Math problem with simple Facing operation

[jeffescott]

I have some stock 19.03mm deep (Z).

I am targeting 15.00mm deep piece (Z).

The piece is centered in the stock.

I selected 0 axial stock to leave.

So 19.03-15.00=4.03mm of total stock to remove.

Since the piece is centered. the amount to remove from the top face is 4.03/2=2.015mm.

When i simulate the operation the bottom of the cut is at 2.006mm.

Top height is set at stock top with offset of 0.

Bttm height is set at model top with offset of 0mm.

Why?

Set up: Facing; Operation Face4

BTW thanks  fusion i got all the way through typing this post and bingo hafta resign in and it dumps everything.....slick.

[programming2C78B]

im sure the math is still acceptable within your tolerance settings 

[jeffescott]

Yes of course however why is there an error?

Seems problematic to me.

Maybe I am becoming a Frodo

[seth.madore · Accepted solution]

That's because your parts are not located where you think they are:

 

 

And please, please, please don't take this the wrong way...

You're using a Genmitsu/Sainsmart desktop router. What's realistic accuracy on a machine such as that, .04/.06mm? Or more? While it's worthwhile to know where the numbers and math are coming from, I encourage you to keep it in perspective of what your machine is capable of.

 

[seth.madore · Accepted solution]

Investigation on the Design side was a bit disheartening..

Your "Level" component is not constrained or jointed in any way, it's free to move about. This could prove quite disastrous on the CAM side..

[jeffescott]

You nailed my accuracy.... although the precision is much better. I have also installed new vee slides and ball screws.  The accuracy error is in the frame twisted just a bit. I will tear it down in the new year and fix everything up.  Hope to hold .0254mm.  

You also nailed what i needed to learn....that is how to measure stock to model.

All in all thank you much.  Learned something to day.

I will clean up model......I only need two more of these and i am done for the year.

I also learned not to let little tiny errors go....they are generally lead to fixing the model, and rechecking the CAM.

I have successfully tested the binding it works better than my store bought ones.   After a long battle learning how to heat treat the Titanium Spring.

[jeffescott]

Quick alignment fixed it up.