Adrians Prusa Notes
Release status: experimental
| Description | How Adrian builds a Prusa Mendel.
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| License | GPL
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| Author | |
| Contributors | |
| Based-on | |
| Categories | Prusa Development
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| CAD Models | |
| External Link |
Introduction
This is my page of notes on how I put together a Prusa Mendel. These are not so much improvements, but more modifications and options done for both personal convenience and the convenience of RepRap Ltd, as this is the one we sell. I have documented them here as others may find them helpful.
This page is intended to be read in conjunction with the main RepRap page on Prusa Mendel Assembly here
The files needed for what's here are in my fork of the Prusa Mendel Git repository here: https://github.com/AdrianBowyer/PrusaMendel in the directory AdriansPrusaModifications.
Configuration
The main components I use in my version of Prusa Mendel are:
- Sanguinololu electronics,
- Aluminium heated bed,
- My Universal mini extruder, and
- XBox 360 203 watt power supply.
I also use some modified printed parts and a few extra ones. All this is described and linked to in the sections below.
Mechanics
The most significant difference between my version of Prusa Mendel and the standard one is that I reverse the X axis. Looking at the front of the machine with the Y motor at the back, the X motor is on the left, not the right. This allows easier wire layouts, and - in particular - allows neat connection of the wiring to both the X axis and the heated bed by cable-tying it along lengths of 3mm filament for support.
I have also made a number of minor mechanical alterations that are listed in the next section.
Altered reprapped parts
endstop-holder.scad
The endstop holder is the left hand image. It holds a microswitch with 9.5mm mounting centres and M2.5x12 mounting screws. Get a microswitch with just a button, not the lever as well - it's more accurate.
If you set the variable pcb_mount=true; in the OpenSCAD file it also generates a PCB holder (right image) to allow you to mount the RepRap control electronics on the machine using M3 screws. See below.
pla-bushings-4.scad
If you have all 12 PLA bushings in an array as a single STL file it makes arranging them in a build less versatile as you can't cram them into small spaces. Arranging them one at a time gives a lot of versatility, but they are so delicate that they can detach, even from a well-heated bed.
My compromise it to have four on their own raft. This prints reliably, and is easy to slide about between other parts to print wherever you want. Print three of these to get 12, obviously. The raft is thin enough to cut from the finished parts easily with a scalpel. Mind your fingers...
x-end-idler.scad
I have replaced the unsupported bridges with thin webs (left picture), which both print more cleanly and are stronger. The M8 nut cavity now has a hole through for the M8 threaded rod, and a 45o conical base to the barrier that rests on the nut (right picture). This again prints more cleanly.
x-end-motor.scad
This has the same webs and cone as above. In addition there are two small holes (A A) that allow a 3mm diameter length of filament to be attached using a cable tie to run the X-axis wiring.
The picture on the right shows the idea, though that was taken with the old design. A 430mm length of 3mm PLA filament is held to the top of the Prusa Mendel beside the Z motor by two cable ties round the threaded rods. It loops through the hole on the right in the OpenSCAD picture and a third cable tie through the hole on the left secures it.
The wires are shown taped here, before they are cable-tied. This is generally a good idea: attach all wires with sticky tape first, then, only when everyting is in place and you're happy with the layout, go round putting the cable ties on and cutting off the tape.
xlr-bracket.scad
This fits on the frame vertex to the left of the Y motor viewed from the back of the Prusa Mendel. It holds a standard RepRap 3-pin XLR plug power connector. Remember to leave the 8mm threaded rods sticking out enough to hold it.
See the power supply section below for wiring details.
ybrac-t.scad
This modification of the standard Y motor bracket has slots rather than holes. This allows it to be fitted to the Prusa Mendel and taken off without taking anything else apart.
The motor has also been rotated about its axis to move one of its mounting screws away from the Y belt pulley. This allows the pulley mounting to be simpler (see the photo), and the toothed drive to sit nearer the motor, thereby reducing the bending moment on the shaft and the forces on the motor bearings.
I leave out the nut between the motor mount and the mudguard washer before the bearing, and just have three washers there.
Y belt clamp
If you use 10mm thick MDF (or similar) for the Y bed lower component then ignore this section.
But I use 6mm MDF, which makes the Y belt run slightly out of line. Fix this simply by printing out two extra Y belt clamps (which are 4mm thick) and putting them under the belt.
Heated Bed
Bill of Materials
| Item | Source | No. off |
| 3mm thick Aluminium sheet 230mm x 230mm | http://stores.ebay.co.uk/Forward-Metals-Ltd/_i.html?_fsub=17853190 | 1 |
| Glass bed | Glass cutter | 1 |
| 12 ohm cased resistors | Mouser 284-HS15-12F | 9 |
| MOSFET mounting kit | RS 7073361 | 1 |
| MOSFET | RS 7165558 | 1 |
| 10K Thermistor | RS 4840149 | 1 |
| Bed springs | Lee Springs LC 047E 06M | 4 |
| M3x30 cs | RS 4829221 | 4 |
| M3 x20 cs | RS 553419 | 4 |
| M3 nylock nuts | 4 | |
| M3 nuts | 6 | |
| M3 x 6 cs | RS 553396 | 20 |
| tmnl block (3) | 1 | |
| stripbd 10x13 | 1 | |
| 3 way pin header | RS 4838477 | 1 |
| 3 way header shell | 1 | |
| crimp connectors | 3 | |
| LED | 1 | |
| 1k resistor | 1 | |
| foldback clips | Stationers | 4 |
| 1.2 m 20A wire | 1 |
Circuit diagram
Construction
Extruder
Electronics
Power Supply
