1rst build, time to do next step

[JAZZCNC]

Hi Gytis,

First don't listen to Jonathan the G540 is a great bit of kit for a small machine. There are cheaper but it's a quality unit with great back up and warranty from Gecko and worth the money.

BUT every thing else he's correct about.

I'm not sure about 15mm rails, it seems to me that is too weak

15mm profiled rails will be plenty strong enough and carry far more load than you'll put on the machine.
The only issue with smaller profiled rails is the small bearing blocks can be a pain, esp with making the Z axis has the low height often means using spacer blocks to allow clearance for ballscrew etc. I find 20mm a much better size bearing and plenty on top of the job.

no, I don't like this design, I want to keep open table design and keep rails & ball screw from dust as much as I can

And finally, this machine will be built not for hobby use, she has to be strong and durable

Your design will be substantially weaker than what Jons suggesting and if you want strong and durable then it doesn't get much better.
Has for keeping the screws protected then that's easy enough with a bit of thought regards covers etc. The high sides don't cause any issues in use for most work and actually help contain the cutting mess to the table area instead of slinging it all around the shop.
The advantages of the much increased strength and far better quality of finish on work combined with allowing higher feeds is well worth the sacrifice of bit of access when loading material. End of the day it's the quality and speed of cut that matters.

Both Jon and I have been there done/seen that route so believe me we speak from experience on this.!!