Posts Tagged ‘ c-bot ’

Building the C-Bot 3D printer: Part 30 : Switching from Bowden to Direct Drive

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The original design for the C-Bot by Carl Feniak had the printer setup with a Bowden extruder: The stepper pushing the filament to the hotend sat off to the side of the printer, thus removing mass from the XY/hotend gantry:  The idea is that if there is less moving mass, you can print faster with fewer artifacts (like “ringing” or “ghosting”).  For comparison, my Makerbot Replicator1 (or say, an Ultimaker) is ‘direct-drive’: Its extruder sits directly on the XY gantry pulling filament into the hotend.  This is what I had experience with when I started building the C-Bot, but the idea of learning something new (the Bowden setup) was interesting to me, so I went with it.

Fast-forward to now:  Not a fan of the Bowden setup, at least when used within the specs of my printer design:  I have a E3D-v6 Volcano nozzle (I’ve used .6mm & 1.0mm nozzles) on my bot, and that coupled with the Bowden design have had some quality issues I’ve been unable to overcome despite hours (days…) of test printing.  Specifically “blobs\zits” & stringing.  My guess is, simply too much pressure builds up in the (long) Bowden tube during an extrude move, so when the print goes to do a retraction, a blob still shoots out and gums-up the print, or strings out during movement.  Have not been happy with this behavior, and have been unable to remove it entirely.  Have greatly reduced it, but it’s always there… lurking…

And during this tuning process I came to the realization that a Bowden doesn’t really help things when you’re using a Volcano nozzle:  The benefit of the Bowden, again, is that it removes moving mass from the hotend, allowing you to print at faster speeds.  But with a Volcano, you actually end up printing at much lower speeds, just a greatly increased volume\flowrate.  Here’s some maths:

  • My Replicator1, with a .4mm nozzle, printing at 200 microns (‘medium res’ for that nozzle), at 120mm/sec, has a flowrate of 9.6 mm3/sec (mm cubed/sec).
  • The C-Bot, with a 1mm Volcano nozzle, printing at 500 microns (‘medium res’ for that nozzle) at 45mm/sec has a flowrate of 22.5 mm3/sec.

The C-bot printing at a little over 1/3 the speed of the Rep1, but over 2x faster print times overall (based on the flowrate).  And when you’re printing that slow, I personally don’t feel the moving mass has such a big effect.

On the flipside, if you’re building one of these bots and running a .4mm nozzle, the Bowden is probably ok:  Smaller nozzle, less pressure, less blobs & stringing.  But since I’ve never actually used one on my bot, this is only a guess.

Time goes by…

After some discussion on the Forms (starting on this page, where you can also find the files for download, and my detailed comments on its design), Carl created a new “beta” direct-drive system.  Which is just amazing of him to do, so again, many thanks Carl!  I printed them out on my rep1, spent an afternoon installing them, and what a difference!

The firs pic shows off the new direct-drive design, and a calibration print of two cylinders:  Zero stringing between them.  With the Bowden, it would look like a spider could live in there.

The 2nd print is of a 3dBenchy, with no cleanup: Almost no stringing or blobs.  Both prints used the .6mm Volcano nozzle.

For both of these, I’m using the same Simplify3D profiles as before, I just dropped the retraction from the 5ish-mm to 1mm.  So much more accurate!  Currently in the process of tuning them even more.

I also modified the rear-plate to accept the 40mm fan mount & duct as designed by trublu832 on OpenBuilds, and you can find his files here on Thingiverse:  No more dual fans, just one ducted one.

As of this post, Carl has released a new version of the parts I have yet to print, but I plan to soon.

But overall, if you plan to build one of these printers and use an Volcano nozzle, I’d highly recommend using this new hotend design.

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2015
11/07
CATEGORY
Electronics
projects
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5 comments

Building the C-Bot 3D printer: Part 29 : Rearranging the Leadscrews

Jump to C-Bot blog index to see all the posts.

The C-Bot build instructions have you create a cantilevered build platform, with two rear leadscrews to drive it up and down.  Other designs have modified this to have a triple-leadscrew system where two screws are in the back, and one in the front:  This provides for better stability for the cantilevered build platform.  I’ve noticed on my larger prints a bit of “bounce/vibration” that happens on the platform as it drops over the lifetime of the print.  It would make sense that attaching the front to something would reduce this.

I seriously contemplated going to a triple-leadscrew system, but this would involve buying more hardware, cutting another leadscrew, etc.  Not the end of the world, but I’d like to work with what I already have.  I got to thinking:  Why not just take one of the rear leadscrews and put it in the front?

