CNC hole matrix 2 piece DI/LN2 Pot

I'm building a new pot for a member of this board, it's an adaptation of the design in post #7 of this thread:http://www.xtremesystems.org/forums/...d.php?t=158034
Thanks for posting that design flytek!

I made quite a few changes to fit the pipe I have on hand, the copper stock I have, etc.

Details:
112 holes 1/8" diameter, 0.45" deep, edges chamfered about 0.02 (didn't measure, but i did them with a CNC so they are all the same)
Base is 2.5" diameter, 1.340" thick, the edge was milled down 0.05" to leave a boss to hold the pipe ID in alignment for brazing. Brazed with safety-silv 45
Contact face is 1.890" diameter, I cut a stepped chamfer to transistion from the base to the side walls, since I was cutting with chamfering end mills and not a lathe.
8" long tube of type-M 2.125" OD copper pipe

I cut the holddown with a stepped hole so that it will hold the pipe at the top, and the armaflex insulation can be one piece. Holes are sized to fit 4mm stainless threaded rod.
I don't have a pic, but I also have stainless springs and nylon bushings to go in the springs.

I've made two pots so far, one (the one with a TC probe hole) I'll be testing with my load tester and dry ice/acetone.

I'm waiting on some aluminum to show up, and I'll make the backup plate, it'll be the same profile as the black Delrin holddown, but the holes will be tapped M4, and I'll use a stainless nut to tighten the threaded rod to the backup plate.

Looks nice, should be a good dry ice pot.

I think it would be better suited for LN2 because of how small the holes are. Not sure if the DI would fit down there.

GJ Erik, thats real nice. I like the catridge heater mounting plate too. Its all pretty sexy. :up:

Are you going to put it on a chip and try er out?

@ Filmbot: it will work if the dice is chipped or in small pellets plus a good mixture of acetone

Let us know how it holds up when you put it to the test. It looks great though!

Dry ice is generally just as cold as possible, while with that much surface area getting Ln2 to avoid coldbugs could really be quite hard.

Thats a nice pot :)

Backup plate.
1/4" aluminum brushed after machining.

Load testing setup.
It's 1.5" wall Armaflex insulation, stainless M4 threaded rods, stainless springs, in the pic they are compressed at a calculated 76 lbf total, nylon bushings.

O_O
soooo thick insulation :D

nice looking

Tested the pot today with dry ice/acetone.

I used a Honeywell PID controller reading a type T thermocouple, this is the best setup I have, adjustable calibration like a Fluke, so I calibrated the TC right before the testing. It looks a bit strange in the pics, but this controller is a temperature controller for a brazing furnace, and it was easy to disconnect the entire control box and slide it out (had to switch from a type K to a type T).

I used a variac to modulate the voltage, and a kill-a-watt to measure power.

Temperature readings are from a hole drilled halfway into the width of the load tester block, and about 0.030" below the contact surface.

I used AS5 paste between the block and pot. I sold and shipped all of the springs I bought for this pot design, so I don't know the force applied to the pot, but from my experience with the springs and the torque they require on the nuts, I'd guess it's 80lbf total.

99Watts @ -67.5C
150W @ -63.5C
200W @ -57.6C
249W @ -53.7C
302W @ -47.2C
350W @ -41.4C