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picoCNC - A modular fabrication robot

Hackerspaces, FabLabs and Open-Eco-Villages need tools to bootstrap their own individual environments. Although RepRaps, Makerbots and Lasercutters are more common these days, many groups are still lacking CNC routers/mills to create really solid tools or parts for bigger machines. Maybe some of the solutions presented here will inspire other groups, to build more CNC machines and extend our ability to make stuff on our own and for each other, by sharing plans how to build machines and plans for parts that can be made with these machines. Luckily we have been able to get a 3D printer so we can bootstrap a lot of the picoCNC parts ourselves now.

Due to Apollo's limited cargo capacity, there is simply no room for three machines: A RepRap/Makerbot to extrude plastic parts, a Laser-Cutter/Engraver for wood and acryl and a CNC Router for more heavy duty jobs. In order to maximize the usability of available cargo volume, a single gantry based 2.5D (X,Y,Z) DIY CNC frame will be used to host the following, quickly changeable, task related toolheads:

  • DIY High-Speend Brushless Outrunner spindle for CNC milling/routing
  • 1000mW blue Laser head for engravings
  • High Quality 1.75mm ABS/PLA Extruder (like the Felix Extruder)
  • Chocolate/Praline filling Extrusion (Moineau pump) → http://www.thingiverse.com/thing:18017

Frame

Building a CNC machining frame is in total contradiction to Apollo's usual requirements:

  • Apollo can only carry small and light things
  • A good CNC machine is as heavy and sturdy as possible

In this case there has to be some compromise, so the frame itself is going to be build from extruded aluminum profiles for easy assembly and hackability. To give it more weight and stability, the hollow parts of the profiles will be filled with a mineral casting (10% epoxy + 90% quartz sand/stones). This also is supposed to help reducing vibrations and noise, the machine is going to emit.

4 Alu Profile 10 50×50 mineral casting filled 50x50x300 1000g
2 Alu Profile 10 50×50 mineral casting filled 50x50x300 1000g

X-Axis

1 Alu Profile 10 Item 10 50×100 800x100x50 1000g ?
2 Linear bearings Hiwin EG/mgw series top/bottom 470x18x15 1000g ?
4 Linear carriages Hiwin MGN09CZ0H 30×27.5×12 40g ?
1 Ball screw Hiwin/Isel 400x16x4 1000g ?
1 Float Bearing Block DCNC-Block 60x20x26.5 ? 20 EUR
2 Belt Gear HTD-3M Z24/9 25×20 15g 15EUR

Y-Axis

2 alu profile mineral casting filled 500x40x80 1000g
4 linear bearings Hiwin MGW09 top/bottom 500x18x7 1000g
8 linear carriages Hiwin MGW9CZ0H 30×50.7×12 40g
2 recirculating ball screw Hiwin/Isel 400x16x4 1000g
2 Shaft Coupler 0-Backlash ADS DCNC-D32-L32

http://cnc-laden.de/cnc-shop/Festlager-8mm/Festlager-8mm-Spindelenden-Nema-23.html

Z-Axis

2 linear bearings Hiwin EG/mgw series top/bottom 500x18x15 1000g
4 linear carriages Hiwin MGN09CZ0H 30×27.5×12 40g
2 recirculating ball screw Hiwin/Isel 400x16x4 1000g
2 NEMA23 Stepper 3NM/4A 0.9° 60x60x70 1000g


This is a good basis to start calculations for LinuxCNC and the basic electromechanics design parameters, should be converted to metric system:

http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Mechanical_Spreadsheet

Shops:

Electromechanics

LPT Breakout Boards

Digital Power Amplififers

Stepper Motors

A # Type Model Torque Current RespW IndpW Dim. (mm) Mass Source
X 1 NEMA23 3NM/4A 0.9° 60x60x70 1000g
Y 2 NEMA23 ST6018M3008-B 1.56Nm 4.2A 0.4 ohm 1.38 mH 60x60x56 770g 60EUR
Z 1 NEMA23 3NM/4A 0.9° 60x60x70 1000g

End-Switches

Toolheads

DIY Direct-Drive Brushless Spindle

To keep costs at a minimum, this high-speed direct-drive spindle is going to be hacked together from commonly available parts from the RC-Model sector, an ER16 Collet-Chuck and a newly designed Universal Mounting Block, that should make the spindle compatible to almost any machine in existence and imagination. The designated maximum cost should not exceed 100EUR, which should make it a really good alternative to commercial spindles, if the design can prove itself.

  • C5045 Brushless Outrunner Motor with 8mm shaft
  • Brushless Motor Controller (ESC)
  • ER16 or ER11 Collet-Chuck with 8mm shaft (100mm length)
  • Quality Ball Bearings
  • Universal Mounting Block (UMB) for direct flange or 43mm “Euro” mounting

Brushless Outrunner Drive

Aeolian C5045 890KV Power C5045 890KV
Parameter Datasheet Real Datasheet Real
Power 1185W n/a 980W-1300W n/a
RPM/Volt (KV) 890 n/a 890 n/a
Voltage 6-28V n/a 12-32V n/a
Idle Current 2.6A n/a n/a n/a
Resistance/Phase 21mOhm n/a n/a n/a
Shaft Diameter 7.9/8mm? n/a 8mm n/a
Diameter 50mm n/a 50mm n/a
Length 45mm n/a 45mm n/a
Weight 210g n/a 224g n/a
Price/Source EUR 59,80 EUR 49,95

Brushless Controller

Spindle control and speed is managed comfortably with a ESC32 or VESC - An open-source/hacker-friendly BLDC ESC brushless engine speed controller originally intended to control our drone motors. Due to the open firmware nature of this module and the possibility to control the ESC through serial/CAN interface another module was purchased (additionally to the ones purchased for our Drone project) to be tested for the spindle setup.

Alternatively, you can hack/use a simple 555 circuit like the following and control another off-the-shelf RC ESC with that:

In the future, a combination of an ESC32 with fully integrated LinuxCNC control may be a good solution to get software controlled spindle start/stop and RPM.

Collet Chuck

CTC-Tools ER16/ER11 collet-chucks, collets and clamping nuts in comparison

Bearings

Angular contact ball bearings

Candidate d D B Max. RPM
INA 30/8-B-2Z-TVH 8mm 22mm 11mm 25.000
INA 108-TVH 8mm 22mm 7mm 36.000

Deep groove ball bearings

Candidate d D B Max. RPM
INA 608-2Z 8mm 22mm 7mm 31.500

Universal Mounting Block

Preliminary UMB draft - work in progress - RFC

Possible Manufacturers for fabrication outsourcing

Lasercutter

Step 2:

1000mW blue laser diode combined with an aluminum block acting as a big heatsink and mounting block. Will only really cut paper/cardboard for stencils and can be used to engrave different materials. This should make it easy to create front-panels and descriptive UI's for other hardware projects.

ABS Extruder

Step 3:

Research currently available extruder options and their usability in this scenario. Find sources.

Software

Open Source Computer Aided Design and Machining software

CAD

  • Inkscape
  • FreeCAD

CAM

Machine Controller

Tools

Endmills

  • SECO Jabro Solid²

Knowledge & Skillbuilding

The following book always comes up again, when it comes to improving metalworking skills. If someone has a copy and could lend it or wants to sponsor the book (ebook prefered): http://www.amazon.de/Metalworking-Sink-Swim-Machine-Shop/dp/0831133627