Detailled Assembly Instructions of the Rostock Mini Kossel 3D Delta Printer

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This Manual is based on the excellent Manual released by www.think3dprint3d.com, adapted to the Mini Kossel Assembly Kit found here. However, it might also work for kits found elsewhere!

There is also a German Version of this Instructables here

Acknowledgements

Our thanks go first of all to Johann C Rocholl for designing this great printer (and its predecessor the Rostock), blogging about it and publishing the designs on Github. Thanks also to Builda3Dprinter and Blomker Industries for linking their build manuals from the RepRap Kossel Wiki, which helped to get us started with the first prototype build.

Revision History

1.0.0 April 3, 2015; Release

Step 1: Chapter 0 - Mini Kossel Kit Introduction

The Mini Kossel is the latest delta robot printer from Johann Rocholl, the designer of the original Rostock delta. It is an innovative and elegantly simple design featuring a small number of parts and easy assembly, with auto-bed-leveling to simplify calibration and keep it in tune.

The version 2 of the kit above has the following new features:

NEW: Pre-Configured Rich Cattel Version of Marlin Firmware with fully automatic Autocalibration!
Simplified Design, with fewer parts needed
Max. printvolume of up to 10,000cm3
Improved MkV J-Head Hot End
Print Speed: at least 60mm/s (max speed of up to 140mm/s)
Larger Print Bed: 190 instead of 170mm!
Dimensions of Printer: ca. 300 x 630mm
Smaller Power Supply
The set now includes all parts, i.e. you don't need to purchase anything in addition
Ballbearing side rails
Closed Belts
Shorter delivery times
Updated Instructions
All plugs are already preinstalled. No soldering necessary!

The kit features everything that you need for a successful assembly of a Mini Kossel 3D Delta Printer, inlcluding Arduino/Ramps electronics, LCD display etc:

28 x Printed Parts
3 x MGN12H Ballbearing Side Rails
12 x Open Aluminium Beams 20mm (more solid than 15mm Open Beams)
6 x Carbon Rods with Traxxas Hollow Balls, already pre-assembled
4 x NEMA 17 Stepper Motors for X, Y, Z Axis and powerful Extruder
1 x Autolevel Probe
3 x closed GT2 belts incl. 623ZZ Pulleys (closed belts are more accurate than open belts!)
Nuts & Bolts
MkV J-Head Hot End with 0.4mm Nozzle for 1.75mm ABS und PLA Filament
RAMPS 1.4 compatible Board
Arduino Mega 2560 R3 compatible Board
4x A4988 Stepper Boards
2004 LCD Display for PC independent Printing
SD Card Reader
110-240V Small-Size Power Adaptor with Power Cable
190mm Diameter Glass Bed
Maximum Print Height: 280mm
Fan 40mm
USB Cable
All Cables, Ball Bearings, Endstops, PTFE Tube with all plugs pre-assembled etc.
Step by step assembly instructions with lots of pictures
Pre-Calibrated Marlin Configuration files (latest Rich Cattel Version!), with SD-Card Reader, LCD Display, fully automated Calibration and M666 Commands already activated!
Reduced number of parts which simplifies the assembly and reduces the price

Specifications for the standard machine are at http://reprap.org/wiki/Kossel

Step 2: Tools Required and Safety Precautions

Please do the following when building this printer:

Unpack the kit and check that all parts have been supplied and none have been damaged during shipping. To help you with this, each box or bag will have its own packing label. There is also a List of Materials at the end of these instructions in Appendix A. Contact the supplier of the kit immediately by email or through the website if you find any missing or damaged parts.
Read through each chapter of these instructions to gain an idea of what is involved and how long it might take, before starting on the work described.
Ensure you have the necessary skills to carry out the work, or enlist the help of someone who does.
Work on a firm table or bench in a clean dry well-lit area.
Observe tool safety and anti-static precautions (see below).
Ask for help if you run into any!

Tools Required

Essential:

Hex key, ball ended, long arm, 2.5mm
Hex key, ball ended, 2.0mm
Drill bit 3mm for reaming printed parts, with printed handle
Utility knife
Needle-nose pliers, small
Small screwdrivers flat-bladed and Philips or Pozidriv, e.g 3.0 x 75mm and PH1 x 75mm
Accurate ruler

Desirable:

Digital calipers
Tweezers
Plastic or wooden mallet (or hammer + wood)
Electric drill/driver
5.5mm spanner for M3 nuts

Safety Precautions

This assembly includes handling of a sharp utility knife for preparing printed parts. You should observe all necessary precautions when using this, such as those at http://safetytoolboxtopics.com/Small-Tools/utility-knife-safety.html.

Printer assembly may also involve the use of other potentially dangerous tools. You should be competent to use such tools and observe reasonable precautions in doing so.

Electrostatic Discharge Precautions

You should be aware of the risk of electrostatic damage to the electronic components of this kit, specifically the RAMPS board, Arduino Mega and LCD controller. These components are fully tested with the other electrical items before packing the kit, and wrapped in protective anti-static packaging. Damage by electrostatic discharges during unpacking, assembly and normal use is not covered under our warranty. You should therefore observe reasonable anti-static precautions which are widely published on the internet. For a short and simple overview see Antistatic Precautions for Electronic Components on eBay.

Step 3: Chapter 1 - Printed Parts Preparation

101 Motor Brackets x 3

Trim off the anti-warping discs and any other flash (excess plastic e.g. the shiny side may have a thin layer of “overhang” plastic) on the underside of the bracket.

Ream all bolt holes with a 3mm drill-bit - push it through and pull out. Hand-reaming is shown but you can do this carefully with a power drill on slow speed instead. This applies to all bolt holes in all parts unless otherwise stated in these instructions.

Repeat for the other 2 brackets.

102 Top Brackets x 3

Prepare generally as for motor brackets by chamfering all nut holes including the one in the centre with the angled hole.

Ream out the idler bearing axle bolt holes, and all other bolt holes.

Repeat for the other 2 top brackets.

103 Carriages x 3

Ream bolt holes as for V-roller adaptors. Also cut off triangular printed support material from conical delta arm attachment points - picture shows before and after.

104 End effector plate

Ream 3mm bolt holes.

105 Hot-end fan bracket

DO NOT REAM! - no preparation required on this part

Do not ream the 4 fan mounting bolt blind holes! The M3 bolts need to cut their own threads when fitted.

