CNC
Getting a BIT Anxious
I received the tiny 3/32 inch milling bits from Bits and Bits last night. Normal machine suppliers do not stock these small size end mills. I bought two. They are solid carbide double flute flat bottom. They also have a 3/4 inch cutting length which I needed to cut the 0.505 inch overall cutting depth on the heat sinks. Most small bits only have about 3X their diameter for their OCL (Overall Cutting Length). The holder diameter is 1/8 inch.
I am figuring a 0.001chip load and will spin them at 10K RPM. That will give me a 20 IPM feed, I only need the small bits to do the fin cuts. But, I dislike tool changes on small projects so I will see if I can do the entire job with these bits. I will be using mist cooling so the tool life in aluminum should be great. Looks like about 90 minutes per side.
I have a trip scheduled next week so this will probably be put off for awhile. (It IS a hobby after all…) 🙂
Just a Coupler of Things
Helical Beam Shaft Couplings
These are the Helical Beam Shaft Couplings I ordered for the HB2 project. The size is 1 inch in diameter and one inch in length. These are the clamp on type and so will not mar the 1/4 inch shafts like a set screw.
These couplings are rated to withstand 42 peak inch/pounds of torque. That’s 672 in/ounces. The holding power of the steppers is a little over 300 oz/inches so there is a 2X safety margin in my selection.
The helical in the name implies a coil and if you look close you can see there are two coils cut into each coupling. The material is anodized aluminum and adds very little weight to the rotating mass.
This may be a bit deluxe, but the motor drive train is a critical operational part in the design of any CNC machine and I want zero binding between the motor and the screws. No steps dropped because of alignment problems.
Heat Sinks
Keeping my steppers cool.
This is a rendering from Rhino. I haven’t made one yet but the drawings are complete and so is the CNC program to produce this part. Material is on order.
It is a combination heat sink (stepper motors get very hot) and a shaft spacer to let me install a larger shaft coupling on my HB2 motor to screw connection.
The overall size is 4″ x 4″ and is 1″ thick. The inset is to fit a NEMA #23A style motor. There is also a recess on the underside for the standard spacer which will be used.
I figured why just do a spacer when here was a chance to get some aluminum fins on the stepper motors. Many CNC designs just hang the motors out on some thin rods, nothing to pull heat from the motor. The motor manufacturers recommend mounting the face of the motors on a metal surface of enough mass to act as a heat sink.
I need four of these for HB2 and if they work as intended, I will market them in the THMStore.
The Color Angle
This is a little “artsy” Photoshop work. These are the steel corner angles I made for the HB2 project. For a little extra finesse, I rounded the corners and they are in their final paint color.
The color I have chosen is “John Deer Yellow”. I like that shade as it seems to have some “character” rather than bright or lemon yellow.
The background in this assembled graphic is actually an extremely out of focus shot of these same components. That way I would be sure to have a color that was compatible but not exactly the same for use as the background.
Now you know the color I have selected for HB2. Yellow is a popular tool color these days and I just HAD to be different than other versions of this machine.
There is of course more pictures and information published in the THMShop website.
Drilling
“
Hey Dan! Ya got yer arm in the way!”
Yep, I guess I do. There are better pictures in the THMS web story.
I have also opened one of the linear rail/bearing packages and taken a closer look before drilling the holes. All is well and construction is proceeding.
It is another one of those 100+ degree Texas weekends. The coolness of last weekend is gone.
Frankly Scarlet, I like doing this so much I don’t give a um… hoot. Turn up the fans another notch!