Hi again,
Indeed it is pretty hard to use spindle load if is doesn't change thru
the corner. I suspect it does on smaller machines but that is not a
generalized solution.
Just for experimental purposes it might be interesting to decrease the
velocity thru a corner see if it helps. Lacking the adding another row
to the matrix should control jerk but the may not be the whole solution
when dealing with a change in direction. So much to learn so little time
(and energy).
I suspect the 'big boys' do some pretty fancy adaptation to get good
smoothing thru the corners. Of course it is all propitiatory and those
patents take a long time to run out. Silvia McFarland (sp?) in her
masters thesis (Uni BC) used sin accel rather than trapezoidal. Might
help. I think traj control get much more critical as velocities get
really radical. Some of the new Brothers with 30 tapers absolutely
scream. When the machinist describes stepping back from the machine when
the tool moves toward him then is must be really impressive.
Dave
On 9/21/20 4:55 PM, andrew beck wrote:
hey dave
I hear you. I might get good at coding myself soon.. but would love to
solve the problem.
I don't think the spindle load could really help much though.
I am machining plastic and aluminium and the spindle load doesn't
noticeably change in corners. I more need a limit on the initial
acceleration for a split second I suppose
or go the full way and have something that analyzes the G code path and
calculates the best speed and path for the machine
regards
Andrew
regards
On Tue, Sep 22, 2020 at 11:35 AM dave engvall <dengv...@charter.net> wrote:
HI Andrew,
Just because I have ideas does not imply I can implement them. ;-)
However, I believe there is a velocity pin that might be used to slow
down in corners. Since the spindle loads up going thru corners it may be
possible to monitor spindle load and back off velocity thru the corner
which should make milling a bit smoother. Adding jerk control involves ,
as you know, adding another order to motion. (see first sentence). ;-)
A lot of bright people are involved in linuxcnc but they all have their
own pet projects. Just the way it goes.
Hang in there, your heart is in the right place.
Dave
On 9/20/20 8:19 PM, andrew beck wrote:
Hey guys
just a few thoughts here.
I have a high speed cnc machining center (cnc mill)
it has 16mm pitch ballscrews and weighs 6ton
linuxcnc is awesome and does a great job controlling it. I make plastic
injection molds and lots of 3d machining all the time. plus all the
little
jobs that a cnc is great for.
I think the only thing lacking from linuxcnc for my use is some sort of
jerk control for corners. there may already be something around that
solves the issue though without jerk control. so what happens is when
the
machine changes direction the whole machine vibrates and jumps around.
its
quite bad. enough that I may rubber mount the electrical box lol.
I have accelerations of 750 (i think it is mm/sec2)
and max rapids of 8m/min
I would love to turn those up to like 25m/min rapid and 2000mm/sec2
accelerations
has any one tried any form of jerk control yet on linuxcnc? or wants to
have a play and code it. I have 3 6 ton cnc machines that will all use
linuxcnc so very keen to solve this jerk control issue.
regards
Andrew
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