Do not ream the 5 holes for mounting the fan/hot-end assembly - they are supplied already tapped M3 for mounting bolts.

106 Endstop Mounts

DO NOT REAM THE TWO SMALLER HOLES IN THE ENDSTOP MOUNTS

The picture shows the flash on the first print layer and oversizing of the 3 or 4 layers due to shrinkage during printing. This needs to be removed so the sides are parallel , so the endstop mounts are flat on the bracket and the bracket flat on the aluminum extrusion.

107 Z-Probe Holder

DO NOT REAM the holes in the side of Printed Z-probe holder

Other parts:

Should not need further work but be prepared to ream 3mm bolt holes and remove excess flash from a few other places during the assembly.

Step 4: 200 – Assemblierung Der Basis

Before starting this chapter, you should watch this video. It seriously can help you save hours of frustrating assembly time!

201 Motor Assembly - Parts required

Motor brackets x 3
Motor x 3
GT2 pulleys x 3
6 x grubscrews
M3 x 8 socket cap screws x 12

202 Fit pulley to motor

The pulley is fitted with the collar and grubscrew at the outer end of the motor shaft. This provides correct alignment with the idler at the top of each tower.

The motor shaft has a flat side - align the flat side with the grub screw. This firmly couples the pulley to the motor shaft. Tighten firmly (but do not overtighten) with the supplied 1.5mm hex key.

NOTE: Some pictures below and in later chapters still show the pulley fitted the other way round on the shaft - please ignore this difference.

203 Fit motor to bracket

Align motor with plastic bracket, with the cable socket on the right-hand side of the motor viewed from the bracket end (hidden in this picture). Insert 8mm capscrews and screw in with the ball end of 2.5mm hex key. There is a groove in the printed part to reduce the angle of the key slightly. Make sure the screws go in straight - loosen and re-align any screws that that have gone in at an angle. Do not tighten fully with the ball-end. Instead use the short leg.

Repeat for the other 2 brackets

204 Base assembly - parts needed

Motor bracket assemblies x 3
Frame extrusions 240mm long x 6
M3 x 8 socket capscrews x 24
M3 t-slot nuts x 24

205 Fit extrusions to brackets

Insert 2 capscrews with washers through the 2 bottom holes and very loosely fit 2 t-slot nuts. Note that the screw head is facing the motor (order: cap screw, plastic bracket, nut, aluminium extrusion).

Slide an extrusion onto the 2 nuts. You may find it helpful to use a pair of tweezers or needle-nose pliers to rotate the nuts into alignment. Very loosely screwed on nuts makes this easier.

Slide the extrusion tightly up against the plastic and tighten the nuts just enough to stop it coming off. They will be tightened fully later, after the whole base is assembled.

Repeat the procedure with the top extrusion…

and with the other 2 brackets.

206 Final Assembly

For each of the three assemblies; fit the 4 M3 x8 capscrews and nuts as before.

Arrange the 3 assemblies in a triangle.

Slide one pair of extrusions onto the nuts. Do not try and slide them up to the second pair of nuts yet. Instead tighten the screws just enough to stop the extrusions coming off the bracket.

Repeat for the other 2 brackets, then loosen the nuts enough so that the extrusions can be slid up to the other pairs of bolts and nuts.

Align one pair of nuts, slide the extrusions onto them and tighten to keep them in place while you work on the others.

Once you have all the nuts in their channels, slacken them all slightly and slide all the extrusions fully home. Lay the base on a flat surface and progressively tighten all the nuts, first with the ball-end of the hex key…

and then finally with the short leg.

The completed base assembly may now be set aside while you get on with the top assembly.

Step 5: Chapter 3 - Top Assembly

301 Idler assembly: Parts needed

M3 x 25 socket capscrews x 3
Top brackets x 3
M3 flat washers x 9
F623ZZ flanged bearings x 6
M3 full nuts x 3
Belt x 3

302 Idler Assembly

Fit the M3 x 25 idler axle capscrew through the printed bracket and progressively add a washer, first F623ZZ bearing (flange left), second F623ZZ bearing (flange right), two washers and the M3 nut. Do not forget to insert one of the closed belts!

Start screwing in the M3 bolt;

You will probably need to hold the nut with needle-nosed pliers as you do up the bolt.

Tighten the nut against the bearings to ensure the bolt can be fully screwed in.

Repeat for the other 2 top brackets.

303 Top Frame assembly - parts needed

Top bracket assemblies x 3
Frame extrusions 240mm long x 3
M3 x 8 socket capscrews x 12
M3 t-slot nuts x 12

304 Fit extrusions to brackets

This is a repeat of the procedure for assembling the base. Fit 2 M3 x 8 capscrews through the holes in the bracket and loosely fit t-slot nuts. Slide an extrusion onto the nuts. Slide the extrusion tightly up against the plastic and tighten the nuts just enough to stop it coming off. Repeat the procedure with the other 2 brackets.

Now arrange the 3 assemblies in a triangle and complete final assembly.

After tightening up all the M3 x 8 capscrews with the top frame on a flat surface, set it aside while you get on with the next stage.

Step 6: Chapter 4 - Spider Assembly

401 Effector and Arms - Parts needed

Printed effector plate
Assembled carbon fibre diagonal arms with Traxxas rod ends x 6
M3 x 25 socket capscrews x 6
M3 Nyloc nuts x 6

402 Fit captive nuts

Fit an M3 Nyloc nut into each of the prepared nut traps in the effector. You should be able to pull them in quite easily by hand using a M3 x 25 capscrew (note that they only go in ¾ of the way as shown in the picture).

403 Check conical ends for squareness

If the conical ends against which the Traxxas rod-ends fit are not completely flat and square, then they may need slight trimming to achieve this.

404 Fit diagonal arms

Fit one end of the arm onto an M3 x 25 capscrew. Fit to effector plate and tighten firmly.

There is not much clearance for the adjacent arm - it will not go past the fitted one so hold it in place first, with its washer, and then insert the bolt.

End effector and carbon fiber arms fully assembled.

405 Spider Assembly - Parts needed

Complete effector and arms assembly
Carriages x 3
M3 x 20 socket capscrews x 6
M3 Nyloc nuts x 6

406 Assemble the Spider

Lay the effector and arms out as shown. The carriages need to be fitted facing upwards and towards the effector plate.

