3000x1500mm table drawing stage

[JAZZCNC]

Aligning the rails should be doable what you need are two taps on each of the pads frame and rail, tabs on the frame get tapped with a fine thread so you can adjust the rail for roll & pitch/align and shim.

Yes, it's doable, I've done it many many times. I've also tried your suggestion and it doesn't work quite as well as you'd imagine on large rail surfaces. It takes an age to get right and can defeat the point of having the rails machined flat because it's so easy to introduce error if the shims are not spot on when tightened down.

The best method I've found other than sending the whole frame away for machining is a mixture of using the pads with set screws for fine adjustment like you say but also to raise the pads leaving a gap of about 3-5mm when tightened down solid. Then instead of shims use an Epoxy metal putty sandwiched between the pads with a release agent so the top rail can be removed if needed.
This method fills any voids or distortion from welding the pads and gives a very solid surface, the epoxy also acts as a vibration dampener.

Was looking for a picture of Boyan's big machine yesterday but couldn't find it, also i believe Boyan has a couple of his machines in CAD if reefy86 was to get in touch, if i remember correctly Boyan stitch welded his frame to keep down distortion.

Boyan's machine is well OTT IMO and still doesn't get away from the epoxy method which is only suitable in accuracy terms for an average machine. It also took him a few attempts and a lot of wasted money in epoxy.!

End of the day it depends on the usage of the machine and what accuracy levels your looking for or expecting. If mostly cutting woods and V carving or panel type work then usually if done correctly any of these lower expense DIY methods work great.

It's often the smaller details that show up the difference in build quality, like the example of one of my customers which I gave Reefy in an email. They produce bespoke large highly detailed doors with 2.5D scenes cut into them and for a long time struggled to produce the quality of door they wanted. They first blamed the machine because it was a merchant dice machine, then they went the DIY route and that didn't end well, so they bought a Chinese machine but still, they couldn't get the quality right.

The problem wasn't the highly detailed 2.5D scenes which were quite complex models, it was the little details like chamfers on the door edges or Grooves around the edges of panels etc, they couldn't get a consistent width along the length of doors or large panles because the rail top surface wasn't flat or on the same plane and anyone who's battled with chamfers nows, they look a mess when not right.

Now you can imagine the frustration after cutting a 12hr 2.5D scene into the door (twice) only for the last details to mess it up.