When we think of robots we imagine some science fiction character from Star Wars, a
Team 2084 is working on their Robot for the FIRST Competition
mechanized device crawling around a war zone, or perhaps a whirling armed machine in a manufacturing facility. A growing number of Pinpoint Laser Systems customers use robotics and rely on our products to calibrate and guide them in their every day routines. Whoever thought that robots could be used to teach young students?
Well this is happening right now in fact, through an educational program called FIRST. The FIRST program is targeted at high schools, around the world, and provides a game challenge in which high school-aged students must design and build a robot device to meet a particular challenge in friendly competition.
Teams have exactly 6 weeks, to the hour, to design, fabricate test, and debug a fully working robot that is then shipped to a regional competition center. In early April, teams assemble, form alliances, make new friends, compare engineering notes, and send their robots into competition. The 2011 competition involved robots working telemetrically to pick up and manipulate 2-foot diameter inflated shapes and hang them on pegs located as high as 10 feet above the playing arena floor in a timed setting. At the end of each competition round the robot would back up to a 10 foot tall pole and release a small climbing robot, called a “mini-bot” that would climb the pole in a matter of seconds and trip a switch to gather more team points. The 2012 Team Challenge is called “Rebound Rumble” and high school teams are working busily right now to develop robots that can essentially play basketball and balance on pivoting ramps – a real engineering challenge!
Team 2084 at work!
These teams are learning how to solve engineering challenges and working with mechanical design, mechanical assembly, electronics, pneumatics, vision systems, software and building impressive robots in the process. The FIRST program is drawing high school students into a fun and challenging program and at the same time exposing them to a wonderful engineering experience. The big take-away from this successful activity is putting young, future engineers together and letting them solve problems as a team, work through their differences, and build their confidence so that they can, together solve large complex problems. This program gives young students a powerful set of skills that are valuable in today’s workforce. Our country needs more of this, it is our future.
Pinpoint Laser Systems is the proud supporter of Team 2084 – “Robots By The C” which operates out of the Manchester Essex Regional High School in Manchester, MA.; http://www.robotsbythec.com. We donate engineering time through the mentor program, financial resources, machine shop, and design time. This international program makes a significant difference in students lives and we hope that you will be inspired by the FIRST program http://www.usfirst.org/roboticsprograms/frc and see how you and your company can participate.
Go FIRST and Go, Go Team 2084!
Illustration of Measuring Squareness
Many machine tools rely on the squareness or perpendicularity between moving tables or slidesand also the axis of travel for a cutting bit. Traditional methods for checking the squareness of machine tools rely on granite squares or jigs and fixtures coupled with precise dial indicators. The lengthy time and effort needed to perform these alignment checks has been a deterrent to their use. The development of the laser alignment system has made the task of checking squareness much easier, faster, and considerably more precise.
Here is how it works. A laser reference beam is projected down the length of one axis on a machine tool. A digital receiver measures the height of the laser beam to the machine table and the readings are used to guide the position of the laser beam until the readings on the table are equal to each other. The laser reference beam is now parallel to the slide table. At this point, a right angle optic is placed in to the laser beam.
CNC Machine Alignment
Pinpoint makes several of these devices and they are called the 90-Line Right Angle. The laser reference beam enters the 90-Line and passes through an optical component called a penta-prism which steers the laser beam until it exits the 90-Line at a very precise 90 degree, right angle. The optical design of the penta-prism, and Pinpoint’s alignment optics, ensure that the exiting and entering laser beams are precisely square to each other, regardless of the position and orientation of the 90-Line enclosure. Furthermore, the nosepiece of the 90-Line can be rotated through a full circle and the square exiting beam forms a square plane of light, relative to the incoming laser reference beam.
Placing the laser on the machine table or slide, in the path of the laser beam, creates a new right angle reference line that can be used to check the orientation and travel of other square machine axes. Moving the laser receiver along the square axis and taking readings will tell you if the two machine axes are square to one another and if they are not square, what corrections are needed. The 90-Line can check machine tools axes that lie in the same horizontal plane or check vertical planes as well. In addition to the great precision of the laser system, squareness measurements can be made over distances of 100 feet or more for checking large machines.
