Gantry Aluminium thickness guidance

[dachopper]

If you rush and make bodge of the Z axis you'll regret it. Z axis is THE most important part of machine get this wrong and you'll always have poor finish and excess tool wear.

The extra time taken to Mill slot, even with hand router will be worth it. It's the little details that are easy to skip that bite you in the arse later.!!

If I mill out 15mm ( 7.5mm from each plate ) that's almost half the thickness of the plate. Surely that is going to weaken the plate sufficiently to cause me more grief, than keeping the plate stiffer and using a spacer to create the clearance.

What is the draw back of using spacers?

Yeah - we need to fit in work pieces up to 200mm high - that is not aluminium, that would be softer material like surfboard or denser foam for shaping.

Making a 1 machine fits all - because my work pieces are generally long, it's the most economical approach and I don't have room for 3 different machines when the mahority of the cutting is foam / fiberglass/carbon/ wood, 3d Printing and the odd smaller aluminium job possibly.


Regarding the z height , I have an area 80mm high to insert a bed, and fit the spindle, and then 200mm of clearance to the bottom of the gantry. I wasn't sure about the spindle overhang, so I assumed it was going to be 40-60mm, but I also made the spindle mount adjustable so If the bed takes up more room, I can raise the spindle by up to another 8 cm if I have some crazy length tool on the end. It will only be a factor for the foam jobs If I have a 200mm thick slab that needs shaping. for the most part, when working on the smaller pieces, I can attach something on the bed to raise the workpiece so the spindle is level X axis, and therefore less tourqe and vibration.

[Neale]

If I mill out 15mm ( 7.5mm from each plate ) that's almost half the thickness of the plate. Surely that is going to weaken the plate sufficiently to cause me more grief, than keeping the plate stiffer and using a spacer to create the clearance.

It's a well-established technique, though! Look at it another way, it's less than half plate thickness and along an axis where there is little bending load, and where at least part of the channel is spanned and reinforced by the spindle mount. It keeps the spindle axis as close as possible to the Y rails to reduce leverage compared to using spacers. Probably won't matter too much for light cutting loads like foam but it seems like a good idea if you have the facilities to do it (and plenty of people have ploughed this kind of channel with a portable router, well-clamped guides, and a bit of care).

[dachopper]

It's a well-established technique, though! Look at it another way, it's less than half plate thickness and along an axis where there is little bending load, and where at least part of the channel is spanned and reinforced by the spindle mount. It keeps the spindle axis as close as possible to the Y rails to reduce leverage compared to using spacers. Probably won't matter too much for light cutting loads like foam but it seems like a good idea if you have the facilities to do it (and plenty of people have ploughed this kind of channel with a portable router, well-clamped guides, and a bit of care).

I see your point, it doesn't really need to be exact, just enough to avoid screw contact.

[Robin Hewitt]

I'm planning on using up to 200 mm z height

Is that scratching the top of something 200mm tall, or 200mm long cutters?

There is a big difference in the designs