Limit Switch for M4

1

Would be nice to have ‘hardware’ limit switches on M4 starting to think of a limit switch as a mechanical element that attaches to the belt near the edge of the workpiece zone and using a spring.

If we coupled a spring to that mechanical belt stop the M4 can soft land and trigger the fault, avoiding damaging or stretching the belt when we hit the limit. Could sense that we hit the spring by the shape of the current profile ramp in the belts then issue the hardware limit event before overly straining the M4.

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2

gazinux wrote:

Would be nice to have ‘hardware’ limit switches on M4 starting to think of a limit switch as a mechanical element that attaches to the belt near the edge of the workpiece zone and using a spring.

If we coupled a spring to that mechanical belt stop the M4 can soft land and trigger the fault, avoiding damaging or stretching the belt when we hit the limit. Could sense that we hit the spring by the shape of the current profile ramp in the belts then issue the hardware limit event before overly straining the M4.

can you explain a bit more what you are thinking? the limits of the edge of the
workpiece are at different belt lengths as you move along the edge?

David Lang

3

Oh dang clip on limit wont work :slight_smile: maybe can use retroreflective tape under the perimeter of the spoilboard and IR emitter detector pair bounce off tape under toolhead.

Also, does M4 have Z limit switches?

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4

Oh dang clip on limit wont work :slight_smile: maybe can use retroreflective tape under the perimeter of the spoilboard and IR emitter detector pair bounce off tape under toolhead.

how would that work if the sled is rotated an arbitrary amount

Also, does M4 have Z limit switches?

no it does not. you set the Z parallel by running it down against the motors
until it stops moving.

David Lang

5

The beam path would be focused to strike at some distance below the center of the toolhead so sled rotation would not be too impacted.

However, it will be challenging to configure a beam to strike there given large variety of bit types, shapes, lengths.

6

and if the beam is aimed directly below the bit, by the time it detects any
difference, you are already over the edge.

In addition, the best practice is to surround your workpiece with material the
same thickness so that there is something to support the sled at the edge.

David Lang

7

Why does the limit need to hit dead nuts on the edge vs allowing it to travel a few mm past it?

You still can, just need to leave a small slot so the edge can be detected

8

Wouldn’t it just then identity every previous cut slot as the edge, or am I missing something?

9

No. I mentioned using retroreflective tape along and under the edge of the spoilboard. Its a half-baked concept.

10

I missed that.