We had our mechanical engineer go through the design of the printer and through the MendelMax 1.5 and make a bunch of small improvements that adds up to a better printer and kit. The MendelMax frame is much more rigid and easier to assemble than the Prusa Mendel, because of the use of T-slot aluminum extrusions. T-slots also make it easier to add-on parts even after the printer is fully assembled. Open frames are quieter and less messy (no burnt carbon residue all over your fingers!) than laser cut wood frames.
The MendelMax MM152 is a 3dBotic version 1.5.1 revision of the MendelMax. The MendelMax is an Open Source RepRap 3d printer designed by Maxbots in December 2011. It is a true reprap, using printed brackets, but instead of using threaded rod for the structural elements it uses inexpensive aluminum extrusions. This gives a huge increase in rigidity for a minimal extra cost.
The MendelMax is based on the Prusa Mendel, and keeps its best parts. The Prusa Mendel kept the frame of the Sells Mendel, but fixed the problems in the X,Y and Z axes. MendelMax 1.5 builds on that by largely keeping the current XYZ axes, but completely redesigning the frame.
In addition to the increased rigidity, the printer is much easier to assemble than a standard Prusa. Even an inexperienced builder should have no trouble building the whole frame in an evening, two at most. And along with the easy assembly comes easy hackability. Almost any part on the bot can be removed with just a few screws, so swapping out literally any part on the bot is now a trivial operation.
Frame and Overall Design
We decided to use the RepRap Prusa Mendel Max (as opposed to the Prusa Mendel) for the following reasons:
- Stiff frame allows for the highest print speeds
- Normal recommended print speed is 60mm/sec
- Maximum recommended print speed is 100mm/sec
- Open frame makes for a quieter 3d printer. Box type 3D printers cause resonance like a folk guitar. The noise from the motors are amplified and these types of printers are very loud during operation.
- Most wooden 3d printers tend to use laser cut wood. This leaves a messy carbon residue on your hands from the burnt edges of the wooden parts. Even a fully assembled 3d printer that uses a wooden box as a frame and housing will leave carbon on your hands if you move it around.
T-Slots and Tabs
Extruded aluminum with T-slots are used throughout the design to connect printed plastic parts.
Rexroth t-slot nuts are used (instead of Misumi t-nuts) because they can be inserted into the aluminum channels wihtout requiring the ends of the channels to be open.
This means you can drop the Rexroth t-nut anywhere into the slot, making assembly much easier. It also makes adding on modifications and adding on parts after the 3d printer is fully assembled much easier.
The design is almost completely metric (using millimeter and meters). Another system for physical dimensions is imperial (inches and feet). The nuts and bolts used are mostly M3 – they have a 3 millimeter diameter thread.
- Qty (2) Aluminum shaft coupler for Z-Axis threaded rod
- Qty (4) 300mm x 20mm x 20mm T-slot aluminum extrusion
- Qty (4) 340mm x 20mm x 20mm T-slot aluminum extrusion
- Qty (4) 420mm x 20mm x 20mm T-slot aluminum extrusion
- Qty (2) 432mm x 20mm x 20mm T-slot aluminum extrusion
- T5 Steel-reinforced, Toothed Timing Belt and Pulley. Won’t slip, stretch or lose calibration. For X-axis
- T5 Steel-reinforced, Toothed Timing Belt and Pulley. Won’t slip, stretch or lose calibration. For Y-axis
- Qty (4) SCV8UU Pillow block with linear ball bearing for Print Platform support – much smoother and lasts longer than bronze or plastic bushings
- Qty (8) LM8UU linear ball bearing – much smoother and lasts longer than bronze or plastic bushings
- Qty (5) 608z Bearing
- MDF (9mm thickness) Print Platform
- Qty (3) 8mm 304 Stainless Steel Smooth Guide Rod for X, Y & Z-Axis
- Qty (2) M8 threaded rod for Z-Axis
- All required bolts, nuts, and miscellaneous
- 2 x Lower Vertex Lower Left
- 2 x Lower Vertex Lower Right
- 2 x Lower Vertex Upper Left
- 2 x Lower Vertex Upper Right
- 2 x Top Vertex cross brace with Logo
- 2 x Top Vertex cross brace
- 1 x Y Motor Mount
- 1 x Y Idler by DanFineArt http://www.thingiverse.com/thing:18189
- 2 x Z Lower Motor Mount for 8mm Smooth Rod
- 2 x Z Top Vertex with Clasp for 8mm Smooth Rod
- 2 x Compact Y Rod Mount for 8mm Smooth Rod by Jmil http://www.thingiverse.com/thing:24510
- 3 x Endstop holder http://www.thingiverse.com/thing:10751
- 1 x Reinforced X Carriage by Jonas Kuehling http://www.thingiverse.com/thing:18657
- 1 x Greg’s Wade Reloaded Extruder with Herringbone Gear http://www.thingiverse.com/thing:18379
- 1 Pair of X End by Jonas Kuehling http://www.thingiverse.com/thing:18384
- 1 x SCV8UU Belt Clamp
- RAMPS v1.4 is a programmable processing unit with USB2.0 connectivity (fully assembled) with ATMEGA2560 based Arduino compatible controller board which comes pre-loaded with Marlin firmware which by far provide the best 3D print quality. It can be expanded to handle dual extruders and dual hot ends.
- Qty (4) Stepstick Drivers with Allegro A4988 DMOS Microstepping Driver. Allegro manufactures the best stepper drivers for low current application such as RepRap machines. 1/8 microstepping with these drivers give you beautiful 3D prints (the two z-axis NEMA17 motors are wired in parallel, so only 4 drivers are required)
- 3DBotic all metal Hot End with cooling fan, (0.40mm orifice, for 1.75mm filament)
- Mark 2 Heat bed with fiberglass Insulated Wire
- Qty (5) NEMA17 Stepper Motors (torque 40 oz/in)
- 12VDC, 30A (360 watt) enclosed Power Supply with integral cooling fan. 110V/220V switchable: Use 110v for USA
- Qty (3) Mechanical End Stop switches. Enables MendelMax MM152 to “home” or self-calibrate (initial calibration still required)
- Omron Relay (for Mark 2 Heat Bed)
- USB 2.0 cable
- Misc wires
- Soldering of wires and connectors is required, but not for the electronics boards (they are pre-assembled)
- All rods are cut to the right length
- No sawing, drilling or other material changes are required
- All fastening by bolts, screws and nuts (no welding, soldering or gluing)
- Minimal or no sanding or post processing of parts is required
- No messy laser cut parts used– laser cut parts can leave carbon residue all over your hands
- No wooden gears that some 3d printer kits use which tend to split.
- Only metric bolts, screws and nuts are used