# Idea for a ball point pen that makes dashed lines

1. Jan 31, 2017

### Andrew Bridges

Ok. So while in my trig class, I had an idea for a ball point pen that, when writing, it has an automatic mechanism for making dashed lines. I mean to say, it lifts the ball point or obscures the path to create a perfect dashed or dotted line, or allows to draw a line of fixed length for measuring before writing. My first inclination was some sort of really basic mechanical calculator, in the pen, to calculate the distance the ball has rolled. Problem is, I don't know anyone who can help me figure out what to do. If anyone understands how these things work, I'd like help designing a prototype for now. Thoughts?

2. Jan 31, 2017

### Staff: Mentor

Do you have any experience yet with Arduino or other microcontrollers (uCs)? You could use a simple rotary encoder on the wheel that the Arduino could read, and use a couple buttons to tell the Arduino that you were measuring a line length, then drawing that same line. I'm not sure of the simplest way to control the up-down actuation of the pen tip (under Arduino control)...

3. Jan 31, 2017

### Andrew Bridges

Not at all. I was personally hoping there was a way to make a purely mechanical system without any electronics. If I were able to make this kind of thing, I wanted it to be cheap and easy to mass produce (ideally with plastic parts like any pen). That's why I was asking about mechanical calculators. I don't really know anything about arduinos, but I am hoping to conceal the whole system in the size of a standard pen, without any kind of external components.

4. Jan 31, 2017

### Staff: Mentor

So just to check that I understand what you'd like to do. You would like to be able to use the pen+wheel and a straightedge to trace the length of the line to be drawn, and then go back and have the pen draw a dashed line with dash lengths scaled so that you get the same size dashes for the whole line, fitting exactly into the length of the line.

Is that it, or am I misunderstanding what you would like to do?

5. Jan 31, 2017

### Andrew Bridges

Oh, no, What I mean is for a pen to draw a specified amount no matter the direction or curvature of the drawing. Ok, I want it be like any other pen, no straight edge, no wheel, Just a basic ballpoint pen, but with an internal mechanism that automatically draws in the ball at specific intervals specified by the distance the ball rolls. Separate from what kind of line you want to draw, so no straightedge.

6. Jan 31, 2017

### malemdk

Think about cylinder with small cuts in the axial direction, when the cylindrical pin rolls it makes dashed lines at specific intervals , but you cannot change the length and gap between dashed lines, any way your line of thought is good

7. Jan 31, 2017

### Staff: Mentor

Oh, okay. I thought you also wanted to address the issue of not having an empty end to the line if the dashes don't line up with the length of the line.

8. Jan 31, 2017

### malemdk

9. Jan 31, 2017

### Staff: Mentor

Whose point? Please use the Quote or Reply feature to make it clear which previous post you are responding to. Thank you.

10. Jan 31, 2017

### malemdk

Sorry, I don't understand what you mean

11. Jan 31, 2017

### 256bits

I think you will have to take a good look at how a ball point pen works. By rolling on the page it draws ink from the chamber above and transfers the ink to the paper. If the ball is drawn into the chamber the increased pressure on the ink will push a little bit more out and when the ball releases there is a good chance of finding a blob of ink on the paper. That is one issue to overcome.

12. Jan 31, 2017

### Staff: Mentor

Oh, you meant me!

Draw a dotted line with 1/4" lines separated by 1/4" spaces. If the overall line you are drawing is 5" long, then the last 1/4" of the line is blank. That is usually considered a bad thing in drawing, since depending on where you start and end the dotted lines, you can end up with a dotted line rectangle with ill-defined corners. That's why I assumed the OP was trying to make a physical pen do the same thing that advanced computer drawing packages do, and auto-scale the dotted lines to be sure to make well-defined corners of rectangles.

13. Jan 31, 2017

### malemdk

Ok , now I got it

14. Feb 1, 2017

### CWatters

How about using ink jet printer head technology to spray alternate colours onto the back of the ball (eg one black, one transparent/white) that then rotates around transferring the ink to the paper. If you could get that working then by replacing the transparent ink you could make any combination (say alternate red and blue dashed lines). If you have enough jets you could make any colour line. I suspect keeping the colours separate would be a problem. The ball on a ball point always ends up messy. I've mostly switched to fibre tip pens.

15. Feb 1, 2017

### Andrew Bridges

I'm aware of how that works. I should have specified that the chamber would have to move itself. I know that when you press on the ball, it pushes on a chamber that draws in the ink. I had figured that could activate the calculator for drawing. At the very least that should help with the issue of making sure that the line fits (brought up by berkeman). The only problem I'm seeing right now is how to make a continuous stroke of the pen if the chamber is being drawn in.

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16. Feb 1, 2017

### Andrew Bridges

And on the issue of tracking the ball point, would a 360-degree gear instead of a sphere be a feasible concept?

17. Feb 7, 2017

### RogueOne

Combine all of the concepts below. If you still need help in making the connection, drive a shopping cart's front wheel over a small puddle of paint so that a portion of the wheel's circumference has wet paint on it. Push the shopping cart around

18. Feb 9, 2017

### Andrew Bridges

Ok. It has been a while since we've talked. I was able to get some ideas going with my physics/robotics teacher.

For now, I'll have to leave you with my notes. If you have questions about what they are, just ask.

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19. Feb 11, 2017

### Baluncore

Maybe consider mounting a small diameter eccentric wheel on the side of the pen. It would have a soft rubber tyre, or maybe a rubber disk on the outside edge, that would keep the wheel turning while the pen was resting on the paper. As you draw a line, the pen rises and falls producing the dashed line.