Development roundup: metal hotends, new print surface, RJMP linear bearings, watercooling

Busy weeks are laying behind us and we are even outdoing our original schedule on preparation for taking preorders for the first production-funding Kühling&Kühling RepRap Industrial 3D printer kit batch very soon. Things are going really well, we made huge progress concerning the RasPi based RepRap controller and with this posting we will focus on some additional aspects of our current development.

New all metal 300°C max. hot ends

We are really excited about how much impact the idea of an industrial grade RepRap – aimed for productive, heavy duty, continuous and low maintenance operation – generated and we received a lot of e-mails asking for even higher grade features like PTFE-/PEEK-free hot ends, guaranteeing ultimate readiness for already available and future high temperature filaments like PA/Nylon etc.

As this was quite on top of our development schedule anyway we decided to go for it instantly and in cooperation with Wolfgang from reprap-fab.org we are currently successfully running the first two prototypes of his all new all metal V3 hot ends specially modified for 3mm filament and direct water cooling. These hot ends actually achieve an enormous gain on performance compared to any hot end we’ve tested so far and allow for up to 300°C maximum nozzle temperature, basically limited by the rating of the thermistors. As an additional benefit the new hot ends are – due to their construction -  precisely adjustable in its height while already mounted in the extruders, which eases dual head calibration one more time and reduces weight and individual part count of the extruders.

Naturally we intend to include the latest version of these hot ends into our upcoming kits. The final iteration will presumably be powered by one 40W ceramic cartridge heater instead of the two resistors you will notice in the photo of our current prototype above.

New advanced maintenance-free continuous polyetherimide print bed

Recently we chose FR4 as an already amazingly reliable print surface for ABS plastic under raised temperature conditions like 70°C used within our build chamber, but there’s one material that still beats the pants off FR4. It’s a really hard to source, aerospace grade glass fabric polyetherimide (PEI) composite and incredibly expensive in smaller volumes, but yet worth every cent you pay for it. We finally found a good supplier and as we will order larger volumes, the individual price tag will be entirely manageable.

Not only does ABS stick to this print surface like glue, without leaving any residue after removing the printed parts by gently flexing the sheet, but so do PLA, PVA, HIPS and possibly even more. This material serves as a true universal, continuous use print surface, that doesn’t require any preparational work except of occassionally removing finger prints with some IPA between two prints. Reliability and usability at its best, this material really makes a difference. Wait for another video to follow shortly illustrating the main advantages during a common printing procedure.

Our printers will come with two interchangeable print surface sheets for almost nonstop printing.

New Igus RJMP solid polymer linear bearings on all axes

As common linear ball bearings are not explicitly rated for use at high temperatures we are experiencing problems using them at 70°C for a long time, so we decided to switch to a lot more durable and – again – truly maintainance-free Igus solid polymer bearings RJMP for all axes. Those are rated for use at up to 90°C and make for noticeable increase of overall positioning accuracy.

Extended watercooling for all stepper motors

While only the extruder steppers of our first prototype knew the true promise of a watercooled body, version 1.0 of our printer will have watercooling in store for every single stepper motor inside the build chamber just to assure reliable operation in the long run.

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