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projects:cncmill

Projektdetails:
CNC Mill

Author:Zeno, Bouni, ??
Projektstatus:alpha
Fortschitt:10% completed
Beschreibung:
DIY CNC Mill

General

We will build a CNC mill for the Hackerspace. We tend to build a portal type because its the approach that uses the given space the best and has a great stability and gives a lot of options.

The Blackmill CNC is the type of mill that fits our picture of a perfect DIY mill the most of what we have seen so far.

Here is our first draft:

Facts

Dimensions

  • Height: 1500mm without the table underneath (not on the picture) and Z in most upper position
  • Width: 1200mm
  • Depth: 1200mm

Workarea

  • X: 760mm
  • Y: 760mm
  • Z: 500mm

Weight

  • 410kg (At this early draft state!)

Motors and drivers

Axis motors

As motors we will use Stepper motors because they are cheap compared to the force and precicion they provide. Furthermore they are easy to control.

We have already purchased 4 stepper motors, 4 stepper drivers and 4 60VDC power supplys:

Motor Driver Power supply Axis Description
85BYGH450C-012B, 11.3Nm DQ860MA S-350-60 X-Axis Dual Shaft
85BYGH450C-012B, 11.3Nm DQ860MA S-350-60 Y-Axis Dual Shaft
85BYGH450C-012B, 11.3Nm DQ860MA S-350-60 Y-Axis Dual Shaft
WT86STH118-6004A, 8.7Nm DQ860MA S-350-60 Z-Axis Single Shaft

Video with a test setup

Spindle motor

We will most likely use a „China spindle“ because they are cheap and good enough for the first incarnation of our mill, and if we see that it doesn't work well enough we can then decide to upgrade to a more professional spindle.

At the moment we go for this one here:

2.2kW spindle motor + Frequency inverter

Update 07.07.2015:
Zeno has bought that spindle kit a few weeks ago and we're happy with it so far. We also implemented Modbus control into the Smoothieboard firmware to control the spindle. — Bouni 07.07.2015

Video with Modbus demonstration

VFD Modbus commands

The Hunayang VFD that comes with the spindle claims to support Modbus, but actually it is a crippled form of Modbus or rather their own protocol going over RS485.

Here are the commands needed to control the VFD. The last two bytes are the checksum and need to be recalculated if a value of the sequence is changed!

Turn spindle on

Request:

 0x01 0x03 0x01 0x01 0x31 0x88 

Reply:

 0x01 0x03 0x01 0x00 0xF0 0x48 

Set frequency

Note: The bytes 4 and 5 (0x13, 0x88) are the frequency in Hz. 0x1388 (hex) = 5000 (dec) = 50.00Hz. That results in 3000RPM for a 2 pole motor.

Request:

 0x01 0x05 0x02 0x13 0x88 0xB5 0x9A 

Reply:

 0x01 0x05 0x02 0x13 0x88 0xB5 0x9A 

Turn spindle off

Request:

 0x01 0x03 0x01 0x08 0xF1 0x8E 

Reply:

 0x01 0x03 0x01 0x09 0x30 0x4E 

CNC controller

The cnc controller will be a Smoothieboard 4x. We decided to use the 4X because the 3X has no Ethernet and the 5X has a additional onboard stepper driver that we will not use anyway.

Update 07.07.2015:
Bouni bought the Smoothieboard a few month ago and it seems to do the job for us. We bought the 4x version to have the Ethernet connectors and PHY soldered onto the board despite we could have worked with the 3x version because we will use external drivers anyway. — Bouni 07.07.2015

Extensions

We work on an extension module for Smoothieware that allows to control the spindle VFD over Modbus, the code can be found on GitHub and will hopefully be merged into the edge branch soon.

For RS485 we need a 3.3V UART to RS485 converter. Therefore we've created a small circuit board that can be plugged into the Smoothieboard.

The Board consists of two parts and can be broken apart. The upper half is the RS485 part, the lower is for converting a 3.3V PWM into a 0-10V analog signal for controlling generic VFD's that do not support RS485/Modbus.

Bill of materials

Electronics

CNC controller

  • 1x Smoothieboard 4X
  • Supplier: robotseed.com
  • Price: EUR 129.00
  • Purchased: ✔

Z Stepper kit

  • 1x Nema 34 stepper motor 8.9Nm + 1x DQ860MA stepper driver + 1x 60VDC power supply
  • Supplier: wantmotor111, ebay.de
  • Price: EUR 129.00
  • Purchased: ✔

X/Y Stepper kit

  • 3x Nema 34 stepper motor 11.2Nm + 3x DQ860MA stepper driver + 3x 60VDC power supply
  • Supplier: wantmotor1207, ebay.de
  • Price: EUR 340.00
  • Purchased: ✔

High Speed Spindle Kit

  • 2.2kW Spindle Motor with up to 24000 RPM, watercooled
  • 2.2kW VFD for driving the spindle, Modbus capable
  • Waterpump
  • Plastic hose for coolant
  • Spindle Mount
  • Several ER20 chucks
  • Price: EUR 389.00 (not sure how much it actually was)
  • Supplier: ebay.de
  • Purchased: ✔

Limit switches

  • 6x OMRON D4N-4131
  • Supplier: Distrelec.de
  • Price: EUR 8.48 = EUR 50.88

Cable for stepper motors

  • 4×1.5mm², 4 numbered wires, shielded
  • ~10m
  • Supplier: Volland.ch
  • Price: EUR 1.02/m = EUR 10.20

Cable for spindle motor

  • 4×1.5mm², 3 numbered wires + PE , shielded
  • ~5m
  • Supplier: Volland.ch
  • Price: EUR 1.54/m = EUR 7.70
  • Purchased: ✔

Cable for limit switches

  • 2×0.5mm², 2 numbered wires
  • ~10m
  • Supplier: Volland.ch
  • Price: EUR 0.24/m = EUR 2.40

Mechanics

Linear Guides

  • 4x 1200mm, 2x 600mm
  • We got used guide rails including 12 bearing blocks for free 8-)
  • Price: free (ebay ~ EUR 480.00 + EUR 150.00)
  • Purchased: ✔

Ball screws

  • Including Bearings, mounting blocks, spindle nut
  • Supplier: cnc-discount, ebay.de
  • Price: 3x EUR 189.90, 1x EUR 161.10 = EUR 730.80
  • 700mm Ball Screw Purchased: ✔
projects/cncmill.txt · Zuletzt geändert: 08.09.2015 16:49 von bouni