Manual focus measures from where?

[mikerogal]

I feel dumb asking this but I’m trying to understand how manual focus is set. I know you put the number in the app but what is it measuring from? The surface of the crumb tray? The bottom of the laser head? The surface of the material? I can’t find anything that makes this clear to me. Thanks

[wesleyjames]

It’s a measure how think the material is so from the very top of the crumb tray to the top of your material.

This is why if you have to remove the crumb tray, you have either use thinner spacers to get your material up to above the same height as the crumb tray or have an item that is at least slightly taller than the gray to begin with.

Here’s an old thread that details the ideas:

Tutorial: How to cut without the Crumb Tray (Honeycomb)

Tutorial: How to cut objects too thick to have the honeycomb in place The GlowForge has a maximum material thickness it can cut through, but there is a maximum thickness you can even put on the honeycomb (crumb tray) even if you are surface engraving as the laser has a limited focus range of 0.01" - 0.4" *** above the surface of the honeycomb at the time of this tutorial. But let’s say you wanted to engrave something thicker that fits quite nicely inside the GlowForge but not with the crumb tray…

This tells the GF how much distance from the top of the material to the focus lens in the head.

[eflyguy]

It’s a little confusing because the “focus height” references the height above the surface of the tray when it’s installed, but this tool will help you determine the correct measurement with or without the tray in-place.

Presenting the Focus Height Ruler (duplicitous edition)

I present the ambidextrous version of the focus height ruler, to accomodate those disadvantaged users of the 3.24078e-20 parsec measurement system. [IMG_7656] [IMG_7657] (The superior strictly colonial edition was shared here) File is at the bottom of this post, and also here. Printing is a two-part process. Act 1 - with your material SECURELY fastened to the crumb tray (this is important!), set the first three print steps to engrave, score and cut respectively, and the remaining two steps …

[henryhbk]

In addition to the tutorial I wrote way back when as @wesleyjames mentions, I also designed this thing to help you support the object with the tray removed

The Trayless Jig-O-Matic

Action shots [image] [image]

[jbmanning5]

It’s a little confusing because there are different things going on. The autofocuser is measuring the distance from the head to the material surface, and then moving the lens in the head so that it is 50mm from the material surface (50mm/2” lens, so the beam comes into focus 50mm from the lens).

Focus height/manual focus, is telling it to focus to that value above where it believes the crumb tray 0.00 is.

The way most people use manual focusing seems to be either a. Defocusing an engrave or score line, or B. Focusing into the material (thicker material) on a cut (for example focusing to 0.180 on .250” material). For this reason, especially the defocusing for scores and engraved, I think a z-offset field makes much more sense.