[SoCalPlaneDoc]

I have .0007 backlash in my X.. I'm OK with that most of the time, but I'd like to be as accurate as possible when doing dowel pins and their mating holes.. What I'd like to do is have HSM basically mimmick a common hand-crank technique and overshoot a hole location, then come back into position for one hole, and continue on to the next hole without changing direction. I've done it using a "fake hole" but there must be a better way... any ideas?

[cygnus x-1]

HSMWorks doesn't have any built in way to deal with machine backlash. What you could try though is to turn off "optimize order" on the hole selection tab and then pick the holes in the order you want them drilled so that they are approached from the same direction. Depending on how many holes you have it might take more than one operation to do this.


C|

[SoCalPlaneDoc]

HSMWorks doesn't have any built in way to deal with machine backlash. What you could try though is to turn off "optimize order" on the hole selection tab and then pick the holes in the order you want them drilled so that they are approached from the same direction. Depending on how many holes you have it might take more than one operation to do this.


C|

Nope.. no matter what order, there will be an error due to backlash.
Imagine a single line of holes in laid out in the X axis. you're starting at an X coord that's somewhere between the least and greatest X.. I want to go PAST the hole on the end (either end would be fine) then come back and do the line all moving in one direction. My screw is dead-on accurate so doing it that way really makes for an accurate hole placement - just like we do with hand cranking..
so far, I've been faking-out the program by drilling a hole in air that's past the hole on the end, then coming back.. just wondered if there was some jazzy way of doing it in HSM.

[cygnus x-1]

Nope.. no matter what order, there will be an error due to backlash.
Imagine a single line of holes in laid out in the X axis. you're starting at an X coord that's somewhere between the least and greatest X.. I want to go PAST the hole on the end (either end would be fine) then come back and do the line all moving in one direction. My screw is dead-on accurate so doing it that way really makes for an accurate hole placement - just like we do with hand cranking..
so far, I've been faking-out the program by drilling a hole in air that's past the hole on the end, then coming back.. just wondered if there was some jazzy way of doing it in HSM.

Oh, I see what you mean now. It's not the sort order but where you start out from. About the only thing I can come up with is to maybe insert a "pass through" manual NC operation (should be under the drilling drop down on the command manager) to have the machine rapid to a position beyond the starting hole (x=0 perhaps). It's not exactly elegant but it's better than drilling a fake hole.


C|

[SoCalPlaneDoc]

Oh, I see what you mean now. It's not the sort order but where you start out from. About the only thing I can come up with is to maybe insert a "pass through" manual NC operation (should be under the drilling drop down on the command manager) to have the machine rapid to a position beyond the starting hole (x=0 perhaps). It's not exactly elegant but it's better than drilling a fake hole.


C|

ooooo pass-though.. sounds like exactly what I need.. thanks so much, I'll get educated on this...
I really only want/need it when doing dowel holes so I don't mind a few extra programming steps.

[SoCalPlaneDoc]

About the only thing I can come up with is to maybe insert a "pass through" manual NC operation (should be under the drilling drop down on the command manager)


C|

Cyg, been unable to locate the drilling drop down menu.. can you give me some direction in "for complete dummies" version?

OOPS NEVERMIND... Found it

-socal.

[SoCalPlaneDoc]

Looks like my post maybe ignoring both the pass-through and action commands.. nothing shows up in the gcode. comment works .

[cygnus x-1]

Looks like my post maybe ignoring both the pass-through and action commands.. nothing shows up in the gcode. comment works .

Your post may need to be modified then. Not all posts support everything.


C|

[SoCalPlaneDoc]

Your post may need to be modified then. Not all posts support everything.

C|

Blasphemy!

actually, that's what the problem was.. had to modify the post to understand what pass-through was, and while I was at it I put the Action in too...

Now I just need to come up with a good routine to get the spindle to do X0Y0 AFTER Z goes high enough to clear the stock. I wonder if it's possible to capture the clearance height from the HSM job?

[Atomkinder]

Does your machine have a Positive Approach code? I would utilize this if it does. The post can be modified to output on a trigger (like an asterisk in the toolpath name for instance) so it's coded with the canned cycle or you can just use Pass-Through (this would be a good option on a Fadal where M46 activates Positive Approach and M47 cancels - so it is active until canceled regardless of cycles).

[SoCalPlaneDoc]

Does your machine have a Positive Approach code? I would utilize this if it does. The post can be modified to output on a trigger (like an asterisk in the toolpath name for instance) so it's coded with the canned cycle or you can just use Pass-Through (this would be a good option on a Fadal where M46 activates Positive Approach and M47 cancels - so it is active until canceled regardless of cycles).

Thanks for that. I have a Tormach runnig PathPilot.

I modified the post. Now when I am about to do dowel pin holes, I use the pass-through and use "dowel,left,(safe-Z)" or "dowel,right,(safe-Z)" as arguments. i.e: dowel,left,.6
The post examines the pass through and if it has either of those entriesit writes code that raises to the safe-Z height value and goes left or right to .050 past zero in X and Y - then resumes. This simulates what we all do when using hand-crank acme screw machines.
My machine has .0006 backlash in the X axis. I had my freind with a CMM at his work measure examples I made on machine without using the mod, the error was the same as my backlash.. with the mod, no error. I'm pretty happy with it.
I also gave him a sample made on one my work's HAAS machines. it had .0003 error.. it was only one example so not really a statistically significant study but hey, I'm gloating all of those CNC guys at work showing them up with my Tormach Seriously though, I love those guys. They've been immensely helpful while on my path to CNC success on a budget.