Laser alignment systems and optical accessories are expanding the measuring capabilities of manufacturing companies and allowing companies to align and repair their own production equipment.
When using a laser alignment system to check a machine or sub-assembly for straightness, flatness, bore alignment and many other geometric parameters, we often need to normalize the laser reference beam to some designated locations on the surface being measured. The laser reference beam is very straight and true but may not be aligned to the surface or mechanical features that you are measuring or checking. For example, imagine a guide rail that you want to check for flatness and at one end of the rail the laser is 2 inches above the rail surface and at the far end of the rail this distance is 2.5 inches. Intuitively, we would like to adjust the laser reference beam until it is a common height above the rail and then make our measurements.
However, the rail surface is not necessarily straight so we need to designate two locations on the rail, called datums, that we can use to establish a straight reference line. We were all taught that “two points in space define a line”. It is at these two designated points, or datums, on the rail that we use to “connect” the straightness of the laser reference beam to the surface that we are trying to measure. This step is frequently referred to as “normalizing” and is in many ways similar to calibrating or connecting the measuring system to the surface to be measured.
We can start by measuring the position or height of the straight laser reference beam relative to the rail surface at two designated locations. At these two locations we have a precise Laser Microgage reading of height and we also know the distance from the laser transmitter to the designated location. Now, we have two options to normalize the position of the laser reference beam to the surface we want to check; bucking in the laser or leaving the laser beam where it is and using math to normalize the readings. Both methods have their advantages and disadvantages.
First, we will consider “bucking in” which is the process of steering the laser so that the laser and the surface are physically parallel to each other at the two designated datum locations. The “bucking in” approach is iterative and involves moving the laser transmitter and/or the surface being measured and re-measuring the values at the two designated locations. This process continues until the readings at the two locations are the same indicating that the laser reference beam and the surface datums are now parallel. The measurement values may not be zero and this is easily achieved with a zero function on Pinpoint’s Laser Microgage display units. The advantage of bucking in the laser and the measured surface is that the receiver can now be moved anywhere and readings that deviate from your zero value indicate high or low regions on the surface being measured. The disadvantage of the bucking in process is that it takes time and sometimes requires finesse to position the laser beam in exactly the correct position and repeat the measuring process. Over the years we have found that many Pinpoint customers have used this process with traditional instruments and prefer to continue with this method.
An alternative to the “bucking in” process is to bring the laser beam generally close to parallel with your two designated datum locations and then use math to calculate the position of the laser beam above the surface that is being measured. Based upon the two selected datum locations on your measured surface, the math involves calculating a rise over run value, commonly referred to as slope, which can then be applied to all the other measurements taken. Based on this information you can now calculate exactly what Microgage reading you should be seeing for each given location on the surface if the surface were exactly straight. The difference between this calculated value and the measured value that you obtain from the Laser Microgage tells you the surface error and which direction (up or down) this error is occurring.
For example, consider a laser reference beam that is not exactly parallel with a machine surface but with your Laser Microgage Receiver, you record a height value of 0.005 inch and 0.010 inch at locations that are 20 inches and 40 inches from the end of the surface, respectively. A simple calculation tells you that halfway between 20 and 40 inches the reading should be 0.0075 inch. If your Microgage measurement does not produce this value then the difference tells you the error in the straightness of the surface and also the direction of this error. Measurements can be made in many places along the measured surface and compared with the calculated values to find the difference in the values or delta values for the surface being measured.
The advantages of this mathematical approach is that it reduces the time needed to “buck in” the laser and is very accurate for measuring. The disadvantage is that for each measurement made you also need to record the position or distance of the laser from the receiver for the calculation at that location. At Pinpoint, we have spreadsheet applications and other tools that make this process quick and easy.
