Known issues:

• No limit switches on Z-axis so be careful. If you hit the mechanical stops and hear the stepper motors skipping, the software will lose track of where the cutter is, and the rest of your job will be messed up.
• Need to check calibrations to verify that cutter moves correct distance.
• Some of the end mills in the toolbox are chipped or otherwise broken.

Hardware information

General

Before using this machine, you should learn how to operate it safely. The easiest way to do that is to take the Basics of using the CNC Mill class.

AMT has the  LittleMachineShop HiTorque Mini Mill with the Solid Column (#3960)

User Manual for 3960 Mini Mill Users Guide

with the CNC Fusion Mini-Mill Kit #5 LMS HiTorque/SX2L (BALLSCREWS)],

and the [https://www.google.com/search?q=425+oz-in+motors+&+drivers+cnc+router&ie=utf-8&oe=utf-8#q=cnc+router+425+oz-in+motors+&+drivers+ 425 oz-in motors & drivers (#2)]

Wiring info

• purple, brown, yellow, black (A+,A-,B+,B-);
• purple-steps(-), brown-direction(-), yellow-common (GND/+5V). yellow goes to steps(+) and direction(+);
• for 36V power, yellow is +, black is –

Driving the mill: hardware

Hardware overview

• Control PC
  • Cart-mounted WinXP box; runs CNC and CAM software.
• 6′ parallel cable
  • When moving the cart, be careful not to pull or damage this cable.
• C10 breakout board
  • The breakout board is physically mounted to the frame, a piece of plywood approx. 2′ wide by 1′ high, mounted to the wall behind the CNC mill.
  • The breakout board appears as an LPT device in Windows, and provides up to 17 pins per LPT port.
    • ”’LPT1:”’ 5 input, 12 output
    • ”’LPT2:”’ 13 input, 4 output
• KL4030 motor drivers
  • There are (3) drivers, one each for the X-, Y-, and Z-axis motors.
  • Each driver is rated 3.0A, 24-40V; 1-1/64 microstepping.
  • The motor drivers are powered by a 36VDC/ 9.7A power supply, also mounted on the control board.
• NEMA 23 motors
  • There are (3) motors, one each for the X, Y, and Z axes.
  • Each motor provides 3.00 N·m (2.21 ft·lb) of torque.

Driving the mill: software

There are two pieces of software in AMT’s CNC toolchain: ”’Deskproto”’ generates toolpaths from 3D models. A toolpath is, naturally, the path the cutter takes across the surface of the material. It outputs a G-code file, which Mach3 reads. ”’Mach3”’ controls the mill motors, handling positioning of the cutter.

Deskproto (CAM)

Deskproto’s manuals can be downloaded [http://www.deskproto.com/download/manuals.htm here]. Don’t try to “wing it;” the software requires a fair amount of training.

Mach3 (motion control)

The mini mill is controlled by a Windows XP workstation running [[Mach3|Mach3]]. Mach3 communicates via the LPT port to the breakout box (see “Hardware overview,” above).

Mach3: Ports and Pins

*General
**Port #1: enabled; 25,000Hz; Sherline 1/2 Pulse mode should be checked
*Motor Outputs
**x-axis: check; 1, 2,check, check
**y-axis: check, 3, 4, x, x
**z-axis: check, 5, 6, x, x
*Input signals
**EStop: check, 1, 10, x, x, 0
**all others – disabled

Mach3: Motor Tuning

*x-axis and y-axis
**16,000 steps per
**50 Velocity
**50 Accel.
**G’s ~0.3237
**0 Step Pulse
**0 Dir. Pulse
*z-axis
**16,000 steps per
**25 Velocity
**25 Accel.
**G’s ~0.4856
**0 Step Pulse
**0 Dir Pulse

Mach3: Backlash

*x-axis and y-axis: 0.006
*z-axis: 0
*backlash speed: 50%

Please note that when the mill moves and backlash compensation is enabled, you may observe a two-stage movement the first time direction shifts; do not be alarmed by this, it is compensating for the backlash before the requested movement occurs.

Update, Nov 2013 for Motor Tuning

Backlash and speed setting have been refined. The Y-Axis was ”’skipping”’ and this was not noticeable except for the staircase pattern that appeared when milling a pocket. Pictures of the latest stepper driver setting for seemingly maximum motor current (there was some ambiguity):

[[File:Motors.jpg|RTENOTITLE]]

New backlash settings (enable!): X: 4mil, Y: 22mil (FIXME: is this accurate? Backlash has been adjusted before noticing that Y-axis was skipping), Z: 0mil

New speed settings:

*X: 16k ‘Steps per’, Velocity: 50inch/min, Acceleration: 50inch/s/s
*Y: 16k ‘Steps per’, Velocity: 25inch/min, Acceleration: 12.5inch/s/s
*Z: 16k ‘Steps per’, Velocity: 25inch/min, Acceleration: 25inch/s/s

Acquisition

For details of how we obtained this CNC, see the [[Mini_Mill_CNC/Acquisition|Acquisition page]].

To do list

*Install limit switches
**In progress. X and Y axis limit switches are installed and working. Z-axis still TBD.
**”’Note: The mill is not protected by limit switches! Unless you really know what you are doing, do not run any G-code through it until they have been installed.”’
*Research and document feed rate for 6061 aluminum
*Build a “swarf shield”
**Encloses machine sides, bottom and rear with MDF panels, with plastic panels on the top and front side, hinged at the top to the MDF.
**Allows a swarf collection system to be attached in the future.

Maintenance Records

While the status system does a great job for short updated longer updates should go here.