3D Printer decisions

RepRap Prusa Mendel (Taken from Wikimedia user Julianh72)

We started a project to build and maintain a 3D printer. After some discussion on 16. June, we decided that we will build the RepRap Prusa Mendel, because it seems to be well suited for a Hackerspace, costs less than 200€ if we get the parts locally and from recycled parts.

The parts needed for the Prusa Mendel are almost entirely standard parts that can be found in almost any hardware store. These are mostly M8 thread rods, M8 screws and nuts, standard skateboard bearings, the common NEMA 17 stepper motor.

Here's a list of the parts needed (taken partly from the RepRap Wiki)

Printed Parts

(Iteration 2)

Frame and motors

Quantity	Description	STL model	Status
4	frame corner with foot	[1]	to be printed
2	frame corner	[2]	to be printed
8	bar clamp	[3]	to be printed
2	rod clamp	[4]	to be printed
4	belt clamp	[5]	to be printed
2	belt clamp nut holder	[6]	to be printed
1	X-axis carriage	[7]	to be printed
1	X-axis idler holder	[8]	to be printed
1	X-axis motor holder	[9]	to be printed
1	Y-axis motor holder	[10]	to be printed
4	Y-axis bearing holders	[11]	to be printed
2	Z-axis motor holder	[12]	to be printed
2	Z-axis coupling	[13]	to be printed
2	belt gear pulley	[14]	to be printed
3	endstop switch holder	[15]	to be printed

Extruder (print head)

Quantity	Description	STL model	Status
1	Wade's extruder body (2 parts)	[16]	to be printed
1	large gear	[17]	to be printed
1	swall gear	[18]	to be printed

Non-printed parts:

Frame and motors

Quantity	Description	Type	Comments	Available
83	M8 nut	Fastener	Buy a 100-pack to be on the safe side.
93	M8 washer	Fastener	Buy a 100-pack to be on the safe side. (Grade 2 works fine.)
6	M8×30 mudguard / fender washer	Fastener	These are also known as penny washers, they have a much larger outer diameter than regular washers.
2	M4×20 bolt	Fastener	To mount the extruder
2	M4 nut	Fastener	To mount the extruder
2	M4 washer	Fastener	To mount the extruder
2	M3x8 screw	Fastener	Anything 6mm or longer should do. Even M3×10 bolts will do the job.
22	M3×10 bolt	Fastener
8	M3×20 bolt	Fastener	The M3x25 bolts are too long for the recent Prusa z-motor-holder, rod-clamp, and couplings.
8	M3×25 bolt	Fastener
4	M3×40 bolt	Fastener
70	M3 washer	Fastener
40	M3 nut	Fastener	8 optionally locknut / stop nut / nyloc
3	608 (roller/inline skateboard)	Bearings	Standard wheel bearings.
4	ballpoint pen springs	Spring	To fit over M3 bolts. About 25mm long and compress to about 10mm.
6	M8×370mm	Threaded rod	3 per side - Can be cut from larger 6x1m pieces (see Threaded Rod Cut Order below).
4	M8×294mm	Threaded rod	front / rear
3	M8×440mm	Threaded rod	top / bottom
2	M8×210mm	Threaded rod	Z-leadscrew
1	M8×50mm	Threaded rod	or M8x30 or longer bolt for X idler. Take care: if the bolt is too long, it may not be threaded along a sufficient length
2	8mm×420mm	Smooth rod	X-bar - 304 Stainless Steel, A2 Tool Steel, or O1 Tool Steel are recommended for smooth rods as it can help to prevent friction from rust and manufacturing (straightness) standards are higher. Rust issues can be prevented on the normal steel rods by maintaining a coat of oil. The smooth rods can also be cut from larger 3x1m pieces (see Smooth Rod Cut Order below).
2	8mm×406mm	Smooth rod	Y-bar
2	8mm×350mm	Smooth rod	Z-bar
1	225mm×225mm print top plate	Thick Sheet
1	140mm×225mm print bottom plate	Thick Sheet	Note: The Prusa Iteration 2 design does not use a print bottom plate.
1	840mm×5mm T5 pitch timing belt	Belt	Y axis
1	900mm×5mm T5 pitch timing belt	Belt	X axis
5	NEMA 17 bipolar stepper motor	Stepper	At least 20mm of shaft length. One should have a torque of > 40Ncm.	13€ each
50	small cable binder / ziptie	Misc
1	Wade's Geared Extruder		for 1.75mm filament RepRap Universal Mini Extruder; or any other compatible extruder for either
1	Electronics + endstops		This can be RAMPS, Sanguinololu, Generation 6 Electronics, Generation 7 Electronics, Generation 3 Electronics, or any other Mendel compatible electronics. End-stops are either optical switches or micro-switches (Recommended), and you need three, one for each of the X, Y, Z axes.