That’s what I did this afternoon, and so far, it’s worked out really well:  I had a long enough 20×40 cutoff I was able to put across the front of the build platform, and some spare printed corner-brackets to mount it in-place. From there, I took the right-rear leadscrew and moved it to the center.  Then I took the left-rear leadscrew and moved it to the new front location.

leadscrew_rearranged

Things noticed so far:

  • Build platform is much more rigid.
  • It’s easy to raise\lower the front\back for bed leveling by just twisting the leadscrews.

Jump to C-Bot blog index to see all the posts.

2015
10/31
CATEGORY
Uncategorized
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4 comments

New 3D Print : Life-Sized Pirate Head

I was recently approached by one of my co-workers, Diego Teran, if I could 3d print a zbrush sculpt he’d done of a pirate head.  Looking at it, I realized it’d be a perfect candidate to print life-sized on the C-Bot.  I’ve done a number of large format prints now (most recent), and am getting comfortable with letting the C-Bot run for extended periods of time.

To start, I did a number of 100mm high versions of the head, and had a back and forth dialog with Diego having him adjust the pose on the head from straight-on to “chin slightly lifted”, so that the only support needed was under the ear-lobes.  Happy with the tiny version, I fired off the “big head print” Friday night. On Sunday morning, it had finished:

Print Stats:

  • 280mm / 11″ tall
  • 683g of “Royal Pruple” Gizmodorks PLA, extruded at 225 degs on a woodglue-slurry-coated glass build plate (unheated).  Works out to be $17 in material.
  • 31 hours, 32 minutes total print time (lol, the print estimate was 24 hours).
  • Sliced in Simplify3D, the .gcode came to 69.6 megs.
  • 2 shells, 5% ‘fast hexagon’ infill, no raft, supports under the ears only.
  • 90mm/sec print speed.
  • .6 mm E3d-v6 Volcano nozzle with 150 micron layer heights.

Overall I’m really happy with the results!

2015
10/25
CATEGORY
CG
projects
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2 comments

Howto: Pause Marlin for filament reload at a specific layer number

I’ve had fun in the past printing maps with water (SF Bay, Oahu) : Using my Replicator 1 & it’s Sailfish firmware, it was easy via the LCD to set a specific layer number to pause at:  Doing this, I’d calculate which layer the print transitioned from water to land, pause it there, and swap filament.

Marlin firmware (which is on my C-Bot) gives you no such feature via the LCD :  Which means you have to monitor the print, and when it appears land is printing, you quickly pause the bot, go through the manual steps (via the LCD) to lower the bed, possibly move the hotend out the the way, and do the reload.  Afterwards (via the LCD) you have to get everything back into position. Awkward.  I am aware that the latest cut of Marlin allows for filament reload via the LCD:  I’ve been unable to get it to work.  And even if it did work, it’s still not accurate enough since I’m guessing at the layer to pause at.  There must be a better way!

There is:  You can directly edit the .gcode to insert a chunk that will do exactly what you need:  Lets say you want to pause just before layer 2 starts:  You’d find the line starting with the layer change comment…

; Layer 2

in your .gcode file, and then paste this right above it (I’ve included the layer change comment in the below code, plus comments for what the commands are doing):

G91                  ; Put in relative mode
G1 Z10               ; Lower bed by 10mm
G90                  ; Put back in absolute mode
G1 X0 Y0             ; Zero (home) the X & Y
M0 Click To Restart  ; Pause and wait for the user
G91                  ; Put in relative mode
G1 Z-10              ; Raise the bed back up 10mm
G90                  ; Put back in absolute mode
; layer 2, Z = 0.45

Works like a charm :)

If your slicing software supports post-processing of the gcode, it’s possible you can do this work directly in the slicer.  I slice using Simplify3D:  In a given process, it has a section in its ‘Scripts’ tab, at the bottom, called ‘Additional terminal commands for post processing’.  This allows you to enter in script to do a text-replace in your file, to edit it for you.  I learned about it on a forum post here.

