My daughter’s birthday is just around the corner, and I wanted to make something meaningful for her.
She has a favorite saying which goes like this, “Believe and Something Beautiful will happen”. I found a nice looking font and used that to write the letters.
She also adores the “Hello Kitty” cartoon. I also wanted to impart some wisdom from the scriptures in the message.
So far, I had bought a few pieces of 1 mm diameter end mill bits which I dared not use since my very first attempt at using it. The very first one that I tried got broken off immediately when it touched the work piece. The work piecw was a phenolic board, which was a hard material. I was quite heartbroken at that first attempt.
Since then, I decided to do some research first before attempting my second try.
And that brought me to the subject of chip load, speeds, and feed. I noted that people had been machining fine objects using all sorts of materials, even hard objects like steel.
How did they do it without breaking their tool? What I found out was that tool manufacturers do publish recommended data for their tools, but because the situations may differ, the machinists had to try them out and adjust along the way.
Well, I have taken that advice, and plucked up my courage to increase the speeds for the feed and the plunge. And I reduce the depth of cut. Luckily I did not break the tool this time. That’s good progress for me. And as a bonus point, I could do the engraving more quickly with minimum tool wear. As my experience with cutting the material increases, I might gradually deepen my depth of cut so as to reduce the overall time of engraving.
This attempt to engrave a birthday message served several purposes:
Tested engraving for 1 mm diameter tool, cutting to a depth of 1 mm without breaking.
Tried out the effectiveness of the anti-backlash nuts for the x and y axes. They worked well. The engraving was done with acceptable precision.
Tested engraving on spray painted masonite board. The results were beautiful.
Previously when I found that there were some backlash at the lead screw nuts of the x and y axis, I managed to solve the problem by forcing the nuts against the lead screw threads using rubber bands.
Rubber band loaded anti backlash nut
I knew it was just a temporary solution, because rubber bands was not expected to last very long. They tended to lose elasticity or even break off within a very short period of time. I had kept my fingers crossed whenever I did any milling project. I knew I had to replace them with steel springs in order for them to last longer and become reliable.
Spring loaded anti backlash nut for x axis
I suspected that I might have some suitable springs stashed somewhere in my diy bin. It took me some period of searching to finally confirm once and for all that I didn’t actually have any spring that would be suitable for my purpose.
Movable bed dismantled
Searching for steel coil springs with the correct diameter, length, and wire size was extremely difficult. While on the internet, I even came across some sites which taught you how to fabricate homemade springs. This seemed promising.
Spring loaded anti backlash nut for y-axis
Then I started searching for steel piano wires for the purpose of fabricating my own springs. Even these were not easy to find. Finally, I found a spring manufacturer who was located quite near my house, who managed to find a spring that would suit my purpose.
7/8″ diameter holes drilled at the sides of the movable bed cnc machine
With the springs finally in hand, I started to dismantle my movable bed cnc machine, starting with the x-axis lead screw. As I had to dismantle the whole lead screw from the housing, I took the opportunity to also improve on the design.
Slot cut at the end of a lead screw
By cutting a slot at the end of the lead screw, I planned to use a screwdriver to turn it, thus avoiding touching the threads of the lead screw. As I had experienced before, I often have to shift the position of my cutting tool by turning the lead screw by hand, and inevitably getting my hands dirty from the oily lubricant film.
Using a screwdriver to turn the leadscrew
After installing the spring for the x-axis anti backlash nut, my attention turned to the y-axis. Because of my box-like design, this was slightly more complicated. As the lead screw nut was attached to the bottom of the movable bed, the latter had to be removed, and turned over in order for me to work on the assembly.
Observation hole for alignment of work piece relative to the milling bit
Again, since I had the opportunity to dismantle and remove the movable bed, I drilled two observation holes of 7/8″ diameters each for the two side housings of the cnc machine. These would solve the problem of not being able to observe my cutting tool squarely from the sides.
As before, I cut a slot at the end of the lead screw for engaging with a screwdriver so that I didn’t have to touch the oily lead screw while turning it. The feature was even more useful for this y-axis because only a small space between the movable bed and the end structure could be used for my fingers to reach in for turning the lead screw.
With the light springs installed at the anti backlash nuts, I am confident that the machine would be able to perform trouble free for a long time to come.
———–
As Chinese New Year is just round the corner, I decided to carve a rooster, since it is going to be a Rooster Year. At that time, I did not have any confidence in using a thin milling cutter, because the last time I tried using a 1 mm end mill, it just broke off as soon as the tool touched the work piece. So I used a 1/8″ (3.175 mm) milling cutter, which I thought would be strong enough to take abuse.
I just wanted to check whether I could program the machine to cut a pocket around the graphic. Well, I managed to create a pocket with parallel cuts close enough so that the cuts overlap and form a continuously flat pocket around the figure of the rooster. That programming part was alright, but because of the comparatively large diameter of the tool, there was not much details.
I read up on the internet and finally plugged up my courage to try again with a 1 mm milling end mill cutting tool with the wordings on Hershey Single-line Text and found that the engraving were perfect despite the fact that they were more complicated than what I had engraved before.
