[dalianharley]

Hi,

I cut a small, flat part out of a 0.5" thick alum stock bar and the part came out to be more than 10% thicker than designed.

Stock - 1" x .05" 6061, actual thickness is 12.64mm

Part - 3.5mm thick, with top offset 2.54mm and bottom 6.566mm. I did all in inches because my passive probe won't work in G21. The part was designed in MM but converted to Inch.

But my part came out to be 3.87mm thick. I'm scratching my head on what could have gone wrong here. I double checked all my Z values and everything looked correct.

I did no face mill the stock as this is just a prototype, 12.64mm is actually slightly less than .5", so why my part is thicker than designed? Where should I start looking?

thanks in adv

Daz

[mioduz]

Make sure your tool didn't move in its holder. Re measure it now and see if the same tool length is stored or if it shrunk at all

Sent from my SM-G900V using Tapatalk

[dalianharley]

but I did not use any pre-stored tool offsets, I zeroed them each time. i used paper method and input 0.002" as the paper thickness offset.

Make sure your tool didn't move in its holder. Re measure it now and see if the same tool length is stored or if it shrunk at all

Sent from my SM-G900V using Tapatalk

[mioduz]

Well the tool could still have moved in its holder. Just harder to tell now

Sent from my SM-G900V using Tapatalk

[pickled]

Start looking back to your CAM model. How and where did you locate zero in the model? Did you add the correct amount of stock to the machining parameters? Usually something that big has CAM or DRO slip up written all over it...especially if it is consistent for the entire part.

[MikeC8]

What did you use for a machine zero? Top left back of stock? Bottom left back? Are you flipping the part for any of the operations?

Some times I will set my part Z zero to the parallels using a 123 block. That way I do not need to worry about the stock varying in thickness if I take the Z height measurement off the top of the stock.

[mioduz]

Just a tip. If you flip the part over it is OK to zero off the top of the part for the first operation but the second operation needs z0 to be located on the bottom (previously top) of the part. Unless your stock is within you intended tolerances.

Sent from my SM-G900V using Tapatalk

[AUSTINMACHINING]

Moving the part after the first op always got me off somehow. Most my part have to be flipped 4 times. I started using the fixed edge of the vise as my zero. I have a set of paralles from .5 to 1.625".
As I rotate the part for my various ops, and use different parallels, my origin in the model is always in the same place. So I only set zero once, and just flip the part evey op and run the code. Its worked great for me.