Using a computer or laptop and Pinpoint’s interface option and Capture software you can record many readings and run the calculations quickly and accurately. The Microgage can be set to record readings at a set interval and export these readings into a spreadsheet application. If the Microgage receiver is moved at a fixed rate, and the readings are recorded at a set time interval, one can gather hundreds or thousands of readings along a moving slide or surface and see with great detail how straight the travel or surface really is.
We have talked about the Bucking In process and normalizing measurement readings by measuring distance and using mathematical techniques for each reading. Both methods have their advantages and disadvantages and we have worked for years with customers that are comfortable with one method or the other and with great success. We encourage questions and comments on these methods and have full write-ups and spreadsheet applications to help with each.
Here at Pinpoint Laser Systems we are frequently asked about what to
Laser Microgage DCU 2D
do with all these measurement readings. Some people set up their Laser Microgage to check the straightness of a machine or the squareness of a Z axis and they just want to see a few readings to confirm that their machinery is set-up and well aligned. They might write down 4, 6, or 10 readings in a notebook and call it done.
Other Laser Microgage users want to record sets of readings and save them. In some cases they might only be interested in a few readings and others might want to record several thousand readings. With our computer interface and Pinpoint Capture software you can do it all. The “Manual” recording mode lets you save one set of readings at a time, each with a personal note, time and date stamp. The “Auto-Log” recording mode lets you automatically save readings over time on your computer – from a single reading every hour up to 50 readings a second! These readings are saved in an ASCII text file on your computer and can be viewed in a variety of programs and industrial software.
Recently, Pinpoint introduced a new on-board storage capability for the Laser Microgage 2D where you can save readings right on your portable display unit. At a convenient time, your Microgage Display is connected to your PC or Laptop and these readings are uploaded, through the Capture program, and saved as a text file. Your readings can then be viewed, anytime, in spreadsheets and imported into manufacturing programs and other production tools.
Screen Shot of DCU 2D
Pinpoint Laser Systems has a number of complimentary spreadsheet templates for analyzing your measurement readings andproviding calculations and useful information to evaluate your machinery and equipment. We can also develop custom software for your specific needs. Please call us or check out our product solutions for storing and recording your readings; DCU-2D and DCU-2000.
Microgage 2D Universal kit
You do not have to be. There are a few key terms and once you understand these you are ready to talk about a wide variety of measuring devices. The important terms include; range, sensitivity, resolution, precision, repeatability, accuracy and reliability. These terms and definitions apply to measuring temperature, distance, pressure, magnetic fields, weight – just about everything you can measure quantitatively. Let’s start with range. This is the difference between the lowest and the highest measurement that the device or instrument can measure. For example, consider your bathroom scale with a range of 300 pounds. From near zero to 300 pounds it will provide readings – outside that range the scale is unreliable or might even break.
Sensitivity is also known as resolution and these are the smallest increment of measurement that a measuring device can detect. For example your bathroom scale might show weight in tenths of a pound so we would say this scale has a sensitivity of 0.1 pound.
Precision and repeatability are two terms that are used interchangeably to describe the consistency of a measurement. Note, that we did not say “accuracy”, we’ll talk about this in a moment. Precision is the ability of a measuring system to provide the same reading value for multiple measurements of the same parameter in the same conditions. This measurement of consistency does not however indicate the measuring values are true, accurate or reliable. Let’s go back to your bathroom scale example; if you step on and off the scale 15 times, do you get the same reading every time? Your precision and repeatability are good if you get the same value over and over.
And finally there is accuracy which is also occasionally referred to as reliability. Accuracy is the ability of a measuring device to not only have good precision and repeatability but also for the values to be correct to some known and accepted standard. Using our bathroom scale example, let’s say you truly weigh 180 pounds but every time you step onto your bathroom scale the reading says 187 pounds. The precision of your scale is good because you get the same reading each time but the accuracy is off by 7 pounds.
Typically, a measuring instrument is designed with a specific range, sensitivity and resolution and these do not change. Calibration is used to adjust the measuring output for optimal precision, repeatability, accuracy and reliability over the range of the instrument.
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