Lab 3 - CNC Tooling
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Transcript of Lab 3 - CNC Tooling
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7/30/2019 Lab 3 - CNC Tooling
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CNC Tooling
Lab 3:
Basics & Calculations
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Vertical Mill Cutting Tools
Identify each cutting tool found on the millingmachine. (Attempt to be specific)
In teams of 3, compete to find the most information abouteach cutting tool One person in the text book One person on the internet One person in a machinery handbook
Limit the entire exercise to 30 minutes
The winning team will have the most individual pieces ofinformation about each cutting tool
Winning teams will have first access to the CNC Vertical Mill
Instructor: Stop Here for Students
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Carbide Inserts
How would you characterize the carbide insert usedon the Vertical Mill?
In teams of 3, compete to find the most information aboutthat specific carbide insert One person in the text book One person on the internet One person in a machinery handbook
Limit the entire exercise to 15 minutes
The winning team will have the most individual pieces ofinformation about the carbide insert
Winning teams will be team captains for the team projects
Instructor: Stop Here for Students
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Vertical Mill Spindle Speed
Feed rate for a cutting tool is dependent upon spindle speed.As 3 member teams, create lists to answer the following (limittime to 15 minutes): In manual mode, how is spindle speed controlled on the
VMC190xi? What options does the operator have for controlling/monitoring
spindle speed? What are the anticipated differences in torque and the resulting
stalling of the tool bit, with relation to driving horsepower of the
mill? What do you anticipate would happen if the mill is in CNC automaticmode and the tool bit stalls while cutting?
Instructor: Stop Here for Students
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Answers
Spindle speed on the VMC190xi can not be accurately controlledby using the manual pushbuttons. Therefore, the only manualmethod of controlling spindle speed is through the Boxford
software. Optionally, an instrument that reads out in RPM can be mounted to
display spindle speed
As horsepower increases, the variation in spindle speed due tocutter loading decreases. Also, for machines with geared or beltdriven spindles, the slower spindle speeds at the same motor
speed will have more torque and less speed variation. When in CNC automatic mode and the tool bit stalls while cutting,
the table will further bind the tool into the work piece and maybreak the tool, damage the work piece, stall the x-y tablemovements,
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Vertical Mill - Tapping
When tapping using a vertical mill, how is
torque on the tap limited to reducebreakage?
Instructor: Stop Here for Students
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Answer:
Recommended Drill Bit size is chosen for tap A cutting fluid is specified for the material
Taps are discarded when worn Taps are matched to the materials machined Spiral fluted taps help minimize the torque while cutting threads
by keeping shavings from binding within the cutting edges A tap clutch accessory can be purchased for about $500 which
can be programmed to slip at specific torques
A reversing motion is needed by some taps to clear metalshavings to prevent binding
Some milling machines have torque sensors that allowfeedback to reverse the spindle when a preset torque isexceeded
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Calculating Spindle Speed
Each material has recommended cutting
speeds listed in sfpm.
Sfpm = 3.14 x tool diameter x RPM12
Solve for RPM
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Calculating Spindle Speed
If a material calls for an optimal cutting rate
of 250 feet per minute, what should thespindle speed be set at?
Assume end mill
Aluminum stock
Instructor: Stop Here for Students
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Calculating Spindle Speed
RPM = SFPM x 12
Tool Diameter 3.14 RPM = 250 x 4 x 12
1 3.14
RPM = 3822 or about 3800 rpm
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Calculating Spindle Speed
Using Appendix C, what size of end mill and
spindle speed should be used when millingaluminum?
As a 3 member team, determine the appropriaterelationships
Limit this exercise to not more than 15 minutes
Instructor: Stop Here for Students
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Calculating Spindle Speed
Aluminum sfpm = 250 when using HSS Sfpm = (tool diameter) x RPM x 3.14 / 12
Solving for variables on one side and constants on the other RPM x tool diameter = SFPM x 12 / 3.14
Therefore, for any tool diameter there is a unique spindlespeed, but there is no ideal tool diameter and speed
combination tool diameter is restricted by available power, clamping of the
material, the smallest radius feature of a machined object,and other criteria
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Calculating Tap Feed Rate
Given the requirement to tap a -20prepared hole in a aluminum plate;
what 2 pieces of information are necessaryto manually control the tap operation alongthe z-axis?
How many seconds will it take to tap each holeusing spindle speed calculations?
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Hint
Aluminum sfpm = 250
1/4x20 tap ~1/4 diameter cutting surface RPM = 250 x 4 x 12 = 4000 rpm
1 3.14
20 threads per inch or 10 threads per
1 revolution per thread
Instructor: Stop Here for Students
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Answer
10 revolutions x min x 60 sec = 0.15 sec4000 rev 1 min
Therefore, such operations can only be performedusing CNC equipment Slower manual operations can be performed at a cost of
labor
Always check the tool manufacturersrecommendations for determining best spindlespeeds, appropriate cutting fluids,
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Calculating Feed Rates
Associated with Feed Rates are the actual
table positions in the X and Y axis Using full size manual vertical mills, how are the
actual positions of the X and Y axis
controlled/measured?
Go to the next page for a picture of a full sizemanual vertical mill
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Full Size Vertical Mill
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Manual Feed Rates
What are the options for manual feed ratecontrol/monitor of the x-y axis on theVMC190xi? Setup the Boxford Software to display the manual
control of x-y axis feed rates Each team should be splitting the tasks
There are 4 computers with identical software, hooked todifferent types of machines
The Boxford manuals can be accessed on all of the labcomputers, and also from the NSF sponsored Wikiwebsite
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Team Problems
Youve had several opportunities thus far to operate
as a TEAM List your insights as to why you believe the team suffers in
certain areas
Separately list what benefits you achieved by working as ateam
As a class, create a comprehensive list of rules foroperating as a team
Limit this exercise to not more than 20 minutes
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Evolved List of Team Rules
Every semester the class has been asked to do this exercise,and the following is a compiled list of rules that students havecited that are believed to contribute to team productivity use the Result Management tool cited earlier if there is a conflict
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CNC machining from CAD Drawings
Capturing the specific features of a design in
a binary file provides the opportunity tomachine parts in an automated mode
Remove the tooling from the VMC190xi andput the mill in the Home Position
See Lab 2
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Selecting a sample CAD drawing
Video for CAM implementation of a sample
CAD drawing goes here
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Run the CAM software without tooling
For the remainder of the lab, every student should remove all tooling and work pieces from the 4 CNC
machines Start each CNC machine
Put each machine manually in the Home Position
then mock machine a sample CAD file Be ready to hit the Emergency Stop Button to prevent a
collision between the spindle, vise, x-y table, chuck, wallsof the enclosure,
If time permits, introduce precision orientation ofthe bench vise