Masters Project 1 - Detecting the Cutting Tip of Different Tools
Principal Aim of the Project
Using analogue data, acquired from rotating tools through a laser beam, produce an algorithm to obtain
the relative tip positions of different tools when moving vertically and horizontally through the beam.
(Enabling effective diameter and length measurement.)
Project Description
Non-contact tool setting devices for determining the position of a tool comprise a light transmitter and
receiver. The laser-based transmitter sends a visible beam in to the receiver unit and system circuitry
produces a signal when a predetermined level of beam is obstructed. The output signals are sent to the
machine controller allowing the position of tips to be rapidly established.
Due to geometry effects every tool tip will be located at a different position in the beam when the
predetermined level is obtained, even when they are progressing at the same constant feed rate, which
incurs positional inaccuracies.
The analogue signal to be analysed is obtained by progressing a rotating tool through the laser beam at
a constant speed. The optical effect of passing a tool through the beam provides oscillations in voltage
around the white level finishing with a large increase just before the voltage gradually drops to zero,
which signifies complete obscuration of the beam.
As a calibration pin passes horizontally through a laser beam, to measure diameter, it
produces a signal of the form shown in Figure 1. The imperfect alignment of the beam
and geometry of the tool gives rise to different signals when passing horizontally
through either side of the beam and vertically.
A rotating tool passing through the laser beam produces signals similar to the form
shown in Figure 2 and Figure 3, corresponding to diameter and length measurement,
respectively. These signals tend to consist of oscillations throughout where obscuration
varies between minimum and maximum voltages. Considering Figure 2 and Figure 3 in
detail, the peaks and troughs in the data form a similar curve as given by the calibration
pin, which is effectively the representation of the cutting edge of the tool.
The ideal algorithm would be one that can be utilised for both diameter and length measurement at any
constant feed rate. The time taken to progress through the beam is different for each tool and has the
effect of changing the slope of the cutting edge of the tool. It can be noticed that when tools are moved
in to the beam to measure length the time to total obscuration varies considerably, however for
diameter measurement the time is similar.
Resources/Background Required
This is a technical project that will require the use of software available in public and/or research
laboratories and requires innovative algorithmic design.
Possible Methods for Solution
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Wavelets
Frequency Domain
Pattern recognition
References
Tool setting for machine centres - http://www.renishaw.com/client/product/UKEnglish/PGP-142.shtml
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6mm Calibration Pin, Diameter
7
6
5
Voltage
4
3
2
1
0
-1
0
1000
2000
3000
4000
5000
Sample Number
6000
7000
8000
9000
10000
Figure 1: 6mm Calibration Pin, Diameter
10mm Slot Drill, 2 Teeth, Diameter
6
5
Voltage
4
3
2
1
0
1
1.05
1.1
1.15
1.2
1.25
Sample Number
1.3
1.35
1.4
1.45
5
x 10
Figure 2: 10mm Slot Drill, 2 Teeth, Diameter
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10mm Slot Drill, 2 Teeth, Length
6
5
Voltage
4
3
2
1
0
1.3
1.35
1.4
1.45
1.5
Sample Number
1.55
1.6
1.65
1.7
5
x 10
Figure 3: 10mm Slot Drill, 2 Teeth, Length
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