A Bowden extruder, an E3D clone hotend, and cooling fans

I have been working on the Bowden extruder for the Delta Pi these days. To test the extruder and the hotend before actually installing them in the Delta Pi, I decided to finish assembling my heavily customized Prusa i3 Twelvepro and to design a Prusa i3 X-carriage mount for the Bowden hotend, complete with both an E3D fan duct and a layer fan system. This is the result of my design effort.

The setup as it stood untested, a couple of days ago. The layer fan was not quite reaching the correct position and angle, so I designed some new parts.

You can see the new Z-shaped arm. The fan duct is also new, this is version V3.

Here it is positioned so that the airflow reaches very exactly the extruded material under the tip of the nozzle

Top view of the print head, ready for the first print tests. The left fan is to cool the E3D aluminum body by providing a proper airflow over the fins; it must be connected to the 12V supply and is on whenever the printer is powered. The right fan is the layer fan, controlled by the PWM D9 output on the RAMPS.

And then the long-awaited first print!

This is a calibration object from Thingiverse. As can be observed, retraction was not properly adjusted yet, but apart from that the print came out surprisingly good, all things considered.

These are the parts required for assembling the Bowden extruder (which is a simple remix of Dominik Scholz's design on Thingiverse): basically two relatively small printed parts (the extruder body and the idler), a 608ZZ bearing held in place by a M5 screw and washer, a MK8 gear, a NEMA 17 stepper with good torque (40Ncm), a push-fit Bowden connector, a small spring, and some M3 screws, nut and washers.

Calibration, sweet calibration

Another video, this one about calibration:

Upgrades!

LED lighting! A new Z-probe! And more!

A better video

I don't have a Bowden extruder and print head with a hotend to show for yet, but at least I made a better quality video of the Delta Steel plotting/printing the Kossel Mini effector. Here it is:

The noise you can hear (apart from the steppers grinding away) is the pen itself shaking! Printing speed is 60mm/s for perimeters and infills and 100mm/s for travels.

First "print"

I have seen this done with a Prusa i3 and I thought I would give it a try with my Delta Steel prototype, until I have my Bowden extruder and hotend ready: use the printer as a plotter by attaching a pen to the carriage/effector. This is quite easy to do with the Kossel Mini effector design that I am using.

The next step was to go through the basic 4-point calibration procedure and adjust the endstop screws on the X, Y and Z carriages, as well as roughly leveling the heatbed. This took a lot longer than I thought it would, I guess because of my inexperience in dealing with linear delta printers. I learned a lot in the process, though, and I'll write about it later in a separate blog post.

After I had reached the point where I could barely insert a small piece of paper under the tip of the pen at the four different points in the calibration procedure, I was ready to test the printer as a plotter, so I sent it the very same Cura-generated and edited G-code that I had used in the previous "in the air" print video. It worked better than I expected:

So this is my first "print" and on the whole, I am quite happy with it!

That, by the way, is the effector that I am using on the Delta Steel itself, as you can see in the first picture above. This is exactly what a RepRap 3D printer should be able to do: print its own parts!

A few details sorted out

I had left a few details to sort out until I got more or less to this point, the purpose of this post is to go over these details, well... in more detail!

It's alive!

YouTube video coming soon!

In the video the Delta Steel is "printing" the G-code for its own Kossel Mini effector, but to get the Marlin firmware to start printing I had to comment out the temperature setting commands at the top of the G-code file I had generated with Cura. Here is a screenshot of the editor showing my edit:

Note that the printer is printing "in the air", way above the heated bed, because I have not set the correct Z height parameter yet in the Configuration.h file in Marlin. I'll adjust this parameter once I have installed the hotend in the effector.

More vases...

Somehow most developers of (big or small) linear delta printers seem to succumb to the temptation of showing off their design's capabilities by printing vases. Here are some more pictures:

Delta-Pi prototype, 30l print volume, photo by its designer Mike Paauwe

Rostock prototype, 12l print volume, photo by its designer Johann C. Rocholl

Cherry Pi  4XL, 150l print volume, photo by its designer AndyCart

A just-printed vase inside the Raptosaur prototype, 240l print volume, photo by its designer Paul Wanamaker

Wiring the endstops, some soldering required. Also why do I braid wires?

As I mentioned before, the Makerbot-style mechanical endstops I am using come with their cable, but the cable is not long enough, so I had to cut it and add an extra 850mm to each wire (I also braided the endstop cables, see below ). That required some soldering and insulating the solder joints with heat shrink tube.

