Because of the limited space for all my projects, it is important that each project, especially regarding tools, becomes totally self contained. When equipment has to be assembled it inevitably takes up more space both to use and to store. For this reason the printer has everything built into a single unit where ever possible. The only exception to this is where parts can be interchangeable or have optional use. This means that single extruder, double extruder, spindle and filament reel holders are not included.
The motors selected are the 28BYGH501 stepper motors from Wantai. I have used Wantai steppers for my CNC Router and found them to be good quality and very reasonably priced. The motors and electronics will be driver from a 24Volt 150 Watt power supply.
This was also purchased from Wantai and is a generic Chinese power supply. The power supply has been sized to be able to supply power to the heating of both the hot bed and the hot end of the extruder.
Control of all the motors and heaters will be achieved by a Sanguinololu Computer board. This unit was purchased fully built and tested to expedite the development time required. There are enough variables to get working together in the beginning without making the task more challenging.
The Sanguinololu Computer board was ordered complete with the Polulo stepper motor drivers and the opto limit switches.
Heating of the hot end of the extruder will be achieved with wire wound resistors as is the current norm. The control is included on the Sanguinololu via MOSFET's fitted. Using 24 Volts will reduce the current required for the heating.
Heating of the hot bed will be achieved by switching the 220 Volt AC mains supply via a solid state relay. This will drastically reduce the heat generated by the power supply. The disadvantage is that the hot bed temperature will vary slightly more than with a switching mode. The temperature hysteresis will however limit the effectiveness of the switch mode.
The 220 Volt 0603 resistors used to heat the GHD hairstraightners appear to be ideal for hot bed heaters. They have a large area for the heat transfer and can easily be sandwiched onto the lower side of the hot bed. Furthermore they are easily available as spares on ebay.
On the front panel of the printer case assembly the power inlet connector will be mounted. This power inlet also contains the on off switch. A fuse and indicators for the 220 Volt mains and the 24 Volt DC supply are also mounted on the front panel.
The front panel will be engraved to identify the respective indicators, fuses and power inlet.