STUDENT ENGINEERING SHOP CNC STARTER MANUAL

STUDENT ENGINEERING SHOP CNC STARTER MANUAL

VERSION 1.0

OCTOBER 19TH 2016

JASON ZENG

GRAEME ADAIR

PHIL LAYCOCK

KENNETH WONG

Contents 1.0 Introduction ................................................................................................................... 1

1.1 Toolpath Generation .................................................................................................. 1

1.2 Allowed Materials ...................................................................................................... 2

1.3 Background Information ........................................................................................... 2

1.4 Equations ................................................................................................................... 3

1.5 Available Tools .......................................................................................................... 4

2.0 Milling Operations ......................................................................................................... 6

2.1 Cutting Methods ........................................................................................................ 6

2.2 Cutting Operations .................................................................................................... 7

3.0 CNC Operations ............................................................................................................ 8

3.1 Turning on the Machine ............................................................................................ 8

3.2 Jogging the Table ...................................................................................................... 9

3.3 Clamping Work Piece .............................................................................................. 10

3.4 X and Y Axis Coordinate Zeroing ........................................................................... 11

3.5 Z Axis Offset ............................................................................................................ 13

3.6 Loading Toolpath onto CNC ................................................................................... 15

4.0 Citations ...................................................................................................................... 16

1.0 Introduction

The purpose of this guide is to introduce the student to using the Computer Numerical

Control (CNC) machine within the E5 student machine shop. Students are welcome to and

are encouraged to make suggestions and additions to this guideline.

This guide is split into 3 sections. The first section will talk about general background on

milling, machining, and tool speed calculations. The second section will introduce some

general Mastercam usage tips. The third section are the instructions for operating the CNC

machine itself.

Consult with a shop technician prior to starting your job. Bring a drawing to discuss your part

with the technicians. Speak with the manager at the main Engineering Machine Shop (E3

2121) and fill out a form to bring to the student shop CNC technicians to set up an

appointment.

You will then need to purchase stock material from Engineering Machine Shop (will need an

account number or money on Watcard) and machine it to proper dimensions prior to loading

it on the CNC.

1.1 Toolpath Generation

Create your CAM (Computer Aided Manufacturing) toolpaths by Mastercam; Mastercam X9

is installed in the Gear, Helix and Wedge lab computers. Students can sign out a dongle to

access the CAD room computer. Students are required to bring in their CAM toolpaths to the

technicians for inspection prior to using the CNC machine.

Students are expected to learn Mastercam through self-study and can get help from the

technicians. There are a number of online resources to help you with this, Mastercam

Getting Started Series is a good start.

Students are also required to know machining fundamentals. This guide will provide some of

the main concepts, more can be found through other online resources.

Mastercam Getting Started Series – see Machine Shop Website for link

Helman CNC G Code - Beginners guide to G code (not essential, good to know some to

understand the language used to control CNC machines)

http://www.helmancnc.com/simple-g-code-example-mill-g-code-programming-for-beginners/

http://www.helmancnc.com/simple-g-code-example-mill-g-code-programming-for-beginners/

1.2 Allowed Materials

Below is a list of the materials that are allowed to be machined on the Engineering Student

Machine Shop CNC.

● Aluminum

● Mild Steels

● Plastics

● Brass

● Bronze

● See Engineering Machine Shop (EMS) CNC Operators or student shop CNC

operators about any other materials

1.3 Background Information

Here is a list of background information and tools for generating the speeds of the CNC

machine for your toolpath. A general milling diagram with important terminology can be

found in Figure 1.

Figure 1 - General Milling Diagram [1]

Feed Rate (Milling Machine) refers to how fast a milling-tool moves through the material

being cut. This is calculated using the Feed Per Tooth (FPT) to come up with the Inches

Per Minute (IPM) that a milling cutter can move through a particular type of material. Thus,

a Four-Flute End-Mill will cut through material at twice the speed of a Two-Flute End Mill.

Feed Rates will decrease with dull tools, a lack of coolant, or deep cuts.

Diameter refers to the diameter of the cutting tool-bit(Mill/Drill). *As the diameter gets bigger

use a slower RPM.

RPM (Revolutions Per-Minute) is the turning speed of whatever is spinning. On a Mill or a

Drill it is the rotation speed of the cutting-tool. *Using Cutting Speed and Diameter you can

calculate RPM as shown further down on this page.

