Milling: creating a smooth end finish in a slot

[Boyan Silyavski]

Interesting, would very much like to see a video of that.

Here is a video overview of what i believe is a correctly build DIY mist fog less cooling system. Hope that helps you and others!

[Rob Meades]

VERY impressive! Especially your worked numbers (2.5 bar, 2 mm inside-diameter feed tubing, 0.8 mm inside-diameter nozzle). I'm working in my loft, so I have nothing like the space that you have, however there are dental compressor rigs that should work well (and quietly) available for around UKP150 on ebay so, using these numbers I should be able to make something similar.

Thanks!

[Boyan Silyavski]

VERY impressive! Especially your worked numbers (2.5 bar, 2 mm inside-diameter feed tubing, 0.8 mm inside-diameter nozzle). I'm working in my loft, so I have nothing like the space that you have, however there are dental compressor rigs that should work well (and quietly) available for around UKP150 on ebay so, using these numbers I should be able to make something similar.

Thanks!

No problem. There are many builds on the net, but when i started making mine i found that they or intentionally skipped explaining the fine details or were just unaware of them. basically almost useless information. So like always i had to start from scratch.

Here are some more details if you have not figured all from the video:

- the brass bar body ideally is >=8x8mm
- fitting holes translate seamlessly to inner bore hole.
- the 2 pneumatic fittings are m5 to 4mm OD tube
- the distance between them should be at least 2cm from center lines
- the way/bore hole/ that connects all is 2mm ID
- the brass tube is 2mmOD and 1mmID. I cramp it at the end with pliers, drill it 0.6-0.8mm, sand it flat, fine sand carefully the edge to chamfer without destroying the flat nozzle face Check correct flow with more output. This is the critical part that defines the blow pattern.
- brass tube is super glued and pushed fit at brass body. Dont overdo it as you will need to exchange tha tube sometimes for some jobs
- for hevy cutting up to 20-25mm cutter 1 tube is ok even blowing heavy chips from working surface, then better 2 tubes positioned from opposite sides
- hose is 4mm OD 2mmID PU hose from China , both air and liquid hose are the same
- quality water filter body will resist even thinners / mine is made in Italy/, a crappy Chinese one will explode if sth else than water, especially using alcohol if you see even one micro crack throw it away.
- 1x baby oil+0.1 x dish washer+ 1x water or kerosine / careful with the container, test it first without pressure and then fill it to the top, full container just breaks, does not explode/

[Rob Meades]

Well, I'm not having much success here. I don't have my compressor yet so I thought I'd try a HSS/8% cobalt end-mill (4 flute, 7 mm flute length, 6 mm diameter shaft) which requires a lower speed. With the tool sticking out 20 mm to avoid my clamps, I've taken the HSM Advisor recommendations and then backed them off, so 5 mm/second feed rate and 0.5 mm depth of cut, tool running at 14000 RPM as recommended. As a reminder I'm cutting a slot in [343-460 N/mm2 tensile strength] brass plate.

Result: tool snapped off in the middle of the first pass. It looks as though the tips have worn quite quickly and then the tool has become clogged with brass:



Here are my tool details, material details and the HSM advisor screen to match. Where am I going wrong?



FYI, until it snapped, it appeared to be making quite a reasonable cut:



Rob

[Robin Hewitt]

Brass should not be a problem, don't understand why you are having trouble.
Maybe we need a close up of the cut edge, is it square, have you got vibration marks, is it smearing at the top?
Maybe a picture of the machine that is doing the cutting?

[Rob Meades]

Thanks for the swift response and offer of help, here's some more detail. First, the machine (High-Z S-400/T):



Then, the material overall:



Then the cut; left is early on when some clear-outs are being cut, middle is at the start of the slot-cut (where the right-hand side of the picture is the earliest, the left-hand side is several minutes later) and finally right is the slot-cut just before the bit snapped:



For good measure, here's a video of the slot-cut phase, taken shortly before the right-hand side of the middle picture was cut.

[Jonathan]

From the third photo it looks like you have issues with rigidity. Your machine has unsupported rails on all three axes, so this is shouldn't come as a surprise. That shouldn't mean you can't make this part though, just makes it more of a challenge.

Is the tool plunging too fast? Ideally it shouldn't much at all.

Have you checked the runout of the spindle? With such a small tool this may have an effect.