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Archive for December 16th, 2017

MPCNC: Tool Length Probe, Reshaped for Plotter Pens

It turns out old-school plotter pen nibs skid right off the rounded top of the switch lever:

MPCNC Tool Length Probe - plotter pen

MPCNC Tool Length Probe – plotter pen

You can’t see the nib inside the cap, but you get the idea.

Flattening the top and adding a snippet of masking tape produces a better outcome:

MPCNC - Reshaped Tool Probe switch

MPCNC – Reshaped Tool Probe switch

I aligned the flat section so it’s parallel to the platform when the switch activates.

Stipulated: plotter pens aren’t a good test for tool length probing, because they have a locating flange to ensure a consistent position in the pen holder and a rigidly controlled flange-to-tip length:

HP 7475A Plotter Pen Body - in holder

HP 7475A Plotter Pen Body – in holder

What’s going on here involves configuring and testing bCNC’s overall tool change process: not using cutting tools preserves both sanity and hardware!

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