This is a summary of my attempt to reinforce the Seig X2.
This mill has a number of well known deficiencies, I tried to address one and this is a summary. Hopefully some lessons can be learned and applied by others.
I wanted to stiffen the mill. I wanted to keep the materials types simple. Space and weight were also a concern.
I measured the deflection of the unmodified mill and compared it to the modified assembly to get an idea how successful I was.
I mounted a dial indicator to the base of the mill and measured the deflection of the head. I used a simple luggage scale to measure the force applied. I applied the force to the spindle. Note I pulled as shown but did not apply a second pushing force. The force that counteracted my pulling went though the floor to the base of the machine.
I have two X2 machines and did the same tests on both. The results were similar but this is my results for machine A.
The stock machine had the following results:
The picture below shows pulling the spindle and the force applied and how the deflection was measured. ( don't pay attention to the readout not matching the results, the picture was a test but looked better)
Pulling in the -Y 56 lbs moved .0104"
Pulling in the -Y 40.6 lbs moved .0070"
Pulling in the -Y; 22.8 lbs moved .0045"
Attachment 452962
I did the same for the +X direction:
Pulling in the +X 60.4 lbs moved .0047"
Pulling in the +X 41.4 lbs moved .0030"
Pulling in the +X 19.8 lbs moved .0021"
So the stock machine is twice as flexible in the -Y compared to the +X direction.
My goal was to increase the stiffness by a factor of 10, that didn't happen.
I designed a frame to sit under the base and behind the column. It is made from 1"x2" x 3/16" wall steel tube. The plates are 1/4" steel. The column is bolted to the steel plate with qty(10) x 10-24 cap screws as well as the original 1" bolt. I TIG welded the frame together using the X2 mill as a welding jig.
Attachment 452968
Attachment 452970
So for the modified machine the results are as follows.
Pulling in the -Y 57.1 lbs moved .0011"
Pulling in the -Y 40.6 lbs moved .0006"
Pulling in the -Y; 20.1 lbs moved .0003"
Pulling in the +X 57.5 lbs moved .0028"
Pulling in the +X 38.8 lbs moved .0019"
Pulling in the +X 20.1 lbs moved .0011"
Comparing before and after stiffness, in the -Y direction the machine is about 10 times stiffer. But in the -X direction it is only about twice as stiff. I did an FEA on the model of the frame and was happy with the results but it was my first time using FEA I and had trouble modeling welds. I think I should have done something on the other side of the tubes ( opposite the 1/4 plates) to take up shear forces in the open areas.
Hopefully this will help other people thinking of doing the same thing. I hope that a discussion will generate improvements, I have a second machine waiting for a stiffening frame.
If anyone is inclined to any calculations of the stiffness of the machine using my measurements that would be cool.
Also if anyone can pinpoint the flaw in my frame that allows for the +X lack of stiffness I would be grateful.
(attached is a model of my frame for others to play with)