Darwin RepRaps are pretty old-school now, but together with thingiverse.com/thing:921 these corner blocks work pretty well with M8 studding for building frameworks.

This is a model of part number 10039. I used it make a new one out of aluminum. I am building a heater to affix to the bottom of this plate. I plan to print on to Kapton.

[EDIT]
Uploaded a current photo with the Kapton tape on the print surface.

Replacement RepMan Extruder Motor Gear for RepMan 3.1

More details on the Bowden extruder system: reprap.org/wiki/Erik%27s_Bowden_Extruder

I just made a serendipitous discovery:
I printed a very narrowly fitting freely rotating coupling and it had such a good grip on the PTFE that I printed another with just a little more contact area. You don't need the nut anymore for the Bowden cable!
I had been looking for push to fit couplings ever since Charles Pax showed me how good they fit to 1/8" PTFE cables. Now it appears that they are definitely printable!

The current push to fit coupling can be removed sideways. If you pull it sideways at the top first, you can pull it out with the plastic filament inside. It's a huge benefit to not have to pull back the plastic first.

A variant with a clip that you can pinch with your fingers would perhaps be even better, but this one is so simple and very functional and it hardly takes up any space.

I also included a cable to cable coupling, you just put in two cables sideways.

When done correctly, this type of friction from printed parts could be used for the extruder drive mechanism too, replacing the metal pinch-wheels that we currently use. In any case it can already withstand more than the force the force that the filament is driven with, and that's with ultra-slippery PTFE!

It would also allow us to print fasteners! Though perhaps a simple plug and a cam mechanism will better do the trick. And if you get a similar friction fit on the filament itself, you can start ysing that as structural material too (with some creep, but you could re-tension things once in a while).

Which other non-printed parts can we eliminate by a superior (I'd like to think this is an improved part, but only time will tell) printed alternative?

I'm introducing the easy way to remove printed models from heated playform, that I tried.
If use this method, you don't need to wait that the heated platform is getting cold.
Also, You don't need to rip the model off with brute force.

An easy to remove and attach extruder for the Reprap. Press the levers and remove the motor part so you can remove the filament from the heater element. I also included a rudimentary exploded view.

Off topic but very important: Have you participated in the RepRapSurvey.org yet? If so, thanks a lot! If not, please do so!

On topic:
If you have a Z-axis that runs smoothly (e.g. by using bearings for the Z-threaded rods), there's really not much need for a heavy NEMA23 motor. For the Darwin's X and Z axis, a NEMA23 motor is only heavy and expensive. This is an alternative setup for your Z-axis to run it of the cheaper NEMA17 motors instead. For using a NEMA17 or your X axis, see my other thing:
thingiverse.com/thing:1525
This will also reduce the moving mass that the Y-motor has to move back-and-forth. You can then use a much lower current for the Y-motor or also replace it with a NEMA17.

For the whole Z-axis assembly, I've now got everything uploaded. I made parts to make a pulley, skate bearing brackets to fit onto the corner brackets.

Want to upgrade your print-speed?

This is an extruder that allows you to mount a beefy, high-torque, NEMA23 stepper motor. You can directly attach it to the Bowden cable. With the Bowden extruder (see my other designs under the Thingiverse tag: bowden), the plastic throughput is your print speed bottleneck. Or should I say, was your bottleneck: With a NEMA23 motor I've been able to extrude more than 15 mm^3 of molten ABS per second. That's about a (fully solid) mendel in 22 hours! So now XY-movements are the bottleneck again. For this, I think I need to further reduce the weight of the carriage (lighter rods, etc.).

Usage:
You can simply press the Bowden cable with an M6 nut into the T-slot (to attach the extruder drive mechanism to the extruder head via a Bowden cable).
Note: An M5 nut will also work (for smaller PTFE bowden cables), it will be able to slide slightly, but its movement is constrained by the filament.

This is only for people who want to print really fast ;)

Its use is shown in this video:
youtube.com/watch?v=cSBqBW1w2wE

This is the filament drive mechanism end of the Bowden extruder. The same coupling could be used on the other end (the extrusion, or hot end), or a special purpose (smaller) coupling could be designed to fit your specific extruder (one that also clamps the heater insulator).

The idea of turning a nut onto the PTFE tube comes from profounddevices. I really liked it so much that I replaced my previous design to incorporate this idea.

I'm thinking of using the nut as part of an electrical switch to get feedback of when the pressure is fully released. This way you can put reversing functionality in the firmware without needing to configure it per material.

The concept of using a Bowden cable as guide was suggested and pioneered by Ed Sells. See his post here:
blog.reprap.org/2009/04/bowden-extruder-concept.html

If you can print to high tolerances or don't mind some trial and error prints, you can use a 'push to fit' variant of this coupling:
thingiverse.com/thing:3775

This new toolhead allow RepRap to manipulate surface mount components. If a milling head and solder paste dispenser could be added to RepRap then production of the required PCBs could be fully automated(except you'll still have to solder on the non SMT components).

How it works:
a small vacuum pump creates suction in the blunt tip needle to pick up SMT components and the gear motor rotates the component into the proper position.


NOTE:
I designed this a while back, it's designed for RepRap Darwin, but you might be able to get it to work with RepRap Mendel.
More useful information in this thread:
dev.forums.reprap.org/read.php?14,15167

This is for a modified version of the Darwin's Z-axis. You can put it on 3 threaded rods instead of four to reduce the risk of over constraining the build platform (that you have with four). This is for the same reason why a tripod is always stable, but a four legged table will wobble on un-even surfaces unless the legs are adjusted.

