student engineering shop cnc starter manual · .002 .004 .005 .003 .008 table 3 - general table for...
TRANSCRIPT
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/
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)
3 3/16” Carbide End Mill (4 Flute)
4 1/4” Carbide End Mill (4 Flute)
5 5/16” Carbide End Mill (4 Flute)
6 3/8” Carbide End Mill (4 Flute)
7 1/2” 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)
13 3/8” Ball Nose End Mill (2 Flute)
14 1/2” 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>.