Fit a nyloc nut into a nut trap, insert an M3 x 20 bolt on the inside and tighten firmly.

Repeat for all 3 carriages to complete the spider.

Step 7: Chapter 5 - Z-probe Assembly

501 Z-probe - Parts needed

Printed Z-probe holder
Prepared Z-probe microswitch
L-shaped 1.5mm brass rod with heatshrink
Prepared safety-pin spring
Spring
Screw terminal block
M2.5 x 12 socket capscrews x 3

Insert the safety-pin spring into the small hole at the top of the printed Z-probe holder. Secure with one of the M2.5 x 12 socket capscrews. Note that the small hole may need slight enlargement with e.g. a needle.

Fit the microswitch with the cable leading to the right as shown in the picture, using another two M2.5 x 12 socket capscrews. Be careful not to overtighten them!

Insert the L-shape brass probe into its groove/hole from above. Ensure the brass probe moves smoothly through the hole - if it doesn’t then smooth the hole and the slot.

Fit the ball point spring and screw terminal from below, compress the spring fully with the rod in the position as shown in the picture, and tighten the terminal screws.

Trigger the probe by flicking the short leg past the safety-pin spring into the deployed position. Confirm it is pushed down hard enough by the spring(s) to activate the microswitch - you should hear it click.

Push the probe leg back up past the safety-pin spring and check that it retracts correctly. You may need to bend the safety-pin spring leg to adjust the force required.

Repeat several times to confirm that the probe will work reliably. You may need to grease the brass rod during commissioning.

NOTE: It may be necessary to add another ballpoint pen spring to ensure reliable operation.

Remove the L-shaped rod, spring and screw terminal - these can only be finally fitted after the Z-probe holder is mounted on the effector plate.

Set aside for the next step.

Step 8: Chapter 6 - Hot-End Fan Assembly

601 Hot-End Fan - Parts needed

Printed fan bracket
40mm fan
M3 x 16 socket capscrews x 4

602 Hot-end Fan Assembly

Fit the fan to the bracket as shown with label facing inwards, against the printed bracket. The M3 x 16 capscrews will cut their own threads into the plapstic - be careful not to over-tighten.

The airflow needs to blow against the hotend, not away from it!

Step 9: Chapter 7 - Effector Final Assembly

701 Effector Final assembly - parts needed

Hotend fan assembly
Assembled J-head hotend
Z-probe assembly
M3 x 16 socket capscrews x 5
PTFE Bowden tubing

702 Fit hot-end to effector plate

The PTFE Bowden tubing goes through the center hole while the hotend and sensor cables are routed on the side of the effector plate.

703 Fit fan assembly to effector plate

The fan assembly fits into a groove in the hotend. Secure it in place with three M3 x 16 capscrews. Do not tighten the crews yet!

704 Fit Z-probe holder, hot-end and effector

Fit 2 M3 x 16 capscrews through the probe-holder base and fit it to the effector. The Z Probe will go through the remaining hole, so keep that one empty.

Drop the long leg of the Z-probe down the remaining hole in the probe-holder. It should pass through the unused bolt-hole in the effector and just fit past the J-head. If necessary, turn the J-head so that the probe can pass easily and without obstruction.

Tighten all capscrews evenly, but do not overtighten them or you you will strip the tapped threads in the plastic!

With the probe in the retracted (up) position, fit the pen spring and screw terminal from below, fully compress the spring and tighten the screw-terminal.

Trigger the probe by flicking the short leg past the safety-pin spring into the deployed position and confirm it is pushed down hard enough by the springs to activate the microswitch - you should hear it click.

Push the probe leg back up past the safety-pin spring and check that it retracts correctly.

Repeat several times to confirm that the probe will work reliably. You may need to grease the brass rod.

Step 10: Chapter 8 - Endstop Assembly

801 Endstops - Parts needed

Printed endstop holders x 3
Microswitches x 3 (already with wires soldered on)
M3 x 8 socket capscrews x 3
M3 t-slot nuts x 3
M2.5 x 12 socket capscrews x 6

802 Endstop Assembly

Fit an M3 capscrew through the printed holder and add a nut.

Fit a microswitch with 2 x M2.5 capscrews, with the blade hinged as shown in the picture. The capscrews will cut their own thread in the plastic. Tighten just enough to hold the switch firmly - be careful not to over-tighten as this could strip the plastic thread.

Repeat for the other 2 endstops and set aside for later.

Step 11: Chapter 9 - Extruder Assembly

901 Extruder - Parts needed

Stepper motor
Spur gear with bolt
625 bearing
M5 x 20 socket capscrew x 1
M3 x 25 socket capscrew x 3
M3 x 20 socket capscrew x 1
M5 full nut x 1
M3 nyloc nut x 1
M3 washers x 4

902 Remove the support material in the extruder gap

Use flat-nodes pliers to remove the temporary support and place the 625 bearing in this slot and screw in the M5 bolt to hold in place. Use a sharp knife and/or a file to remove all remaining plastics until the bearing fits in tight but comfortably and can run smoothly. Don’t over-tighten the bolt!

Mount the spur gear on the stepper-motor and tighten the little bolt so that it touches the flat part inside.

Drop in the M5 nut.

Mount the assembly on the stepper motor using 3 M3x25 bolts. Be careful that the M5 nut doesn’t drop out.

Mount the M3x20 bolt through this hole and place a nyloc nut on the end.

Step 12: Chapter 10 - Frame Assembly

1001 Frame - Parts needed

Base assembly
Tower extrusions 600 long x 3
M3 x 8 socket capscrews x 6
M3 t-slot nuts x 6
Top assembly
M3 x 35 socket capscrews x 3
M3 x 8 socket capscrews x 3
M3 full nuts x 6
M3 washers x 3
Side Rails x 3
Endstop assemblies x 3
Extruder bracket
M3 x 8 socket capscrews x 3
M3 t-slot nuts x 3

1002 Fit towers to base

Fit two M3 x 8 socket cap screws and nuts to one of the motor brackets (you can hold the nut still with a pair of tweezers). Keep it loose and align the top nut with 2 parallel sides vertical as is shown in the picture.

