Author Topic: Simple drawing robot / XY plotter  (Read 7001 times)

0 Members and 1 Guest are viewing this topic.

Offline Ecir HanaTopic starter

  • Jr. Member
  • **
  • Posts: 13
  • Helpful? 0
Simple drawing robot / XY plotter
« on: August 08, 2009, 08:44:39 AM »
Hello,

sorry for very newbie questions, I'm very new to all this.

I would like to build a robot which can draw curves with a pen. The size of drawing area would be something like 30 x 40 cm (A3), it would plot just in 2D so X and Y only. And for now, the pen could just either touch the paper or not (i.e. no Z, or pressure) and is just glued to the arm.

I really would like it to be very precise (so it could draw straight lines or circles or Bezier paths, even very small ones, like 6 pt letters). It doesn't have to be very fast and it's ok to have complex software. I also like Arduino, if that limits the choices down a bit. Oh, and cheap is ok, too.

My questions are:

- What "kind" of robot do you recommend? Should I go for "Cartesian" type, like:
http://www.garagefab.cc/contraptor
or "Scara" type, like:
http://maschinenringraum.blogspot.com/2009/06/articulated-plotting-robot-for-10.html

- What kind of steering should I use? Servos, DC motors, steppers? Isn't it the case with steppers that to draw a curve first it has to be broken up to many tiny lines?

- It is possible to know when a line to draw ends so the robot could gradually slowdown - what kind of motor do I need for this? Is it possible to regulate the speed of simple DC motor, say by this thing "PWM" (pulses)?

- I like that Scara-one very much, however it seems to be very imprecise (~0.5 cm). Is it possible to improve it? I mean, maybe I need to get some servo with say 10 degrees precision, attach it to a gear box with 1000 : 1 ratio and for the size of arm like I want it would more than precise?

- Does it make sense to put all the gears and motors off the arm and to somehow couple its rotations to the joints? Or maybe the servos are so light that this is not needed?

- For lifting and lowering the pen is it ok to use solenoid?

Well, sorry once again for such a basic questions and thanks for any answers!
« Last Edit: August 08, 2009, 08:49:25 AM by Ecir Hana »

Offline wil.hamilton

  • Robot Overlord
  • ****
  • Posts: 207
  • Helpful? 6
  • rtfm
Re: Simple drawing robot / XY plotter
« Reply #1 on: August 09, 2009, 07:27:09 AM »
- What "kind" of robot do you recommend? Should I go for "Cartesian" type, like:
http://www.garagefab.cc/contraptor
or "Scara" type, like:
http://maschinenringraum.blogspot.com/2009/06/articulated-plotting-robot-for-10.html


I would definitely use a Cartesian type. you would have much more control  over what you are drawing

- What kind of steering should I use? Servos, DC motors, steppers? Isn't it the case with steppers that to draw a curve first it has to be broken up to many tiny lines?

if you're building the cartesian type, i would use either stepper motors or DC motors with encoders, they both allow for infinite rotation and position control
if you're going to build the arm type i would use servos because the motor wouldn't need to spin the whole way around

- It is possible to know when a line to draw ends so the robot could gradually slowdown - what kind of motor do I need for this? Is it possible to regulate the speed of simple DC motor, say by this thing "PWM" (pulses)?

yes you can regulate the speed of a DC motor using PWM, if you were using dc motors with encoders you could, for example, say you're drawing a line 100 units long.  you can draw at full speed for the first 90 units then slow the motor down for the last 10

- I like that Scara-one very much, however it seems to be very imprecise (~0.5 cm). Is it possible to improve it? I mean, maybe I need to get some servo with say 10 degrees precision, attach it to a gear box with 1000 : 1 ratio and for the size of arm like I want it would more than precise?

you can buy higher precision servos.  look into digital servos they are more precise than standard servos

- Does it make sense to put all the gears and motors off the arm and to somehow couple its rotations to the joints? Or maybe the servos are so light that this is not needed?

servos are not very heavy, you can use higher torque servos if you feel the arm might be heavy

- For lifting and lowering the pen is it ok to use solenoid?

you could use a solenoid, it might be just as easy to use a servo to lift and lower the pen

on other notes, i found an instructables on how to build an xy plotter http://www.instructables.com/id/Low_Cost_Hobby_Servo_XY_Table/
use the google.  it's your friend.

Offline Ecir HanaTopic starter

  • Jr. Member
  • **
  • Posts: 13
  • Helpful? 0
Re: Simple drawing robot / XY plotter
« Reply #2 on: August 10, 2009, 01:22:49 PM »
Thank you very much for the answers!

Quote
I would definitely use a Cartesian type. you would have much more control  over what you are drawing

I see. There is even this project http://www.reprap.org where one can find lots of useful info on how to build Cartesian plotter.

Quote
on other notes, i found an instructables on how to build an xy plotter http://www.instructables.com/id/Low_Cost_Hobby_Servo_XY_Table/

Interesting!


Offline wil.hamilton

  • Robot Overlord
  • ****
  • Posts: 207
  • Helpful? 6
  • rtfm
Re: Simple drawing robot / XY plotter
« Reply #3 on: August 10, 2009, 02:06:06 PM »
no problem, if you have any more questions i'd be glad to answer them
use the google.  it's your friend.

Offline sonictj

  • Supreme Robot
  • *****
  • Posts: 416
  • Helpful? 11
Re: Simple drawing robot / XY plotter
« Reply #4 on: August 10, 2009, 06:24:30 PM »
Take this into account
A DC motor + encoder has more precision than a stepper, but it is difficult to control a dc motor with a higher accuracy with out well tuned control algorithms. It may be easier to use steppers if you don't understand control theory very well.

 


Get Your Ad Here