Home Brew 2
Finished the Flip Side
I was able to run the Taig CNC today to finish cut the motor side of my trial heat-sink. It has a few flaws here and there but fairly minor. They were caused by broken milling bits and having to start over several times.
Actually this is “good enough” for actual use if that term is acceptable. It is perfectly functional and ready for use.
I have four more to make so I will be well practiced by the time I do the last one. The time on this side to cut all the fins and a finish pass on the inside took almost five hours.
That doesn’t include the 1/4″ end mill time for cutting the center recess and the big hole. That is about 60 minutes more to do both sides.
The fact is it takes a LOOONG day to make one of these. OK for personal use but hardly worth doing for production. That is the time cost in making what is a fully machined prototype (or five). For volume production this would be best be a casting and then the only machining would be to set the desired inside thickness and create the flat heat sink contact area which is seen on this side.
All the fins on both sides have been cut using only one 3/32″ 2 flute solid carbide end mill. Looking at its cutting end and how it was performing when this side was done, I would say it still has a lot of linear feet left to travel.
BTW, the Taig mill is performing wonderfully spinning for many continuous hours at 10,600 RPM at the spindle; Which I must add, doesn’t even get warm.
HB2 Milling Heat Sink
I spent the weekend getting the last of the CNC milling bugs out of making the stepper mounts/heat-sinks for the HB2. Here is a picture of the trial version. I finally have all the speeds and feeds correct for the fragile little 3/32 end mill I am using to cut the fins. This thing is beginning to look like the cylinder head on a lawnmower.
The oversize holes near the top were a mistake. I could also say they were an experiment.
I use mist cooling when doing the milling. The air compressor broke on Saturday that sprays the mist. Today with the new compressor everything went fine. The DeWalt is a good brand. I really like the lower noise level. It is not silent but a lot more bearable than the Kobalt.
Here is a link to a short video showing the milling of the heat sink above. There is actually a fine cooling mist coming out of the nozzle as well a good bit of air. The air compressor was NOT running in this video.
I have the four blanks cut today for the real parts. I feel confident in starting on the real product.
Getting Together HB2
Making Progress
The parts are going together for the HB2 assembly. At last is is starting to look like a router machine. I like the yellow but no one else has to agree.
The biggest problem has been the bolt sizing. The shopping list wasn’t exactly correct but close enough. I am using Alan cap screws where possible and some Phillips head. Almost all the nuts are nylon lock type.
The rails are extreamly nice and should prove to be very accurate. More pictures as I get it closer to finish.
10/28 – Update from this mess!
Follow this link: HB2 Section #3
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.