Insert a tower extrusion while trying not to bump the base so as not to disturb the nut alignment. With luck the nut will slip into the channel in the tower extrusion, allowing you to push the tower down to the second nut. If it won't move and the head of the capscrew begins to move upwards, then luck was not with you. Remove the extrusion and try again. Repeat until you succeed! You can also try to adjust the capscrew slightly using a hex key.

Once the tower has been pushed down in the bracket and reaches the second nut, invert the frame, align the second nut with the channel and push the frame extrusion into alignment with the bottom of the printed motor bracket.

Tighten the two capscrews and repeat for the other 2 towers to complete the most difficult part of the build.

1003 Identify X, Y and Z towers

From this point on in the assembly, it is necessary to identify the 3 towers individually. As shown, the front left tower will be X, the front right tower Y and the rear tower Z. The motor brackets in the picture have been labeled accordingly and the extrusions joining them will be referred to as X-Y, Y-Z and X-Z.

1004 Fit ball-bearing siderails

First, attach one of the plastic endstop holders to each of the corner extrusions so that they are 10cm away from the base assembly. They will serve as holders for the ball-bearing siderails.

It’s not important that they are EXACTLY 10cm away from the base. What’s much more important is that they are EXACTLY the same distance away from base!

Then fit 5 t-slot nuts onto the siderails, using five M3 x 8 capscrews, leaving 3 holes empty between each screw.

Then ease the side rails with the t-slot nuts into one of the corner extrusions (facing inwards). Tighten.

Repeat for the two other corner extrusions.

1005 Spider Installation - Parts needed:

Assembled frame
Assembled spider
M3 x 16 socket capscrew x 6
M3 x 8 socket capscrews x 6

Attach the spider to the sliding rails with each two M3 x 16 on top and two M3 x 8 capscrews on bottom. Adjust the spider in such a way that the fan points forward towards Y and the narrow portion of the carriage adaptors point downwards.

1006 Fit endstops

Fit an endstop to the top of each tower against the sliding rails, facing inwards. Tighten it flush against the sliding rails.

Note: The central endstop connector tab gets in the way when tightening the capscrew. As it is not used, it can be bent slightly so the hex key can fit past it.

1007 Fit extruder

Fit the 2 M3x8 socket cap screws with M3 t-slot nuts (loose) and slide it onto the Z-tower, facing outwards. Screw in place near the bottom of the Z-tower, then attach the extruder to it with 2 M3x16 capscrews and nuts.

Fit the PTFE tube into the extractor and tighten the screw.

1008 Fit top frame

You will need to place the frame base on a fairly low support to gain easy access to the top of the towers.

Fit an M3 x 8 socket capscrew and t-slot nut to each top bracket.

Fit the top bracket to the towers (nut hole facing down), aligning the nuts so they slide into the channels.

Once all 3 corners are fully onto the tower extrusions, push them further down until they are flush against the endstops and about 10mm of extrusion is protruding above each bracket. Do not tighten the M3 x 8 socket capscrews yet!

Fit an M3 x 35 bolt with washer into the angled belt tensioner hole in the top of each bracket.

Fit an M3 nut onto each bolt from underneath and tighten just enough to draw it into the nut trap without raising the bracket on the pillar.

Do NOT yet tighten any of the screws on the top frame!

Step 13: Chapter 11 - Timing Belt

1101 Parts needed

Top Frame with 3 x GT2 closed-loop timing belts already installed

1102 Fit timing belts

BEFORE tightening any of the screws on the top frame, loop the three timing belts over the flanged bearings of the top frame as well as over the GT 2 pulleys of the bottom frame.

Once the belt is loosely looped over the bearings and pulleys, pass the belt through the grooves of the carriage, around the top fixing peg on the carriage from right to left.

The belt should have enough slack to do so, otherwise check if the top frame is really as low as possible, flush against the endstops.

Check again that the belt is properly engaged on the motor pulley and properly looped over the top bearings.

Repeat for the other 2 belts, trying to get all 3 as near to equally tensioned as you can.

1103 Tension timing belts

Make sure the capscrews holding the top brackets in place are still loose on the towers. Tighten the belt tensioners until the belts are all equally tight and make a low twanging note when plucked.

Once the belts are tensioned to your satisfaction, re-tighten all the capscrews on the top frame.

Step 14: Chapter 12 - Endstop Wiring

1201 Parts needed

Prepared X, Y and Z endstop cables with black Molex plugs on the controller end.

Make once again sure that all three endstops have EXACTLY equal distance from LOWER bed. This is crucial for the accurate operation of the printer! The distance from top frame doesn’t matter.

1202 Secure endstop cables

Route the endstop cables around the towers and into the channel on the outer or side face of each tower. Ziptie in place.

Tighten the X, Y and Z endstop cables and ziptie at the bottom of the towers.

If you like, you can also fix the cables inside the profiles with these clips:
http://www.thingiverse.com/thing:655787

Step 15: Chapter 13 - Reel Holder

1301 Fit reel-holder

Note: Design might differ from the pictures.

Install the filament reel holder on the ZY axis using a t-slot nut fitted to the ZY extrusion.

Drop a nut into the top channel of the top frame on the ZY axis. Screw the reel-holder to the nut just fitted. Attach it as far left as possible.

Step 16: Chapter 14 – Wiring

1401 Wiring - Parts required

Electronics:
Arduino Mega
RAMPS board
LCD ribbon cable x 2

1402 Other Parts installed during wiring

For the printbed mount:

Glass tabs x 3
M3x8 socket capscrews x 3
M3 t-slot nuts x 3

For the Z-probe retractor:

Printed Retractor
M3x8 socket capscrew x 1
M3 t-slot nut x 1

1403 Hot-end wiring Stage 1

Ziptie the cables from the effector at intervals and route them to the RAMPS board in the bottom frame.

1404 Fit Glass tabs and Z-probe retractor

Before routing the the cables the rest of the way to the electronics, you need to fit the printed support tabs for the glass printbed and the Z-probe retractor.

Drop an M3 t-slot nut into the extrusion of each base frame top channel.

Fit an M3 x 8 capscrew to each glass tab and fit the tabs as shown in the picture. Do not tighten yet.

Assemble the Z-probe retractor from the M3 x 8 capscrew, and a t-slot nut.

