The default Prusa couplings just would not grip the 8mm shaft, even when tightened to and/or even past full capacity. A little research of the RepRap wiki revealed another potential design solution as made by Chris Hanton, however I would need to machine the part. Instead I decided to utilise the design as a basis for the development of a printable solution. The above picture shows the bespoke part and the original coupling (with tightening damage).

As you can see the new design is much simpler in implementation.

Essentially the part has been dimensioned and shaped so that the bar can be used to cut a thread into the plastic forming a tight grip. The grip is further enhanced via use of a grub screw in the form of a 3mm * 10mm bolt. Once again the hole has been dimensioned so that the bolt is self threading, cutting into the plastic upon tightening. This can be further enhanced via use of a pillar drill to form a slight recess in the bolt so that the grub prevents turning.

In order to thread the socket the bar needs to be turned slowly into the shaft with mild pressure until it hits the step inside where the hole transitions from 8mm to 5mm. Once completed a bolt is tightened against the base of the socket. Care must be taken at this stage not to force the threaded socket to unscrew and/or the cut thread to break. This is not a problem if the grub is attached beforehand. The above images show the socket befor and after threading.

Once complete the stepper shaft is then pushed into the 5mm hole until it meets with the 8mm bolt. This is a tight fit as I dimensioned the hole smaller than the stepper shafts. Again a pillar drill can be used to create a recess to enhance the effect of the grub. Also as before the bolt is self tapping. The following image shows the completed unit with the grubs threaded and attached.

With the coupling issue resolved Its time to get back to finishing the build of the Z axis. I started by attaching the plastic bushings to both the X carriage idler and motor mounts. I eventually plan to replace these with a more robust bushing and/or bearing option so this was done via application of a small amount of superglue to the base of each bushing only.

This will enable me to easily snap them off when the time comes for an upgrade, but due to application use, is also robust enough for temporary and/or short term use. At this stage I realised that I have seemed to have not received or forgot to obtain (must check my parts order!) needed to implement backlash prevention on the Z axis (the two large springs mounted in the X carriage ends). This means that I will not be able to fully complete the mounting at this stage but will be able to get things assembled for a few functional tests.

With this in mind I then mounted the motors and shafts on the frame and provisionally mounted the X carriage. The above images show the positioned motor and new Z coupling attatched to the main frame (left). Also included above (right) is the default coupling setup, for comparison.

As always I’ll finish up with an image showing the current state of the build:

I hope you will agree things are really beginning to take shape now and the build is well on its way. Tomorrow I hope to finish off the rest of the X carriage by mounting the stepper and the pulley belt. If I get chance I’ll also mount the Y belt leaving me with just the inclusion of the backlash springs (as soon as I get hold of some) in order to finish the frame and/or mechanical elements of the build.

As promised yesterday I have uploaded the .stl for the Z couplings here. Feel free to download it if you wish however please be aware that I plan to decrease the diameter of the hole for the 8mm bar so that a greater grip can be achieved (although perfectly functional, I believe that this will greatly enhance the robustness of the design). I will upload this .stl also as soon as I have finished drawing/updating the CAD and have had chance to print and test etc.

Update: I have included a second .stl in the download, however please be aware that I have not tested it yet. Its only a .2mm difference though so should be ok its up to you. The original I used is the 2.6mm option, enjoy

Eventually one of the couplers snapped due to purpose over tightening (not surprisingly) and this brought a halt to proceedings for most of today’s build. The above image shows the snapped coupling. Despite this issue however, I decided to continue mocking up the axis so I could get a feel of how things go together ready for my next attempt.

Once completed I decided to have a go at developing my own coupler utilising the “more durable design” developed by Chris Hanton and as suggested at reprap.org.

The following images show what I came up with:

The large hole (right) will be threaded and two 3mm bolts are to be used to clamp both the rod and motor shaft firm. If they work I’ll upload the .stl’s so that others can use them If they so wish. Otherwise if you are doing a Prusa build I recommend that you go for the Haton coupling design.

The following image shows the current state of play with the mocked up Z Axis.

As you can see Leonard is beginning to look like a RepRap. Rather than do nothing I then decided to have a go at putting together the extruder. All in all the print-head came together quite smoothly, however I did need to clear out the 4 channels that spring load the keeper head.

Hopefully tomorrow I will be able to print out the new couplings at work and the build can continue. If not on to the electronics

With this achieved (maybe a little to tight in places) I then moved onto assembling the Y Carriage. This like all of the build so far was a fairly easy process that consisted of adding the two running bars and attaching the MDF base plate (via gluing to 4 slide on bushings). With this achieved and a little adjustment to ensure that the bed runs the length of the bars smoothly, I also decided to attach the Y stepper motor.

This is done by bolting the motor onto the provided mount, via use of three 3mm bolts (and washers). A little tweaking was also applied to ensure that the cog lines up with the pulley guides. An additional length of wood was used to ensure that the pulleys line up.

