Time to rebuild my large Kossel

It’s more than a year and a half since I published my large Kossel build blog entry. Since then I have upgraded it many times. Several people have built 3D printers based on this design, and some have asked for a more complete bill of materials. So I decided to create a page on this printer as it is now, including yet more upgrades.

If you’ve built my original 2020 Kossel variant and upgraded it, them you are already using the most advanced 3D printer electronics available – the Duet WiFi. So my focus this time is on upgrading the mechanics, so as to get the best out of the electronics. The new upgrades are:

  • 2017-03-22-20-17-04.jpg2040 extrusion for towers and top horizontals instead of 2020, for increased rigidity
  • Linear rails instead of wheeled carriages, for better alignment
  • Magnetic joints
  • Toothed idler pulleys, to reduce belt vibration
  • PCB effector with built-in lighting and nozzle contact probe, and matching PCB carriage adapters to ensure uniform rod spacing
  • E3D Titan extruder

This is not intended to be a budget printer. If you are in the UK, you can expect the parts to cost over £1000 including VAT.

I considered moving the tower motors and electronics to the top, so that the electronics are more accessible instead of being under the bed, and better separated from the mains wiring. However, if the Robotdigg metal corners are used then the base would be only 40mm high, which is not enough to accommodate the power supply and the mains inlet components. One possible way round this would be to bolt three 2060 horizontal extrusions to the corners even though they are intended for 2040, and to mill an opening in one of the 2060 extrusions to accommodate the mains inlet components.

You can find the full instructions and the link to the parts list here.

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70 Responses to Time to rebuild my large Kossel

  1. Jan Fervers says:

    Thanks for this update… Regards Jan

  2. Damian Fernandez says:

    Comparing to carriages do you see a difference in quality using linear rails? where do you get 480mm magnetic rods?

  3. CEP says:


    Can’t wait to see additional pictures of this new updated version 🙂 . I’m currently following your path and intend to move to a Duet and a larger frame. But I’ve got 2 questions which didn’t find answers in your post :
    -#1 why did you change horizontal extrusion from 355mm to 390mm ?
    -#2 your ratio Rod/HorizontalExtrution changed in this configuration, from 355mm extrusion with 350mm rod eye-to-eye (~98%) to 390mm extrusion with 360mm rod ballCenter-to-ballCenter (~92%), why ? It doesn’t seem to be due a big change of offset ( from metal effector to PCB effector and from pulley system to linear carriage).

    Sorry if its a bit “technical for noob” but I’m still struggling with the dimensions of my future project :). Your choices are not random so there must be a good reason behind these 2 changes.

    thanks in advance for your answers.

    • davidcrocker says:

      It’s because the 2040 corners push the motors further in towards the centre of the printer than the 2020 ones did. So you need longer extrusions to get the belts at the same distance from the centre. I didn’t realise this until I started rebuilding it, so I am actually using 355mm extrusions with 17mm printed spacers at each end.

      I increased the rod length slightly to reduce the maximum joint angles needed, after my experience of hitting the limits of the Igus joints. But with the magnetic arms, I probably needn’t have bothered.

  4. gregchodaczek@gmail.com says:

    First off, thanks for all of your great work and advice.
    Second, why did you choose 16 tooth pulleys instead of 20 tooth?

  5. Joseph Tarling says:

    Hi David,
    I really like your Delta. I was going to build a corexy C-bot but after seeing your posts i’m now interested in build your clean looking printer. I saw in the bom that you have 2020 extrusion but in your updates you replaced it. Is the bom up to date? Thank you very much for spending your time to document this awesome build.

    • davidcrocker says:

      There is a link to the current BOM in https://miscsolutions.wordpress.com/dc42s-large-kossel-build/. I hope to post more photos of the assembly steps next month.

