Ex-Cell-O Spindle Wizard to retrofit

[usfwalden]

I took the table top off so I could get to the inner workings of the ballscrew preloading mechanism.  It wasn't all that hard--just very heavy.  Basically had to remove the motor assembly which is on one side of the x ballscrew, undo the bellow from the table top, unbolt the bearing block at the other end of the ballscrew from the table top, and unbolt the table top from the linear guides, then lift it off.


Here it is with the table top off, one of the linear guides out, and the cover off of the saddle to expose the ballscrew nuts.



Here you can see the ballscrew nuts.  The screw on the top with the nut on the left is the x axis.  The rod preloading the x axis is on the bottom and you can see the spring thats pushing the rod to apply the preload down there.  The screw on the bottom is the y and you can see the rod applying the preload on it extending in from the right.  You can't see the spring because the rod is much longer.



Here you can see the rod, and the spring, and the adjusting mechanism after I pulled them out.  The spring pushes between the adjustment mechanism and the lock nut on the rod to apply pressure through the rod to the ballscrew nuts.  When I took the picture I had already backed the lock nut out a quarter inch or so to make up for some shortening of the spring over 30 years.



While I had the table top off I greased the linear ball bushing bearings for the x axis.  Here's a picture of one of them before I greased it.  They have 5 channels of recirculating balls that the round linear guides slide on.  I found some info on the Thomson website recomending ep2 grease so that's what I used.

[usfwalden]

After having moved that lock nut out to increase the spring pressure and putting the table back together I quickly able to set the adjustment to get zero backlash with minimal preload.  I set up a dial indicator with a magnetic base on the table and used a flat point for getting a good indication against the spindle.  I used a dial indicator graduated in .0001"  I moved the table so that the indicator touched the column just enough to move then moved it .001" more then back then increased the spring tension and repeated.  I only had to do this a few times and it quickly jumped from over .001" backlash to zero backlash.  Then I tightened down the pin on the end to set the spec'ed .015 air gap from the end of the rod and tightened down the nut locking in the adjusment.






My facemill, arbor, and speed and feed calculator had come so I returned to "making chips."  I got a sandvik coromant arbor (actually I got both a 3/4" and a 1" but this one is the 1") and 3" diameter iscar tangimill cutter.  I liked the quality of both.  The inserts that came in the facemill were pretty badly beaten up but all had 1 good cutting edge left.  My finish quality was at first less than I expected so I checked the squareness of the spindle again and what do you know it showed a couple thousandths run out.  I adjusted it again and still didn't get the finish quality I was hoping for.  I checked it again and what do you know it showed run out.  At that point I'm confident my adjustments aren't coming loose or anything.  Now I started moving the table back and forth with the indicator on it to see if it's flat and what do you know the center of the table is 5 thousandths lower than the left and right ends.  I found a section dead in the center of the table that gave the same indication over a length longer than needed and reset the head to actually be square, finally.  I then put the facemill and the piece of steel back into the mill and used a feeler guage to check for run out by measureing the distance between insert cutting edges and the steel.  I marked a point on the steel and turned the spindle to measure the gap between each cutting edge and that mark.  Doing that I found that there was a couple thousandths variation.  With some cleaning off broken edges on the inserts and shuffling of the inserts I was able to get them all at least close enough that the .008 feeler gage would slip through but the .009 wouldn't.  I then moved the table to put that mark at 4 opposing sides of the cutter to check for run out and it was good.  I'm sure I'll do better with new inserts but I wanted to go ahead and give it a go with these.  It came out pretty well (the bottom right quadrant is the one i did this time).  It's smooth to the touch now.  With new inserts there may not be any visible mill lines at all.  I did one pass with a .010" cut depth and then another with a .0015" cut depth both with a feed rate of 25 ipm and spindle speed of 530 rpms. 

[budman68]

Excellent info here and great pics as always.

I feel like I'm learning al little bit more each time you post - 

Thanks for sharing all of this-
Dave

[usfwalden]

Thanks,  It's my hope the info on what I go through may save others some head scratching.

Excellent info here and great pics as always.

I feel like I'm learning al little bit more each time you post -

Thanks for sharing all of this-
Dave

[usfwalden]

I machined my first non scrap piece of metal today.  I machined what is called a "step deck" into a flat 6 block.  Most engine builders machine the deck of a block flat and the cylinder head mating surface flat in order to get even pressure accross the entire head gasket.  On this particular type of engine I use a step deck which is where you machine the rest of the deck a slight step lower than the cylinder liners.  This increases the pressure on the head gasket around the cyllinders where it has to hold in combustrion pressures and decreases the pressure on the head gasket around the coolant and oil passages where there is really very little pressure it needs to hold in.  Doing this allows me to hold in higher cylinder pressures with less torque on the head studs allowing for more thermal expansion of the block without stretching the studs past yield.

Running the machine from a laptop proved to be a huge benefit for this.  I was able to walk around and peak around all the tight corners as I jogged the machine from the laptop.

[Glenn]

Great Job usfwalden!

  Great idea and use of your laptop too!
        Thanks for sharing,  Glenn

[usfwalden]

Thanks,

I've got my vice mounted now.  If anybody wants me to make plates to mount their motors or something like that I wouldn't mind some paying work to fund licensing and tooling.