Design for 1800x800x80 wood router

[njhussey]

You shim the main beams not the linear rail, either using proper shim material or this forums favourite method...metal from an aluminium can (Guinness being a favourite) and then using a straight edge and feeler gauges find the high spots and file/scrape them and fill any low spots. Then the linear rails can be mounted straight on the beams.

[jimbo_cnc]

Ah thanks, shimming the linear rail didn't seem quite right.

By shimming the main beam, I assume that means shimming an intermediate rail on the main beam.

My acetal rails plan would do the same thing, as long as the larger cnc has a flat bed. I'm not sure how my cnc place would feel about helping me make my cnc machine though! It's an obvious money loser for them.

I'm thinking now that a welded steel frame is making life hard for me. This is for wood mostly so an aluminium extrusion design might be more suitable. I quite like this design. It looks easy to move/install elsewhere which also makes it more re-sellable than a great big welded frame.

The question I need answering is: Can you just bolt a hiwin rail to an aluminium extrusion, and the result will be straight enough for wood panel cutting ?

[jimbo_cnc]

You mentioned a larger screw being needed, I guess that depends on feed rate as well.

The other structural option is single screw with a long beam.

Can someone help out with rough estimate of the cost comparison. I need the cost of a twin ballscrew set-up versus a single screw for 1800mm travel. That includes the screw assembly, and the motors and motor drives. I realise there's a lot of calcs in that, and it will take me some time to track them all down on the forum.

Here's the single screw layout, I'm not sure I even like it. If the beam is going to need to be deeper then that's already counteracting the single screw cost saving.

If someone was to say forget single screw, you need 2 screws, I wouldn't be upset.

[njhussey]

Have a look through some of the build threads and all your questions will (OK not quite all) be answered.

Here's a good starting point http://www.mycncuk.com/threads/8242-...ght-ply-cutter

Then there's Jonathan's first build: http://www.mycncuk.com/threads/2288-...outer-building

Another couple of Matt's builds...

http://www.mycncuk.com/threads/5174-operation-cnc
http://www.mycncuk.com/threads/6530-...ine-in-a-month

Read the above build logs as a minimum, download yourself the free version of Sketchup and have a play drawing up frames with dimensions on etc and then post them up for critique. I'm not saying that the way they've built their routers is the correct but it's a proven route so can't be bad....