BME - Machine Shop on-line manual: Milling Machine

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MILLING MACHINE (MILLMASTER CNC)

Table of Contents

Introduction
FAQ
Ways to operate the mill
User tips
Communicating with the CNC
Library of ISO programs (G-code)
Software
CNC customizations
Manuals
Supplies
Maintenance
Contacts

Introduction

The MILLMASTER turret milling machine is a manual knee-type mill that has been retrofitted with a Fagor 8040MC CNC (Computer Numerical Controller). As such, the machine is somewhere between a manual mill and one that is completely computer controlled.

The milling machine consists of the following components:

Tool changer (a manually activated pneumatic drawbar)
Spindle speed control (a manual handwheel for continuous speed adjustment + hi/neutral/lo range lever)
Spindle brake (manual lever)
CNC (controls the quill depth, spindle on/off, table X-Y motion, etc.)

The most complex of the components is the CNC, shown here, and you must read up on it before using the machine. Navigating the various CNC screens is not at all obvious, but is straightforward once you have learned the key sequences. The milling machine, itself, is easy to operate.

Click on the image to see a larger version. (File size 464KB)

You will find on-line recommended reading material to fast-track you to being able to operate the milling machine.

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FAQ

Q: Do I need to know CAD/CAM to make a complex part?

A: Perhaps not. The CNC has a graphical interface (called the conversational mode) which allows one to make many parts without knowledge of CAD or CAM. Provided that your machining requirements may be described as a sequence of machining operations that are predefined in the CNC's library (called cycles), all that you need is an accurately dimensioned diagram or sketch of the part that you need to make.

Q: Can I do manual machining?

A: Yes, in JOG mode.

Q: Where do I start?

A: Below are suggested readings that should fast-track you to becoming familiar with operating the mill, CNC machining principles and the CNC.

Turret Milling Machine Operation Manual

Basic Machine Specifications (p. 3)
Operating Instructions (pp. 14-20)

Self-teaching Manual (MC Option):

Chapter 1: Theory on CNC machines
Chapter 2: Theory on tools
Chapter 3: Hands-on training
Chapter 4: Automatic operations
Chapter 5: Summary of work cycles
Chapter 6: Conversational part-programs
Appendix I: Programming examples

Note that our CNC has a different keyboard layout than that shown in the manuals. The self-teaching manual refers to sections in the operating manual, which is in the same PDF document. You will get a better understanding of the CNC if you read the relevant sections of the operating manual as well.

The operating manual is a bit weird particularly in the beginning sections as it mixes operating key sequences (what you would do as the user) and their relation to variables and programs in the CNC's PLC (what a technical support representative from Fagor would tweak.) Ignore the PLC details in your readings, as they only distract from the goal of learning how to use the CNC. (This would be akin to learning how to use an application as opposed to learning about its source code.)

The hybrid nature of the system makes reading user manuals somewhat awkward, as some parts of the MILLMASTER manual are now irrelevant and some functions of the CNC cannot be used with the hardware that we have. (Examples: Manual quill feed is disabled on the mill because the CNC takes care of this, though adjusting the spindle speed remains a manual operation despite the spindle speed being shown on the CNC screen.) See the manual section on this page for more information on disabled features.

Q: How do I turn on the milling machine?

A: This document details a typical startup and shutdown sequence for the mill. (The instructions presume that you are familiar with operating the CNC.)

Q: How do I transfer programs between the CNC and a computer?

A: Use Fagor's WinDNC software. Click here for more information.

Q: What is the policy regarding a program left in the CNC's memory?

A: Somebody will eventually delete it without notice. (See How do I transfer programs between the CNC and a computer?)

Suggestion: Include your name in the name of your program so that ownership is clear. You stand a better chance of being contacted before your programs are deleted.

Q: How do I generate Fagor code from a CAD file of a part?

A: We have a post-processing file for MasterCAM that will generate Fagor 8040MC ISO code. The post processor is actually for the 8055MC controller but has been tweaked to be compatible with the 8040MC. The file may need more tweaking. (Always do a dry run to check the generated ISO code.)

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Ways to operate the mill

Hand operation (DRO)

Impractical.
In principle the CNC may be placed in a digital readout mode (DRO) by touching the key with the symbol of a hand. This turns off the X, Y, and Z drive motors, but the CNC continues to display the X and Y coordinates as read by linear scales. The table can be easily displaced in X and Y using the handles. The quill is the problem. Firstly, there is no Z-axis information since this is reported via the motor's encoder — which is off. Secondly, it is very difficult to move the quill with the quill feed handle.

