Re: [CAD_CAM_EDM_DRO] Re: rE:Re:RE: programming by hand

Here is another one from the old controller
at the beginning when they put the cad system at work and on complicated parts
I used to go to the cad office and ask the draughts man to please change the sizes
to specify 3 decimal places (on metric) on the tangential points of lines and curves
they would always said why? the it is only a profile and it does not matter, it took me
about 3 months to make them understand that other ways the controller will give me
and end point error.Now I got no problem as the new controller does not need it and
I have direct access to the cad files and fin them by myself.
regards
mariano (who just finished an stint of 22 days 12 hours a day with no break while the others
were in vacation.

ballendo@... wrote:

> Smoke asked:
> >It appears to me your saying a drawing for a part should not have any
> >tolerance at all Bill.
> >Is that what you mean to convey...or did I mis-read something there?
> >From an engineering standpoint there are very good reasons for using
> >a nominal dimension and then adding a plus or minus (as required)
> >tolerance on the part.
>
> Smoke,
>
> I'm not Bill, but I believe you misunderstood his point.
>
> He is saying that using a 3 inch dimension (contained in the
> electronic file of the drawing) as the BASIS for CUTTING the part
> WILL result in bad parts IF the part tolerance (in the TEXT
> DIMENSIONS of the CAD DWG) is not FIGURED INTO THE CUTTING PATH.
>
> Using the numbers given; 3 inches +0/-.010 we have a tolerance range
> of 2.990 to 3.000. If the CNC programmer USES the "drawn" line (which
> is 3.000) to generate a toolpath, standard machining variations will
> mean that a lot of parts will not meet tolerance (they'll most likely
> be too big).
>
> The 'generally considered' CORRECT way to do this tool path will
> split the tolerance given, and program a 2.995 length. This way the
> machining variations will fall on either side of the "programmed"
> path, and MOST(if not all) parts will meet spec.
>
> It is a VERY GOOD point to have made on this forum! I'm glad he
> brought this up...
>
> Hope this helps.
>
> Ballendo
>
> Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the discussion of shop built systems, for CAD, CAM, EDM, and DRO.
>
> Addresses:
> Post message: CAD_CAM_EDM_DRO@egroups.com
> Subscribe: CAD_CAM_EDM_DRO-subscribe@egroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@egroups.com
> List owner: CAD_CAM_EDM_DRO-owner@egroups.com, wanliker@...
> Moderator: jmelson@... [Moderator]
> URL to this page: http://www.egroups.com/group/CAD_CAM_EDM_DRO
> FAQ: http://www.ktmarketing.com/faq.html
> bill,
> List Manager