Drop the nut into the extrusion at the left-hand end of the X-Y base frame top channel, slide it along until its about 40mm from the Z-Tower; Do not tighten the screw yet, you will measure this exactly later.

1405 Hot-end wiring Stage 2

Ziptie the extruder/hotend/endstop cables at the base of the Z-tower and divide the cables, routing the fan, Z-probe, thermistor and Z-endstop cables along the Y-Z channel and the motor and hotend resistor cables along the X-Z channel - these can only go as far as the Z-probe retractor. Ziptie in place and route into the base of the printer.

Similarly route the Y-endstop cable along the Y-Z channel, the X-endstop cable along the X-Z channel, and ziptie.

1406 Electronics installation

Make sure you take precautions not to build up electrostatic charge while handling the electronics - refer to Introduction for more details.

Carefully fit the 4 Motor Shields onto the X, Y, Z and E0 sockets on the RAMPS. E1 Socket remains empty. Make sure the small silver Potentiometer face AWAY from the green power connector of the RAMPS! Also make sure that all the pins are properly aligned with the RAMPS sockets. Add the cooler grills if needed to the Motor Shield ICs.

Now connect the RAMPS with the Arduino Mega, checking that all the mating pins are properly aligned. Note that the two front socket holes left and right of the Arduino remain empty. Push down firmly and progressively to seat it fully.

Screw the power cable into the RAMPS. Note the polarization! Red cable goes into (+) and black cable goes into (-) connector of the RAMPS board.

Plug the USB cable into the USB socket on the Arduino Mega.

1407 Motor wiring

Fit the motor cables from the X, Y Z and Extruder motors, ensuring the correct cables match the right pins next to the X, Y, Z and E0 Shields. The RED cable goes into the 1B Pin. For the Z-connector, there are two sets of pins; use the outer one, i.e. the one that’s farther away from the shields.

1408 RAMPS wiring

Bring all the loose wires together around the RAMPS board.

NOTE: If in any doubt about the wiring, consult the official RAMPS wiring instructions and diagram shown opposite. The diagram is from http://reprap.org/wiki/RAMPS_1.4#Pre-Flight_Check (click on the wiring diagram at that link to enlarge).

Note that the diagram is for a conventional printer, not a delta, so shows 2 x Z-motors. It also shows a second extruder and a heated print-bed - just ignore these.

Connect the hot-end fan to the D9 connector on the RAMPS. Check for the correct polarization!

Next connect the endstops. The RAMPS board has 6 three-pin headers labeled ENDSTOPS at the top right corner of the board next to the 4-pin I2C header, which is not used. The endstop headers are, from left to right: X-min, X-max, Y-min, Y-max, Z-min and Z-max. Only the outer (S) and centre pin (-) of each 3-pin header are used with mechanical endstops. As the Kossel has maximum endstops only, the X-min and Y-min endstops are not used. The Z-min position is used for the Z-probe. The jumpers on the picture are not needed.

Begin with the Z-endstop on row 6 (Z-max), as shown. If I2C header is present on your RAMPS, be careful NOT to put it on the 4-pin I2C header by mistake!
Next the Z-Probe on row 5 (Z-min)
Followed by the Y-endstop on row 4 (Y-max)
Finish with the X-endstop on row 2 (X-max).
Connect the hotend thermistor cable to the first pair of thermistor pins labelled T0.
If not already done in step 1407, connect the X, Y, Z, and E motors as shown. There are 2 rows of pins for Z- you can use either one.
Connect the hotend to the + and- pins Marked D10 on the RAMPS board. The hotend wires are not polarized.

Fit the LCD controller ribbon cables to the connector board and the board to AUX3 and AUX4 on the RAMPS board. Make sure EXP1 und EXP2 go into their respective connectors!

This concludes the basic wiring. It will be tidied up later, after commissioning, once it is all confirmed as working.

Step 17: Chapter 15 – Printbed

1501 Printbed - Parts required

Glass plate 190mm diameter

1502 Install Printbed

Flatten the wiring over and around the RAMPS, and gently fold the yellow fuses away from the power plug as far as they will go, to provide clearance for the glass printbed.

Move one of the previously-installed glass tabs at 120mm along the Y-Z extrusion but do not tighten yet. Repeat for the tab on the X-Z extrusion.

Fit the glass onto two tabs, ensuring it is slotted in the 2 tabs. Tighten the 2 tabs.

Slide the third tab along the X-Y extrusion until it engages with the glass plate. Push it as tight as possible towards the glass plate. Note that the tabs do NOT to be in the center position of the extrusions.

Tighten down the third capscrew until the printbed is firmly seated in the tabs and the tabs are firmly on the extrusions.

Congratulations! You are now ready to start commissioning and calibration. Finishing touches like tidying up the wiring.

Step 18: Chapter 16 - Commissioning, Calibration and Testing

1601 Overview - CAD/CAM Toolchain and Software

The installation of all the software will be covered in detail later on in this chapter. This section provides a general introduction.

The sequence of processes involved in producing a physical object by Computer Aided Design (CAD) and Manufacturing (CAM) is known as a toolchain. The picture below from the RepRap wiki illustrates this sequence. Versions of all the computer programs needed for the toolchain are available for download as Free and Open-Source Software, in keeping with the philosophy of the RepRap Project.

CAD design and production of 3D .stl models is well beyond the scope of these instructions, but a vast range of prepared designs for printable objects is available on sites such as Thingiverse.

Turning a design into printable Gcodes using a utility such as Cura or Slic3r is also outside our scope, but is well documented on the respective websites, and we provide setup files to suit the Kossel Mini. Optional but certainly helpful for calibration is the communication program Printrun/Pronterface which you will need to install to start commissioning and testing your Kossel Mini. Mac OS X and Linux versions are also available for download.

The Kossel Mini version of the controller firmware Marlin needs to be loaded on your Arduino Mega, we supply a pre-configured version for your printer. Some settings can only be determined by calibration of an individual printer, and this chapter will guide you through the calibration process. The changed settings will have to be uploaded in Marlin, and this is described in detail on the Arduino website.

