The OpenBeam Kossel Family, Part III - The OpenBeam Kossel Reprap

Hello Deltabot community!

At long last, Johann and I are proud to announce that we are design releasing the OpenBeam Kossel Reprap.  This branch of the Kossel features 100% sub assembly level compatibility with the upcoming OpenBeam Kossel Pro.  

We started with the already very good Mini Kossel release by Johann Rocholl and changed the following:

1)  Ball bearing idlers.  A common complaint about the Kossel's top bearings and the make-shift flanged bearing solution is that it is very easy to slip the belt off the ball bearings.  For the Kossel Pro, we sourced 8mm bore GT2 timing belt pulleys and MF83 flanged ball bearings to create this new ball bearing pulley subassembly.  Terence then back-ported the ball bearing assembly into the Mini Kossel's upper vertex to properly center this new pulley, locating the flanges the correct distance away from the vertical support beams.  Johann will be back porting this new geometry back into OpenSCAD for others that would like to experiment with this design.

2)  Support for open looped belts.  Most GT2 belts sold on the market are of the open loop variety - and for longer and shorter lengths, that is the only option.  Terence ported the design geometry of the Kossel Pro's integrated belt loop clamp for terminating an open loop belt back into a Reprap version of the mounting block.  No more zip ties!  

3)  New and improved auto-leveling probe.  We spent a significant amount of engineering time to come up with a repeatable design, tuning the spring force of the switch against the spring force of the compression spring.  Then, Johann released FSR levelling, and we decided to follow suit. :-P

4)  Improved bed clamping.  The Auto Leveling routine relies on the glass plate centered in the printer's space frame rather accurately, in order to execute the retract move.  Unfortunately, this is rather difficult to do consistently under the old design; it is not intuitive to center a circle inside a triangle for most people.  Failure to put the glass back in the right spot can destroy the old auto-leveling probe in a probe / bed crash.

Back ported from the Kossel Pro is an interchangeable, quick-release bed mounting system.  We designed the new bed clamps with a V-block geometry to center the glass plate, every time.  We've added a clamping feature to allow the glass bed to be easily removable.  Normally, when we run print test, we have a second glass surface prepped with tape so that we can quickly swap beds after a print and perform the print removal offline.  That's how the big boys do it on the professional 3D printers - it's a real time saver.

5)  Different cold end extruder options.  By default, the OpenBeam Kossel family will ship with SeeMeCNC's EZStruder, with OpenBeam mounting brackets.   SeeMeCNC was the first to bring a Deltabot kit to market (the RostockMax) and the first to  move to injection molding for critical printer parts.  We applaud their efforts in using mass production techniques to build common 3D printer parts and as a way of supporting them, we qualified their cold end extruder kit and found that it performs wonderfully for our printers as well.

Developers often suffer from "Not Invented Here" syndrome; while I (Terence) can easily design an injection molded extruder, I feel that instead of reinventing the wheel, it's better to support an existing solution that does the job just fine.

The side benefit of using the EZStruder with OpenBeam mounting brackets?  The brackets are stamped out of 5052H32 Aluminum alloy.  It happens to be a really good heat conductor.  We noticed on our thermal camera images that the frame of the printer actually acts as a heat sink and the extruder motor runs cooler as a result.  Pretty cool, huh?

6)  We are extremely proud of the engineering that went into the OpenBeam Kossel Pro's new end effector.  To maintain compatibility for an upgrade path, we have design released a 3D Printable end effector for the OpenBeam Kossel Reprap's end effector as well.  Both of these end effectors allows for interchangeability of the connectivity PCB / ring light assembly and the new Auto Levelling probe (both reprap and injection molded versions).  

Where to Buy:

I (Terence) refuse to play the "race to the bottom" game and I believe in building a sustainable business and giving back to the community.  Over the past year, I have been refining the efficiency in our material handling and supply chain and quietly building out our Amazon Fulfillment infrastructure, and today I am happy to announce that all the Kossel components can be sourced from with Prime benefits for Prime households and free shipping on all orders over $30.00.  Once you factor in the shipping cost, you'll find that my prices are very competitive. offers many advantages to the consumer.  Fast shipping and ease of returns aside, the Amazon Affiliates program allows up to 8% referral on products being sold on Amazon.  This percentage is taken out of the 12% commission that Amazon charges me.  Johann had signed up for Amazon Affiliates, and if you were to buy Kossel components in the future by clicking through any of the links (that are currently not up yet) on the page, Johann will earn 5-8% of the purchase price.  This is a great way for people to give back to original developers!  It makes no difference to my bottom line whether you clicked through my site or searched for it on, but we've made it easier for you by linking to them here to get the components you need, and everyone wins.  (For the rest of the OpenBeam products, clicking through the links under "Where to buy" on OpenBeamUSA earns 8% commission into a fund that gets donated to folks like Seattle Hacker Scouts, our local Maker Faire, and folks doing OSHW related software such as Slic3r).  The Amazon Affiliates program is by no means exclusive; you too are welcome to sign up for an affiliate ID, write good documentation, and link to ANY items in question on  By offering a monetary incentive for people to write good documentation, we are hoping to raise the bar for how Open Source Hardware is documented.  

As for the CAD files, we have released both the STL and the Solidworks source for the files onto my GitHub.  (I'm new to GitHub, so please bear with me!)  Johann will be back porting the new parts back into OpenSCAD so that the general Reprap community can benefit from these files as well.

It's been a lot of hard work to get here, and we are all very excited for what the future holds.  We have in place a development road map to keep pushing improvements onto the Kossel / Deltabot platform, and we look forward to sharing these improvements with you in the near future.

Thank you,

-=- Terence and Johann