When calculating spindle speed (RPM), round down to the slower speed option offered by

your Lathe/Milling Machine/Drill. Operations like Threading, Knurling, or Parting-off, require

much slower speeds (Generally 1/3 to 1/4 Calculated RPM for Threading, Knurling &

Parting-off).

1.4 Equations

Using the following formulas and Table 1-3, calculate the spindle speed, cutting feed and

feed rate for your part. Use the lower bound speeds, only use higher speeds after consulting

a technician.

Spindle Speed (RPM)

𝑆𝑝𝑖𝑛𝑑𝑙𝑒 𝑆𝑝𝑒𝑒𝑑 =𝐶𝑢𝑡𝑡𝑖𝑛𝑔 𝑆𝑝𝑒𝑒𝑑 (𝑆𝑢𝑓𝑎𝑐𝑒 𝐹𝑒𝑒𝑡 𝑝𝑒𝑟 𝑀𝑖𝑛𝑢𝑡𝑒) × 12

𝑇𝑜𝑜𝑙 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟 (𝐷) × 𝜋

*note SFM values are different for milling and drilling

Cutting Feed (IPR)

𝐶𝑢𝑡𝑡𝑖𝑛𝑔 𝑆𝑝𝑒𝑒𝑑 (𝐼𝑃𝑅) = 𝐹𝑒𝑒𝑑 𝑝𝑒𝑟 𝑇𝑜𝑜𝑡ℎ (𝐼𝑃𝑇) × 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑇𝑒𝑒𝑡ℎ

Feed Rate (IPM)

𝐹𝑒𝑒𝑑 𝑅𝑎𝑡𝑒 (𝐼𝑃𝑀) = 𝐶𝑢𝑡𝑡𝑖𝑛𝑔 𝑅𝑎𝑡𝑒 (𝐼𝑛𝑐ℎ𝑒𝑠 𝑃𝑒𝑟 𝑅𝑒𝑣𝑜𝑙𝑢𝑡𝑖𝑜𝑛) × 𝑆𝑝𝑖𝑛𝑑𝑙𝑒 𝑆𝑝𝑒𝑒𝑑 (𝑅𝑃𝑀)

Table 1 - Approximate Material Cutting Speeds

Material Cutting Speed High-

Speed Tool (SFM)

Cutting Speed Carbide Tool

(SFM)

Low Carbon Steel i.e SAE

1020

80-120 300-400

High Carbon Steel i.e. SAE

4140, 4340

60-100 200

Aluminum i.e. 6061 400-700 800-1000

Brass & Bronze 110-300 600-1000

Plastics 200- 500 1000

Table 2 - Approximate feed rates for end mills (Feed Per Tooth)

Material .050’’ Depth of Cut .250’’ Depth of Cut

1/8" 3/8" 1/2" 3/8" 3/4"

Plain Carbon Steels

(SAE 1020)

.0005-.001 .002-.003 .003-.004 .001-.002 .002-.004

High Carbon Steel

i.e. SAE 4140, 4340

.0005-.001 .001-.003 .002-.004 .001-.002 .003-.004

Cast Aluminum -

Hard

.001 .003 .005 .003 .006

Brasses & Bronzes .0005-.001 .003-.004 .004-.006 .002-.003 .004-.006

Plastics *Much

Variation

.002 .004 .005 .003 .008

Table 3 - General table for drilling speeds (DFM, RFM)

Material AISI/SAE/ASTM Designation Drilling

Feet/Minute

Reaming

Feet/Minute

Free machining

plain carbon

steels

1108, 1109, 1115, 1117, 1118, 1120,

1126, 1211

100 - 120 75 - 80

Free machining

alloy steels

(resulfurized)

4140, 4150 30 - 90 15 - 60

Wrought

aluminum

6061-T6, 5000, 6000, and 7000 series. 350 - 400 350 - 400

The student machine shop has tool libraries available for aluminum and steel for use in

creating toolpaths Mastercam. The tools in these libraries have calculated feed rates and

spindle speeds contained within them. Ask the CNC Technicians from the Student

Engineering Machine shop in order to obtain the libraries. You can use the equations and

tables above for reference and for future calculations for any new tools or perhaps on your

own CNC machine.

1.5 Available Tools

Choose the appropriate tools for your job. Pick a tool with a length and diameter that is

sufficient for the cutting procedure.

The tools in Table 4 are available in the Engineering Student Machine Shop. Please inquire

about additional tools from the Student Shop Technicians if additional tools are required.

If you load in a new tool by yourself, it is VERY IMPORTANT that you enter tool offsets

properly and get a technician to verify it before starting your job.