JOG mode (manually with CNC)

This is equivalent to hand operation but is a nicer way of doing manual operations. Operations are limited to displacing the tool in one of the three machine axes at any time. Here are a couple of examples.

1. Use the X+/-, Y+/-, and Z+/- keys to move the tool in one axis, alone. Observe the coordinate value on the CNC display and release the key when final destination is reached. (This is akin to rotating a table displacement wheel by hand, but by remote control.)

2. Say that you wish to mill a slot along the X axis and that a 50mm travel is required. Position the tool at the starting point (call this the origin.) Set the machine's X-coordinate to zero (type in X 0 <Enter> <Enter>). Now instruct the machine to move the tool by +50mm (type X 50 <Cycle Start>). Done.

In all cases, the tool moves at the feed rate set in the CNC. See Chapter 4 of the Self-teaching manual and Chapter 2 of the Operating manual (both in the same document.) The mill is not equipped with an electronic handwheel.

Automatic operations (cycles)

While at the CNC, you touch icons on the keypad which bring up a native graphical user interface. From here, you select one of several automatic operations built into the CNC. The graphics screen presents a generic form into which you enter, at the keyboard, the defining dimensions for the particular cycle. This is called conversational programming.

Examples of cycles include milling pockets and profiles, surfacing, drilling, drilling on an array or at multiple points, etc. For a circular pocket, the required form data is pocket radius, depth, tool to use, cutting speed, and so on.

Cycles may be assembled into a parts program. Programs may be offloaded from the CNC onto a computer for future use. Cycles and programs may be graphically simulated before execution to check for programming errors.

Programming by ISO code (G-codes)

The CNC may also be programmed using its own language (called ISO code.) ISO code is to MATLAB scripts as cycles are to Simulink models. Programs may either be manually entered at the CNC console or may be developed on a computer and uploaded to the CNC. Programs may be graphically simulated before execution to check for programming errors. A program is not lost when power is shut off to the CNC.

Sample programs may be found in the library section. See the programming manual for more detail.

As with any machining operation, you also need to give thought as to how the raw material will be held during the machining process (e.g., clamped to the table or held in a vise) as well as corner limitations as a result of tool radius. It is easy to design a part that cannot be manufactured.

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User tips

This document lists reported CNC idiosyncrasies, user tips and how-tos. It is a good idea to have a copy by your side when you are at the mill.

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Communicating with the CNC

The CNC is able to work in DNC (Distributed Numerical Control), enabling communication between the CNC and a computer to carry out the following functions:

Directory and delete commands.
Transfer of programs and tables between the CNC and a computer.
Remote control of the machine.

The CNC has an RS-232 serial port on its right-hand side and is also connected to the department's LAN. Both may be used with DNC software to communicate with the CNC and we use Fagor's WinDNC software to do so.

WinDNC configuration for Internet access to CNC:

Install Win DNC ver 4.0 or higher (Win 9x/2000/NT/XP)
Run Win DNC
Click on the Setup icon
Click on the New (+) icon. Fill in fields as follows.
Name: MILLMASTER-CNC
Model: 8050 M/8055 M
Type: Network Node
Connect on Start up: Leave blank
IP address: xxx.xxx.xxx.xxx (fill in appropriately)
Back at the Devices main menu, click on MILLMASTER-CNC.
Click on the Connect icon

Hit Esc on keyboard to get back to main menu.

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Library of ISO programs (G-code)

For those inclined to try some simple ISO programming, here are examples of hole patterns used to mount common connectors onto instrument panels.

Click on an image or the links next to it to download a text file containing code snippet showing how the hole was programmed. Figures show a top-view of each hole.

Banana jack (standard)


		Mastercam version

BNC bulkhead receptacle (Amphenol 31-10)


		Mastercam version

DB receptacle	Front Panel Mounting	Rear Panel Mounting
	DB15 connector (horizontal) DB25 connector (Mastercam ver.) DB37 connector (horizontal) DB37 connector (vertical, rotated 90 deg CCW) DB37 connector (Mastercam ver.)	DB9 connector (Mastercam ver.)

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Software

The department has the following application software:

Mastercam X4 + post processor for our Fagor controller
We have one, sinlge user license which is locked with a sim (a hardware dongle.)
The sim needs to be connected to the USB port of the computer running the application.
ProENGINEER
Fagor WinDNC (for communicating with the CNC from a computer.)
This is a free download from Fagor's web site. (See contacts.)