RD3D/1.0

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Revision as of 16:39, 22 September 2017 by Lkcl (talk | contribs) (GPLv3 PCB Board Source code)
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RD3D 1.0

Release status: in development

RD3D 1.0 eagle.jpg
Description
RepRap Due 3D Printing shield Arduino DUE based modular RepRap electronics.
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CAD Models
External Link



RD3D v1.0 - Reprap Due for 3D Printing

This board is derived from Ramps 1.4.2 and has the following features and improvements:

  • Suitable for use with Arduino Due: uses selectable 3.3v or 5.0v supply
  • Suitable for up to 24v on both or either Power inputs
  • Removed all double Stepper connectors (motors should be wired in series)
  • Reorganised all AUX ports (I2C, AUX3 remain same)
  • Removed Thermal Pads to increase power handling capacity between layers
  • Removed screw-holes from PCB (saves space for components)
  • Added MicroSD Card (for porting RepRapFirmware)
  • Added buffers on MicroSD and 5v to 3.3v regulator (allows Due or 2560 use)
  • Added 3.3v / 5v selector jumper (for either Due or 2560 power)
  • Moved D8, D9 and D10 LEDs next to their outputs
  • Increased current capacity of 3V3 trace to MicroSD, AUX3 and AUX4
  • Increased Main Power copper pour (inc. to VMOT) widths, added extra VIAs
  • Moved Thermistor jumpers down to end of PCB, linked to closer ADC pins
  • Added 4th ADC next to thermistors, with VCC for use as Z-Probe (no 4.7k res)
  • Changed ADC capacitor type to 0805 (saves space)
  • Added 0.1uF Decoupling Capacitors, close to each VMOT Power pin
  • Added MC7808CDTG 1A 8V Power Regulator, to supply Arduino from up to 24v
  • Added extra 6th Stepper Board. Can now do auto-bed levelling (triple Z)
  • Added 4th MOSFET. Can do Bed, 2 fans, 1 extruder or Bed, fan, 2 extruders
  • Added Twin Header for 2 always-on fans (connected directly to Power In)
  • Added a SN74HC125 to the MOSFETs to achieve full RDSon (Due is 3.3v)
  • Added an AT24C512 I2C EEPROM
  • Added D12 GPIO (with a 10k pulldown) to disable MOSFETs on Due startup
  • Added GND Shielding VIAs, significantly reorganised power planes.
  • Significantly adjusted pinouts so that wires do not cross (reduce EMC)
  • Simplified Copper pour: single GND on TOP and BOTTOM with low priority
  • Rotated top 3 stepper boards to give greatly improved GND and VMOT supply
  • Added 6x2 AUX pinheader taking spare pins from 2x18 arduino connector
  • Removed reset switch (kept reset header) to increase GND plane integrity

Being based on RAMPS 1.4.2 it also has the following features:

  • Improved current-carrying capacity (2oz copper instead of 1oz)
  • Standard removable Blade fuses
  • Suppresion capacitors on endstops
  • Extra jumper on the reset switch

Design features gallery

Here are some of the design features, with images (in order), below:

  • LEDs next to each power output: Heater, Fans, Extruder
  • Improved copper pour for VMOT power (includes extra VIAs)
  • MicroSD card added with level-protecting buffers; Thermistor terminals moved right next to ADC
  • 6th Stepper Driver added to handle Triple Z-screws.
  • Tri-state Buffer on MOSFETs (3.3v to 5v conversion for Due); D11 disables MOSFETs (defaults to off)
  • LDO with an 8V 800mA output supplies power to Due from input voltage, accepts anywhere between 12v and 24v

GPLv3 PCB Board Source code

Full GPLv3 source code is available at http://hands.com/~lkcl/rd3d

git clone http://hands.com/~lkcl/rd3d/.git

Connectors

Endstops

RD3D Endstops.jpg

TODO table

BOM, PDFs

Why is the RD3D Board being done? Why not use an existing board?

In the markets in Huaqiang Road, in the Futian District of Shenzhen, RAMPS 1.4 boards can be bought cash for around 27 RMB, which is about $USD 3.50. Adding an Arduino 2560 plus four A4988 cloned stepper drivers brings that total to under $USD 15. The STP55NF06L MOSFETs of course need replacing for the heatbed to operate but IRLB304PBF MOSFETs can be bought in the same market at ridiculously low prices.

However RAMPS is only really suitable for the 2560, which, being an 8-bit controller is really too slow, and it's extremely inconvenient to upgrade a RAMPS to 24v. It's not actually possible to upgrade RAMPS to pure 24v: it's necessary to do hybrid 12v (for powering the 2560) and 24v for the heatbed alone. If you want 24v for the fans, heater and Motors, this is not really possible without cutting tracks in the PCB.

In addition, the hard limit of 5 stepper boards makes it unsuitable for use in auto-bed-levelling scenarios (triple Z screws).

So if you prefer to use 24v all-round, or prefer to use a 32-bit microcontroller, or would like to consider doing auto-bed-levelling, RAMPS 1.4 is not an option.

So in looking around for alternatives, several came up. The extremely good Duet 0.6 would be perfect (and a reasonable cost at around $60), except it's no longer made. Likewise the Duet 0.8.5 is no longer manufactured: it was $USD 120 which is almost as much as an entire 3D printer may be sourced for in Shenzhen. The absolutely superb DuetNG is $USD 150, which is simply far too much when you compare it to $USD 15 for a RAMPS 1.4 plus an ATMega 2560 Arduino plus 4 A4988 drivers, in Shenzhen (even if it's not apples-for-apples).

Also investigated was RADDS (because it uses the same RepRapFirmware as the Duets) - unfortunately whilst it would be perfect it's also proprietary: PCB files are "available under request and only for non-commercial personal use". This is not the spirit of the Reprap movement.

Also investigated was Smoothieware boards. The team seems to have a good sense of camaraderie, excellent support and, being based outside of China, take considerable care in manufacturing and QA testing. Unfortunately, their manufacturing and sourcing... takes place outside of China. Basically anything that is sourcing its components in Europe or the USA results in a huge premium.

Also, unfortunately, when boards are typically cloned by Chinese Manufacturers, a number of things tend to happen (which are exactly the reasons why people in Europe and the USA typically don't risk buying China-sourced boards...)

  • They typically "tinker" with the design (adding in EMF and unacceptable noise)
  • They completely forget to label which version they are selling (including their own modifications)
  • They don't honour the GPL license or the spirit of the Reprap movement
  • They don't provide firmware source code
  • Cost-shavings are carried out, such as using 0.5oz copper or replacing critical components, often without consent or clear marking.
  • Actual manufacturing is often not properly QA'd
  • Known-bad boards continue to be sold even after they are informed of this fact.

Clearly this is not the case for absolutely every single Chinese Manufacturer: the difficulty comes for a Westerner in identifying exactly which Manufacturers may be trusted, in order to make reliable, consistent and safe use of the pricing advantage that China has to offer.

So there is this very strange and paradoxical failure to combine the best of a Western mindset with Asian pricing and sourcing. The RD3D therefore endeavours to combine the advantages of Chinese component sourcing and manufacturing with a Western mindset, where GPL licenses will be fully honoured for both software source and hardware designs, and proper QA will be carried out to ensure that the resultant PCBs work 100%.

In short: there are no *low cost* 32-bit, 6 stepper, 4 MOSFET, 24v-capable Reprap 3D printing boards that fully honour the GPL and the spirit of the Reprap community, hence why it has been necessary to create one.

Discussions