      • Joseph Tarling says:

        Awesome! That’ll be a great help.
        I was actually referring to that excel sheet. If that’s up to date with all the newest mods because I saw 2020 in there and I wasn’t sure if that’s a mistake or not. I should have looked at the steps to find out. Unfortunately it was really late last night when I pondered that question lol. If I only read the steps it’s right there in the base framing. Doh! Thanks again David for responding so quickly. I’m looking forward to seeing more photos of the assembly. 🙂

  6. Joseph Tarling says:

    Hi David,

    I’ve got another question for you… Have you looked into the flex2drive extruder or a “flying extruder with counterweight” setup?


    I’ll leaning towards the flex2drive setup for dual extrusion… Which one would you think would be best for this printer?

  7. davidcrocker says:

    I haven’t tried either, so I can’t comment.

    • Shabnum Bhat says:

      Congratulations the printer looks awesome, I work for a 3D printing service firm in Canada and somehow landed on your blog page. You have in a great way modified the printer and looks like it can produce large format prints too. I am just wondering does it maintain a good details and finish for small complex shaped objects?

      Shab Bhat
      Custom Prototypes

  8. Hi David.

    Will you be publishing the last few printed parts shown in the BOM soon?

    (Endstop switch mount / Carriage stop / Titan extruder mount )

  9. Randy Smyth says:

    question regarding the Vertices from Robotdigg in your BOM. On the Robotdigg site the 2040 vertices come in 2 sizes (nema 17 & nema 23) . If I select “blue” as a colour the size says “both”.
    Will that still work with the build ? Or do I need to purchase all of 1 size ?

    • davidcrocker says:

      I am using the blue vertices, they are drilled for both Nema 17 and Nema 23 motors.

      • Danal Estes says:

        Robotdigg’s website says different things in different places… if you read them all, and put things in the basket and read the (yet again different) descriptions there, I have come to believe that the black and blue both have the holes for 17 and 23.

  10. Randy says:

    In regards to moving the board to the top, could you leave the frame as it is, move the board up but leave the motors on the bottom?

    • davidcrocker says:

      Yes. If doing that, I suggest using 2 x twisted pair cable (preferably shielded) to connect the stepper motors to the Duet, to reduce radiated interference from the long cables.

  11. Pierre Minnieur says:

    I’m going to build this printer, but I’d like to know what I have to do do get somewhat lower build height. I need the ø300mm build space, but only 100mm of build height (on the edges, I’m fine with slightly taller build height in the center), since all the stuff I’m printing is <60mm tall. So I'd like to shrink the printer a bit in height if possible.

    Will it be a problem to use 400mm extrusions for the sides? Does it effectively change something big? Because I have many leftovers from another printer in that size (so I don't need to reorder in 390mm length).

    My problem is I actually don't know much about Delta geometry and dimensions, any help would be appreciated. I guess I can buy shorter MGN12 rails and shorter 2040 extrusions, but I don't know by how much.

    • davidcrocker says:

      There is about 215mm wasted height due to the height of the horizontal extrusions, bed, hot end etc. Using 1m verticals and 360mm rods, the build height is about 425mm at the edges, so for 100mm build height at the edges you would need at least 675mm vertical extrusions. The linear rails need to be shorter than the verticals by between 140mm and 300mm. 400mm extrusions would be OK for the sides.

  12. For people copying your design can you share your duet config to give us a head start 🙂

  13. When I look at the Delta Smart Effector at Filastruder (which appears to be the production version of the PCB effector you added in this upgrade), the form factor severely limits hot-end options. In the case of the DSE, it goes so far as to come with a custom E3DV6 heatsink. Given your [originally] stated desire to add a second extruder, how does this effector setup allow for, hinder, or preclude that route. (I ask because I’m seriously considering a build like yours, using a Chimera dual extruder.)

    • davidcrocker says:

      Our priority was to produce an effector that works with the most common configuration (single E3Dv6 hot end) and wasn’t too large, because a large effector reduces the printable area. I am still interested in adding multi extrusion, and I have it in mind to design a version of the smart effector suitable for a Diamond hot end.

      • I figured as much. I also figured that if there was a way to use alternative configurations, you would know. Thanks for the confirmation, that’s one less ambiguity to deal with.

