A tool to help assemble the Traxxas 5347 ball joints used in the Delta Steel

Delta printers use joints, there are basically three kinds available right now:

1. Clevis joints. These were used in the original Rostock and also originally used in the Delta-Pi. However apparently they wear and when there is some play in the joints, printing becomes noisy and loses accuracy. Mike Paauwe, the original designer of the Delta-Pi, has recently switched to Traxxas ball joints (see below).
2. Magnetic ball joints. These require - obviously - strong magnets and steel balls. Imho this considerably adds to the weight of the effector and carriages, however, these joints do not wear and there is no play. The main problem here is availability.
3. Mechanical ball joints, such as the Traxxas 5347 originally used for R/C models. These are inexpensive, widely available and weigh very little. Wear is probably tolerable (we'll see how that goes) and there is little to no play (again, we'll see) . These are the ones I will be using for the Delta-Steel prototype.

Now, it must be possible to assemble those Traxxas 5347 ball joints with pliers, but I honestly think I have found a better, simpler, and less damaging way of assembling them:

I designed this little tool in OpenSCAD (source code and .stl file are available on Thingiverse). Then I printed it in less than 30 minutes on my P3Steel.

Now all it takes to assemble one of these Traxxas 5347 ball joints is a firm press on the pusher part of the tool and the ball will snap in place. I assembled all 12 ball joints used in the Delta Steel in less than 5 minutes, and only one of them is showing a little bit of play.

Bad quality 3D printer kits

Wow! I just saw this video on YouTube:


 and read the comments, so I had to write a small bit about this.

Bad quality 3D printer kits are neither the norm nor the exception. What generally happens is that one is looking to buy a 3D printer kit and since there are relatively few reviews, the kit is ordered without proper knowledge of the quality of the components in the kit and whether proper support will be available when problems occur (and they will occur!).

Also, some sellers make quite wild claims about their kits that you just know are not true - if you have already built a couple of 3D printers, that is. Putting together a proper kit for any 3D printer is not a simple task, there are many pitfalls in this business.

So, if you are buying a 3D printer kit, first spend some time on forums or IRC, try to talk to people who have already built one or a similar kit.

Delta Steel BOM - I am working on it

Unsurprisingly, the Delta Steel BOM should end up very similar to the BOM for the Delta-Pi, which can be downloaded from the Delta-Pi Thingiverse page.

Since I am living in Barcelona and we definitely use metric standards here in Catalunya, I am using 20mm stainless steel square tube. The MDF for the base and top is 16mm, but that's just for this first prototype. I am hoping I can get some nice CNC machined 10mm thick metacrilate parts for the final version of the Delta Steel. We'll see.

Anyway, here are two pictures showing most of the parts set aside for assembling the first prototype.

The power supply is a very nice quality Lepa 450W ATX PSU which I bought on Amazon Spain. It's semi-modular so that should help to keep things clean and organized by cutting down on the number of cables that will go to the printer. On the picture above one can also see the MK2B PCB heatbed with cork insulation, the mini Kossel effector with an E3D hotend mounted and some PTFE tubing, and the carbon fiber tubes and Traxxas 5347 ball links.

And here we have the three stainless steel columns with the carriages already assembled and installed, the electronics, the steppers and some more parts. Still missing because I have not printed it yet: the entire extruder assembly. I haven't made up my mind yet on whether to use a Greg's Wade extruder with a hobbed bolt, or a direct drive extruder such as the very popular Airtripper Bowden extruder. Each type of extruder has its advantages and disadvantages. Either way, I have both the MK7 and MK8 gears and I also have a couple of hobbed bolts so it's more a matter of printing both kinds of extruders and testing/comparing them; but that, as usual, takes time.

New carriage design

I have been working on a lot of things at the same time these days, so I couldn't dedicate myself to advancing the Delta Steel design.

However, this weekend I managed to finish the OpenSCAD design of my new carriage for the Delta Steel: basically it's a mix of the Delta-Pi and mini Kossel carriages.

Now, unfortunately only the STL files for the Delta-Pi parts are available, so I had to import the STL for the Delta-Pi carriage into OpenSCAD and add the code from the mini Kossel carriage, plus a couple of small changes.

The end result is this:

The carriage slides on a 20mm square stainless steel tube using 8 x 623ZZ bearings. The 25mm M3 screw and nut on the right make up the endstop adjust assembly.

The two "horns" are the same as those used in the mini Kossel carriage, with the very same spacing, so that I can use the mini Kossel effector directly here.

The M4 20mm screw assembly is used to stress the entire carriage structure and provides the necessary force for the bearings to properly contact the square tube. This very elegant solution was designed by Mike Paauwe for the Delta-Pi and even though I had some a priori reservations about it, after trying it I must say it works perfectly.

I also modified my earlier RAMPS holder design to use evenly-spaced wood screws. I am going to use this part to attach the Arduino / RAMPS / drivers / fan stack to the underside of the Delta Steel base.

Since this is a 100% Open Source project, all my OpenSCAD and STL files will obviously find their way to reprap.org and Thingiverse once I am done verifying that they indeed work.