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Ramp Out line on VMC part

mjk

Titanium
Joined
Oct 20, 2005
Location
Wilmington DE USA
making a couple shafts out of 6061 and 7075 on an older vmc Omb control
new 1/2" 3flt from Frank

3 jaw chuck holding 3/4" material in vertical position

Detail is lowest diam .65, next level .57 cam profile, top .435 total length of cuts 1.5"

I can hold the diameters and good finish

Final exit point leaves a small unmeasurable vertical line
part will probably be accepted but would like to improve.

Currently leaving diameter from G2 to a small G1 away from radius move before canceling G41

Not looking to spend hours tweaking ballscrew issues etc
Looking for suggested good practice to add/modify code

if it wasn't for the cam I'd pop them out on the lathe
 

mjk

Titanium
Joined
Oct 20, 2005
Location
Wilmington DE USA
leadouts are at 3 o'clock position heading away from detail in both X+ & Y-

with Omb is G40 a lookahead that requires "room to clear"
 

couch

Cast Iron
Joined
Jun 10, 2009
Location
Anaheim, California
Add an overlap so it leads out past the point of the lead in, or just simply add a spring pass (repeat finish pass) if the cycle time allows, without coming off the part. Go around twice once engaged, only leaving the part after the second one is finished.
 

mhajicek

Titanium
Joined
May 11, 2017
Location
Minneapolis, MN, USA
Lead in with a line (turning on comp), then an arc in, then the cut pass, a spring pass, arc out, then line turning off comp.

Comp the cutter away just a tad before cutting your first one, as the spring pass will shave a hair. On super tight tolerance parts I'll sometimes do two or three spring passes.
 

Booze Daily

Titanium
Joined
Sep 18, 2015
Location
Ohio
You need your G40 and G1 lead out on the same line. The tool is still in comp mode and hasn’t completed the arc currently.
What you’re seeing is leftover cutter radius.
 

mjk

Titanium
Joined
Oct 20, 2005
Location
Wilmington DE USA
The lead out is a G01 G40 line after completing the G02.
I've also tried having the final comp ramping away from the part on the last 180 deg.
I'll be trying w/o comp and also one with a spring pass or 2 as soon as the shop warms up
 

Booze Daily

Titanium
Joined
Sep 18, 2015
Location
Ohio
Sometimes I end up having to do kind of a loop-de-loop like this:

(1" boss)
X.6 Y.5
G1 G41 D1 X.5
Y0
G2 I-.5
G1 Y-.5
G40 X.6
 

dandrummerman21

Stainless
Joined
Feb 5, 2008
Location
MI, USA
Yes, I do a loop de loop as booze mentioned above, and combine it with a couple spring passes as mhajicek suggested

You could even have it exit at a different quadrant than you entered. Taken from the example above:

(1" boss)
X.6 Y.5
G1 G41 D1 X.5
Y0
G2 I-.5
G2 I-.5
G2 I-.5
G2 X-.5 I-.5
G1 Y.5
G40 X-.6
 

mjk

Titanium
Joined
Oct 20, 2005
Location
Wilmington DE USA
I've been entering w G01 at 9 o'clock with comp already on
1-1/2 G02 rotations leaving at 3 o'clock with a G01
There's no "line" at 9 o'clock just at the 3 o'clock
If tweaking the code won't solve it I'll spend some time in the spring working with the ball screw comp

I'll be trying the spring passes later this morning
 

dandrummerman21

Stainless
Joined
Feb 5, 2008
Location
MI, USA
A couple of questions then:

What feed rate are you running at?

and what are the values of parameters 535 and 536? Those are the backlash comp values for x and y, respectively.
 

mjk

Titanium
Joined
Oct 20, 2005
Location
Wilmington DE USA
F20 ipm 6500rpm 1/2" 3flt 1.75 loc in a BT40 stubby holder w/collet produced a good finish (except for the line)
Customer stopped by and said first impression was its not a problem, especially since he can barely see it, and only barely feel it. Then he showed me the steel part its replacing. The line will most likely be a non issue
He's going to install my sample in the final assembly and seem if failure mode is affected by line.

par data
535 3
536 10
537 50
Backlash something I should look into but haven't
 

triumph406

Titanium
Joined
Sep 14, 2008
Location
ca
making a couple shafts out of 6061 and 7075 on an older vmc Omb control
new 1/2" 3flt from Frank

3 jaw chuck holding 3/4" material in vertical position

Detail is lowest diam .65, next level .57 cam profile, top .435 total length of cuts 1.5"

I can hold the diameters and good finish

Final exit point leaves a small unmeasurable vertical line
part will probably be accepted but would like to improve.

Currently leaving diameter from G2 to a small G1 away from radius move before canceling G41


Not looking to spend hours tweaking ballscrew issues etc
Looking for suggested good practice to add/modify code


if it wasn't for the cam I'd pop them out on the lathe

Comping the ballscrews after you've done it a few times is 10-15 minutes.

On your part I would do an arc in and arc out, so the tool enters and exits as a tangent, and a couple of spring passes.
 








 
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