1602 Software supplied

The programs and configs that are supplied or need to be installed are:

Download: Arduino: Arduino-1.0.5-r2: Arduino website
Printrun/Pronterface: Printrun-Win-Slic3r-10Mar2014: Printrun/Pronterface
Kisslicer or Cura

Supplied: Kisslicer config files
Marlin: Special pre-configured version of Marlin
(Unconfigured version can be found here: https://github.com/jcrocholl/Marlin)

1603 Connect USB to the printer

Plug a USB A/B lead (supplied) into the printer and your computer. Do not plug the power lead in yet.

Windows Users

Windows should find the Mega as new hardware and try to install it. Otherwise, please follow the instructions as described at http://arduino.cc/en/Guide/Windows#toc4

Windows should tell you the COM port number it has assigned to the Arduino Mega during driver installation, or you can get it from Device Manager. Make a note of it as you will need it in the next stage.

Note for Windows 8

By default, Windows 8 will reject third-party drivers like "arduino.inf" because they are not digitally signed. You can turn this behaviour off by following the instructions on the Arduino forums.

Mac OS X Users

The Mega will be automatically recognized and installed. It may be recognized as a USB Modem by your Mac but this is not a problem.

Checking connectivity

Windows Users

Download copy Printrun-Win-Slic3r-10Mar2014 into a folder of your choice, then run the program pronterface.exe. It opens immediately - there is no installation process required. You may like to make a desktop shortcut as you will be opening it frequently during commissioning and calibration.

Check that the COM port (COM 8 in the above example) and speed (250000 Baud) are correctly set, tick the Watch box and connect to the printer. You should get a screen display similar to that below.

Mac OS X Users

Install Pronterface

Follow the instructions here: http://reprap.org/wiki/Printrun#Mac_OS_X . The link there will take you to http://koti.kapsi.fi/~kliment/printrun/ where you can download the latest version (Printrun-Mac-10Mar2014.zip at the time of writing). Once it is downloaded and extracted you may want to move it to your “applications” folder. The file name will start with “printrun”.

Open printrun, ensure it it set as the screen shot below, and click connect. You should get a display similar to this:

Now you can follow the Commissioning Tests instructions below.

1604 Run Commissioning Tests

Throughout the following sections there will be reference to commands, called G-codes, which are the instructions the printer follows. All manual commands, as well as files to print, consist of G-codes. Manual commands are entered using the text entry box and the Send button at the bottom right-hand corner of the Pronterface screen. Manual commands can also be sent by clicking on the buttons within Pronterface. Some G-codes cause the printer to undertake an action, others report back in the text area above the box on printer status.

If you need to look up a G-code (most of which, confusingly, start with M not G), there is a complete list on the RepRap G-code wiki. They must be entered in UPPER CASE. Note that not all G-codes are supported by all varieties of RepRap firmware, including Marlin which is running on the Mini Kossel RAMPS board by default.

Some of the more commonly used G-Codes (do NOT try them yet, before you have tested the endstops!):

G28 Home all axis
G29 Autolevel
M106 S255 Fan On
G1 X0 Y0 Z50 Move head all to the center and 50mm above the glass surface
G1 E50 F1000 Extrude 50mm of Filament
M302 Override “Extruder Safe”

Test endstops

Endstops allow the printer electronics to register where the carriages are. The Kossel has its endstops at the maximum of the X, Y, Z axes, and it has a fourth endstop attached to the Z-probe, which allows the printer to register where the bed is and also to compensate for slight bed misalignment. These tests will confirm that the endstops are working correctly. Note that X, Y, Z endstops work in the opposite way to the probe endstop; they are “open” when not triggered, while the probe is “closed” when not triggered.

Move the carriages to about 50mm below the endstops by hand so that the end-stops are not triggered, and release the Z-probe into the deployed position (push the top of the brass bar side-ways until it snaps down).

In the text box at the bottom right hand corner of the screen, type M119 and click Send or press Enter.

It should report all end-stops are open, as below:

Now test if all the endstops are wired and working correctly: First push the Z-probe up to the retracted position to release the Z-probe switch. Type M119 again in Pronterface and press enter to send the command, Z-min should now report “triggered”.

Now move the Z-carriage up to trigger the Z endstop, send M119 again and z_max should now report triggered. Repeat for Y and then X, checking with M119 each time.

Troubleshooting:

If the endstops do not show triggered in the correct order, double-check the order of the endstop cables where they are plugged into the RAMPS board
If an endstop does not show that it is triggered, double-check the wiring and ensure the plugs are seated correctly
If the probe (z_min) does not show as “open” when it is deployed, the spring may need to be compressed further by moving the brass screw terminal block further up the brass shaft. If the spring is already fully compressed, try lubricating it where it passes through the plastic with a small dab of grease. If it still doesn’t show as “open” when deployed, try adding another spring from a “click” style ball point pen.

Connect power supply to printer, and check motor direction and homing

Power on the printer. With the carriages about 50mm from the top of the towers and one hand on the Power plug, ready to power down, send the command G28 or click on the Home All button:

The carriages should move up and hit the endstops. If they move down, power off immediately, before they reach the bottom, disconnect in Pronterface, unplug the X, Y and Z motor cables from the RAMPS board and plug them in the other way round to reverse the direction of motor rotation.

Troubleshooting:

If nothing happens, double-check the power supply connection to the RAMPS board (green plug), there should be 12V present on the plug
If they move in different directions (ie. some up some down) check that the motor plugs are all plugged in the same direction

Check Fan Rotation

With the power on, enter command M106 S255 and the hot-end cooling fan should start to rotate counter-clockwise and so be blowing at the hot-end.

Troubleshooting:

If the fan is not turning on then reverse the orientation of the plug on the RAMPS board and recheck
If the fan is blowing away from the hotend then unscrew the fan and reverse it so the label faces the hotend

Test Hot End

Select Heat 185 (PLA), click Set and check the Watch box. Confirm the graph line rises to 185C and steadies there.

1605 Calibration

At this stage it will be necessary to make some changes in Marlin.

Set Z-height:

NOTE: A more detailed Z-height calibration procedure is given on Tony’s Blog.

IMPORTANT: During this procedure it will be necessary to Home the printer several times. This parks the tip of the hot-end at top centre of the printer, at coordinates X=0, Y=0, and Z= MANUAL_Z_HOME_POS (as set in Marlin). This is an important starting point, but powering off the printer or resetting the controller will cause the loss of these coordinates. After powering up the printer or reconnecting/resetting in Pronterface, always Home the printer with the Home button or by sending G28 to update the hot-end coordinates, unless these instructions specifically say not to Home it. Connect in Pronterface and power on. If you have started this section with the hotend cold, set the extruder temperature to 185C. This is because the hotend expands slightly when it is heated, so for an accurate calibration it is best to have everything at print temperature. Do not feed any filament into the extruder, and if there is already filament in it, remove it.

