Another off idea...

[dazp1976]

Thanks for the hint dazp1976. I was thinking to go with BST Automation BK supports with AC bearings - they are a bit more expensive than "standard" ones, but nowhere near the brand name prices I saw on ebay.

Re ballscrew shaft rigidity, 20mm dia 1100mm travel shaft has about the same rigidity as 8mm dia 180mm travel shaft :)

Sounds good.
I was glad to have the Seig X2 to make my own parts for the new bigger PM25 size machine.
I'm using budget and Dunlop AC bearings sizes 12x32x10mm & 10x30x9mm with DFU1605 all round. Both brands work well.

[mbele]

I decided to make base out of 150mm thick granite slab, with glued-in steel inserts that are going to be ground to provide accurate rail mounting surfaces.

I toyed arround with twin tube + expanding concrete fill, and while it's much better solution in weight/deflection context, I cannot predict what will happen with it after welding and I couldn't find a place where I could get it stress relieved. Here's the link to a shop that has expanding mortar https://www.moertelshop.eu/buy-durfill-cheaply if anyone is interested, they also have ingredients for a special concrete with extremely high youngs modulus https://www.moertelshop.eu/buy-refra...gate-cheaply_6 (check the description).

Full size granite slab is to heavy to handle for me, so I need to reduce weight but keep it from bending while/after the rail supports are machined and before it's mounted securely.

Here's what I came up with:


It also opens up possibility to make it as a construction from thinner slabs...
I realy like the overhang variants, but am I asking for trouble?