Friday, December 28, 2012

Sherline Lathe - Chip Guard

I needed a chip guard for a while but I'm particular, so when I finally designed it in my mind I started looking through the scrap metal bin and found the perfect aluminum extrusion.

I was looking for the smallest screen possible, not a whole machine type cover. The only way a minimum chip shield works is if it travels with the tool bit. The chips come off of the tool bit and go radially from that point. My machine is not set up to bathe the parts in coolant so I am only protecting myself from chips and oil spray. I use a needle point tip on my oil can (see in background) and put the absolute minimum drop by drop on my work.

I also wanted to attach it the same way as the tool holders. I leave the holder post in each T slot on the cross slide and spin out the Allen screw for each tool holder change so there is always a post available to the right or left of the tool holder post in use.

Sunday, December 2, 2012

Sherline CNC MILL - Diamond Circle Square Test

The reason I went to the 20kg motor was because of the problems I was having with my millings specifically the motors skipping steps. The most important thing that I think I have done to mitigate this problem is slowing down the feed rate to 75% of top speed; 16ipm.

I performed a Diamond Circle Square test milling with the new motor and my 75% speed setting. The milling took about 30mins and went off fine.
I will provide all of the inspections data in a few days.

I am not a statistition but I do have a lot of inspection room experiance. This is the over - under graphic with dimensions for the DCS test.

I think that the circles are the most out of spec and because most of the dimensions came from a circle to a flat it is difficult to figure out. Ultimatley the X axis has most of the errors, Y axis is evry good.

The next time I run this test I will make two decrete runs: multiple concentric circles and multiple "concentric" squares.

Sherline CNC Mill - Motor Upgrade

Like so many Sherline owners I too had questions regrading the Z axis with respect to the motor capacity to handle the weight.
I found a 20kg - cm 6 wire motor to replace the 10kg - cm original equipment motor.
For installation I carefully reviewed the two spec sheets and  matched the color coded wires, making a temporary set up on a breadboard to test things at every stage.All went fine and the 1.8deg. motor was a perfect match but it turned in the wrong direction. Luckily for me the Mach 3 software has a reverse motor direction switch so with a few clicks I was up & running.

Unfortunately I did not get the dual ended version, I don't recommend this; you will want the hand wheel someday I'm sure.

Standardization is a wonderful thing isn't it?
I don't think I' am going to replace the other two axis right now but it would not hurt.