  14. J says:

    Hi David

    I actually want to build nearly the same printer. The last 4 years, I printed with a seemecnc rostock V1, and now I want something more professional. I want to reuse some parts from the rostock like the, duet3d, heated bed 300mm, hotend.
    In the BOM I have seen that you use 360mm rods, how do you calculate this length? How was your experience with the Igus KBRM-03?


    • davidcrocker says:

      With the dimensions of my printer, the 360mm arms give an arm angle of 60deg to the horizontal at bed centre and 25deg to the horizontal opposite a tower at the edge of the 300mm diameter print area. Those angles are good.

      The problem I had with the Igus joints was that the range of movement was a little too small. Also I found the wheeled carriages less accurate than the linear rails I switched to.

  15. R says:

    I am in the middle of putting together the 2040 precision kossel design. In regards to squaring up the frame, what would you consider to be an acceptable tolerance when measuring the distance between towers top to bottom to be equidistant? Also the Robotdigg 2040 corners and the T-nuts allow for a lot of movement within the slot when fastening the horizontal extrusions to the base (at least the t nuts I have allow a lot of movement). Did you just push them to one side of the slot? or was there anything you did different to adjust the lean of them in the squaring process?

    • davidcrocker says:

      The distances between top and bottom of my towers are about 0.3mm different. I haven’t measured it before. I relied on the ends of the 2060 base extrusions being cut square and the vertices also being square, so I just butted them up against each other.

  16. redfox says:

    Hi David, tk for sharing your delta, i just look your BOM list, and make a check list shops, and see no spacers to extrusion, it because you put 390mm right?

    Any other update/new mod of this excellent printer?
    (I’m will be crasy but, this one will be my first one)

    And one more tk tk so much for sharing the knowledge.

    • davidcrocker says:

      I only needed the spacers because I used 355mm long extrusions. You don’t need them if you buy 390mm extrusions. The only updates I have done are to add a printed part to hold a PTFE tube to one of the upper horizontal extrusions to act as a filament guide, and to replace the Bowden tube with Capricorn tubing, which has allowed me to reduce retraction to 5mm. There will be a filament monitor upgrade soon.

  17. Hans Øystein Brændjord says:

    hello 🙂
    i plan to build this awesome printer, hope it´s ok with a couple of questions.

    regarding the base (bottom triangle), do you use 2 sides with 2060 extursions and 1 with 2×2020 extrusions (based on your BoM list and from the picture)? and the vertices you use, will they fit the 2060?
    and last question, what is the yellow/orange part on the top and bottom triangles (on the end of each extrusion before entering the vertices

    best regards

    Hans from Norway

    • davidcrocker says:

      Yes, I use 2060 extrusions for 2 sides, and 2 x 2020 for the 3rd side so that I can fit the mains inlet components between them. It would be better to use 2060 for the 3rd side too and mill a large slot in it to make room for the mains inlet components; but I don’t have access to a milling machine.

      The yellow parts are printed spacers. I needed them because I upgraded a previous design and the horizontal extrusions I had were a little too short. You don’t need them if you purchase extrusions of the correct length.

      btw I will be at the 3D Meetup in Sweden in April, in case you are able to be there too.

      • Hans Øystein Brændjord says:

        thanks for the reply:) hoping too get to travel to 3D Meetup i sweden, hopefully i will get some time of from work.

        awesome job on the delta printer, can wait to start building 🙂

  18. matthias says:

    Hello David,
    can I find somewhere the config files to your large Kossel?

  19. Jeff says:


    I am in the process of building this printer and am almost done. I have a question regarding the Z probe wiring and was hoping you could advise. Forgive me if the answer to my question is obvious.

    When I wired the 8-pin Z-Probe/PT100 sensor connector I used all 8 wires, including Pin #7 (Control Input: Z-Probe connector MOD Pin). I later read that this pin may not be required. Can I safely leave this wire connected? Or will leaving this wire connected create an issue?

  20. Jeff says:

    Hello again,

    I have (2) additional questions.

