RepRap Interface Standard

RepRap Interface Standard defines interfaces between the various components of a printer. Like an interface between carriage and extruder, between extruder and hotend, between bed base and heated bed and so on. Effectively we have such standard interfaces already, but they're neither discussed nor defined.

With interfaces defined, components become exchangeable. If an extruder complies with extruder-hotend interface standard and a hotend does as well, a user can rely on both of them fitting and working together. No longer guessing by blurred pictures or even buying many versions just to find one that fits.

Discussion Thread in the RepRap forum

Intentions

• Easily port new features implemented in one printer to another printer.
• Ease the enhancement of printers by changing only one module and not having to invent/build/maintain a new printer thereby lowering the entry bar for new developers.
• Not to invent new interfaces, instead document those interfaces that are commonly used.
• Standard interfaces come with a price. So 100% compatible is not as important as new functionality. If a module needs to break the interface then that should be clearly stated. Best possible compability is still the target.

Definitions

A complete printer consists of a combination of modules. Each module has a different responsibility. All together let the printer work correctly.

A Module might have sub modules. This allowes for more variation. Several types of sub modules may be available. They all must be able to work with their main module.

If modules or sub modules do not comply to all the stated requirements, or if they require more from the other modules in the printer then defined here then these modules must be declared as not fully compatible. The additional requirements or the not met requirements must be stated. Otherwise the module may not be declared to be fully or partly compatible to this standard.

RIS 1: Electronics Feature Set

The electronic module provides the home for the firmware that drived the printer. The CPU and Motor driver ICs are part of the electronics package. RIS 1 defines the interface towards the printer. The interface towards the controlling PC and/or the user is defined elsewhere.

• Power supply for all other modules.
• Support for at least 4 (four) stepper motors.
• Support for at least 3 (three) endstops.
• connectors for Fans (optional)
• connector for temperature sensor (at least two thermistor-type sensors (Extruder + heated bed))
• connector for heating elements (at least two resistor-type (Extruder + heated bed))
• UART/RS232 Serial Interface (optional)
• USB interface to controlling PC. (optional)
• SD Card Slot for printing without PC.(optional)

mechanical interface

size of box? position of screws?

RIS 1: Electronics Submoduls

end Stop

The end stop must fit into the holding mechanism defined... The end stop should have a 3 pin connector(VCC, Signal, GND). Vcc can be 3.3V or 5V.

temperature sensor - heated bed

The temperature sensor for a heated bed must fit into the holding mechanism defined in the heated bed module. The temperature sensor must either create a voltage that represents the temperatur in a range of 0-3.3V or 0-5V depending on the supplied Voltage. A pt1000 would be an example for such a sensor.

temperature sensor - extruder

The temperature sensor for a extruder must fit into the holding mechanism defined in the print head module. The temperature sensor must either create a voltage that represents the temperatur in a range of 0-3.3V or 0-5V depending on the supplied Voltage. A pt1000 would be an example for such a sensor.

heating element - heated bed

The heater for a heated bed must fit into the holding mechanism defined in the heated bed module. The heatermust be able to withstand a voltage of up to 24V.

heating element - extruder

The heater for a extruder must fit into the holding mechanism defined in the print head module. The heatermust be able to withstand a voltage of up to 24V.

Others

Print head

This Module transforms the raw material(PLA, ABS,..) so that is can be deposited on the printbed to from the print. If the intention is not to create a 3d printer but a CNC mill then the milling head will be a print head module.

mechanical interface

mounting holes?

• Groovemount

This is a standard for many Hot end designs such as the Jhead. 4.64 mm wide with an OD of 12mm, using 5/8" stock

electrical interface

• Heating element

A through hole wire wound resistor is traditionally used as the heating element in the hot end. enamel coated resistors are rarely used in electronics today and can be difficult to source, but are often best as a heater element because they can withstand very high temperatures. Look for shiny British-Racing-Green colored resistors. Many other resistors are silicon coated and will have a significantly shorter usable life, as they are often operated way outside of their spec.

• temperature sensor

thermistors, are the most widely used temperature sensor for printing because of their simplicity, cost, and relative accuracy at the working temperatures of common printing thermoplastics.

nominal thermistor specifications is as follows:

• 100k thermistor
• Tolerance: 1-4%
• Diameter of Glass Bead: 1.35-2.3mm
• Length of Glass Bead: 3-4.1mm
• Lead Length: 45-67mm
• Lead Diameter: 0.15-0.3mm

(Heated)Printbed

The print bed is the platform that the printer uses to create the print on.

mechanical interface

For a carteasean bot like a mendel-derivitive, the standard is the Prusa PCb Heatbed.

PCB Heatbed MK1 is developed by Josef Průša

• 200 mm x 200 mm active heated area
• 209 mm center-to-center mounting holes (outside the active area). The holes are M3, usually using standoffs to mount to the Y carraige, such as you would use when attaching a motherboard to a PC case.
• 214 mm x 214 mm total PCB size

electrical interface

• temperature sensor (heated only)
• heating element (heated only)

Mechanic

The big parts of the rinter that allos the print head to move in 3 dimensions relatively to the printbed.

mechanical interface

so that the others can be mounted into it?

electrical interface

• (Stepper) Motors

Existing Modules

In this section all existing Modules can be listed.