Feeds and speeds. Some tips for a newbie please!

[Dave_stoke]

It's is pretty hard for anyone to diagnose the problem fully unless they are there. A few very simple and basic pointers that are basics you need to know and cover, if you you dont cover these then you are fighting in the dark.

Machining is a process of logic and forethought. If those are not applied when you are trying to learn and its going wrong, stop and think to yourself, 'apply logic and forethought.'

1) What is the brass you are trying to machine? I'm fairy sure i know the grade looking at your pics, without seeing it in person, but the point is do you know? It's so important SO important to know the material you have to machine. Different material have different properties and are for different purposes. I think what you have there is known as 'half hard' ... and the clue is in the name, half hard meaning it's ductile, Not gummy (No such material property has ever existed) This means it can be bent and is not generally used for machining. You should be using CZ 121 which is a fully hard and free machining brass and is the go to brass for general machining. It chips beautifully and there is no need for coolant, brass self lubricates and tools should last a very long time. The only real needs for Coolant is for chip removal if making a lot of swarf or an air blast, It will add little to nothing to machining ability in this instance. Softer brasses are totally machinable but its not the right stiff to learn on, experience counts for e Everything in this game. Brass is one of the simplest materials in the world to machine, so if its not going right then something is radically wrong.

The way your image shows the brass burring up indicated either: It's half hard or a soft brass or tool tool was blunt from the outset. You said the tool was new tool (assuming an acceptable quality) so go back to the material and look again

2) Your cutting tools. Only buy from reputable seller. If you have crap tools then expect crap results. Just because it's carbide doesn't means its good..and there is a lot of crap carbide out there. It's pretty simple fundamental basics. You don't have to spend fortunes, go to somewhere like shop apt (google it) The quality is fair for the price point and perfectly usable for home and small business. The odd problem can occur with cheaper produced cutters from places like apt but its pretty rare from my experience.


Generally when using a helical entry into the part the (pending software also) you should denote X and Y feed rate and a Z feed Rate. The Z federate is the helical plunge rate and pending machine, cutter size, cutting conditions will be about half of X, Y feed rate.(this doesn't apply to larger heaver machines where this can be wacked up) The info from speeds and feed calcs unless they ask for a machining strategy will not take things like helical entry into account.. Its a big learning curve I'm afraid

If you cover the basics and its still not right, then you need to start looking else where.

A small vid of brass being machined with small tools, a light air blast only is used and see how cleanly it cuts with the slotting using a ramp strategy. The slot is 2mm.

https://www.youtube.com/watch?v=pGAoW4KAGeA

Wow thanks for that,

I hadn't even considered the brass hardness. It's just a strip off ebay. I know the bars I had cut an awful lot better. But there's never really a spec on those ads.

The tool was from ew in Stockport. It's where I get them all from.

The machine really doesn't function very well in helix you can hear the motor clunk back like it's hitting resistance just before it gets to a full step. Yet mach is counting down so it can register - 0.9310mm when it's still at +2.5000. Which might also be the case when it does actually plunge. It might be over plunging?
It's set for multiple depths of 0.5mm looking at the piece it seems deeper than that.

So it must be partly the machine or software and the rest the user.

I have a great deal to learn before I can work a machine even half decently. And if I don't do something with the steppers, the software and myself. I'll be forever buying bits.

I did think it can't be that hard. Usually very quick at picking things up. But if it was that easy, everyone would be doing it.

What I need is a source of income now. And stop fkn about. That way I will have a clearer frame of mind and I'll grasp it better.

Sent from my F8331 using Tapatalk

[Richard]

So anyone any ideas why that carbide endmill is showing so much wear?

Feeds and speeds were not a million miles away from G-Wizard.

I am surprised how ali can erode carbide so easily!

[Chaz]

So anyone any ideas why that carbide endmill is showing so much wear?

Feeds and speeds were not a million miles away from G-Wizard.

I am surprised how ali can erode carbide so easily!

We havent ruled out that you are using cheap / crap endmills. Try with something semi decent first (https://www.shop-apt.co.uk/) would be the supplier for me for something 'OK'. Id select a 2 flute uncoated endmill to start with. Plus, as Mr Ward suggests, the material might be the problem. Dont focus on the blunt endmill.

[Snapper]

So anyone any ideas why that carbide endmill is showing so much wear?

Feeds and speeds were not a million miles away from G-Wizard.

I am surprised how ali can erode carbide so easily!

Is that end mill coated? Looks like it might have tialn coating, which will cause build up pretty quickly, that's probably not erosion but almost certainly a build up of aluminium on the cutting edge. You want uncoated cutters really for ali. And yes find out what the material is, even different batches of the same grade can cut differently but stuff like 1 series ali is horrible for machining.

[Richard]

Is that end mill coated? Looks like it might have tialn coating, which will cause build up pretty quickly, that's probably not erosion but almost certainly a build up of aluminium on the cutting edge. You want uncoated cutters really for ali. And yes find out what the material is, even different batches of the same grade can cut differently but stuff like 1 series ali is horrible for machining.

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!

[Chaz]

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!

What is the highest speed your spindle can rotate at?

[Richard]

What is the highest speed your spindle can rotate at?

Man this thread is getting confusing! LOL!

I don't know how fast it can go. I will have a look at see what it actually tops out at.

It's a Schneider altivar 12 VFC with a water cooled 2kw spindle.

[Dave_stoke]

Man this thread is getting confusing! LOL!

I don't know how fast it can go. I will have a look at see what it actually tops out at.

It's a Schneider altivar 12 VFC with a water cooled 2kw spindle.

Yes sorry richy I somehow derailed and hijacked your thread.

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[Richard]

Man this thread is getting confusing! LOL!

I don't know how fast it can go. I will have a look at see what it actually tops out at.

It's a Schneider altivar 12 VFC with a water cooled 2kw spindle.

I just tried 20k rpm. VFD says 326hz and spindle was going at 19600rpm.


This is what the bed looks like and what the finish was initially and after the tool degraded.

[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.