additions

UrumbotXYZ/moving_z_axis/README.md

@@ -9,7 +9,7 @@ Build frame for slightly smaller machine designed to mill in a 150x150x50 mm vol
 
 ###  Mar 14-20, 2022.
 
-Assemble and tweak tension to try milling.
+Assemble.  When integrating z-axis on moving beam, it is necessary to insert at least 5mm between the x-beam plate and the z-axis plate, to allow clearance for screws.  If we take this approach seriously, we need to revisit the spacing of these plates so that the stepper capstan sits closer to the motor body.  The line attachments are made in this iteration using 3D printed clamps on the plates.  Perhaps better to integrate these attachments into plate design.
 
 <img src=./img/z_axis.jpg width=40%>
 
@@ -17,3 +17,23 @@ Assemble and tweak tension to try milling.
 
 <img src=./img/integrated.jpg width=40%>
 
+
+###  Mar 22-23, 2022.
+
+#### Ran tests for force and milling with this setup.  Information about the setup:
+
+ - Use green fishing line that has been stretched for several days.  Newly tightened. 
+ - Measured stiffness of xy stage dF/dy = 40 N/mm. 
+ - At tip of end mill dF/dy = 12 N/mm and dY/dz = 9 N/mm.  This feels weak.
+ - In order for stepper motor to hold wieght of spindle, I need to set vref on stepper chip to 2.0V (1.5V does not work).  At this setting, the chip gets warm to touch, but seems to be happy for hours.
+ 
+
+
+#### Results
+
+ - While cutting wood block,
+ 
+<img src=./img/wood_mill.jpg width=40%>
+ 
+<img src=./img/moving_z_wood.cmp.mp4 width=40%>
+