Ensure the Z-probe is retracted and the print-bed is firmly mounted on the glass tabs
Home the axes
Send M114 to display the X, Y and Z positions:
X and Y should both be 0.00, and Z should be 280 mm. This is the MANUAL_Z_HOME_POS we have set as the default starting height in Marlin. Record this figure as Z-original. (249.8mm in the example image above, taken after some calibration had been done).
Send the command G1 Z20 to move the hot-end down to about 20mm above the centre of the print bed. In fact it will be less than this because we have deliberately set the starting MANUAL_Z_HOME_POS to be higher than is actually achievable. This means the hot-end is closer to the bed than Pronterface thinks it is. This will save you some time in setting it, but means you will need to be careful when moving it further downwards.
Place a strip of standard 80 gsm bond copier/printer paper on the print bed to serve as a feeler gauge to check the nozzle height.Using the Z +/- buttons in Pronterface move the Z axis progressively down until the nozzle is nearly touching the bed. Move 1mm at a time until you estimate the gap is about 1mm. While moving the paper under the nozzle, continue to lower the Z axis but now using 0.1mm steps until the paper begins to drag against the nozzle. Now send M114 to show the current Z-position:
Record this as Z-error - in this case only 0.2mm, though you should get a value of 3mm or more.

Troubleshooting:

If the nozzle won't go down far enough then the Z-height setting in Marlin is too small (this should only happen when resetting Z-height after removing the print-bed). Estimate how much more travel you need, probably no more than 1 or 2 mm. Power down and disconnect from Pronterface. Open Arduino, open Marlin.ino, click on the configuration.h tab, find the #define MANUAL_Z_HOME_POS (around line 350) and increase the value by the estimated amount needed, plus a few spare mm, re-upload the firmware, save it and repeat the procedure above.

Once you have established Z-error, change the setting in Marlin around line 350 #define MANUAL_Z_HOME_POS from 280.0 to 280 - Z-error (in the example this would be 280 - 0.2=279.8mm)

Note that you do not have to deduct the thickness of the paper (~ 0.1mm) when calculating MANUAL_Z_HOME_POS because the hotend needs this gap to protrude the filament when printing.

Save, disconnect in Pronterface, upload and repeat the Z-height checking procedure to confirm it all went correctly.

Check Z-probe trigger position

To deploy the Z-probe, the effector moves to the deployment position, then travels across in the -X direction so that the short leg of the probe snags on the Z-timing-belt and is flicked over until it can be pulled down by the spring.

Test it by homing the printhead (G28), then send G29 to deploy the Z-probe, with one hand on the power switch or cable. If it fails to deploy as it passes the Z-timing-belt, power down at once, disconnect in Pronterface and follow the troubleshooting paragraph below.

You can lengthen the arm slightly if necessary with a small piece of 1.6mm heat shrink tubing (supplied). It is a good idea to fit this anyway to avoid possible long-term wear on the belt by repeated triggering of the probe.

Troubleshooting

If the Z probe fails to trigger on the belt, you need to adjust the starting position in Marlin. The relevant settings are in the Marlin_main.cpp file under void deploy_z_probe() on line 826, about a third of the way down this very long file. A couple of lines below it the positions are given as:

So if the trigger needs to move close to the belt by 5mm add 5 to the number after “destination[Y-AXIS]” (in this example 95 would be increased to 100.

If the belt needs to start or stop further left or right of the belt the adjust the Two “destination[X_AXIS]” numbers, the first is the start position, the second the end position.

Set and test Z-probe retract position

After probing the print-bed levels at a grid of positions, the probe is moved to the retract position and lowered until it hits the plastic retraction tab which pushes it up until retracted.

We have set the probe retract position in Marlin so that it should work by just adjusting the position of the orange tab.

Once the probe is deploying correctly, allow it to run through the whole probing sequence and attempt to retract itself. Once the printer moves to the retract position, cut the power and mover the plastic tab under the Probe and tighten the belt. Repeat the test until the retraction works correctly.

If the position needs adjusting, then use Pronterface to move the probe exactly over the centre of the retract-bolt, lower it until it just touches, and then send M114 and make a note of the coordinates reported. The retract position is in the Marlin_main.cpp file - find void retract_z_probe() on line 839, and a few lines below it the positions are given as:

Change the X and Y values (ONLY) of the destinations to the values you have just determined, save, upload and test. Note do not change the Z positions to the results you got using M114 or else the probe will crash into the bed and retract tower.

Set Z-Probe offsets (optional)

The distance between the tip of the Z-probe and the tip of the hot-end needs to be set accurately. The offsets are defined in Marlin configuration.h, around line 355:

The first number (0 in the above screenshot) is the X-offset - normally close to zero as the probe is directly behind the hot-end.

The second number (13 in the above screenshot) is the Y-offset: the distance between tips in the Y direction.

The third number, the Z-offset, is critical and will be measured and set as below, following Johann Rocholl’s procedure at https://github.com/jcrocholl/Marlin (bottom of the Readme).

Place a piece of blue painters tape on the Printbed near the centre. Make a small cross-mark on the tape with a marker/felt-tip pen near the centre of the bed.
Move the tip of the hot-end in Pronterface to position it exactly on the mark and touching the bed (Z=0), then move the nozzle up 0.1mm using PronterfaceDisplay this position by sending M114:
>>>M114
SENDING:M114
X:-0.60Y:0.90Z:0.80
This will be “Nozzle Zero” position
Raise the hot-end by 20mm to ensure there is clearance for the probe.
Manually trigger the Z-probe and use Pronterface to place it directly over and almost touching the mark on the print-bed.
Lower the probe 0.1mm at a time until you hear the click of the microswitch as it is released. If you can’t hear it, send M119 in Pronterface after every 0.1mm to check when the Z-min endstop triggers.
Now send M114 in Pronterface to get the position of the probe, which gives the offset values.
Record these values as “Probe Zero” and subtract the “Nozzle Zero” positions from them.
Probe Zero Values - Nozzle Zero Values:
X:2.90Y:-17.00Z:3.60 - X:-0.60Y:0.90Z:0.80 equals
X:3.50Y:-17.90Z:2.80
and enter them in the define Z_PROBE_OFFSET field in Marlin, changing the signs:
#define Z_PROBE_OFFSET{-3.5,17.90,-2.8, 0}
Now disconnect in Pronterface, re-upload Marlin, reconnect in Pronterface, set the extruder temperature to 185C, home the printer (G28), and then probe the bed (G29).
Enter G1 X0 Y0 Z10, then use Pronterface to move the hotend towards the bed, using a piece of paper as a feeler gauge. The paper should just drag when the hotend reaches 0 on Z (use M114 to confirm)

Troubleshooting:

If the hot-end reaches zero before dragging on the paper then the Z value of the offset in Marlin is too little, so increase it by the estimated amount plus a mm more and repeat until you have the correct setting.

