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.

Continue reading Do you really need a Nema 23?

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?).

Continue reading Kossel – The Ratio

Thermal fuses and 3D Printers

Preamble

I had the idea of employing thermal fuses in my 3D printer designs, after reading Build a 3D printer workhorse, not an amazing disappointment machine. Coincidently, I had been replacing thermal fuses, when repairing fans and rice cookers in Bangkok, and so I was familiar with them.

The question that came to mind, however, was “Where would you place a thermal fuse, and would you use more than one?”. Would you use them at the power supply, on the heat bed, on the hot end, for each of the stepper motors?

From Build a 3D printer workhorse, not an amazing disappointment machine:

It’s rare, but 3D printers can catch fire. Use the safety features provided by the firmware, but don’t solely rely on them. Both plain MOSFETs and solid state relays typically fail in their conducting state, which can result in runaway heating with disastrous outcomes. Thermal cutoff fuses are $1 components, but they are well able to prevent a runway heated bed from turning your workshop into a crater.

Continue reading Thermal fuses and 3D Printers

The extraordinary extruder

Preamble

Following on from Kossel 3D Printer, and the tutorial videos (see Kossel construction videos) the BuildA3DPrinter kit comes with an extruder stepper motor with a planetary gearbox. This results in a very high torque. However, as stated below, it has been replaced by the 3325_0, a motor with the same NEMA size and same torque.

Continue reading The extraordinary extruder