Table 4 - Tools available in the Engineering Student Machine Shop

Tool # Tool in use

1 1/4” Spot Drill

2 1/8” Carbide End Mill (4 Flute)






8 3/4” HSS End Mill (4 Flute)

9 1” End mill (3 Flute Index able insert) Used for Facing and Roughing

10 2” Face Mill Used for Facing

11 3/8” Bull Nose End Mill (4 Flute) Used for Roughing

12 1/4” Ball Nose End Mill (2 Flute)



15

16

17

18 Drill Chuck

19 Drill Chuck

20 Drill Chuck ( Used for set up)

2.0 Milling Operations

This part will introduce methods and operations of milling.

2.1 Cutting Methods

There are two methods of cutting when milling, conventional and climb milling, which can

be seen in Figure 2.

Conventional Milling

Cutter rotates against the direction of the feed

Width of metal chip starts from zero and increases as the cutter finishes slicing

Upward forces are created that tend to lift the workpiece during face milling

Surface finish is worse because chips are carried upward by teeth and dropped in front of cutter

Tools wear faster than climb milling

Climb Milling

Cutter rotates against the direction of the feed

The width of the chip starts at maximum and decreases

Chips are dropped behind the cutter, less chips getting cut

Less wear, with tools lasting up to 50% longer

Improved surface finish because of less recutting

Figure 2 - Conventional versus Climb Milling [2][3]

Conventional milling is suggested on manual machines since these machines are prone to

backlash. The table and the workpiece tends to be pulled into the cutter when climb milling. If

there is any backlash, the tool may break if the cutting forces are great enough.

On the CNC, conventional milling can be used to make rough cuts, and a fine or smooth

surface finish cut can be done by climb milling.

2.2 Cutting Operations

These are some of the basic operations that can be used on the CNC machine. They can be

generated in a toolpath through Mastercam.

Facing

milling of work piece surfaces

produces flat surfaces to required length

Tool #10 on the CNC tool carousel

Figure of facing to the right [4]

Pocketing

An end mill is fed across the workpiece at a certain

spindle RPM to make features such as a profile, slot,

pocket, or even a complex surface contour

The depth of a feature can be made in one pass or in

multiple passes of small depth of cuts. Multiple passes is

generally preferred to reduce load on cutter tool

A roughing pass with a rough cutting tool is typically first

used to cut most of material and then a final finishing

pass with a sharper tool is used for a better surface

finish

Figure of facing to the right [5]

Drilling

Use tools #18 and #19 for attaching desired drill bits

Use a spot drill or center drill the hole to initially mark hole

positions

Make the drill operation deeper for through holes such

that the drill passes the bottom of stock

Can also drill a pilot hole and drill at a manual drill press

Figure of drilling to the right [6]

3.0 CNC Operations

The CNC is NOT to be operated without supervision by an approved CNC technician.

Students should be first trained by a technician prior to using the machine. The following

sections should only be used for reminders/references.

3.1 Turning on the Machine

1. Press “POWER ON”

2. Make sure “EMERGENCY STOP” is off

3. If machine has not been operated on for more than 3 days, run a spindle warmup

program. This will be a half hour long program.

Figure 3 - Start and Emergency Stop

3.2 Jogging the Table

To jog the table:

1. Press the “HANDLE JOG” button on the panel

2. Select the axis you would like to move

i. E.g. Move X axis, press “+X” or “-X”

3. Select the jogging step size. 0.01’’ or 0.001’’or 0.0001’’.

4. Rotate the handle jog dial to move the axis

Figure 4 - Manual Jog Controls

Figure 5 - CNC XYZ Coordinates

3.3 Clamping Work Piece

The following is an example of clamping in a cubical work piece. Setup may be different for

different work piece shapes and sizes.

1. Make sure that the work piece is clamped in the vice

2. If workpiece is mounted parallels, half tighten clamp and use a rubber hammer to

hammer down the work piece until the parallels are tight and cannot slip out. Then

fully tighten the vice

Figure 6 - Clamping Workpiece in Vice

3.4 X and Y Axis Coordinate Zeroing

An example is shown below for finding the X and Y coordinate zeros for a rectangular work

piece. Depending on your work piece, the edges may be different but the process of

inputting the zero coordinates into the machine will not.