I'm hoping that the Z-axis will run more smoothly (less resistance from running it through the M8 nuts and less inertia (1 rod less). You need two of these parts and two skate bearings to fit inside it.

This is a RepRap part for the Darwin design that I couldn't find, so I designed one. It will allow you to use common 608 skate bearings. This obsoletes the Z-Studding tie bracket, which require more material than this object, but needs no bearing (does need an M5 bolt and two nuts).

For other bearings, simply adjust "bearing_OD" and export the model with OpenSCAD.

The parametric model also includes a corner bracket based on accurate measurements of the STL file. This might be useful to someone! You can see it when you uncomment the following line:

//translate([-8.8,-8.8,-32-3]) corner_bracket();

If your Z-platform is not completely accurate, the slotted holes allow you to adjust the precise location of the bearings so that the platform exerts no force perpendicular to the threaded rod, just that it puts a static force on it because of its weight. This is very important to prevent a wobble which you could see across the vertical surfaces of all your prints.

Because you need 7 of these, or at least 3 of these at the bottom, I tried to minimize the material needed. Of course it can be further reduced, but I didn't want to push it before trying it first.

At 0.2 fill, the volume extruded is 4.8 cc and takes 25 minutes. At 0.45 fill (more than needed) it's 5.2 cc.

This is a pretty generic part that allows you to connects two shafts/rods perpendicular to each other! The 8-8mm version is used in the RepRap for the diagonal tie brackets, to connect the 8mm threaded rod to the 8mm diameter studs.

You can specify the diameters of each of the holes.

In version two you have more control over the sizes of the exterior of the shafts. One of the shafts needs more material, because in the Z-direction the part will be weaker. Shaft 2 can be very thin, configure this with a higher negative value of "shaft_2_exterior_difference".

Note: It requires my teardrop.scad module to be present in the same directory, but you can uncomment my module at the bottom of the script.

Tip for RepRap Darwin users: I designed this part to have thinner rods as diagonals. This reduces the weight of your machine. M3 rods are more than strong enough! This will save the weight difference for each of the 10 diagonal rods! You can probably save about 1 kg.

Very slightly adapted from Travis77's fine original design, simply to add depth and export the parts as .stl.

These should print just fine on a makerbot, but make sure to check the size first as I haven't had a chance to. The depth of the pieces is very slightly less than the exact fit (1.27mm) to allow for printing error and ease of fit.

Thanks to Travis77 for this great classic puzzle and the Sketchup source file!

An alternative Z-axis for the RepRap Darwin using four Airpax A83709-M4 motors available cheaply on the surplus market.

These are spring feet that fit on the bottom of a RepRap machine to damp the transmission of vibrations from the machine to whatever surface it is resting on.

If that surface is resonant, a RepRap machine without these feet can make quite a bit of noise. These reduce that noise significantly.

This is a design of the RepRap extruder drive that is compatible with the Darwin quickfit clamp system and the Ponoko lasercut kit. It will take either 16mm PTFE or heatsink based heaters. It is designed to be made with no lathing or machine tooling. An opto sensor may or may not be fitted to regulate rotation speed - I found that this was definitely required with an all-metal heater assembly. If you develop software to do that, we'd love to see it!

Development stage: Work in progress

It measures 30 cm or 12 inch diameter. The discs will be 6 cm apart.

This is a filament spool that can be be mounted on the side of the Darwin. The image is an artistic illustration. When I've refined it an laser cut it, I will also post the final SVG that I have used for it.

If you have suggestions, please let me know.

It was made in Inkscape.

You don't want you precious RepRap Darwin to do destructive work, such as ruining the lacquer of your desktop. Instead it should be a purely constructive machine!

Warning: with these feet, your machine may still walk around over your table top (no anti slipping included), but with *style*, of course. You might want to add rubber soles for extra anti slipping.

N.B. I'm merely uploading it, design and photo by Tony (tofletcher).

This is really a single piece that can be printed twice and used to clamp a smooth rod into place on top of a 'Darwin' corner block, or a 'Pythagoras' corner tie clamp.

Some choose to have all the electronics slave boards near motors and on the X-, Y- or Z axes. I like to have them safely within the body of the RepRap.

It solves the problem that the Sanguino has no mounting holes.

You can fit it to the bottom 8 mm rods. If you've made your Darwin to specs, it will fit.

Made with Joris at Protospace.nl

Allows you to bind a strap around an object. Most usually used for packing stuff on crates and pallets with plastic strapping. I made this so that I can use it instead of steel rods for a RepRap Darwin design. As yet, I have not tested it so use it at your own risk!

An unexpected survival situation could happen to anyone, anywhere! The most critical 'bootstrap' file you need for any CNC device is this arrowhead template. Only after cutting out this variety pack of classic stick barbs will you be ready to survive, to remain alive, to live. Ancient man cut these same arrowheads, and that is why you are here today. To defend your valuable laser cutter, to overcome challenges, as a handsome decoration for your shop, and to win Lazzzor Battle 2008!

An alternative design for the RepRap Darwin Z endstop. It allows the machine to home the z-axis away from the workpiece, so that homing is always a safe operation, regardless of what state the machine is in. More details in my blog: hydraraptor.blogspot.com/2008/08/alternative-z-endstop.html