(I’ve moved this to the AxiDraw forum.)
The AxiDraw normally does not apply downward pressure — it allows a pen to fall under its own weight. That’s likely not enough pressure to activate the keys on a mechanical keyboard.
We’ve done a demo once with the WaterColorBot (another machine of ours), detailed here, holding a stylus. If you’re using a capacitive-sensing trackpad (the most common type), you’ll also need to add a ground connection to your stylus. (There’s a ground tap available at the pen-lift servo, so it’s quite possible.)
