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Crystal Clear action run.png
Kossel Clear

Release status: Commercial (Kickstarter)

Delta robot 3D printer with extrusion frame.
to be defined.
CAD Models
External Link

The Kossel Clear is a parametric delta robot 3D printer project funded through KickStarter in 2013 by Blue Eagle Labs, probably based on the Kossel printer. The printer has a relatively large printing envelope of 11" (diameter) and 11" height, which is smaller than the original Rostock delta printer but larger than the more recent Kossel. The design relies on aluminum beams, acrylic laser cut parts and printed parts.

Assembly guide and resources

A collection of videos has been made available by BlueEagle Labs. See [1] for a nice playlist.

  • Brackets
  • Rollers
  • Extrusions
  • Belts: to tighten them properly, use a guitar tuning application on your phone (gTune on Android) and tighten them to 80-110Hz.
  • Arms and Effector
  • Electronics
  • Extruder

Tools Required for Build

The following list is a subset of tools that are required to assemble the 3D printer:

  • Scissors
  • Wire Cutters / Strippers
  • Soldering Iron
  • Electrical Soldering Wire and Flux
  • Heat Shrink Tubing (various sizes recommended) / Electrical Tape
  • Heat Gun (alternatively could use a lighter or heat from soldering iron)
  • Kapton Tape (~8mm or 5/16" wide)
  • Screw Driver (Phillips and Flat Head)
  • Long Nose Pliers
  • Metric Allen Wrenches (Ball head Suggested)
    • Look out for screwdriver shaped ones.
    • Sizes needed:
      • 2.5mm (for all the 3mm screws)
      • 2mm (for the few 2.5mm screws)
  • Calipers (Digital Highly Recommended)
  • Drill
  • Drill Bits (Assortment of Sizes Recommended, metric sizes, conversion to closest 1/64 also works)
    • 3mm (1/8")
    • 2mm (1/16") - used for reaming out the inside of the Bowden tube after screwing in the 4mm nut onto it
  • Zip Ties (small size recommended)
  • Multimeter
  • Blue Painters Tape (PLA - only if you are covering the borosilicate glass)
  • Bottle of Acetone (for cleaning/melting ABS)


  • Glue Gun
  • Binder Clips (Medium Size) - There should be enough in the kit.
  • Primer and Paint (ABS - to paint the MDF)
  • Desk Fan (Ventilation)
  • 3mm lock nuts (for moving parts)
  • 0.25" female insulated crimp-on spade lugs (4) (for power switch instead of soldering)
  • spare 18 gauge stranded wire, red & black (for routing heatbed and extruder power)
  • 3/16" rubber beads or screen door spline (to keep end stop wires in place in channel)

Reference for list above: [2][3]

Mechanical parts assembly

mounting nuts

List of the extra nuts on the lower assembly beams (not including the attachment 4 nuts). That are shown in assembly video 3.

For ABS with LCD:

upper front bar: top: 6: (4 for PS, 2 for bed)

upper front bar: outside 3: (for LCD)

lower front bar: outside 3: (for LCD)

upper left bar: top: 2: (1 for W/C which is optional, 1 for bed)

lower left bar: top 2: (2 for Arduino if mounting it inside)

upper right bar: top 5: (1 for bed, 2 for extruder, 2 for PS)


Blue Eagle Labs shipped two different types of extruder. The first was made with printed parts. The second was made with acrylic parts and used a larger M8 screw for the idler bearing to reduce slop and be all around better than the first. Take great care when assembling the acrylic extruder - the video is much better but the two main pieces are almost identical. An easy way to identify the top piece is the M8 screw should fit its place as a through hole while the bottom piece will thread onto the M8.

  • Bowden tube pops up: you must use an M4 nut and thread the Bowden tube in it. See [4]
  • It is highly recommended to upgrade from the first (printed-type) extruder to the design created by Shane to reduce skipping. The new design uses a 4mm (OD of input) push fitting in a 5mm threaded hole. Available both for the MK7 (original) and MK8 (higher torque) extruding gear here.
  • The acrylic, if properly assembled, appears to provide an extruder competitive to Shane's.