To do the above using that system, you’d need to enter this text into that field:

{STRIP ";   postProcessing,"}
{REPLACE "; layer 2," "G91 \nG1 Z10 \nG90 \nG1 X0 Y0 \nM0 Click To Restart \nG91 \nG1Z-10 \nG90 \n; layer 2,"}

Some really important things to note:

  • The fist line that says ‘STRIP’ is super important:  If you don’t do this, Simplify3D will embed a copy of the REPLACE line in the header of the gcode, but won’t properly comment it out, basically ruining the gcode.
  • In the STRIP line, there needs to be exactly three spaces between the semicolon ‘;’ and the ‘postProcessing text.  Any more or less will screw up the strip.  If you copy-paste this code, make sure there are three spaces in there.
  • As you can see, you need to insert newline characters (\n) into the string you’re building for it to show up properly in the gcode later.

Other notes:

  • Handy-dandy gcode reference.
  • If you don’t enter in some text after the M0, it’ll never un-pause (at least for me).
  • I got most of the code on my own, but was able to finish it off based on the help from this thread.
  • My printer starts off in absolute mode by default:  I know this because up at the top of the gcode, I can see a G90 command.
  • The S3D forum post here (under “Additional Terminal Commands For Post Processing”) list other post-processing commands you can use.
2015
10/20
CATEGORY
projects
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2 comments

New 3D Print: Mini-Me

Or “Really Big Me” depending on how you look at it:

A few months ago I stopped by the “Artec3D Scanning Service and Showroom” in Palo Alto (CA) to check out their scanner tech.  While there, they offered to do a full-body 3D scan of me in their “Artec Shapify Booth” : Only takes 12 seconds, so why not?  Later that day there was a web-link to my scan, which I downloaded (for $40).

I’ve been wanting to throw something really big and complex at my C-Bot 3d printer, and this seemed like the perfect thing.  After cleaning it up a bit and making a base in Meshmixer, it printed without any (major) issues:

Lucky bonus: It was on one of two days in the whole year I had my “sexy-trucker” ‘stache still firmly in place.

Print Stats:

  • 500mm / 19.7″ tall
  • 663g of eSun gray PLA (the last of an old spool I had, purchased from ToyBuild Labs) extruded at 210 degs on a woodglue-slurry-coated glass build plate (unheated).  Only had about 5 turns left on the spool when complete, close one!
  • 35 hours, 39 minutes total print time (lol, the print estimate was 24 hours).
  • Sliced in Simplify3D, the .gcode came to 161 megs.
  • 3 shells, 5% infill, no raft, no supports : The 3 shells was to help with all the overhangs since I printed no supports, may have been able to get away with 2.
  • 90mm/sec print speed.
  • .6 mm E3d-v6 Volcano nozzle with 150 micron layer heights.

Overall, I’m really happy with it.  But, there are a few things that struck me a strange, and I believe they’re both related to the slicer, Simplify3D.

Wobbles in the infill

While it was printing, I noticed wobbles showing up in the “triangular” infill:

slice_wobble_web

Watching the print, I figured out what is going on:  When Simplify3D prints its infill, when any of the lines cross, they don’t do anything to pause the print.  So in this case, since three lines are crossing, 3x the filament starts to form at the vertex.  Over time, this builds up, and the nozzle physically ‘bumps’ over it.  When it bumps, it shakes the whole machine, and those wobbles start to show up in the infill.  This is never seen since its on the interior of the print, but I don’t like that it’s happening.  Sometimes I could really hear the hot-end ‘thunk’ the vertex and shake the whole thing :(

High-res, low-quality

I’ve been seeing this in my prints recently, but haven’t yet had a good enough test case to show the issue, until now.  I’ve noticed that when I print “really high-res” mesh in Simplify3D, it tends to make the surface quality a bit like a bowl of oatmeal.  My low-res prints are nice and clean, but high-res:  Quaker Oats.  In the below images, you can clearly see what’s happening:

Click on the images to zoom in, but you can clearly see a print quality change as soon as the dense mesh layer is hit.

I’ve had this feeling that S3D is trying to print ‘all’ the detail, even though some is smaller than the diameter of the toolhead itself.  And because of this, there’s a lot of shaking going on.  I know from my years using Makerware that it specifically would ‘smooth out’ this high-frequency detail, and I noticed a major difference printing the same ‘high res’ mesh in Makerware, and S3D:  The Makerware print would look\sound nice and smooth during print, while the S3D one would try to shake the machine apart.  It looks like this is still happening, and at least I have a test case that exposes it.  If this is the issue indeed.  I’ll ping the S3D support an see what they say.

I have a few next steps to troubleshoot this:

  • Make a test print that varies from low to high-res.
  • Print this in S3D, and contrast that print in other slicers (like Makerware, Cura, Slic3r), and see what sort of behavioral differences show up.
2015
10/12
CATEGORY
art
CG
projects
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