The endstop cables are routed inside the square stainless steel tubes all the way from the top of the printer down to the RAMPS 1.4 board.

Remember to connect each endstop cable and stepper motor cable to its respective pins on the RAMPS board: Z is the column at the back, X is front left and Y is front right.

Below is the Delta Steel prototype just before I connected the endstops to the RAMPS (obviously I had to lay the printer on its side to do that), with the belts still loose.

Braiding cables

I have this habit of braiding electrical cables

L-shaped plywood reinforcement

Check the pictures of the Rostock prototype and you'll notice that there is an L-shaped plywood reinforcement at the back of the printer. There is also a similar reinforcement structure used for the Delta-Pi. The Kossel Mini does not need this reinforcement because it is, well... mini, and in fact Johann C. Rocholl hints at this in the RepRap.org wiki page for the Rostock:

A shorter printer may be more rigid / stable and may not need the extra plywood frame on the back and side.

Yesterday I went to buy the wood to reinforce the Delta Steel prototype (which by the way is slightly taller than both the Rostock and the Delta-Pi prototypes), and 15 wood screws later this is what I got:

As can be seen in the picture above, I also got started on one of the belts but didn't tighten it as I was just checking the alignment of the pulleys and through-holes. Everything seems fine at this point so the next step is to route the three belts and tighten them. I am using approximately 195cm of 6mm GT2 belt per column here.

Edit: after tightening the belt and trimming the excess length, I have calculated that I am using approximately 188cm of 6mm GT2 belt per column or 5.64m total.

For the reinforcement structure I am using two wood pieces, the wider one is 16mm MDF like the top and bottom plates, the narrower one is 10mm plywood, as well as 15 x 3x40mm wood screws. The dimensions of the wood pieces are:

• MDF: 840 x 200 x 16mm.
• Plywood: 840 x 150 x 10mm.

They are screwed together and to the back right corner of the bottom and top plates to form an L-shaped reinforcement that prevents the printer "tower" from leaning in any direction.

Ugly? Yes indeed. Functional? Absolutely!

The humble RepRapDiscount Smart Controller and why I am using it for the Delta Steel

And also a simple stand design for the RepRapDiscount Smart Controller, see below!

In my opinion all 3D printers should be equipped with an LCD controller, for simple practical reasons:

• An LCD controller gives you immediate visual feedback about the status of your 3D printer.
• An LCD controller, as its name implies, allows for direct control of the 3D printer, before, during and after the print.
• An LCD controller which is equipped with an SD card reader allows you to print G-code files from the SD card.

Besides this, it should be noted that LCD controllers are relatively inexpensive components and readily available from a number of suppliers. I have been using "made in China" clones of two different LCD Controller models in my P3Steel's:

1. The RepRapDiscount Smart Controller which is a 20 characters x 4 lines LCD with a rotary encoder, a buzzer and a stop button.
2. The RepRapDiscount Full Graphic Smart Controller which is a 128 pixels wide x 64 pixels tall LCD with, again, a rotary encoder, a buzzer and a stop button.

They both work fine with a RAMPS board, displaying as much useful information as one could need or want, both are equipped with an SD card reader and both cost < $15 per unit. For the P3Steel, although I have used both and am equally satisfied with either design, I recommend the RepRapDiscount Full Graphic Smart Controller, simply because it looks slightly better and the price difference is minimal (about $2).

For the Delta Steel I decided to go with the RepRapDiscount Smart Controller. First, it's the same LCD Controller that has been used in the past for many linear delta printer prototypes, including the Delta-Pi prototype itself. And second, there are reports that the Arduino graphics library used to drive the LCD in the RepRapDiscount Full Graphic Smart Controller is CPU intensive and can cause problems when printing at high speeds on a linear delta printer, where the Arduino also has to deal with the Cartesian to delta transformations.

A simple bracket to mount the RepRapDiscount Smart Controller onto any wooden surface

I designed a rather basic bracket to mount the RepRapDiscount Smart Controller onto the MDF base of the Delta Steel prototype, which I have published on Thingiverse.

You'll need to print a mirror pair of these like in the OpenSCAD render above, and they additionally require two M3 10mm screws and nuts and two wood screws.

The main advantage of these brackets versus a complete cover and base is that they use very little material and print very quickly. They are strictly functional though, I didn't attempt to make them aesthetically pleasing in any way.

And did I mention that the knob with the Open Hardware logo is a previous design of mine, published on Thingiverse too?