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  #1  
Old 06-19-2018, 04:28 PM
kjoiner kjoiner is offline
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Default Adding hold down screws to part during part run

Hello,

I'm going to be cutting some UHMW bars that are 12" long, 9/16" wide and 3/4" high. They have .260 countersunk (csk .438) holes drilled in them as well. I've already made prototypes and learned that tabs are not the best for tall parts and can allow the part to rock during profile cutting leading to poor surface finish or being yanked free.

I decided to take advantage of the holes and run screws down through them before the profile cut. Screws hold the part much better and would allow me to avoid using tabs. I would like to be able to pause the program after drilling so I can install the screws then start back up. Pausing does not allow me to jog the gantry out of the way so the first time I did it, I hit escape and aborted the program. Rather than use the restart and risk going back to the hole operation and hitting a screw, I just made a quick toolpath of the outer profiles and ran it.

Is there a more efficient way to do this? I think there are a couple of options:

1. Insert a dummy tool change so the machine does a tool measure operation just to get it to move out of the way and pause
2. Run a separate profile tool path program after inserting the screws (like I did today)
3. Edit the G code and insert some move commands and pauses to get the machine out of the way - I have not done this before but would like to know how. I do know that when I aborted the program earlier, line 16103 was right around where the holes ended and the outer profiles began. How can I find that line in the G code using a text editor - it looks like I can search for the toolpath name.

I'm open to any suggestions! :)

I should mention I'm running an FTC


Kyle
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Last edited by kjoiner; 06-19-2018 at 04:30 PM. Reason: Adding FTC
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  #2  
Old 06-19-2018, 05:06 PM
Charlie_L Charlie_L is offline
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If you are running the same file over and over making many parts, I would just edit the tap file.

Notepad++ works really good for editing. You will see the line numbers on the left side of the screen as you scroll down. Or, just us a find command to locate something else.

Looking in your G code book you will read about the G4 command, which pauses the machine. You can add a line of code by simply adding a row.

Before the G4 you could move the x and y to a position out of the way.

Or, after you have done the restart a few dozen times it will not be as scary. I always have my hand on the space bar, just in case.

Or, if you are changing the tap file often because of many new designs, you can probably change the post processor in a way that would add pauses when a new tool path is called for. There was a similar post a month or so ago.

This isn't very detailed, just something to help the thinking process.
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  #3  
Old 06-19-2018, 07:19 PM
Jim_in_PA Jim_in_PA is offline
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Dummy tool change along with having your machine setup so that it goes to a particular areas out of the way for said "tool change"would likely be pretty easy, but I agree with Charlie that if this is a production situation and you feel comfortable editing the file, just put in your pause and relocate manually.
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  #4  
Old 06-19-2018, 08:58 PM
Rlee1972 Rlee1972 is offline
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This may not assist you at all but I thought I would throw in a few lines about our experience.

Before the recent arrival of our Raptor gun and composite nails hold down, once I designed my cutting toolpaths, I would then set up a drill toolpath that I would run first by placing my hold down screw locations in Aspire. This allowed us to quickly follow behind the spindle placing screws in the drill holes to hold parts. It has worked well for us and many of our parts have places where molding or trim will be placed that hides the hole anyway.

Today was the first day I really used our composite fastner gun in production and I was amazed at how much difference it made vs all those screws.


Please share with us what you wind up doing and how it works out!
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  #5  
Old 06-19-2018, 09:40 PM
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Gary Campbell Gary Campbell is offline
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Kyle...
Here is what you will want to add to your file:

G53 Z0 [lifts head
G0 X# Y# [rapid to out of the way location
G4 [pause until ENTER is pressed

The "#" after X and Y are the coords where you wish the machine to move to


IF you do this often, open the editor and save in the macros folder as "PAUSE.MAC

You can then enter this in the CNC.MAC file:


"M69= M98 C:\WinCNC\Macros\Pause.mac"


This will allow you to simply enter "M69" anywhere you wish the file to park and pause
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  #6  
Old 06-20-2018, 08:24 AM
kjoiner kjoiner is offline
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Thanks for all the tips! I'll definitely let you guys know how the new toolpath turns out.

By the way, the Stinger is really paying for itself. I did a quick design on these parts the previous afternoon, had material from McMaster Carr by mid morning, machined them in the afternoon and shipped them out by the end of the day. In the past, I would have had to send these to our machine shop and wait a week or two for the turnaround. Now I can look at making these in low volume production and bring the fabrication in house.

My next set of questions will most likely be about setting up some type of fixture - I forsee some type of plate with 1/4-20 threaded inserts to hold the material as well as more robust threads for screwing down the parts before cutting the outlines. I'll wait on that for a little while though.

Thanks again!

Kyle
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  #7  
Old 06-20-2018, 08:40 AM
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Gary Campbell Gary Campbell is offline
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Kyle...
Plus 1 to using bolts and inserts. Most guys that use a few screws, tape or tabs will never realize how well, or how aggressive one can cut when material is bolted down.

Look near the end of this video (4:15) at the profile pass. Very few hold down methods will hold material well enough to cut this aggressively. You can see the heads of the connector bolts (Fastenal) that are holding the material down.

Also note that this is a 3D file (that I seldom if ever cut) that is zeroed to the bed, dispelling the myth that setting a temp Z to top of material is more accurate.

Enjoy: https://youtu.be/fjk9FjHg4vg
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  #8  
Old 06-20-2018, 09:50 AM
kjoiner kjoiner is offline
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Hi Gary,

Cool video! What is holding the part in place during the profile cut as more material is removed around it? Are you using tabs or an onion skin?

Kyle
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  #9  
Old 06-20-2018, 12:25 PM
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Gary Campbell Gary Campbell is offline
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Kyle...
I left a .1" onionskin and removed it with a trim router. Much stronger and easier to remove than sanding tabs
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  #10  
Old 06-21-2018, 06:10 PM
Rlee1972 Rlee1972 is offline
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Thanks for sharing Gary!
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Blackshear, Ga
2018 Cobra Elite 5 x 10
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20 Tool Holder
25HP Regen Vac

2017 Panther 408
HSD 5HP ATC
6 Tool Rotary Carousel
Recoil Lathe
Laser
Aspire 9.0
PhotoVcarve



Be humble.
Be kind.
Be grateful.
Life is too short and prone to quickly change to live otherwise.
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