Multi-Color Pen Holder with Automatic Pen Change

Projects
1

The title says it all! I am looking for input from the community to create a device that:

  1. Holds multiple pens, pencils, markers, etc (4 would be ideal).
  2. Adjusts easily to hold different size writing/drawing implements
  3. Allows easy centering/positioning of the pen
  4. Is able to swap/change from one pen to another automatically (ideally without additional motors/servos, electronics)
  5. Moves up/down using the Z-axis
  6. Is robust enough to draw on plywood
  7. Is cheap/easy to print/build

There are some nice single-pen holders on this forum including: krkeegan, Matt Nelson, Sharpsburg_Woodworke. Elsewhere there are commercial or 3D printed ones such as: Rock Cliff Machine, Kronos Robotics, Widget Works, and many others.

As far as I can tell, none of the devices hold more than one pen let alone switch pens automatically! Here are my initial thoughts:

  1. Attach holder to router chuck
    a. Allows quick/easy attachment/removal
    b. Doesn’t change weight of sled
  2. If we use holder similar to this:
    penholder
    but “mirror” the holder to hold 4 pens (90 degrees apart) AND use retractable pens like these Sharpies:
    sharpies
  3. There could be a mechanism that, when the Z-axis goes up, the pen gets clicked closed and the device is rotated 90 degrees and the next pen is clicked open.

I am confident that there is a way to make this work! I’d love to hear from y’all

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2

Hi @sprdad,

  • What and on what do you intend to draw, ideally with four colors?
  • What is the difference you see between pens, pencils, markers regarding the holder?
  • How would you describe something that adjusts “easily” to hold different size writing/drawing implements?
  • Relative to what do you evaluate the “easy” centering/positioning of the pen? (would you also include depth positioning?)
  • How do you expect to describe the color selection in a gcode file so that the resulting movement would swap/change automatically the pen?
  • Which drawing software do you like to use for drawing (Inkscape?)
  • Why “ideally” would the selection be performed without additional motors/servos, electronics?
  • What do you mean by “robust enough to draw on plywood”? Could you describe the surface “problems” you forsee?
  • What is your bugdet for “cheap”?
  • Do you intend to use your MaslowCNC to machine the parts?
  • Would you agree to work on this under a GPL licence where any design and improvement has to be shared back freely to everyone?
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Maybe to help simplify (not sure this fits all proposed criteria) the ‘sharpie’ pens pictured could just be clicked open or closed. The mechanism wouldn’t have to spin if the pens were spaced so that they (writing tips) share the same space when retracted. This may require 4 (or more… Because now we don’t have to spin anything accurately) ‘clicker mechanisms’ .
Ok, admittedly this premise may not be simplifying now that my thoughts have taken their course! :thinking:

1 Like
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The problem with using markers is that they would dry out and quit marking fairly quick. I have thought on the same issue and would use thick lead colored pencils. the pencils would need to be on a spring to hold tension on uneven surfaces. Early thoughts is you would need to have the pencils spaced and placed at a certain location then move to the location for the color you want. You would need to have a press release mechanism push in against the back board to release the pencil keep the tension and raise the z axis. Once the pencil is cleared move off backboard and go to the next position press up against the back board to open the holder lower z axis over new color then move off the back board to release tension on opener and add tension to the pencil grabbing mechanism. Not very hard to do with a normal CNC machine that has a much larger movement on the z axis. Does not have to be top down on z axis could be side grab. The easiest way is to have two different sleds one for drawing and one for cutting. How hard would it be to change sleds on the maslow? I have the Maslow kit but have not had a chance to build it as of yet.

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To reduce re-calibration due to sag depending on weight, I would suggest to load the sleds to carry the same weight.

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Great questions!

* What and on what do you intend to draw, ideally with four colors?
I was thinking the Maslow would make a great “wall-plotter” (half-joking here). Drawing on paper, plywood, foam-board, etc to make toys, art, stage sets.

* What is the difference you see between pens, pencils, markers regarding the holder?
Different diameter, length, and amount of pressure needed.

* How would you describe something that adjusts “easily” to hold different size writing/drawing implements?
An opening large enough for a thick marker with a thumb-screw to hold it in place

* Relative to what do you evaluate the “easy” centering/positioning of the pen? (would you also include depth positioning?)

  1. Lower the device to make a mark at the center. 2) Raise the device. 3) Slide the pen through the holder until the tip of the pen touches the center mark. This should give the right height and position.

