[deleteallusers]

I'm building a CNC machine to do plastics and some light weight wood.

Do measurements really matter? As long as I make it large enough to
cover my required work area, and just make a reasonable design.

Can I not callabrate it to my work area after it is all put together.

I'm just goning to make the frame about 2-3 inches bigger than my work area.

Or do all the measurements need to be some kind of scalled and all perfect
design.

Thanks,

[NutmegTech]

Some components are sold in certain lengths-threaded rod, linear shafting, etc. and you will need to know what size machine to get the right amount of material with out waste. It doesn't really matter what size you make it, but at some point, you will have to nail down those dimensions to make the mating parts fit. I don't know the exact cutting area my machine will have but I do know that a single piece of 36" long acme rod will give me enough travel for what I'm doing. Start with the maximum size of the work you plan on cutting and work back from there. Depending on your design, this may mean your table needs to be 2-3 inches larger than your cutting area or in my case, about 6" larger. My goal is to make a machine that has a cutting area of at least 24"X24".

[vger]

You said you were thinking of making the frame 2-3 inches larger than your work area. You might want to make it just a little larger than that. You will need to take the carriage sizes into account. Say you have an X carriage that has 12" outside dimensions on the bearing truck (or whatever). That effectively makes your work space 12" shorter than your frame size. And end supports for the rails may take out more. I am building a small machine (5" X 7" work area) and early on I realized that the total size of the base was going to be much larger. I had to take the carriage width's into account and the offset of the tool from the carriage etc. I started from the "inside" and worked out... That is I sketched up the spindle and Z axis with rough dimensions, added the Y axis taking into acount the width of the spindle carriage, then added the X taking the width of the Y axis carriage and the offset of the spindle. I ended up with a base that is 10" X 14". With a larger work area the dimensions would not double but the frame would still be a good bit larger than the work area. Depending on the accuracy you need there may be some measurements more critical than others. As mentioned, "at some point, you will have to nail down those dimensions to make the mating parts fit". You will also need to be able to get the rails/slides very parallel to avoid binding. Enjoy

building it is half the fun
Steve