Tool drags from WCS to first tool path

[jtromboukis]

Hey y'all,

I'm new to this and I'm having some trouble. After a bit of searching around, I wasn't able to find a solution to my issue. I don't have limit or home switches on my machine and I am setting home manually.

For this project, I set the WCS in the top center of the stock. After manually setting 0, 0, 0 on the machine and I press start, the bit drags along the stock surface to the start of the first tool path. Once there, it moves up to the clearance height then back down and starts milling. How do I fix this so the tool doesn't drag along the stock?

From my understanding, the clearance height it where the tool rapids to before it's moves to the first or next tool path. I have no problem when it moves to the next tool path. The only issue I have is when it moves to the first tool path.

Thanks in advance!

Johnny

[Anonymous]

Yea that's probably because you are starting your program under your settings for retract and approach.  Try moving Z up a few inches before hitting cycle start

.

[jtromboukis]

What do you mean by I'm starting under my setting for retract and approach?

[LibertyMachine]

What post processor are you using for your machine? Is it the proper one?

Could you share your NC code here (don't copy/paste the code, rather attach it as a file) If it's a >TAP file, it will need to be renamed to .nc or .txt

[jtromboukis]

Yes I'm using the proper post processor. It's tiny g for a shapeoko 2.

Here's the code

[Anonymous]

If the tip of your Tool is dragging on your part that means it's already at Z0 since the first line of code isn't a positive Z move it's dragging it to its first position then it's pulling back up to its approach height and retract tight.

[LibertyMachine]

You say you have no homing switches?

I would delete the G53 Z0 line and replace it with something simple, like G0 Z1.0

This is a temporary fix, just to determine what is going on. I suspect that the G53 is being ignored, as there are no homing switches. I wonder what it would do with a G28 Z0. My guess is that it would be ignored as well

[difalkner]

I haven't been doing CNC very long but I had the same issue when I started.  So I began editing the file to add Z1.0 at the beginning of the file so the bit wouldn't drag (or break). After a few times of doing that I realized all I had to do after setting Z zero was to raise the bit an inch or so - it still knows where Z zero is and will go there when the program begins.  That way it doesn't drag and I don't have to edit the file.

David

[jtromboukis]

This didn't work. If I raise the bit, it goes back to zero and then drags to the start

[jtromboukis]

Thanks! I'll give this a shot

[Anonymous]

Pretty sure you should have your x and y moves before your z move. That makes more sense. Maybe you need to have your post altered.

[difalkner]

I'm using "CNCRouterParts Mach3 Mill" for post processing and it always puts the X and Y movement ahead of the Z, so I assumed they all did.  Sorry, haven't been doing this very long myself.

David

[Anonymous]

Everything that you run does this "drag the tool" trick??

[Anonymous]

also...how and where, are you setting machine "home"?

[difalkner]

If I set Z zero by touching the bit to the top surface, leave the bit on the surface, and then execute the program then yes, the bit will drag.  But after I set Z zero in Mach4 then I raise the bit an inch or so, doesn't matter, and then execute the program.  When I hit 'Cycle Start' the bit stays at the raised level until it gets to the first XY position and then lowers into the piece or begins to ramp.

I edited the G-code on the first dozen or so programs I ran to add a line before the first XY commands - something like G01 F100 Z1.0 - just to make sure the bit was not on the surface.  Then I realized all I have to do is manually jog it up an inch or so and that accomplishes the same thing without having to edit the file.  I believe one of the first lines of code, when the XY position is reached, is to move the Z to 0.6" so no matter what height I jog to it's going to end up at 0.6" before beginning the cut.

I copied this from something I'm working on now and I think they all come out this way (different coordinates, of course).  So if the bit is on the surface when I start then it will drag to X1.157 Y0.8539 before raising to Z0.6.  So I just circumvented that by raising it above 0.6.

G0 X1.157 Y0.8539
G43 Z0.6 H21

I hope this makes sense - I've only been doing this for about 10 months but it seems to be working for me.

David

[Anonymous]

I believe this was my initial reaction to your post. To manually jog it up before your cycle start. I'm glad you're having some success.

[jtromboukis]

Yes the bit drags for every operation. I'm sure it's something that I'm doing incorrectly and haven't realized it yet. I ussually set home in the center top of the stock or bottom left corner depending on the operation. I'm setting home by manually moving the spindle to the XY locations and then using a touch plate to set Z. Occasionally I'll set Z0 by manually lowering the bit the work surface, this is if I don't need that much accuracy.

I copied this from another project I'm working on. I'm not sure what the code means. Which line would I change? I'm always nervous to edit this.

(1001)
(T1 D=0.125 CR=0. - ZMIN=-0.25 - FLAT END MILL)
G0 G90 G94 G17
G20
G53 Z0.

(2D POCKET5)
M5
M9
T1
M3 S5000
G54
M9
G0 X0.6322 Y-0.7824
Z0.4
Z0.2
G1 Z0.1125 F40.

[Anonymous]

I think the problem might be that you are setting machine home (g53) to your WCS 0,0,0 (g54) ....is that possible?  At G53 it should goto machine home...not 0,0,0.  At G54 it should go to 0,0,0

[Anonymous]

Fine the procedure for setting your G53 Machine home and set it far away from the table as you can.  Then when programs call G53 they will go there first before dragging across to G54

[Anonymous]

M9 is coolant off....why do you have 2 of those? just curious..