Next, inspired by my successes so far, I decided to start on the X Carriage. As I suspected last time, I did need to drill out holes for the bar mounts. The model print had (as feared) filled both of the 8mm bar to nut holes where the springs are to be situated to help prevent backlash on the Z Axis. You can see an example of the holes added in the photos showing one through a Z motor mount.

Further inspection of the plastics also identified a similar issue with the 8mm hole within the body of the extruder motor mount, so whilst I had the bit in the drill I also decided to rectify the extruder mount at the same time. With the plastics rectified I moved onto starting to put the X Carriage together. This commenced via inserting eight 3mm nuts into the provided mounts and adding the two 8mm * 420mm bars these are then held in place via 8mm * 10mm bolts (hand tight only). The design of the carriage draws the bars parallel (great design).

Once completed, attention then moved to the addition of the pulley bearing. This is simply done via threading a couple of washers, fender washers and bearing in the familiar style as utilised via the Y Carriage and as shown in the above image. The following image shows the current state of play:

I decided to stop here for today and will continue from here next time out, when hopefully ill also get chance to check out the electronics.

Everything now needs tightening and squaring up, but I’m more than happy with progress so far.

The only real issue that I have had is need to develop a custom pulley to facilitate a T2.5 belt (I should have ordered the T5 to fit the downloaded pulley .stl). In future I aim to swap these over to metal solutions but for now the home solution is fine.

The photo shows the original pulley and the one I developed. You can get the .stl for the T2.5 pulley and/or sprocket here.

One impact that this did have on the build was that I did not need to add the additional spacer washers to line up the guide wheel with the motor pulley as the home one is much shorter in length. More info on this can be found detailed in the reprap.org build instructions.

From reading the build instructions it looks like that some of my plastics (x carriage support mounts) will need to be drilled in places. I wont know for shore until I get onto that part of the build as I cannot make it out.

Hopefully I’ll get the frame squared up and get onto the x-carriage tomorrow. More updates as things progress

Just for ref: there is a great printable Prusa Mendel build guide put together by Gary Hodgson avaliable here.

For those of you not in the know:

RepRap is an open-source desktop 3D printer capable of printing plastic objects. Since many parts of RepRap are made from plastic and RepRap can print those parts, RepRap is a self-replicating machine – one that anyone can build given time and materials.

For my build I have opted for the Prusa Mendal variant as it is stated to be:

• It’s much simpler to build it.
• It’s much simpler to modify it.
• It’s much simpler to print it for your friends.
• It’s much simpler to repair it.

For the electronics I have opted for the RepRap Arduino Mega Pololu Shield, or RAMPS (1.4).

The RAMPS official spiel states:

It is designed to fit the entire electronics needed for a RepRap in one small package for low cost. RAMPS interfaces an Arduino MEGA with the powerful Arduino MEGA platform and has plenty room for expansion. The modular design includes plug in stepper drivers and extruder control electronics on an Arduino MEGA shield for easy service, part replacement, upgrade-ability and expansion. Additionally, a number of Arduino expansion boards can be added to the system as long as the main RAMPS board is kept to the top of the stack.

Once complete I aim to use Leonard to develop mini Netduino/Arduino bot kits as inspired by Geir Andersen’s excellent Timing Belt Tank.

Ill add more information as things progress, but for now here are a few usefull shopping links and personal reference for me:

Hardware – http://thingfarm.org/

Electronics – http://reprapworld.com/

I aim to get things back up and running smoothly before the new year and thought that I would take this chance to also have a bit of a revamp etc. the wiici and blog sub-domains have gone completely hay wire at the moment – sorry about that.

Rest assured that I am on the case, d

As you can see the quality is greatly enhanced in comparison to the last attempt. If you look closely you can make out the IR dot markers and also the grid pattern.

As a bonus it’s ready for some Image manipulation via EmguCV too.

Sourcecode is available here.

By default the example is running the standard WPF code to get is to show the EmguCV image as shown above in MainWindow.xmal.cs comment out:

imgVideo.Source = _kinect.IrImageSource;

and replace with:

imgVideo.Source = ToBitmapSource(irGrayCVImage);

Kudos must go to Vangos Pterneas who’s excelent work  provided most of the groundwork for this demo.

Enjoy

First up is a quick chat with my PC closely followed by a quick XNA integration:

Source code to follow shortly as soon as I have cleaned up the threading disposal a little.

Resources: Download the SDK, Check out the Kinect Quick Starts and view the Kinect Project Gallery on Coding 4 Fun.

The wiring is as follows:

DIN – Port 1
DOUT – Port 0
5V – 3V3
GND – GND

The software in this example can be downloaded via: http://www.dyadica.net/journal/netduino-serialporthelper-to-winform-and-xna

The ArduinoXbeeShield mod can be found via: http://www.dyadica.net/journal/arduino-xbee-shield-mod-for-netduino

Enjoy