Re: [CAD_CAM_EDM_DRO] Re: aspiring CNC machinist wants to dip his toe in

Hi Pete,

I think a trip to your local library would also be beneficial. Some
introductory metalworking and machining books would answer a lot of your
questions such as precision, accuracy and repeatability. These concepts
are fundamental to all manufacturing - CNC or manual machining. As to
what accuracy you need - that depends on what you want to make... What
is the required positional accuracy and tolerance required in the hole
positions (e.g. +/- .01mm or +/- .1mm)? That will be a starting point
as to what accuracy your machine will require - obviously, it has to at
least meet the required specs for your project. The more accuracy you
need, the more $$$ you'll spend to get there. CNC machines are generally
pretty good for repeatability. If you are drilling a big area, you'll
need to think about how you are going to hold your part in an accurate
(and repeatable) position. Fixturing is almost as complicated or more
so than the catual part you want to make! If the part is thin and you
have a lot to make, probably a vauum fixture would be the way to go, but
it depends on what you want to make.

Happy reading

Cheers, Peter

Andrew Werby wrote:

>Message: 12
> Date: Sat, 26 Jun 2004 14:30:51 -0000
> From: "aspiringmachinist" <aspiringmachinist@...>
>Subject: aspiring CNC machinist wants to dip his toe in
>
>Hi,
>
>I am familiar with CAD, fairly familiar with CAM and CNC and G Code
>although I don't get real hands-on, but I am no machinist and not
>very familiar with terms like precision, accuracy, repeatibility
>although I have a fair idea. I have do very very limited with a
>CNC'ed Sherline desktop mill (not mine).
>
>I have been approached for help by a manual machinist who knows
>nothing about CNC about a potential job which will be too expensive
>to do with a real professional CNC mill, too time consuming (many)
>to do manually. The first job/jobs consist of just drilling a series
>of holes on a non-metallic material. I feel it is a good opportunity
>to try my hand at some "real world" work, I do not know how or where
>to get information about the kind of
>precision/accuracy/repeatibility so that I figure out whether I can
>meet whatever requirements that may be imposed. I hope to get some
>feedback from this group regarding the feasibility of taking up a
>job like this.
>
>There is also a possibility that the required x-travel on one of the
>jobs? will be 12 inches. Will this be achievable with a 2000? Would
>there be any other machines CNC'ed or CNC'able that would be a good
>start for me to try something like this?
>
>All responses will be highly appreaciated.
>
>Pete
>
>[Sorry, Pete, the X-travel on a Sherline 2000 is the same as on the rest of
>their mill models - 8.68" (229 mm) See http://www.sherline.com/specs.htm. If
>you want something a little larger, but still in the "micro" category, check
>out Taig's CNC (or CNC-ready) mills - they make a model 2027 that has 12"
>travel in X: http://www.taigtools.com/cmill.html . I think you'd find them
>more than accurate enough for the sort of job you're talking about here.
>What non-metallic material is it? Each has its particularities...]
>
>Andrew Werby
>www.computersculpture.com
>
>
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