Here I go again.

[Robin Hewitt]

I want to rework my laser to cut Perspex in bigger sheet sizes.

I'm thinking smallest HiWin rail for the X with the laser tube bolted over the top and aiming down in to a slot with some black sand at the bottom.

For the Y, some means to grip the sheet and move it a reasonable distance while holding it square.

Fast X for engraving, relatively slow Y for cutting.

This makes the machine a lot smaller and simplifies everything apart from the Y.

Unless someone has is a positively brill solution to the Y

[EddyCurrent]

Robin, would it make more sense to swap the axes, i.e.

For the X, some means to grip the sheet and move it a reasonable distance while holding it square.
Fast Y for engraving, relatively slow Y for cutting.

That way the material could move 'through' the machine in the X direction

[Robin Hewitt]

X,Y? Y,X? I think we are agreeing. For the purposes of exploring this design concept let us assume the head moves quick the material moves slow.

But how to hold the sheet without making the machine enormous when unloaded.

Right now the picture in my head is deliciously compact, borderline bijou

[EddyCurrent]

I'm only guessing here as I can't fully visualize the set up but what about friction rollers, think 'old fashioned washing mangle', the roller could be driven by a stepper motor or have an encoder fitted to measure the material position. There would need to be mechanical guides to stop the material skewing.

[Robin Hewitt]

It is tricky. If you add mechanical guides you are depending on the sheet being square sided. Rollers mean wasted margins.

Perhaps some kind of frame that you attach to the sheet end before feeding it in to the cutter?

Limiting the head movement to one narrow axis solves all kinds of problems with space, mirrors, air connects, beam catching, smoke clearance, no honeycomb required. Dreamy.