RepRap Kossel

This is a review of the "MINI KOSSEL 3D PRINTER FULL DIY PACKAGE" from Makergeeks.com. I ordered this printer in July and it arrived in October. My emails got quick replies with status updates. The kit came with everything I needed except a 30 mm fan for the all-metal hotend. This is a tricky part to source and I had to go to digikey after looking around at various shops nearby. The kit is set up for 3mm filament with a built-in z probe that uses the hotend nozzle itself as the probe. While this is an interesting idea, it allows some slop in the hotend alignment and I had a crooked hotend after I ran the G29 leveling procedure. I would much prefer a manual release z-probe to something that adds a degree of freedom to the hotend. The carbon rods came preassembled but were different lengths by as much as 2mm, this can lead to uneven printing and is one area where tight tolerances are important. The hotend quality is questionable and mine jams regularly. I attribute this to a misalignment between the heatsink and the heatbreak. I have trouble even hand-feeding filament through it as the filament gets stuck at various edges within the constructed hotend. The extruder runs off a simple spur gear and that combined with the high extrusion force for 3mm filament led to slipping and stripping filament. The printed parts are generally good, with the exception of the carriage mounts that attach to the rail slides. The point where the belt end grips the carriage is too thin and broke loose in all three of my carriage pieces. There are many better designs for this part, or the alternative is a zip-tie to clamp the belt end. Finally, the included power supply specifies 5A output but is insufficient to power 4 steppers and the hotend (causing blackout of the Arduino board). Using a bench power supply, I can run the printer and it shows 4.2 A at peak current draw. This suggests the provided power supply is not operating as specified. I've chosen to replace the hotend with a 1.75mm Prometheus and will convert the rest of the extrusion path to 1.75mm. Hopefully that will make this kit workable. This was my only experience with makergeeks.com and while the contact at the company was always polite, it does not excuse the low quality of this kit. I am an experienced operator and kit builder and this tested my patience and led to an uncomfortable amount of frustration.

More value than expected works great!

Linamorph or metamorph (working name), my fully 3D printable 3D printer has been printed with this one ;)

Automatic calibration works well, it can print fast.

The buildplate absolutely needs kapton for the PLA to stick, sometimes adding 3DLac does not hurt. Or you can buy a heated one separately, might be provided in different versions of the kit.

There are printed parts, stl files are provided on the µSD from the kit, along with firmware, tools to edit and flash the firmware, slicer/control software, build manual. Very handy ! I broke one part during assembly and was able to print a new one quickly with another 3D printer.

Well calibrated, you can have pretty amazing results for such a cheap machine ! Plus there is a lot of upgrades available on Thingiverse : http://www.thingiverse.com/nak...

This kit only misses a fan for the hotend and clips to hold the glassplate in place correctly. But you can print those.

Other than that, it is great !

This review is for a slightly oversized scratch built Mini Kossel. This printer is my second 3d printer and my first delta style bot. This printer is very easy to build, very easy to commission, and very easy to operate. This printer has a slightly larger base (+30mm per side) and uses 600mm rails instead of the standard 400mm.

~Mechanical~

All plastic parts were printed with my original Pursa i3 printer (another rock solid design that I love)

Metal parts were cut from two 8' sticks of 20x20mm extrusion using a chop block saw.

Hardware was purchased from several suppliers both in and out of the US.

T-nuts were made from printed parts with 3mm nuts pressed into them.

~Electronics~

I have used both Smoothie and RepRapPro firmware with this printer. There are pros and cons with each. I had some problems with the Smoothieware (which may be fixed by now) so I am currently running RepRapPro. The Bowden extruder was printed and connected to a RepRapPro all metal hot end. I designed and built my own bed sensor which is available here on PinShape. The bed is heated with glass plate.

~Build~

This printer is very easy to build. Pretty much just bolt it together. I have 30-40 hours in the build which included many custom mods to keep it looking nice.

~Commissioning~

Both firmwares are easy to setup and commission if you have an accurate bed sensor. The hardest part was setting the bed height correctly, then a few test prints to dial in the exact arm length so dimensions are accurate.

~Software~

I use several tools depending on where I have the printer. The delta bot is very stable and travels well. This printer is normally on my desk at work and travels with me for presentations at schools. I mostly use Simplify 3D with this printer now.

~Operation~

The web interface works extremely well and makes using this printer a breeze. I slice, upload, start print then walk away. I very rarely get a bad print. The XY dimensions are a little constraining compared to my i3 but the height is excellent and the printer is very quiet when operating. A nice change from the Makerbot Gen5 that is also in my office.

~Conclusion~

I love this printer. I don't have to level the build plate or maintain calibration/alignment. It just works once setup.

My i3 generally produces slightly better prints but it is more of a function of speed of operation. The Mini will run much faster than my i3 so I tend to design with the Mini and print final parts on the i3 when I want the best output.

I have ~$400 in this printer as it sits today and ~$600 in my dual extruder i3. Both of them print as good or better than the $3500 Gen5 and both of them blow the Gen5 out of the water when it comes to reliability.

Having built both Delta and XY configurations I'd say that the delta, with modern controller and firmware would be easier for a first timer to build but doesn't offer quite the same finish quality unless what you are printing is very curvy.  Deltas excel at round, curvy, tall and fast. The Mini Kossel is a very solid Delta design that is easy to build and maintain while printing excellent parts in a dependable way.

Hi, calibrating the chinese K800 Kossel and tunning the firmware are probably the most difficult parts. 

have to understand and deal with the concept, but this type of printer is a good choice for people need start printing on higher objects (normally higher than a maximal cube larger). Most of the printer parts can be printed as spare (and is recommended as soon as you finish the calibration). 

Printer have better speed than regular x/y ones and quality vary by materials and printing speed oprtions.

My advice is start with a cube, untill you can calibrate to have the same face dimensions.

Good luck and enjoy printing !

Amazing printer for the price