Electrical and Electronic parts assembly

Wiring Diagram

Go to this page: Instructions & Guides @BEL Homepage where you will find the wiring diagram. Direct link to PDF: Wiring Diagram.

Wiring the endstops for the X, Y, Z motors and the auto calibration probe

Wiring the 4 motors

The motors are driven by Polulu steppers. Their voltage usually needs to be adjusted. See here.

NOTE: the extruder motor's cable is plugged into the board in reverse orientation to the other 3 motors. Note carefully on the wiring diagram, how the red wire only for the extruder motor is not like the others.

While looking at the front of the printer, X = left axis, Y= right axis, Z = Back axis.


1. Attach the square and triangular pieces with m3-10 screws. Make sure the triangular piece with the slot for the SD card is positioned to the left.

2. Mount them on the front of your printer, on the extrusions using M3-8 screws. Additional washers may be required to prevent the screws from bottoming out in the extrusions.

3. Screw the LCD to the faceplate. Spacers of some sort (not included) are recommended during this step to prevent the LCD assembly from being mounted warped or uneven. Spare nuts and washers have been used successfully, or any other type of spacer should do. Be aware that the length of spacers you choose will affect the SD card alignment with the gap in the left triangular part. Filing or grinding the SD card hole to enlarge it may be required for a completely flat LCD installation with SD access.

4. Attach the front plate with the LCD to the triangular pieces, and use m3-10 screws as well.

The thermistor probe and the extrusion head heater power wire

Wire the Hot end

  • Use caution when installing/taping the thermistor. If plastic insulator tubes do not completely cover the wires to and from the thermistor, it could cause a short that will result in a "max temp" error that prevents printing.
  • 8mm kapton tape is recommended to secure the thermistor and resistor.
  • Crimping ferrules may be a good alternative to soldering the wires.

Cable management

To hold the end stop wires that run up the vertical columns, Screen retainer spline works very well while also improving aesthetics (Easily found on Amazon or local hardware store). Just push the wire into the channel of the extrusion and then press in the spline on top of it.

Software for the 3D Printer

The latest pre-packaged software can be found here: Software Download @BEL Homepage.

For now only windows package is supplied. Linux and Mac users can try finding the respective programs for their OS or just use a virtualbox virtual machine.

In the RAR archive file you will find:

  • the Marlin Arduino Firmware - you will have to install this into your arduino (aka flash or upload it) using the video instructions in the main youtube video playlist. Its one of the end videos.
    • Briefly, install the latest Arduino IDE, open marlin.ino with it, set your board to Arduino Mega 2560 and, with the printer connected to USB, press Upload.
  • the Pronterface program (for raw 3d printer head control and the printing itself, includes slic3r)
  • the Kisslicer program - for STL files slicing

Here is how it works:

  1. You install the Arduino program on your PC at the begining. It allows you to install the Marlin firmware onto the arduino.
  2. You download an STL file from the internet
  3. Using Kisslicer, you open the STL file, check your slicer settings and save a .gcode file
    • You can also use slic3r in the Pronterface directory, but you should update it first - there's a newer version on slic3r's website.
  4. Using Pronterface, you open/load the .gcode file and print it

Pronterface Setup

In Pronterface click Settings, then Options, and change the value for build_dimensions to:


This tells Pronterface that the build volume is 200mm x 200mm x 250mm (x,y,z) and that the center of the build platform is offset by 100mm in x, 100mm in y and 0mm in z.

Repetier Firmware

An alternative is to use the repetier firmware in its Kossel Clear version. This version has been made for a modified KC with 1/32th micro-stepping by user Steffen from KC Google group. A "vanilla" version for the stock KC is available from GitHub here. Instructions to compile and install on Mac-OSX (Maverick) are available in this thread.

Usage after the printer is ready

(Auto) Calibration

See here: Auto Calibration Instructions @BEL Homepage.*

A traditional calibration seems to bring the best results. See [5] and [6].

  • Repetier firmware has different g-code for auto-calibration, and can calibrate the z-level through the LCD screen.

