for a first shot.

 

Crappy color balance on the camera - those white squares are actually blue. But yes, they are the heat transfer pads. My PCB was actually sagging along the edges. I used small binder clips to level things out. So would you think a single solid piece of the heat pad would be better than the smaller ones spaced out? Or just reduce the spacing between them?

 

Hi i am new here and so attracted by Carl's beautiful design c-bot and a lot of nice build there.

Just would like to check if the attached BOM are the latest?

Are the hex head socket bolts used in all the v-wheel are 40 mm? would 35 mm do the trick since 20(2040 width) + 5(printer part front) + 5(rear) will be 30 mm only. I am thinking to use a 35mm bolt with anti-slip nyloc nut instead.

 

I've been following the discussion and slowly planning my own C-bot. Here's a proposed variant with the intention of putting the lead screws centered on the front to back balance point or center of gravity essentially. It would use the same Z guide wheels but with this approach there would be no torque on the Z guides due to cantilevering the Z bed and it would hopefully lead to a more robust construction. Any input is appreciated, thanks.

 

With this design it looks like you can print some very tall items. If you have stability problems with the cantilever design, it looks like you could add two more roller unites. The design does looks stable and very straight forward.

 

Thanks Carl for the enlightenment. i totally forgot about the spacers and gaps between the plates and the 2040 profile.

I am too doing the center z-screw style and not sure this will work well. Any input is appreciate.

 

Can you explain what you mean with the pre-loaded balance?

 

I'm just starting my build. You should take a look at the triple screw version that has been listed as a separate build.
I'm using 3 leadscrews - 2 back similar to the original build & then 1 extra at the front.
I'm also then using 2x brass nuts per screw which are going to be pre-loaded (like a traditional anti-backlash nut) by a spring. The spring pushes the nuts apart pre-loading them against the screw thread & removing all backlash.
This setup should provide a rock solid z-axis *fingers crossed

 

Yep, i'm sure that the bed weight will take most of the backlash out - I'm over engineering to a certain degree just to make sure.
I'm going 12"x12" & 3x leadscrews - trying to minimize any issues that could potentially creep in with z homing/rapids.
I've done a desktop test & it looks like it will work well, just need to print more parts & try it for real. For the minimal extra cost, I think its worth it.

 

The current plan is to use an 8"x12" bed with a 12" printable height. Three screws seems like a good approach for a bigger or heavier bed.

On an unrelated note, could someone attempt to clear up the wheel assembly setup? Open builds changed their kit since Carl's original BOM and I'm not clear on the setup with how many shims, spacers and bearings and where they go. I'm going to attempt to source the bearings, shims, and spacers separately since OpenBuilds prices are high for the kits.

 

What are the correct dimensions for the spacers? If the spacers are correct are some shims still needed?

 

Thanks for the follow up. What's your opinion on printing spacers/shims?

 

I've been gathering parts to make a C-Bot to upgrade from my MakerFarm i3 (pre-vslot) and the only thing that's been bugging me was the fully cantilevered bed. The way it was suggested that the Z-arms be 20x60 extrusion for a 12x12 bed made me wonder just how close to the edge of the design the standard parts were. I was going to go by the mantra that if Carl said it is fine then it must be, but I am really excited about trublu832's design which offsets the weight of the bed.

@trublu832 did you have to widen the frame at all to re-position the Z motors, or does it all fit inside the same cube that would be created if you followed Carl's BOM calculator?

 

I haven't modified the frame other than adding leg height compared to Carl's original design. Here is a side by side comparison of the stock configuration and my variant. Other than one extra bottom rail it just involves moving parts around so it is a relatively easy change in that sense. Also the whole Zmotor/leadscrew assembly can be moved from front to back to find a sweet spot to lift from.