We’ve danced around this question a few times on the forum, but I don’t think a dedicated thread has been started about it yet. I just can’t shake my opinion that the camera-dependent homing routine is a solution looking for a problem. I figured starting a dedicated thread would be better than potentially derailing an established thread.
I have the opinion that limit switches are a tried and true method for homing a CNC machine. They are certainly the go-to method used by the vast majority of hobbyist to “prosumer”-level machines that I can think of. Sure, if you don’t know what you’re doing you might end up smashing them (probably not a real worry), or a switch might fail now and then (theoretically), but their ubiquity must surely be a testament to their viability in machine design.
Dan has said that the/a reason Glowforge isn’t using limit switches is because the cost of routing the wires would be too high. I don’t expect Glowforge to share their bill of materials or anything like that, but if anyone would like to help unpack the costs/complications involved with routing wires I am all ears! Seems to me that the Glowforge would basically only need two limit switches (one for X, one for Y) and both of them could be stationary. The head has a variety of wires running to it to serve the focus mechanism, sensors (material height, accelerometer, others?), fan, and camera; are limit switches more complicated than these other electronic doodads?
Using the lid camera for homing has apparently also introduced some complication to the design. The lens(es?) on the camera must be capable of taking an exceptionally wide angle photo while also being able to focus close-up on the head. Is this dual-purpose lens part of the reason the center of the camera’s field of view is apparently the sharpest and most accurate? Are the two lights next to the camera dedicated to homing duty?
The possibility of modifying our Glowforges appeals to many of us. Unfortunately, using the head as a reference point complicates any modifications that involve removing or repositioning the head. And using the Glowforge™ logo as a reference creates a hurdle for any companies or individuals that want to build and sell a head accessory (possibly to fill a niche too small for Glowforge to want to bother with).
Will the coding necessary to home the Glowforge using the lid camera and head logo be included with the planned basic open-source firmware?