Extruder (Print-head)

Wade's extruder design (Taken from the RepRap wiki)

Quantity	Description	Type	Comments	Available
Feeder
2	608 bearings, skateboard bearings	Bearings
1	M8×50 bolt	Fastener	to be hobbed, M8×60 has a longer smooth part, allows a second lock-nut, and may be easier to find
1	M8 nut	Fastener	Nyloc works better, but a pair of nuts will also work
4-5	M8 washers	Fastener	to space the large gear clear of the motor retaining bolt heads
Idler
1	608 bearing, skateboard bearing	Bearings
1	(M)8×20	Threaded rod
4	M4×60 or M4×45 hex head bolts	Fastener	Hex head will work best (they won't turn), and longer than 45 mm will be easier to assemble if you can find them.
4	M4 nuts	Fastener	typically wing nuts
8	M4 washers	Fastener
4	~4mm ID springs	Spring	Sized to fit over an M4 bolt, unsprung length of 10-12mm, each spring providing 25-35N load. For a given filament drive force, you'll need about twice the spring force - i.e., if you want 100N of filament drive, your springs need to push with about 50N each.
16	M4 washers	Fastener	optional; 4 washers on each M4X45 idler bolt between the main block and the idler block will limit the idler travel and make reloading filament easier.
NOTE: Some users have their extruders working without springs, but springs are recommended. A good source for these springs is in the cloth-cabinet on spring loaded skirt-hangers or trouser-hangers. Just cut the right length off the springs.
Hot End Mount
2	M3×35 bolts	Fastener
4	M3 washers	Fastener
2	M3 nuts	Fastener
1	2.5mm drill		See section Hot End
Stepper Motor Mount
3	M3×10 bolts	Fastener	Low profile bolt heads might work better here
3	M3 washers	Fastener
1	M3 grub screw	Fastener	To secure the pulley, ideally 8mm long, but anything 6mm+ should be fine
1	M3 nut	Fastener	To secure the pulley
Stepper Motor
1	NEMA 17 bipolar stepper motors	Stepper	5 kg*cm (=49 N*cm, 69 ozf*in) works well; Kysan 42BYGH4803 is what I used. Should be capable of creating a holding torque of at least 40Ncm (4.07 kgf*cm, 56.6 ozf*in), at the very least.
Extruder Mount
2	M4×20 bolts	Fastener
2	M4 nuts	Fastener
2	M4 washers	Fastener

Electronics

The Generation 7 Board is easily self-made and extensible. It uses no SMD devices, needs only one layer of copper so it can be etched or possibly milled.

This list is ordered to match the order of assembly.

Electronic Components

Name	Count	Designations	Vendors						Remarks
0.6 mm Wire	50 cm			Völkner			Digi-Key	Mouser	for the wire bridges on single sided PCBs
Resistor 10 Ohms	2	R11, R12	Reichelt			RS
Resistor 560 Ohms	2	R14, R22	Reichelt	Völkner	Farnell	RS	Digi-Key	Mouser
Resistor 1 kOhms	6	R2, R6, R8, R10, R16, R18	Reichelt	Völkner	Farnell	RS	Digi-Key	Mouser
Resistor 4.7 kOhms	2	RT1, RT2	Reichelt	Völkner	Farnell	RS	Digi-Key	Mouser
Resistor 10 kOhms	1	R30	Reichelt	Völkner	Farnell	RS	Digi-Key	Mouser
Diode 1N4004	2	D1, D2	Reichelt	Völkner	Farnell		Digi-Key	Mouser
Coil 100 uH	1	L1	Reichelt	Völkner	Farnell		Digi-Key	Mouser
Crystal 16 MHz or 20 MHz	1	U6	Reichelt	Völkner	Farnell		Digi-Key	Mouser
Reset Switch	1	RESET	Reichelt	Völkner	Farnell		Digi-Key	Mouser
Ceramic Capacitor 0.1 uF	12	C5, C8, C9, C10, C11, C12, C13, C14, C16, C17, C18, C19	Reichelt	Völkner	Farnell	RS	Digi-Key	Mouser
LED 3 mm Green	3	LED2, LED5, +5V	Reichelt	Völkner	Farnell		Digi-Key	Mouser
LED 3 mm Yellow	1	Standby	Reichelt	Völkner	Farnell		Digi-key	Mouser
Ceramic Capacitor 22 pF	2	C3, C4	Reichelt	Völkner	Farnell	RS	Digi-Key	Mouser
Electrolytic Capacitor 10 uF	2	CT1, CT2	Reichelt	Völkner	Farnell		Digi-key	Mouser
Electrolytic Capacitor 100 uF	4	C1, C2, C6, C7	Reichelt	Völkner	Farnell		Digi-Key	Mouser
Jumper Header 2 Pin Pairs	4 pair	J2/J3, J5/J6, J8/J9, J11/J12	Reichelt			RS	Digi-Key	Mouser	cut them into appropriate pieces
Jumper Header 2 Pin	2	J13, J14	Reichelt	Völkner		RS	Digi-Key	Mouser	cut them into appropriate pieces
Jumper for the two above	9		Reichelt			RS	Digi-Key	Mouser
ICSP Header	1	CONN6	Reichelt			RS	Digi-Key	Mouser	alternatively, assemble this out of the remainings of the Jumper 2 Pin Headers
Pololu Header	8 or 4	U2, U3, U4, U5	Reichelt	Völkner			Digi-Key	Mouser	cut them to appropriate length, you want 8x 8 pins
Socket for the ATmega	1	U1	Reichelt	Völkner	Farnell		Digi-Key	Mouser
ATmega 644 (or 644P)	1		Reichelt		Farnell		Digi-Key	Mouser
Alternative: ATmega 1284P	1		Reichelt					Mouser
MOSFET IRFZ 44N	2	Q1, Q2	Reichelt	Völkner	Farnell	RS	Digi-Key	Mouser

