Feeds and speeds. Some tips for a newbie please!

[Snapper]

OK, I'll get a 2 flute uncoated from APT and see how it goes. The cutters I have are coated but I don't know what with.

The part I was machining is the bed of the machine, so no idea what grade it is. I just wanted it flat(er) and level.

Once I get the new 2 flute cutter, is 6k rpm and 500mm/min, dry, still in the right ball park for taking a shallow finishing cut at say 90% engagement?



Just for my own interest, if there is build up on the tips of the cutter, how does that erode the tip?


Thanks for the input!

Noooo. Don't cut the bed.

Get a board, sheet of ali, whatever you want to use and stick it on top. The bed is made of several independent pieces of extrusion and even if you machine it 'flat' they will flex independently anyway. Also you're then tied in to the cutting area, you can't really load a bigger piece in and clamp it outside the work area.

[Richard]

Noooo. Don't cut the bed.

Get a board, sheet of ali, whatever you want to use and stick it on top. The bed is made of several independent pieces of extrusion and even if you machine it 'flat' they will flex independently anyway. Also you're then tied in to the cutting area, you can't really load a bigger piece in and clamp it outside the work area.

Not on my machine. The bed is actually a big thick slab of cast iron, onto which is bolted an ali plate, which is drilled and tapped for tooling. It's basically sacrificial. As this is used machine, the plate had a few cuts in it and after transit and moving ect, it needed leveling.

[Snapper]

Thanks mate, so run the earth into the control box and connect to an earth point there?

Can I use hdmi for the spindle? I have a thicker rca shielded somewhere. I presume most of it is just signal wires?

Sent from my F8331 using Tapatalk

No. It's a 3ph motor in there so what you should have currently is just the 3 U V W power wires. I can't remember off the top of my head what the optimal core diameter is for the cable but depending what power spindle you have it isn't hard to figure out the max current and find out on google.

Not on my machine. The bed is actually a big thick slab of cast iron, onto which is bolted an ali plate, which is drilled and tapped for tooling. It's basically sacrificial. As this is used machine, the plate had a few cuts in it and after transit and moving ect, it needed leveling.

Ah, I see. Very nice. Likelihood is it's a cast 5 series aluminium. In which case try drop your RPM by 20%. Have to feed a bit harder in that stuff.

[Dave_stoke]

No. It's a 3ph motor in there so what you should have currently is just the 3 U V W power wires. I can't remember off the top of my head what the optimal core diameter is for the cable but depending what power spindle you have it isn't hard to figure out the max current and find out on google.



Ah, I see. Very nice. Likelihood is it's a cast 5 series aluminium. In which case try drop your RPM by 20%. Have to feed a bit harder in that stuff.

It's 800w the spindle. So I need initially a shielded cable capable of 1500w

Sent from my F8331 using Tapatalk

[Snapper]

It's 800w the spindle. So I need initially a shielded cable capable of 1500w

Sent from my F8331 using Tapatalk

No, it's 800w @ 220v over 3 phases so, roughly 270 watts per phase or about 1.25 amps. Maybe you could get away with repurposing some sort of signal cable... but I wouldn't personally. Get a proper flexible copper braided cable and do it properly.

[Dave_stoke]

No, it's 800w @ 220v over 3 phases so, roughly 270 watts per phase or about 1.25 amps. Maybe you could get away with repurposing some sort of signal cable... but I wouldn't personally. Get a proper flexible copper braided cable and do it properly.

OK being an ex mechanic and a crafty bugger, I have shielded the original spindle cable and run it separately from the rest. I have also earthed all bodies.

Let's see how it fairs. Its running a program now its always struggled with. Lego block lol.

Anyway after reading and thinking about what you said it dawned on me. Yes before I was running spindle speeds above 5000 rpm there wasn't much current so little interference, since its been running upto and beyond 15000 rpm that's when it started going haywire.

Let's see if my DIY shielding worked



Sent from my F8331 using Tapatalk

[m_c]

If you've only been taking a light surface cut, then the wear on that cutter would be as expected, especially if chip clearance has been poor along with no lubrication.

If chips start getting re-cut (I.e. not cleared from the cutter), then in soft materials they will start welding to the cutter. As soon as that happens, your nice sharp edge is now covered by a blunt layer of material, and the problem will compound from there as heat builds up at an ever increasing rate, until something finally fails.

I never realised you were machining aluminium with that cutter (I'd assumed you were still working with brass), but in aluminium you want polished cutters so there is as little roughness as possible on the cutter to avoid chips sticking (coated cutters are often rougher, but in aluminium coatings make little difference, which is why uncoated polished is usually preferred). You also want a bit lubrication to help stop things sticking. Lubrication can vary from an occasional spray of WD40, to mist, to full flood coolant.

On something like that bed surfacing job, a light spray of WD40 across the part at the start along with just enough air to clear chips would be more than ample to keep things running smoothly.