Sunday, 25 October 2015

Mini Kossel: Think3dPrint3d Release 3

Think3dPrint3d Mini Kossel Release 3

We have been selling our version of the Mini Kossel delta 3d printer for 15 months now. As is the nature of RepRap projects it has evolved along the way. We have marked these tweaks and upgrades and improvements as different versions of our kit and we are now ready to release our 3rd version - the Think3dPrint3d Mini Kossel Release 3. Though it builds on our other upgrades it is by far the most significant revision yet.

More detail is set out below but in summary we are switching to 32 Bit Duet Electronics, 20x20 extrusions, IR probing for true autocalibration, as well as some other more minor improvements to the usability or ease of assembly of the printer. Of these the single biggest change is using the Duet electronics with David Crocker's improved RepRap Firmware which allows for segmentation free delta printing and easy autocalibration.

Since David implemented delta support in the RepRap Firmware we have had many enquiries about buying the kits with the Duet (and some customers chose to help out as unofficial beta testers). It has taken until now for us to bring everything together into a kit form, including thdetailed documentation, to ensure builders will get the same great experience assembling this version as the previous ones.

Improvements in detail


The Duet is a high powered 32 bit ARM-Cortex-M3-based 3D printing electronics solution which runs the powerful RepRap Firmware; more on this and the web interface later. With our kits in mind we designed a new 5-channel version of the Duet board with all the connectors, switches and power LEDs along one side. This allows for the electronics to be neatly mounted in the base of the printer with the USB, Ethernet, SD card, switches and power LEDs still fully accessible:

Duet 0.85 mounted in the Mini Kossel base showing accessibility

The new Duet V0.8.5 also has 2 extruder channels and so allows an easy upgrade path to dual extruders without an extension board, like the RAMPS in previous versions of the Mini Kossel, but unlike previous 4-channel Duets.

RepRap Firmware and Web Interface

David Crocker's RepRap Firmware takes advantage of the ARM chip's 32-bit processing power to provide true segmentation-free delta movement for improved smoothness and accuracy. Unlike most 8-bit firmware like Marlin, RepRap Firmware is precompiled and there is not normally any reason to modify or recompile it. The firmware is easy to configure with all the settings controlled through Gcodes in simple text configuration files. David has documented the setup of the configuration files in some detail on the RepRap wiki, for Cartesian printers, Delta printers and CoreXY printers.

The Ethernet support allows direct connection to a network or ethernet port on a laptop, or connection via Wifi. The web interface by Christian Hammacher is simple yet powerful and can be run on any device that is on the same network as the printer.

RepRapFirmware Web Interface running on Duet 0.8.5

I have taken to using my phone to control my printers:

RepRap Firmware Web interface on an Android Phone

20x20mm extrusions

These provide increased frame stiffness and allow the use of T-slot nuts which can simply be dropped into the extrusion channels when required, making assembly much easier.

Mini Kossel part way through assembly showing 20x20 extrusions

Frame assembly is greatly simplified with T-slot nuts

Differential IR Probe

David Crocker also developed a really great mini IR probe which, when combined with the functions within RepRap firmware allows for quick and accurate printer setup and calibration.

Hot end assembly showing DC42's differential IR probe mounted next to the E3D V6 heater block.

Below is a video showing the probe in action:

Other Improvements

To further simplify the printer wiring we designed an effector wiring breakout PCB
Effector breakout PCB
Breakout PCB connected to hotend, IR probe, fans and wiring loom

The extruder and E3D V6 hot-end are preassembled and tested. 

Assembled and tested extruder
Assembled E3D V6

While the majority of our customers have had no issues since we switched from the JHead to the V6 in Release 2, a few have struggled with the V6 assembly. As this kit is designed for hassle free assembly we want to eliminate all the potential issues. The V6 is assembled, heated to 290C and the nozzle tightened in accordance with E3D's recommendations.

We have included a top mounted spool holder for some time now, along with other tweaks and improvements suggested by our customers. For a full specification of the kit see our website.

Open Source Hardware.

As with everything we do the changes to the printed parts are available on our Github.

More to come!

We are also finalising the design and kit contents, and working on the documentation for a much larger Kossel, based to a large extent on David Crocker's supersized Kossel. It will optionally have a E3D Cyclops/Chimera dual extrusion hotend, 24V power and a massive 300mm diameter by ~480mm high print area. If you are interested in getting your hands on a Beta Kit then feel free to email us! Update 17 November 2015 - all 10 beta test slots have now been taken.