"DoN. Nichols" wrote in message
...
On 2012-05-24, Ignoramus6562 wrote:

On 2012-05-24, Bob La Londe wrote:
I finished a prototype mold for somebody yesterday. Just a little 2
cavity
to test the concept. The I nested it out and blew it up to a full work
envelope 22 cavity mold and started it cutting about 10:00 last night.
When
I ran a simulation on it it said it would take 23 1/2 hours. WHAT? Its

I am not an expert on CNC, or anything, but I remember that I also
made a mold cavity for my kids toy.

I started out with this job taking 1 hr 50 minutes.

After some optimizations, it became a 10 minute job.

Hmm ... are the cavities cylindrical? Is the program actually
making a gazillion tiny straight line cuts, instead of making use of the
ability to cut curves? The start and stop times of all those tiny cuts
add up compared to something making a circular cut. But if it is not
circular, then you are stuck with all those tiny cuts.

Even so -- you are also limited by the total cut length, and the
maximum feed which the cutter can handle. If you're after fine detail,
you are using a small cutter, and it is limited in the number of inches
per minute which it can handle, even if the mill itself can move a lot
faster. Breaking a thousand cutters for one project does not make much
sense. :-)

After the miscut I got frustrated and put some aggressive roughing in, and
cut the time in half... and as expected my cheap spindle bearings are now
ready for an upgrade to better bearings after that.