* How do you expect to describe the color selection in a gcode file so that the resulting movement would swap/change automatically the pen?
By adjusting the z-height. Move up a few millimeters to lift the pen off the surface (to move the sled without drawing). Move up a few centimeters to engage a mechanism that turns the device 90 degrees to the next color. Lets say you have Red/Green/Blue/Black pens and you are using Red. Code 1 “up/down” cycle to move to Green or 2 to move to Blue, etc.

* Which drawing software do you like to use for drawing (Inkscape?)
Yes, Inkscape rules!

* Why “ideally” would the selection be performed without additional motors/servos, electronics?
KISS principle! With a mechanical solution, we wouldn’t have to buy, connect and program more stuff.

* What do you mean by “robust enough to draw on plywood”? Could you describe the surface “problems” you forsee?
Enough lateral stability and enough vertical flexibility to handle a rough or slightly irregular surface.

* What is your bugdet for “cheap”?
$25

* Do you intend to use your MaslowCNC to machine the parts?
Yes, Maslow and/or 3D printed parts.

* Would you agree to work on this under a GPL licence where any design and improvement has to be shared back freely to everyone?
Definitely! (Unless you think this could be the next “iPod” in which case we should keep it between us :wink: )

2 Likes
7

How many pen change do you expect in a plot job? Once for each color? In that case, going automatic might look a little overkill?

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“We’re captive on a carousel of time…”

Here is an idea for a carousel that fits in the base of the router in place of the motor. It is shown holding 4 colors but could fit more. It could turn automatically or manually (good point, c0derpr1sm). As the device is rotated the pen at the center drops down a little bit to reach the writing surface. Below is a TOP view and a SIDE view. The grey is the base.

g4970
g4970.png600×882 52.4 KB

4 Likes
9

Nice!
And if you use a clickable pen to let the tip go out, you seem to have access to those click button for all pens.
So the sequence would be:

  • Click to close the pen at the center.
  • Rotate the carousel to move and drop the next pen in sled center and close to the worspace surface
  • Click to open the newly popsitioned pen.
  • Start the next Gcode file.

It would be a good thing to include an index notch to dial in each pen exactly a the right place.

And a lock mechanism to prevent drawing side forces to move the pen.

But again, I recommend to load weight on the sled to compensate for Router removal, or the calibration will be off. Alternately, you could simply change the sled weight value in a future Ground Control implementing the Holey Calibration update.

2 Likes
10

The carousel that holds the pens could be tilted so that it reaches “0” at the position desired.

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I like the tilted idea - very simple/

pen_tilted

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Not sure about that.
My intuition tells me there is a need to gauge this carefully because:

  • Pens will be somewhat spring loaded to limit pressure on the tip.
  • If they slide up under pressure, then tilt will also make them shift sideways.
  • Also, tiping might create directional sensitivity where the pen may have a tendancy to pick into the surface then ripple when pushed in the direction it has the largest angle with the workspace surface.
2 Likes
13

Yes, a little springing for flexibility but secured well enough, it may be fine. Maybe the whole carousel could have a suspension instead of the individual pens.

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You might be able to adapt that tilted spool of pens to something like the links in this post:

As @TheMerryYeoman mentioned, putting the spring at the mounting point would solve any directional misalignment.

1 Like
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For what it’s worth here is a 3D printed pen that is spring-loaded and simply replaces the router bit. I 'm using it to track outcomes on a lower quadrant tension design and I just didn’t want to waste plywood with the test cuts. I use Fusion 360 and just use one pass just low enough to press the spring loaded pen to paper to draw the pattern. https://www.thingiverse.com/thing:3339190

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16

This is a cross-section diagram showing two parallel wheels that are held at the edges and rotated by a single motor. The pens are held by a small sleeve with an axle that lets the pens hang vertically.

diagonalpenholder

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17

The 1980s are calling with some inspiration:

The HP 7475A pen plotter which spoke HP Graphics Language (HPGL). The video is not mine, sorry for the lack of focus. I would love to have a Maslow-like pen plotter with multi-color pens. In particular, I think it would be a great way to test out designs before cutting them into wood.

2 Likes
18

I really think we want the ability to have multiple calibrations stored and
switch between them. That will be far better than trying to make everything
weigh the same.

David Lang

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19

@sprdad and @c0depr1sm - Have you guys thought any more about this? This is really cool.

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20

Maybe we could adapt this!

2 Likes