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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35 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.

  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 ?

  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. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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 🙂

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