Connectors

Name	Count	Designations	Vendors						Remarks
Molex KK100 2 Pin Header	2	TEMP1, TEMP2	Reichelt			RS	DigiKey	Mouser
Cable Connector for the above	2		Reichelt			RS	DigiKey	Mouser
Crimp Contact for the above	4		Reichelt			RS	DigiKey	Mouser
Molex KK100 3 Pin Header	3	X_MIN, Y_MIN, Z_MIN	Reichelt			RS	DigiKey	Mouser	Reichelt are tested to be fully compatible with Molex
Cable Connector for the above	3		Reichelt			RS	DigiKey	Mouser
Crimp Contact for the above	9		Reichelt			RS	DigiKey	Mouser	same as for TEMP1, TEMP2 above
Molex KK100 4 Pin Header	4	X_MOT, Y_MOT, Z_MOT, E_MOT	Reichelt			RS
Cable Connector for the above	4		Reichelt			RS
Crimp Contact for the above	16		Reichelt			RS	DigiKey	Mouser
Molex KK100 6 Pin Header	1	SERIAL				RS	DigiKey	Mouser	alternatively, use the same as for Jumper 2 Pin
Optional: Cable Header for the above	1					RS	DigiKey	Mouser	only needed if you intend to solder your own USB-to-TTL cable
Optional: Crimp Contact for the above	6					RS	DigiKey	Mouser	only needed if you intend to solder your own USB-to-TTL cable
Heater Header Molex 26-48-1045 (2 Pin)	2	HEATER1, HEATER2				RS	DigiKey	Mouser
Cable Connector for the above	2					RS	DigiKey	Mouser
Crimp Contact for the above	4					RS	DigiKey	Mouser
Alternative to Heater Header: 2 Pin Screw Terminal	2	HEATER_1, HEATER2	Reichelt				DigiKey	Mouser
Disk Power Header	2	CONN2, CONN3	Reichelt			RS	DigiKey	Mouser	also see DIY 4 pin molex connector
ATX24 Power Connector	1	CONN1				RS	DigiKey	Mouser	Molex Mini-Fit 44206-0007. Also known as VAL-U-LOK (20 or 24 Pins).
Heatsink for the MOSFETs	1 or 2		Reichelt			RS	DigiKey	Mouser	Please note that Reichelt ones are quite wide (18mm). Two of them won't fit.
Bolt M3 x 8 mm for mounting the MOSFET heatsink	1 or 2
Washer M3 for mounting the MOSFET heatsink	1 or 2
Nut M3 for mounting the MOSFET heatsink	1 or 2								Not needed for the Reichelt heatsinks, which come with an M3 tap already.
Heatsink for the Pololus	4		Reichelt	Völkner		RS
Heatsink Glue	1		Reichelt	Völkner					For the Pololu's heatsinks, cut in appropriate pieces. Loctite(-like) screw locking glue works well, too.

Miscellaneous

Generation 7 Electronics uses a TTL header for serial communications to the host. As many modern PCs lack a serial port, these need an appropriate USB to TTL cable:

USB to TTL Cable	DigiKey	Mouser	Adafruit Industries	MAKE Store	MakerBot Industries	Watterott

An alternative to the USB to TTL cable is the same electronics in form of a small breakout board:

USB to TTL Breakout Board	Watterott	Sparkfun
Cable for the above	Watterott

Another alternative is the E'go USB-TTL adapter, see instructions and limitations below.

Last not least, you need four stepper drivers, of course:

Pololu stepper driver boards	Pololu stepper driver boards
Open Source Alternative	StepStick