Monday, August 20, 2018

Rebuilding my CNC with T Slot aluminum and Fully Supported Linear Rails.

I am rebuilding my CNC with T slot aluminum extrusions, fully supported linear rails and a smaller Z axis.  My book "Inexpensive CNC Projects has been my best selling book for 2 years.  During that time I have added USB interface with an Arduino Uno and a Laser.  Now I am changing the frame to T slotted aluminum among other improvements.  I was able to get a great deal on six pieces of 18" 2020 aluminum extrusion.  Then I had them professionally cut to length.  Afterwards I discovered that the 16.5 length should have been a little shorter.  The length was based on 18" -(2 x 20mm).

Once I got the frame together this is what it looked like.  The red bearings were problematic as the outside diameter is 7/8" and I could not find anything that fit them.  That is about 22 mm diameter.  There are some 22 mm clamps that are used on Drones but they are wimpy as they were not designed for use on a CNC machine.
T Slot CNC Frame

The new Z axis is only four inches wide.  This next picture shows the new Z axis in front of the old six inch wide Z axis.
New Z Axis
These are some things I have learned about 2020 T slot aluminum:
1. A 10-32 screw fits the T slot nuts.
2. A 10-32 Truss head screw head fits the T slots.
3. A standard 10-32 nut, once filed slightly, fits the T slots.

Here is my current state of construction, the fully supported rails and matching bearings is a huge improvement well worth the $40.
T Slot CNC being assembled
Here is a close up on the experimental Z axis with 22mm Drone clamps holding the bearings.
Close up of Z axis
GRBL has changed since my book was written.  You now have to manually extract the zip file and copy the "GRBL" directory to the Arduino/Libraries/ directory.
Installing GRBL

Then to load GRBL select grblUpload and open it.
Loading GRBL
Then when you upload it you will get an error message.
GRBL Error
Then when you run G Code Sender select 115K for the communications speed.
Next set your steps per mm as in $100=320, $101=320.
Then check to see if a 10 mm move in X and Y move exactly 10 mm.
Then check to see if a 100 mm move is in fact 100 mm.
Next attach a marker and print something.
I found a file that prints a 5 inch ruler that is a nice test of the CNC.

Here are the drawings for the smaller Z axis.  Sorry the drawings are from Visio not Autocad.

Z Back:
Z Front:

Z Top (and Z bottom with no holes for stepper motor):

Z Back for Continuously Supported 12mm X axis (1" x 1.1" or 26 x 28 mm bearings):
Note that 10-32 screws will fit the 12 mm bearing blocks.

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