Kossel construction notes

Preamble

Following on from Kossel 3D Printer, these are some points that I have noted, whilst constructing a Kossel XL using the Sintron kit and a Kossel mini using aluminium vertices…

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Magnetic personality

Preamble

Following on from Kossel 3D Printer, I purchased some magnetic balls and ball joints on eBay, because they were extremely cheap (or cheaper than the other balls/joints that I had seen elsewhere), without really thinking about what I was going to use them for, or how I was going to mount them.

This is the tale of what happened.

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Kossel – Sintron parts list

Preamble

Following on from Kossel 3D Printer, I was unable to locate a comprehensive parts list of the Sintron Kossel 3D printer, in particular a list of the fasteners. So, after examining the guide (Kossel mini instrution by sintron technology_v2) and the printed parts kit, I came up with my own list.

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Do you really need a Nema 23?

Preamble

Back on the topic of stepper motors again, folks!

Whilst looking a parts for a Kossel, a large Kossel (see Kossel 3D Printer), I came across these aluminium vertices for 2040 aluminium from RobotDigg, see 2040 or 3030 Alu Vertex for Kossel XXL or XXXL. On that product page they recommend using Nema 23, en lieu of Nema 17, stepper motors and, indeed, offer a vertex machined especially to take a Nema 23 stepper motor.

Now, Nema 17 stepper motors are pretty well covered in the RepRap forums, and there are three common favourites. However, the choice is not so clear for Nema 23 stepper motors. I decided to do some research on which Nema 23 stepper motors would be appropriate.

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Kossel – The Ratio

Preamble

I came across this problem, when looking into building and sourcing the parts for a Kossel printer in Bangkok.

The correct length of the push arms of a Kossel 3D printer is a bit of an enigma. The length is related to the length of the Horizontal frame lengths, that form the triangle. The ratio between the length of the push arms, from eye to eye, and the length of the horizontal lengths, is apparently 80%, or 0.8.

However, not all designers stick to this ratio, and often go higher, up to 92%.

I wondered why this is. Surely it is simple enough to cut a length of aluminium extrusion to the correct length? Certainly it is easier to cut aluminium than a carbon fibre rod to the correct length, although the latter is still certainly possible.

There are constraints, the most likely of which is the sizes of borosilicate glass discs (commonly 170/180/220/260 mm), and custom heated beds, but there may be others, such as a minimum horizontal length (in order to accommodate the steppers), the carbon rods come in pre-cut lengths (seems unlikely?).

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