Hi everyone, so far doing fine running the cnc and trying to practice more, I have thought about it but not yet practiced this process because I feel it would need a lot of trial and error and I'm trying to minimize that with your guidance.

first background:
I built my machine recently ( http://www.mycncuk.com/threads/8334-...ewbie)?p=66167 ) and so far so good with cutting alu and wood. of course I'm far from best setup and all but it is acceptable heh.
Spindle is 2.2kw ER20 collet so I have to manually change the tool if I want to use more than one for the operations on the work piece.
I also have a simple probe for auto Z height and it works with a macro I got from the net wonderfully.

now I have a couple of questions:
-first most important question. at the moment I'm using solidworks and HSMExpress, in that software I can setup the tool library and select the endmill size, type and etc that will do the operation, that of course is necessary to produce the correct G-Code. but I'm a bit confused because I see in the commercial machining center software control you also maintain the tool information. so my question is why do they maintain the information on the machine computer if the G-Code was already adjusted at design stage? aside from pre-storing the actual tool heights so that the machine can figure the starting depth I'm not sure the process flow.

-since my machine is DIY I figure in order to do a job with multiple bit setup is just a matter of pausing at tool change M code and manually replacing the bit and then setting the zero Z again (maybe??) and resume. assuming I put the correct tool size and changes in the G-Code and the cam software modified based on that and all. is this the correct way or am I missing something?

-for parts that need machining on multiple sides what is the process here? for example do we machine one face and make sure the shape that comes out can be clamped so that we can put it upside down and do the other one? do we probe the edges and set something in mach3? I know the answer might not be straight forward or easy but just a bit of pointers from you guys I'm sure I can understand much faster than trying myself.


thanks so much and appreciate any comments, as always.