    1) On the picture of your finished printer there are (3) binder clips attached to the bed plate. I assume the clips must be holding a rigid removable print surface onto your heated aluminum plate (although I can’t actually see that in the picture). If the clips are holding a rigid removable print surface, can you tell me what removable surface you chose? If the picture shows an adhesive backed print surface attached to the aluminum plate, can you tell me what the clips do?

    2) On your BOM you specify a Ø300 mm silicone heater. I purchased my heater and it is on its way. The bolt holes for the bed plate are on a Ø283.5 mm bolt circle. How did you account for the small interference between the standoffs (male-female pillars) and the slicone heater?

  21. davidcrocker says:

    1. I have two build plates of 4mm float glass, each 330mm diameter. One has PEI bonded on top, the other has PrintBite.
    2.The aluminium bed plate is 330mm diameter, the heater is 300mm diameter. So the 3 bolt holes to secure the bed plate to the frame are outside the heater, on a diameter of about 315mm.

  22. Sorin says:

    Hello Mr David,

    I have to give you a very big beer for the BOM.
    As I see you’re nice enough to answer questions, please answer mine as well, even with just yes or no.
    I made your list, but Robotdigg was a real challenge. The site is a mess. Most of items I found comparing the prices in your list and the ones on the web store.
    1. Still, when you say “Set of 6 2040 aluminum vertices”, do you mean the 6 “corners” of the frame? Delta2040Black ? I ask because they are now 68$ (from 73$ on your BOM), and I want to be sure.

    2. I want to build it 1100mm in height, but I don’t see a linear rail longer than 750mm, and I have a feeling this is a bit too short for 1000mm.
    I’ll make it 1000, but can you please comment?

    3. Do you have anything against Bondtech extruders? I like the idea of the filament pushed from both sides. Plus they’re cheaper for me, and shipping is cheaper too.

    Thank you!

  23. Jeff says:


    I have completed this machine build and sadly I have a temperature fault for my extruder sensor and it lists the temperature as 2000°C. I know I have done something wrong but I’m not sure what and was hoping you could offer some advise on troubleshooting.

    I am using a PT100 sensor and daughter board with an e3d V6 hot end.
    I am also using (4) wires to connect the sensor to the daughter board.

    Below are the parameters in my config.g file.
    1) Can you tell me is these are correct for my harware?
    2) Do you have any suggestions to help pinpoint the problem

    ; Thermistors and heaters
    M305 P0 T100000 B3950 R4700 H0 L0
    M301 H0 P20 I0.5 D1000 T0.85 W150 B5
    M301 H1 P10 I0.10 D100 T0.50
    M305 P1 X200
    M570 S200

    ; Tool definitions
    M563 P0 D0 H1
    G10 P0 S0 R0
    M92 E420

    Any help would be greatly appreciated.
    Thank You

  24. David Posea says:

    Hi, I built my own large Kossel and it’s almost idential to yours. I took a long break from the printer world, and coming back saw the smart effector. However,I have an 0.85 duet and I’m not sure what to do withthe Z probe. Can you suggest a pin to use for control input? If you have not already added a build for the 0.85 to your firmware version I can do that. I will probably scan the source to chose a pin, but thought I would ask also. Thank you so much for all you have done for so many of us!!

    Also, my arms are 360mm from filastruder. I couldn’t find 390 mm ones. Am I ok? My previous arms were also 390mm pivot to pivot, and I swear I did not copy your design. We came up with almost the exact same dimensions!!! Please let us know if you try out a new diamond hotend design. Dual extrusion with water soluble support may soon be a must have. I also like 3mm ABS so I’ll have to have a hot end machined to fit. An adapter for starndard E3D parts would be great!!! hint.

  25. David Posea says:

    Thanks, I found it, I was trying to use the extruder endstop as the 0.85 instructions I found suggest. There is really no info on using the smart effector with an 0.85 board that I could find with google. Thanks again for all of the improvements you made to the Kossel design. I also think I am going to use your bed design. I don’t have a good way to hold the glass and the aluminum heater disk flexes as it heats up.I believe the product was discontinued.

