|Old School||03/07/2019 08:50:33|
|323 forum posts|
I have the machine set up and running and have done the Sieg logo test piece. I have drawn a couple of simple parts I want to make in Fusion 360 I want to make on the mill.
i am struggling with putting in the data required by Fusion 360 for cutter speeds and feed rates etc. The milling cutters come with some of this information but my machine does not achieve anything like the spindle they suggest.
i want to machine mild steel and aluminium primarily, is there an idiots guide to this subject to get me going. Found lots of complicated formulas on the Internet but maths is not one of my strong points.
Any help rear fully recieved.
it will not let me edit the title it should be step.
Edited By Old School on 03/07/2019 08:52:17
|Jim Guthrie||03/07/2019 09:06:38|
|93 forum posts|
I found the same problem initially with my KX1 where I wanted to use small diameter mills and the recommended spindle speeds were much higher than the KX1's 7000rpm. But I found a feed and speed calculator which allowed for wide spindle speed ranges and I used it to calculated feeds and speeds for the typical mills I would be using - 0.5mm - 2mm carbide slotting cutters. I can't now remember which piece of software it was since it was quite expensive and I used it on its 30 day trial period. But I've just found another calculator online which allows the the maximum spindle speed as a parameter and that might be worth a try.
I still had to do a bit of experimentation and it got a bit expensive for a while with the ends of small carbide bits pinging off during cuts. But I've now got a set of feeds and speeds which give me a reasonable life from the cutters.
Edited By Jim Guthrie on 03/07/2019 09:08:54
|John Haine||03/07/2019 09:56:06|
|3013 forum posts|
Look for FSWizard app for phones tablets and PC
|357 forum posts|
All these feed and speed calculators are meant for industry where cycle times are important, they are way out for model engineers.
|Andrew Johnston||03/07/2019 12:00:35|
5411 forum posts
When I first got my CNC mill I had a foray into speed and feed calculators (won't say which one to protect the guilty) but it gave silly numbers, even for the professional user.
However, the arithmetic isn't complicated. There are two basic parameters, surface speed (which gives spindle speed) and feedrate. There are charts available for surface speeds depending upon material and cutter type. I don't stick to surface speeds exactly, I may be a little lower for materials like cast iron. If the nominal speed is above my maximum spindle speed I simply use the maximum. Feedrate depends upon spindle speed and chip load per tooth. Cutter manufacturers give recommended chip loads for various diameters of cutter and the type of cut in terms of depth and width. I use these as a guide, slightly biased to the lower end. Feedrates are probably more important the spindle speed. If the chip load is too low then the cutter will rub rather than cut especially when conventional milling. The old saying that published charts are for production doesn't apply to chip load. If it's too low the cutter will rub and be damaged irrespective of amateur or professional..
Width of cut and depth of cut are set by experience and the feedrate may be adjusted accordingly. A full depth but shallow width of cut can be run at a higher feedrate than full width at a shallow depth of cut.
Ultimately Jim is right, the numbers give you ballpark figures which you can then adjust by experience. Once you've got that experience one can refer back to it and not bother with the calculations.
17856 forum posts
I think it is the feed rates that can seem a bit fast at first. If in doubt think about how fast you would be turning the handle on your manual mill for the same sort of cut and what speed you would be using using.
For example if you were running the manual machine at 2000rpm and winding the handle (10tpi) at one turn per second then you would be feeding at approx 150mm /min. So if the cutting speed for that cutter is now 6000rpm which is with your higher top speed then you also need to increase the feed 3 fold to keep a similar loading (6000/2000). If in doubt set it a bit low while you get the feel of things as it is safer to override the speed upwards as it starts to cut if you feel it could have been more than to start cutting and get a lot of vibration or a bogged down cutter and then desperately rush to slow the feed. You can also react faster if things go wrong.
As Andrew says if you know where the cutters are from the makers give feeds and speeds for different types of cut, cutters and different materials so you can get an idea of where to start and then make a note of what works for next time. The hardest one I found was working out how fast you tend to feed a drill down into a hole.
I did some practice cuts in plastic first just to get the feel of things before moving onto practice cuts in metal and then finally parts I actually wanted. You will soon start looking at the statistics on the F360 simulator to see how long a part will take to cut and then seeing where you can get the time down.
I've not had much chance or need to play with my KX3 recently but should have something a bit more challenging for it to do in the next few days when the metal arrives, will post in my thread.
|34 forum posts|
Old School, I feel your pain.
I have a KX3 and no prior machining experience or talent. By far the best source of information I found was this:
It's a pdf all about using the mill, with a feeds and speeds table at the back. It follows the excellent tactic of assuming its readers are ignorant but not stupid.
|Old School||03/07/2019 20:23:05|
|323 forum posts|
Thanks for all the advice, I feel a lot more confident now in taking the next steps. I have had a quick look at the document that John has posted its tight at my level thanks again.
|Ian Johnson 1||03/07/2019 21:27:18|
|248 forum posts|
I have a KX1 and find that it is happy cutting most material ..... but only after I fiddle around with the speeds and feeds to get it sounding and feeling okay, starting off nice and slow. It is after all a little diddy hobby machine and should be treated as such.
I find all the speed and feed tables are absolutely meaningless for a machine this size, maybe if I was making a thousand off pieces I might, just might, look at feed and speed tables. But until then nah!
|Jim Guthrie||04/07/2019 23:30:02|
|93 forum posts|
When working with the KX1 toiday, I just remembered another thing from my experiences at the start. I suspected that my spindle speeds were not as requested by the GCode. So I got a cheap tachometer which I checked against my Cowells and found it pretty accurate. I then checked the KX1 spindle speed and it was running much slower than reported by the Mach software. It wasn't too difficult to adjust to get the correct speed and the life of my small cutters improved no end.
17856 forum posts
I've put the cutting details of the part I did yesterday in the KX3 thread, don't expect the KX1 will take off quite as much but gives an idea of what it will do and is more than in the linked article. I only upped the 3D contour feed speed 10% for part of the job so must be getting the hang of what works.
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