…code, cg, electronics, 3d printing…

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.

I’ve been using my Makerbot Replicator (1) to print all the parts for my new C-Bot build.  However as of a few days ago, it suddenly quit extruding correctly.

I print almost entirely in PLA, usually from 200-210 degrees.  Suddenly, I couldn’t get anything to print unless I raised the temp to 230-245:  Pretty crazy for PLA.  And the surface quality was terrible.  Any lower in temp and I could hear the extruder stuttering, and it wouldn’t really extrude much at all.

Leading up to this I had been printing at 120mm\sec, at .3mm layer height:  Squeezing a lot of plastic out of the nozzle at that rate.  I noticed a bunch of melted filament around the top-rear of the heater block (you only noticed it when specifically looking for it, couldn’t see it from the front\sides):  The only way it could have got there would have been backpressure from the nozzle squeezing it out of an improper location up-stream.  My guess is that this somehow started the domino effect to cause whatever was screwing up my current extrusion.  It had completely encased the back of the heater cartridge and wrapped around the thermocouple wires.  I had to heat the whole block up and carefully pick it away without damaging any of the wires.

Thanks to tips from this forum I got it resolved:  One suggestion was that the kapton tape that insulates the thermocouple had worn through, and by grounding to the heater-block it was giving inaccurate temperature readings.  This seemed like a prime culprit since I had to crank my temp settings so much higher.

I’m not sure specifically which steps fixed it, but this is what I did:

General rule of thumb is that PLA does not print reliably over 10 mm^3/sec with a typical Replicator type hardware setup. At 0.3mm layer height, 0.4mm extrusion width, and 120mm/s, you’re doing 14.4 mm^3/sec. That’s reasonable for ABS (which melts faster) but not for PLA. Raising the temp may cover the symptoms for a while but it can also lead to charred filament and worse clogging issues later on.