The process is as follows:

1. Switch to tool 20, the empty drill chuck, to hold the edge finder

2. Press “MDI”, then “ORIENT SPINDLE” to lock up spindle to tighten edge finder

easier (DO NOT TORQUE TOO HARD)

3. To switch the tool:

i. Press “MDI/DNC”

ii. Type in “T20” This will select Tool #20, which is the empty chuck

iii. Press “ATC REV”

4. The edge finder needs to be rotating when it is finding an edge

i. Press “MDI/DNC”

ii. Should read “S750 M03” on the Memory panel. Can also manually type in

“S750 M03” to start spinning the spindle at 750 RPM

iii. Press “ENTER” to run program, spinning spindle at 750 RPM

5. Handle jog the edge finder to the Y axis reference point

6. Slowly jog the edge finder until it touches the edge and the bottom moves

Figure 7 - Using the Edge Finder to Find Y Zero Offset

On the panel:

1. Press “Position”

2. Select the axis you want to zero and then press “Origin”

3. Offset the radius of the edge finder by moving in 0.100’’

4. Press “Origin”

5. Press “OFFSET” until “WORK ZERO OFFSET” is highlighted

6. Scroll over to the Y axis column

7. Press “PART ZERO SET” to set the zero coordinate to this location

Figure 8 - Y Axis Zero Offset On Panel

Above is an image of the work panel screen after you have found the zero coordinate for the

Y axis. Notice at how for the “Work G54” column, the value is 0.0000.

Figure 9 - Using the Edge Finder to Find X Zero Offset

For finding the X axis zero coordinate, the process is the same as above, except the edge

finder needs to be moved to the edge you want to zero.

3.5 Z Axis Offset

To pick up the zero coordinate on the z axis:

1. Mount a dial gauge into the empty chuck (Tool 20)

2. Place a 123 bar vertically onto the platform

3. Adjust the dial gauge such that the tip will touch the 123 block at an angle

4. Slowly jog the Z axis down for the dial gauge to touch the 123 block

5. Bring down the dial gauge until you get a reading on the dial gauge (remember the

value of the reading on the dial gauge)

6. On the panel,

i. Press “POSITION”

ii. Press “Z+ or Z-“ to access the Z axis coordinates

iii. Press “ORIGIN”

7. This process will give you a reference point for zeroing the top face of your work

piece

Figure 10 - Z Axis Zero Offset

8. Next, jog up the dial gauge to touch the top face of your workpiece

9. Lower the Z axis until the dial gauge reads the same value as previously on the 123

bar

Figure 11 - Z Axis Offset On Panel

10. On the panel,

i. Press “Offset” until the “WORK ZERO OFFSET” panel is highlighted white

ii. Type in the value indicated in the operator column for the Z axis on the “Work

Zero Offset” Z axis column

iii. Press “F1” to zero the work piece top face

3.6 Loading Toolpath onto CNC

To load your toolpaths:

1. Insert a USB stick onto the side panel

2. Press “LIST PROGRAM”

3. Select over to the “USB” tab

4. Select your NC toolpath

5. Press “SELECT PROGRAM”

6. Press “Enter”

After going through these steps, your generated toolpath will be copied over to the machine

and machine is ready to run your toolpath.

Figure 12 - Loading NC Program into CNC

4.0 Citations [1] CustomPartNet. Milling Speed and Feed Calculator. Digital image.Custompart.net. N.p., 2008.

Web. 24 May 2016. <http://www.custompartnet.com/wu/milling>.

[2] Rocketmagnet. Conventional Milling. Digital image. Wikipedia, 13 Aug. 2007. Web. 24 May

2016. https://commons.wikimedia.org/wiki/File:Conventional_Milling_01.png

[3] Rocketmagnet. Climb Milling. Digital image. Wikipedia, 7 Aug. 2007. Web. 24 May 2016.

<https://commons.wikimedia.org/wiki/File:Climb_Milling_01.png>.

[4] CustomPartNet. Face Milling. Digital image. Custompart.net. N.p., 2007.Web. 24 May 2016.

<http://www.custompartnet.com/wu/milling>.

[5] CustomPartNet. Axial Depth of Cut. Digital image. Custompart.net. N.p., 2007. Web. 24 May

2016. <http://www.custompartnet.com/wu/milling>.

[6] CustomPartNet. Drilling. Digital image. Custompart.net. N.p., 2007.Web. 24 May 2016.

<http://www.custompartnet.com/wu/milling>.

https://commons.wikimedia.org/wiki/File:Conventional_Milling_01.png

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STUDENT ENGINEERING SHOP CNC STARTER MANUAL