Repeat the home/probe/measure sequence until there is no further error between the probe height and the measured height with the feeler gauge.

Finally, home the printer, which removes the Z-height determined by the auto-levelling process and resets the Z-height to the MANUAL_Z_HOME_POS value. Send G1 X0 Y0 Z5 and lower the tip onto the paper again. Exactly the same amount of drag as in the original Z-height measurement means you have now exactly measured the offset.

Check the range of X and Y travel

This is a check to ensure the printhead can move around the extent of the printbed when close to the surface without snagging on anything.

Move the printhead to 1mm off the bed (G1 X0 Y0 Z1)
Move to:
G1 X85 Y0
G1 X-85 Y0
G1 X0 Y85
G1 X0 Y-85
simply move to X=85 and -85 with Y=0,
and to Y=85 and -85 with X=0, using the G1 command with the appropriate coordinates. Check visually that the hot-end tip is about 5mm from the edge of the 180mm mirror glass printbed. Finally home the printer.

IMPORTANT NOTE: Don’t try moving the printhead in the X and Y direction when it is homed. One or more of the carriages will try and move upwards past the endstops and will not respond to endstop triggering. This could damage the motors, belts and electronics. Always move the printhead down in Z at least 100mm before moving in X and Y.

To achieve a good adhesion of PLA filament of the glass plate, please use a UHU glue stick and apply a thin layer of glue on the glass bed before each print.

Check and calibrate the extruder

Do not load filament yet! Send M302 to override cold extrusion prevention in Marlin. Set Pronterface to extrude 10mm of filament and click Extrude. The large gear on the extruder should rotate clockwise viewed from above. Click Reverse and confirm it rotates counter-clockwise.

Temporarily detach the filament Bowden tube at the extruder by pressing in the black or blue plastic flange while pulling the tube gently out. Cut off about 500 mm of filament and cut a point on the end to be inserted. Click the Motors Off button in Pronterface. Feed the pointed end of the filament into the opposite side of the extruder from the bowden tube by hand, rotating the big gear slowly clockwise, just as you did when checking it after assembly.

Once it emerges a little way from the other side of the extruder, put a small piece of tape on it in line with the face of the extruder.

Set the extrusion distance to 30mm in Pronterface, and the speed to 100 mm/min.

Click Extrude, wait for it to finish, and now measure the length of filament as accurately as you can.

In this the distance extruded was actually 29 mm so the DEFAULT_AXIS_STEPS_PER_UNIT for the extruder in Marlin needs to be increased in the ratio 30/29 to make it extrude more filaments. Disconnect the printer in Pronterface and find line 329 in Marlin configuration.h:

The E-steps setting needs to be increased to 30/29 x 625 = 647. Make this change and then upload Marlin again.

Connect again in Pronterface and send M302 again to override cold extrusion prevention. Mark the filament again with tape in line with the face of the extruder. Extrude 30mm again - the amount extruded should now measure 30mm, within the limits of measurement. If it does not, then repeat the calibration procedure. Once it is accurately extruding 30mm, repeat with the amount extruded set to 60mm. Adjust the E-steps as necessary in Marlin and re-test. Once it is correct at 600mm, run a final check at 100 mm. The length extruded should be within 1mm of 100 mm, giving 99% + accuracy, which is good enough. Save the settings in Marlin.

Now remove the short length of filament used for calibration and discard. Replace the Bowden tube and feed in the end of the filament sample provided by hand until it emerges into the Bowden tube. Connect in Pronterface, power on, Home the printer and set the hot-end temperature to 185 (PLA). Once it reaches this temperature, use the Extrude button to feed 100 mm of filament at a time at 300 mm/min until it is close to the effector end of the Bowden tube. It should need 4 goes.

Then feed 20 mm at a time at 100 mm/min until molten filament begins to emerge from the tip of the hot-end.

You have now successfully completed the calibration process!

Step 19: Chapter 17 – Upgrading and Improving Your Kossel

The fact that your Mini Kossel Printer is open source is a huge advantage as there are endless upgrades and extensions available online for your printer! Here is just a small selection of what you can do to further enhance, upgrade and improve your printer:

Add a Hot Bed which allows you to print ABS:

http://www.hkbay.com/store/product_info.php?cPath=17&products_id=134

OctoPrint and OctoPi

Besides controlling your printer from a PC via USB, you can also print files directly from the SD Card Slot that’s integrated in your LCD display. Another very cool option is to use OctoPrint or OctoPi, which allows you to control your printer remotely from anywhere via a standard browser window. You can even connect a camera and monitor your prints remotely, add a WiFi connector and so on. This is probably the best and most flexible way to control and monitor your printer:

http://octoprint.org/download/

Stuff on Thingiverse.com

Ramps 1.4 + Arduino Holder: http://www.thingiverse.com/thing:521888
J-Head MkV Dual Cooling Fan Attachment: http://www.thingiverse.com/thing:447127
Improved Spool Holder: http://www.thingiverse.com/thing:352833
Housing for Raspberry Pi: http://www.thingiverse.com/thing:89745
Cam Mount for Raspberry Pi: http://www.thingiverse.com/thing:237252
Advanced users can try to attach Dual Hotends: http://www.thingiverse.com/thing:493584

Also feel free to join our Facebook Group to get lots of tips and tricks about assembly of Delta Printers:

https://www.facebook.com/groups/3dpahk/