  26. Jeffrey Jacobs says:

    Can you tell me if it’s possible to use the Duet Web control to help isolate the cause of an emergency stop and correct it?

    Also, is there a better place on the web for me to post questions regarding this build? I certainly don’t wish to post questions to the inappropriate website.

  27. David Posea says:

    I was using a SeeMeCnc Aluminum heater plate for the bed base. Running the mesh compensation today shows the bed is higher at the three supports and sags in the middle. Should i try supports or try to source an aluminum disk ? I think 1/8 inch may flex, but I’m having trouble finding 1/4″ aluminum. You just use three standoffs under the plate to mount it? My current bed deviates by 0.75 mm from lowest to highest spots. I haven’ tried reducing the smart effector sensitiviy yet eiher. I think that may help.

    I could not find 300mm round borosilicate glass recently, so I bought square glass and a cutter ($8.95) . It was easy to use the circle glass cutter and I rounded the edges wih emory cloth. I’m including this info for anyone else that can’t find round boro glass.

  28. davidcrocker says:

    If the pattern shown by the mesh compensation is aligned with the towers, then it’s not necessarily caused by the bed not being flat. It could instead be caused by the rod length not being configured quite correctly, ot the steps/mm being slightly out.

    If the bed includes an aluminium heat spreader, then you don’t need to use borosilicate glass. Ordinary 3mm or 4mm float glass will do if it is flat (which it usually is)..

  29. Joseph T. says:

    Hey David,
    did you end up switching to a bondtech extruder? If so which version and did you see any improvements? Thanks!

    I finally got back to working on this beast. I’m looking forward to finally finishing it lol.

    • davidcrocker says:

      I’ve bought the Bondtech extruder but I haven’t installed it yet.

    • davidcrocker says:

      I got round to installing the Bondtech extruder earlier this year. I am very pleased with it, I prefer it to the Titan.

      • Joseph T. says:

        Cool to hear. I finally got around to the final stages of calibrating my printer. I’ve got the BMG flying. Seems to be functioning well but I haven’t gotten too far as I’m struggling with getting my measurements in order. I’ll post in the forums my issues i’m encountering.

  30. R says:

    Being great at starting projects and poor at completing them, I finally have gotten around to completing this build. And I have to say, I am thrilled with the Smart Effector The precision and repeatability is fantastic. Overall this thing is a joy to print with. Very quiet even using the robotdigg smooth pulleys.

  31. R says:

    Question about your build, did you have any quality issues with the bearings that came with the robotdigg corners? I had one set start clicking after the first print, replaced them with extras that came with the corners, and that same tower is starting to click again, this time after considerably more printing and not as bad.

  32. Dominic says:

    Hello David,
    I have a Smoothieboard and you listed 4. steps I have to do, so that the sensor is working correct.
    Do I have to do all or just one of them?

  33. Eugene Raven says:

    Hi David!
    Excuse for troubling. Thank you for your blog with instructions on how to assemble a delta printer and specification of the necessary components. I started to assemble just such a printer, purchased all the necessary parts according to your specification. The only difference with your printer is that I am going to use optical endstops like these: https://www.aliexpress.com/item/Optical-Endstop-Switch-RepRap-Mendel-Prusa-RAMPS-v1-4-3D-Printer-For- Arduino / 32825369483.html? Spm = a2g0s.9042311.0.0.27424c4dMjedFv and cooling Berd-Air MAX-24. Everything else is exactly according to your specification.
    But now I wanted to ask you about a little help with the Duet 2 WiFi firmware settings. I visited the site configurator.reprapfirmware.org but not all the parameters that I need to make there are clear to me. It may not be difficult for you to share the settings for your printer, or you could tell me the main parameters that I need to make in configurator.reprapfirmware.org to generate the settings, please.
    Thank you very much.

  34. dwisetiyadi says:

    There is a complete kit on sale for this?

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