Adding a "porch" to the Maslow 4 sled?

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I’ve been musing about how to attach assorted sensors and effectors to the Maslow 4 sled. One notion I’ve considered involves adding cantilevered supports (e.g., for cameras) and/or a “porch” that would extend the diameter of the sled (e.g., for a laser or inkjet printing head). Comments, clues, suggestions?

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To motivate the discussion, here is an opinionated overview and some possible use cases.

Overview

I see the sled as kind of an off-road vehicle (e.g., Jeep) for woodworking. So, it should be tolerant of a fair amount of additions, hacking, and even rework.

Mounting Locations

Add-on hardware (e.g., sensors, effectors, electronics) must be mounted in locations where they won’t get in the way of the belts, router access, etc.

Because open space on the sled is quite limited, it should be reserved for items that need short cables, robust mounting, Z-axis control, etc. Most other items can be relegated to the porch.

Construction

My basic construction plan (details TBD) is as follows:

  • For the porch “flooring”, use something cheap, easy to machine, flat, reasonably light and strong, and very stiff (e.g., 1/2" MDF).

  • Mount the flooring to open spots in the interior of the sled
    (using epoxy, #10 threaded inserts, and knob screws)

Additions

This section details possible hardware additions.

Cameras

I’ll want to mount several cameras on the sled, e.g.:

  • 2 ea., ~6" up and out from the edge, for large-scale scanning
  • 2 ea., low and just out from the edge, for small-scale scanning
  • 2 ea., low and placed to watch the router tip in action

The cameras near the router will have short, high-speed links to the RasPi; the others can share a USB hub.

Since cameras are light and USB cable length isn’t an issue, the large-scale cameras can use cantilevered mounts attached to the porch or the sled.

Computer

A Raspberry Pi 5 can provide plenty of processing power, access to digital I/O, high-speed video, USB, Wi-Fi, etc. Anything else (e.g., analog and power circuitry) can be handled by HATs and other Add-on boards.

Ink jets, etc.

There are various popular ink jet cartridges, in both B/W and color version. These are are light and USB cable length isn’t an issue, so they can reside on the porch.

If I’m doing lots of drawing, I’ll look into a pump-fed ink supply, sprayers, etc. However, this seems likely to be more expensive and/or challenging.

Lasers

Laser engravers have several nice attributes:

  • They needn’t be very height-sensitive.
  • They can be turned on and off quickly.
  • Their “diameter” (i.e., focus) can be adjusted.
  • They can do exceedingly fine work.

Note, however, that dust and/or fumes will need to be handled, along with any beams going all the way through the workpiece. All told, a
20-30 Watt engraver could serve as a convenient and versatile alternative to a router bit.

As a side note, laser pointers could be very handy (perhaps coupled with cameras) as a way to check positional accuracy.

Markers, etc.

A fine-point marker can be installed in a simple spring-loaded mount. However, I might add a computer-controlled solenoid to switch between “move” and “draw”.

Using different colors and permanence levels should provide a lot of versatility. For example, one could trace a path several times using different colors and compare the results. Then, wipe off the drawing surface (e.g., whiteboard) and repeat the experiment.

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Rich Morin wrote:

I’ve been musing about how to attach assorted sensors and effectors to the
Maslow 4 sled. One notion I’ve considered involves adding cantilevered
supports (e.g., for cameras) and/or a “porch” that would extend the diameter
of the sled (e.g., for a laser or inkjet printing head). Comments, clues,
suggestions?

How would your add-ons handle the fact that the sled will rotate during use, so
you can’t count on the position of any sensor.

David Lang

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I’ve been wondering about this. I think I’ll have to calculate the position using cable lengths, etc. A tilt sensor on the sled might also be useful…

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remember the frame may be flat, so it would need to be a full 3d compass. the
firmware knows it’s position as well as the belt lengths, no need to do the
calculations again.

If you are looking over the side of the sled, you also won’t be able to get at
the full workspace.

David Lang

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I certainly wouldn’t be able to view the entire workspace at one time, but I could move the sled about and get overlapping views. One notion I’ve had is to scan the sled rapidly, taking large-scale views. Then, for any areas of interest, I could return and scan them at fine scale. This might be useful for certain kinds of image data (e.g., a large circuit diagram or printed map).

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Rich Morin wrote:

I certainly wouldn’t be able to view the entire workspace at one time, but I
could move the sled about and get overlapping views.

No, if your sensor is mounted to the right edge of the sled, you would have to
have the sled go off the left edge of the workpiece (unless you are talking
about remounting the sensor to the other side of the sled)

One notion I’ve had is to scan the sled rapidly, taking large-scale views.
Then, for any areas of interest, I could return and scan them at fine scale.
This might be useful for certain kinds of image data (e.g., a large circuit
diagram or printed map).

Even the most rapid movement of the sled is very slow compared to what cameras
can do.

David Lang

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