Facing Operation Removing Too Much Material

[richardsalzman]

I just started machining this small part.  I set it up with .100 for the Stock +Z offset.  I confirmed the height of the stock before I started machining to be 1.34 inches.  When I ran the second facing operation it appeared to be taking a very heavy pass.  It was supposed to only remove .009" of material.  I looked like it was removing about 80/1000. 

After running the second facing operation I measured the remaining stock.  It should measure 1.34 - .1 = 1.24

In reality it measures about 1.16 which confirms that too much stock was removed (.080 too much).

Is there some mistake that I am not seeing here?

Thanks... Richard

[a.laasW8M6T]

Its not a CAM problem, it can really only be two things

1. You didn't set your work offset correctly in the machine
2. You didn't set your tool length offset correctly in your machine

I would go back and check your setup.

Also I'm not a great fan of using relative size box when you actually know your stock dimensions.

If you know the size of your stock, best to use fixed size block and directly enter in the stock size

You can set the Z offset by selecting offset from top and then entering the 0.1" there

Pic is just an example

[richardsalzman]

Thanks so much Andrew!  Yes... I had checked the work offset but did not check the tool height as I have been using this Fly cutter for quite some time.   Right before running this part I had increased the width of the cut for the Fly cutter and totally forgot to account for the change in tool length.  Thanks so much... I spend an hour trying to find what I had done wrong.  Also, thanks for the tip on using the fixed size box.  You made my day!

One quick question.  I used the 3D adaptive to rough out this part.  Why didn't it rough out the portion that is circled below?

Thanks for all your time... Richard

[a.laasW8M6T · Accepted solution]

Not sure why exactly, but the default minimum stepdown value for flat area detection seems to be causing this.

I increased it to finestepdown*0.1 and now it removes the section in the middle

[richardsalzman]

Thanks so much Andrew!  I did not think of changing that setting.  That is excellent.

OK.... I lied... One last question.  I machined the soft jaws below.  The holes in the flywheel are 7/16 inch diameter.  When I machined the registering pin in the soft jaw, I made the width exactly 7/16" wide.  Now it does not fit in the hole in the flywheel.  Is there a rule of thumb as to how much smaller I should make this pin so it fits without being too loose?

Thanks... Richard

[CNC_Lee · Accepted solution]

Not sure about a rule-of-thumb, but I would make the pin at least .0005" smaller than the holes to allow for easy alignment.

[richardsalzman]

Thanks Lee.  I am totally new to this so I really appreciate your help.  Have a great day.

Best.... Richard