Lets say your cutting graphite electrodes for edm machines.
High tolerance. +- .0001 is the goal.
So imagine you have eight positions that hold 8 graphite blanks.
Your program consists of 4-5 cutters.
Lets say we have a 30 grand rpm machine.
How do we cut eight parts the same, at high rpm's with spindle heat and
bearing heat dealt with.???
Well, it starts in programming!
Lets say we have a cutter running at 5 grand. it roughs.
Next cutter runs at 20 grand, it roughs.
Next cutter runs at 20 grand, it finishes.
Heres the problem with this...the spindle is moving usually in Y- due to
heat, pushing it off the base.
X is usually centered, and heat plays no role.
Z is uaually changing from heat causing the bearing to fit.
And it's A lot.
If you cut with t1, then t2 then t3, etc... then do part 2, the temps are
all different from part one.
It just keeps getting hotter and hotter till part 8.
If you cut all tool one, then all tool 2, etc... thru all pieces at once,
there's the same change in heat.
Program rpms closer together if possible. Try to use cutters you can run at
the same rpm range.
Another thing you can do is program rpm dwells, try to create the same
condition part to part.
Let the cutter dwell for a minute above the part. Type them in by hand if
you have to.
maybe group cutting types. If you have a cutter running 3 grand, run just
that cutter thru all parts, then run the 20 grand cutters thru it.
Also, if you have a laser, give it a dwell also, let the bearing get
adjusted by the working temp, at least 1 minute.
Pick it up at the working rpm, at the working temp, and it will be within a
If you decide to mill an inspection skirt, or an area you can check for
location, use the main finishing cutter.
Most people use a larger endmill type for this running at low rpm, so it
will go fast. Problem is at 3 grand the location is different than at
running 30 grand.
Use the important 30 grand cutter to skim that skirt, then you can use it to
check location within tenths.
When making adjustments, and down to a couple of tenths, make half moves.
Makes it easy to average zoom in.
- posted 8 years ago