# PM45 CNC Assistance!



## Jamespvill (Dec 12, 2014)

Hello Gentlemen!

Somehow I managed to get myself in all of this CNC business! Opps....

So I've been tinkering for a few weeks now, nothing really useful, just engraving and cutting to see the machine cut, But I finally cut something that I indented to use and was very confused!

So here is my part...
	

		
			
		

		
	




The outside I wanted to be 1", and it is right around there. But the inside was supposed to be .75, and ended up being only .60

I am using the same endmill on both outside and in, same setup. Tool is measured to be what it is labeled to be. Looked back at Geomagic and it is in fact .75. Im not sure if its a CAM issue on my end or what. 

I'm not sure where to go from here! Input would be welcomed with open arms.

Thanks folks!


----------



## JimDawson (Dec 12, 2014)

I'm going to say that you need to take a look at the CAM tool path.  I'm not familiar with your CAM program, but I'm going to guess that there is an offset that is not correct for the pocket routine.


----------



## Jamespvill (Dec 12, 2014)

JimDawson said:


> I'm going to say that you need to take a look at the CAM tool path.  I'm not familiar with your CAM program, but I'm going to guess that there is an offset that is not correct for the pocket routine.




I'll have to double check that come morning time. I am running BobCad, for what it's worth.

I did a hex pocket too and it was off almost 20 thou so I am going to assume it must be my preschool-level Cam knowledge...

Still getting used to not being able to feel the machine, that's taken me for a loop.


----------



## countryguy (Dec 13, 2014)

Jim's usually spot on... I also have a setting in my Dolphin CAM for each toolpath command.  radio button for No offset, left offset, and right offset.  and for whatever reason it's usually never set to none?    I had to toss a nice engraving run on that one...   

Do you have a CAM emulator?   There is a free CAM simulator here: http://openscam.com/

Best ,
CG


----------



## Jamespvill (Dec 13, 2014)

Okay, So I _may_ have gotten it figured out. I think it is a combination of using too much stick-out as well as my feed rate being off.

A little more close looking made it obvious that my hole has quite the taper to it.

What is the best way of measuring my feed rate? I have it set to cut at 12 (Inches per minute?) In BobCad. I'm no pro, but it is cruising at 12 and I am getting quite a bit of chatter. It looks to me like a lot more than 12 IPM, but I may very well be wrong.





countryguy said:


> Jim's usually spot on... I also have a setting in my Dolphin CAM for each toolpath command.  radio button for No offset, left offset, and right offset.  and for whatever reason it's usually never set to none?    I had to toss a nice engraving run on that one...
> 
> Do you have a CAM emulator?   There is a free CAM simulator here: http://openscam.com/
> 
> ...



I'm not familiar with CAM emulators- mind elaborating a little for my slow self? I'm assuming it's more accurate than BobCad's cut simulator?


----------



## Boswell (Dec 14, 2014)

just an idea off the top of my head but what if you measure out a long distance on the table, say, 24". Then use a stop watch measure the the time to move 24 inches.  In fact you probably don't even need the measurement, just do a G1 X24 command and time it. Try it a different Feed rates to see if that makes a difference.  The longer the movement, the more accuracy you will get.  You might need to do it several times and average the results but I bet you will get enough accuracy to know if there is a problem or not.


----------



## medlin6 (Dec 15, 2014)

Jamespvill said:


> I'll have to double check that come morning time. I am running BobCad, for what it's worth.
> 
> I did a hex pocket too and it was off almost 20 thou so I am going to assume it must be my preschool-level Cam knowledge...
> 
> Still getting used to not being able to feel the machine, that's taken me for a loop.



check your offset setting and which way tool is going. if offset is wrong it will cut on wrong side. I've used Bobcad for over 10 years and love using ver. 23. try feeding at 8


----------



## Jamespvill (Dec 16, 2014)

I measured the runout on my er-20 collet and it is coming in at a whopping 6 thou of runout. this may not be the source of the problem, but that sure teaches me to skimp and go cheap on the collet purchases! More investigating to be done tomorrow!


----------