How to change filament rolls

1. Heat the nozzle to a temperature appropriate for the plastic type being used. (Approximately 180°C for PLA, 203°C for ABS)

2. Release the clamp on the extruder.

3. Remove the old filament.

4. Insert the new filament and manually feed it all the way into the hot end. Check to see that it extrudes properly by applying some gentle force. (Optionally you may choose to manually extrude the new plastic until the color change runs clean.)

5. Clamp down the extruder.

NOTE: Some users have found this process to be easier by including a removal of the bowden tube from the hot end during the filament change procedure.

NOTE: Cutting the end of the filament into a point may also aid when manually feeding the filament through the system.


Autocalibration Probe Deployment Piece (APDP)

Print it

Modify your software to use it

  • You need to modify your calibration software routine ( g29 ) so that the printer head goes to the "autocalibration piece" to deploy the probe and after calibration is done, go there again to retract it. To do this, open the file KC_Software/KOSSEL CLEAR ABS/Marlin/Marlin_main.cpp from the software archive you downloaded from the BEL homepage. Open this file with a text editor and find the lines (around line 1070) :

      calibrate_print_surface(z_probe_offset[Z_AXIS] + (code_seen(axis_codes[Z_AXIS]) ? code_value() : 0.0));
  • There, delete the "//" before "deploy_z_probe();" and "retract_z_probe();" , so that the two lines become uncommented. Save the file.
  • Then open the Arduino software and install the Marlin firmware again onto your arduino.
  • Then carefully watch how the calibration with G29 happens and be ready to manually flip the probe with one hand and press the arduino reset button with the other. This is while/if you have no actual probe deployer created/installed in place. This precaution should be taken, because if something goes wrong, the extruder end might crash into the bed, having no endstops probe to tell it to stop.


  • One fan to cool the extrusion head's top-part and 2 or 3 fans to cool the just printed layers on the bed. See this mod by Shane : Print head fans plus lights mod

Filament Spool Holder

Bowden restrictor - to not allow bowden getting torn out by one of the rollers


Sometimes after auto calibration the bowden gets strained and may pop-out some day off of the extruder head. To restrict the bowden from getting broken by the roller - just put a pencil on the roller and a clothespin. See picture.

The idea is to not allow the bowden tube to get torn by the roller in some occasions. Things to test: roll the roller to the top and watch if the pencil hits the frame. Also roll to the downside and watch for problems.


LCD becomes scrambled
This is caused by interference with a stepper motor. Move the LCD cable away from the motor or wrap the LCD cable in aluminum foil. If you are printing from an LCD, you can pull out the SD mid print, put it back in to refresh the LCD, then continue the print.

Auto level probe doesn't reach the bed
open Marlin_main.cpp find "destination[Z_AXIS] = -20;" and make it a more negative number.

Auto level probe misses a click
This is ok, sometimes the electrical connection is made before the mechanism in the switch makes a click noise.

Filament drooping on overhangs
Try printing with a cooling fan. Try this mod by Shane : Print head fans plus lights mod

Motors dont stop at top endstops and stutter very loudly there``` You have mis-wired your endstops. Additionally you may have the endstop and roller screw mis-aligned.

To fix the wiring - either try and double check against the Wiring Diagram ( found on the BEL website under instructions ) or do it via trial and error. NOTE: always change wiring plugs when all the system is powered OFF.

To fix the alignment - you can put 2 3mm nuts in between endstops and the acrylic part they are attached. Photo later.

Auto level probe is digging into tape on bed

Use the offset (aka Z ) parameter when doing auto-calibration - for example "G29 Z0.1" means that when you do auto calibration (G29 command ), you are telling the printer that the Z=0 level is 0.1 mm higher than normal. Begin experimenting with G29 Z10.0 or Z1.0 and then issuing g1 Z5.0 , then g1 z1.0 and on and on with little increments until you go to z=0 with g1 z0. For futher info see the block scheme at [http://www.blueeaglelabs.com/blogs/news/10017821-auto-calibration-instructions Auto Calibration Instructions @BEL homepage]

My print head flies off towards the Y and Z corner until the X arm gets so low it begins to jam

In your slicing program, print center should be set to X:0 Y:0. By default it is X:100 Y:100. This is not correct for Delta printers such as the Kossel Clear.