LEGO Mindstorms NXT X-Y Plotter

PDF24    Send article as PDF   
I’ve have built my first LEGO Mindstorms NXT Plotter (printer) which is programmed with RobotC. The plotter draws pictures by drawing whole lines, known as vectors. An X–Y plotter is a plotter that operates in two axes of motion (“X” and “Y”) in order to draw continuous vector graphics. The term was used to differentiate it from standard plotters which had control only of the “y” axis, the “x” axis being continuously fed to provide a plot of some variable with time.

LEGO Mindstorms NXT X-Y Plotter
LEGO Mindstorms NXT X-Y Plotter

Plotters differ from Inkjet and Laser printers in that a plotter draws a continuous line, much like a pen on paper, while inkjet and laser printers use a very fine matrix of dots to form images, such that while a line may appear continuous to the naked eye, it in fact is a discrete set of points.

A ‘NXT Touch Switch‘ is used to track the Pen’s Position: Up or Down. The Pen Position is calibrated by slowly raising the Pen via a Gear Rack, driven by a third NXT Motor. Once the switch is activated the motors encoder is reset to enable accurate Pen Positioning.

The pen on the plotter is raised and lowered by a NXT Servo Motor. The Pen has a ‘Gear Rack’ glued to it. This way the pen can be placed tightly onto the paper. This solution however slows downs the printing process, as raising and lowering the pen is set quit slow.

LEGO Mindstorms NXT X-Y Plotter: Y-axis & Pen Control
LEGO Mindstorms NXT X-Y Plotter: Y-axis & Pen Control
LEGO Mindstorms NXT X-Y Plotter: Y-axis & Pen Control

Calibration of the the X and Y motors relies on a ‘RCX Touch Sensor‘ each. I prefer to use these older sensors as they are considerably smaller the their NXT version. The motors are backwards until they hit their respective touch sensors, and then reset the encoders on the Motors. The touch sensors serve the simple purpose to calibrate the robot.

LEGO Mindstorms NXT X-Y Plotter: X-axis
LEGO Mindstorms NXT X-Y Plotter: X-axis
LEGO Mindstorms NXT X-Y Plotter: X-axis

The paper is held firmly between the bottom of the ‘Plotter Bed’ and the table top via Double Flexible Axle Connectors. The pen is moved by a motors on the X-axis and Y axis rails. Using the NXT servo motors, the plotter can move very precisely, allowing the plotter to draw almost anything with some extra programming.

LEGO Mindstorms NXT X-Y Plotter: Printer Bed
LEGO Mindstorms NXT X-Y Plotter: Printer Bed

Download RobotC Source Code: X-Y_Plotter.C

 

 

For ease of construction, and to make life a little easier for me  whilst producing the [LDD] CAD drawings I split the Instructions into three separate parts. You will need a considerable number of extra Technics parts than comes with the standard ‘LEGO Mindstorms NXT’.

 

I was surprised how well this LEGO Mindstorms NXT “X-Y Plotter” worked. After viewing a few other versions of LEGO Mindstorms NXT plotters on the internet, among the manual feed versions this seems to be the simplest to construct. Despite of it’s appearance, thanks to the LEGO Technics 5 x 7 Open Centre Lift-arms and Technics 5 x 11 Open Centre Frame Lift-arms, the whole structure is extremely rigid.

Only if the the ‘Open Centre Lift-arms’ were available years ago, it would have save a lot of frustration and bad language!

Previous Post

RobotC: Autonomous Holonomic Platform using 4x Sonars

This Autonomous Tri-Drive Holonomic Platform is fitted with [rotacaster] and uses 4x Ultrasonic Sensors for navigation. The RobotC Code is based on my previous post on using multiple Sonar Sensors ... Read more

Next Post

Using LEGO Mindstorms RIS (RCX) KIT with Windows7

Installing LEGO Mindstorms Robotics Invention System (RIS) on to a Windows7 PC is frustrating to say the least, as I've just discovered this while setting up my son's computer to ... Read more

Short URL: http://tinyurl.com/hssvnvt

Leave a Reply

Your email address will not be published. Required fields are marked *



Do NOT follow this link or you will be banned from the site!
error: Content is protected !!