4' x 4' x 8" Router Build

[JonnyFive]

Thanks for the replies.

Graham:

If you are still thinking of the pinion drives then please be aware that the spur gear they use is a US imperial pitch size

I knew it was an imperial rack but had assumed it was of the standard DP type that isn't too hard to find? Do you know what pitch it is? What is the solution you have come up with?

routercnc:

1) An extra 1" travel will be fine to allow the machine to go slightly over the home switch/prox and reverse back to settle at the home position. Gives a small amount of room before any physical hard stop.

OK, I'll go with 50" travel, I'll round up to 1300mm as I'm a metric kind of guy.

2) When the Z is at maximum travel the collet needs to be close enough so that the cutting bit can level the board. I notice on your design that there is still plenty of Z travel left when nearly fully down, which is a bit of a waste. It also means when the Z axis is fully up/home it is still fairly close to the board which will limit the maximum height of the part you can cut. If you want to do vice work this gap looks too small. Most people work to 150 mm from a typical tool tip to the spoil board when fully raised. Yours looks considerably closer.

This is why I was asking so that I can adjust the offset between the spoilboard and the gantry, it's at a random arbitrary dimension at the moment which I agree looks too small. I guess my question should have been how much does the shortest cutter stick out from the spindle, so long as that just touches the spoilboard then I can adjust my gantry height from that point.

Just check this is what you want the machine to do. You will see other machines on here use vertical risers on the bed, or vertical extensions of the side members for the base frame to get the main beam high enough that the gantry then runs on.

Not entirely sure waht you mean by this, can you explain please?

4) I've seen racks shimmed in using a DTI mounted to the carriage of the rail, ensuring it runs parallel. Either use proper shim stock or aluminium foil if the gaps are not that big.

I can see the advantage of a ballscrew as there are only two points that need shimming.

One thing to consider is that the stiffness of that axis depends on the stiffness of the rack mounting so I wouldn't favour angle brackets and the like, rather a very solid shimmed mount back to the main gantry.

I hadn't considered this, it's a really good point thanks!

Best bit is when it is all built and moving you will be able to say JonnyFive is alive

This day is a long way off but I can't wait!

Cheers!