I would like to cut out a section of the bottom of the K40

I would like to cut out a section of the bottom of the K40 to allow recessing in my rotary attachment to allow bigger diameter objects to be engraved. I want to make a set sheet metal sides to raise up the K40 to allow for this, what gauge sheet metal do you think I will need to support the weight of the K40? (I would make it out of one long piece folded at the corners with a top and bottom lip folded at a 90 degree angle)

Can you do it a bit differently where you make a cut out in the table or bench you have the K40 on and then build a shelf under that for the rotary attachment? You could put the shelf on threaded rods that would allow you to raise and lower it like an adjustable Z-table. Then you only need to remove enough of the bottom of the K40 to be able to allow the rotary attachment to drop or raise. The existing sheet metal of the k40 would be fine for continued support - there are a couple of horizontal stiffeners under there now that are outside the laser able area so shouldn’t need to be cut for the rotary access hole.

If cutting into the supporting bench isn’t something you want to do, you could build a box that gives you the machine support with the same kind of hole built in for the adjustable shelf.

Build a frame under it with Vslot and skin it with some sheet metal

I like the V-slot idea. Thanks @Alex_Krause

Planning to chop the bottom out of mine soon, going to mount a box onto the bottom to maintain rigidity (even though I suspect it would be totally fine) and keep the beam contained and safe. Going to remove the gantry to modify the air exhaust and a few other things while I’m at it.

Can anyone think of anything else obvious that should be done at the same time? Might as well do everything at once.

Also, is etiquette on this forum to start a new topic or dig up an old one if it’s on topic?

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Contributing to old topics is intentionally left enabled. But for a new project, usually more engagement to have a separate topic that references the old one as a matter of practice. A nice thing about Discourse is that it’s easy for a mod to move comments into a new topic and Discourse maintains links so people can find the information.

I think @Bill-CNC cut out the bottom as well as expanding his working areas to the whole case, so maybe you want to look through the pictures he posted? (K40 Laser Cut Area Enlargement) High voltage wire and Flyback

I’d think that if you just want 60 or 80 mm, you could make a box with 2060 or 2080 T-slot or V-slot (whatever is cheaper) and attach the bottom piece you cut out of the frame to the bottom of the extrusion instead. Relatively inexpensive, certainly sufficiently stable, should be easy to do. Leave an 8mm lip on the current bottom cutting it away, and then you could use t-nuts and 5mm wide-head screws to attach the extrusion to the bottom, and that would leave enough to drill holes in the remaining piece you cut away to attach it to the bottom. Does that make sense?

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