# To get focus height

when using thick materials and when the tray has to come out you have to use blocking to get into the focus zone. but for the life of me I can figure out how to do the math to get what I should focus at. I have put in a feature request for a update to the UI with or with out the tray so if with out tray you just put in the measure of the full stack of blocking and material.

but in the mean time well dev works on that does any one know the calculation to get focus number based on bottom of head to top of material ?

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This question is outside our teamâ€™s scope. Iâ€™ve moved it to Beyond the Manual so the discussion can continue there.

Have you seen @henryhbk 's tutorial on how to set up a cut without the crumb tray?

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Some folks have used a deck of playing cards to be able to slide in between the head and top of material. Then they measure how thick the cards that it takes to bridge the gap between bottom of the head and the surface of the material.

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Great tip! Gonna keep that one around.

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not outside scope for all you know I am using a box made out of PG that I wanted to go back and engrave but does not fit on the grate any more

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ya but what formula do you then apply to reverse it

The crumb tray is about 1.37"-1.38" thick. Measure your material and any shimming underneath. Subtract 1.37" and thatâ€™s the new material height.

If you want to use a measurement from below the head then take the deck of cards measurement and subtract the head to material distance. If itâ€™s a negative number then you need to add more shims. If the number is bigger than 0.43" then you need to subtract shims.

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I guess I have been far over complicating it, but I did try that and the precession preview was a MILE off. but I measured my tray at like 1.54 so that could explain it maybe I caught a foot or something who knows. this has been a EXTREMELY bad night with glowforge

and really @dannyc could not have answered with what you provided instead instant transfer very poor CS.

what is stake height max then ? 2 or 2.5 ?

Remember that the tray sits in dimples on the floor. 1.54" seems high. Need to measure the tray in place from the floor.

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A very quick gander with a founderâ€™s ruler says itâ€™s about 1.4" from the bottom of the head to the top of the crumb tray, which is 0.0 for focusing purposes. (Definitely less than 1.5, not promising a lot of accuracy on that). So that would make 1" down from the head about 0.4, which is about as high as you can go without bashing the air assist vent. Hope that helps a little. But remember, donâ€™t go sticking measuring or other things up against the bottom of the head unless youâ€™re really sure you know what youâ€™re doing.

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If my math serves me, itâ€™s ~1.37" +0.43" max. 1.8" max from floor.

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well that explains why I keep messing up and trying to create over complicated math

from the specs page

Maximum material height: 2â€ł (50mm)

but in practice the machine can only do 1.8 â€¦ so not designed as advertised

Original specifications had it as 1.5" maximum. The current max material height above the tray is a S/W thing and limited right now to 0.43". You could probably fit something 2.0" in there but the material height focus limitation would currently be 1.8" without the tray.

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We have to calculate the height all the time with the K40. We use a special technique called â€śGuessingâ€ť

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ugh hair pulling

ya but this is the iPhone of lasersâ€¦ it should just work

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Iâ€™ve had good luck with just doing a small sample engraving and then applying Kentucky wendage

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?