Being new to CNC I will need as much help as I can get. Planning on building a small (12" x 16") PCB router and trying to determine the rail sizes I need. During my digging I have encountered a few problems.

First, want to keep the project cost WAY down, but want accuracy of course. I have been looking at linear rail systems and here is my problem. I would love to use a supported rail system, but seems I cant find a seller in Canada. Buying outside (via Ebay etc) runs a problem o shipping and damage. First, any banging in shipping could damage the rails or bend them, and since they are VERY expensive I sure dont want that. Second, ANYTHING from the US has a shipping tag equal to or MORE than the product.

So, the option now is using TGP rod and linear bearing pillow ...... BUT, do they NEED to be matched (ei sold as a set) or can these bearings just be used on the same size TGP rod (so is for example 20mm leaner bearing a good fit for 20mm TGP rod). Here in lies another problem, what would be the min size of unsupported rod I could use without having to worry about flex messing up accuracy. Obviously the amount of flex will be dependent on unsupported length, but is there are formula or "rule of thumb" that say xx" dia per yy inches ?

I really want to finalize my plans and start on the project, but the more I dig it seems the more the costs go up, and they are now pretty close to reaching a point that will terminate the project. Seems the more I talk to people, the more "bits" are better bought than "made", and its slowly starting to kill the project before it starts (steeper controller has really put a dent in the budget when most say the Ebay ones, 6550 i think, are crap, and to use gecko, twice the cost). Sure looking for for advise and news (good or bad) so I can decide if I should continue or give it up. After all my digging it seems this project will cost almost 3 times as much as my home made large mill (including a purchased R8 spindle and bearings I had to buy)

Hope I can keep this alive, but seems if I want to "build" a CNC, either I pay a fortune doing my small router, or pay less making a 8 x 16 foot monster one (seems there is no problem using ACME and roller bearing rails with big ones, plus it uses the same controllers and motors)



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