Thread: It's begun....
Even quicker update: looks like all parallel cables are not equal, as I have just replaced that for the old one and all is now well - test job ran without any e-stops :-)
Now for some cutting.......
I ran a couple of jobs yesterday: one was some text in plywood for a sign, which was long but ran fine. The other was a first go in aluminium doing some roughing 3D work (I'm using Vectric 2 and 3D for my toolpaths).
The aluminium didn't do too well and I'm pretty sure I'm being a plank with regards feeds and speeds. Material is 6082 as per previous posts and I was running a Carbide 2Flute End Mill @ 12000rpm and 1200mm/min with 2mm DOC and 30% stepover (maybe a bit aggressive on the DOC?) and was blowing air. Anyway the machine seemed to hold up well i.e. nothing broke but was grumbling a lot so I hit Feedhold and saw that the edges in the pocket were clean, but it was obvious the cutter was trying to erode its way through rather than cut as there was a good "weld" of aluminium on the cutter and a "lip" around the edge of the pocket.
My guess is my feed rate is too low (possibly rpm to high) and I'm re-cutting chips?
What was cut didn't have visible chatter marks on the walls of the pocket, so I'm tentatively confident the rigidity is OK (2 ballscrews does indeed help :) ).
Will have a play later with a less aggressive DOC and high feed rate, but if anyone has their own feeds/speeds I can try then it may save me some time in trial and error.
Assuming that's a 6mm cutter, then the feedrate and speed you posted should be fine. With only 30% stepover you could actually increase the feedrate slightly due to chip thinning, but I'd leave it for now. I tend to agree that rigidity shouldn't be a problem.
You're problem is almost certainly the lack of coolant. Air will help to cool the cutter, but not much compared to coolant (i.e. mainly water). Also, with no lubricant the co-efficient of friction is greater, so more heat is generated. You'll probably find that even a small amount of coolant will do the trick, or if you've not got any then WD40 works well on aluminium. I certainly wouldn't advise using it regularly though as it wont be good for the bearings.
If you think the rigidity of the machine is a problem, as a general rule don't change the feed or speed, instead lower the depth or width of cut. The reason is if you've chosen the 'correct' feedrate and rpm, then the chipload will be a particular value which you want to maintain. If you just change the feedrate or the spindle speed the chipload will change.
Last edited by Jonathan; 30-09-2013 at 09:50 AM.
A good clue to cutting correct is to check heat of material and chips.? When your cutting correct the Chips will be scorching hot but the material just slightly more than warm.
When your more experienced you'll here the sound and know if your close to cutting correct but at the moment these sounds will probably be
making you nervous and weary.!! . . .Put some ear plugs in and listen to it you'll not be quite so on edge and it dampens mechanical noises and lets you hear cutting sounds better.!!
Also Set your VFD to display Amp's rather than RPM this will give clue to how well cutter is coping, also shows when cutters getting worn while jobs running. If Amps are low while cutting then this gives a clue that you can probably take deeper cuts.
Regards sticking then Mix some paraffin and old engine oil in a squirt bottle and give the cutter a blast every now and again to help with sticking but when you have found the correct chip load blown air is enough to clear chips and stop re-cut/sticking. I never get sticking and for most Jobs only use blown air with few squirts of coolant, for jobs where finish matters then I run a mister system. (just can't bloody breath when it's at full chat.!!)
Now test it properly for accuracy and cut the Aztec calendar.!! . . . That sorts the Baggy fanny's from the tight chuff's .. Lol
Thanks Jonathan as ever.
I'll try with some liquid coolant next and see how that goes - reason I thought I was being a numpty in the F&S dept. is that most calculators are throwing up higher feeds generally e.g. 18-1900 mm/min, which I can try but that sounds aggressive, although maybe its not aggressive enough?
Must try and remember where I got my last batch of mills from, I'm likely to be placing some more orders ;-)
Lol - I'll have a crack at the Aztec calendar soon I promise :-)
You're right the sound is a little disconcerting - was even louder than my bloody noisy compressor ;-)
A big milestone tonight, thanks again and as ever to Dean and Jonathan (I would be really struggling without you guys).
Firstly, the talk of slack Alices and tight chuffs had me checking over the machine for loose stuff and I found a couple of bolts that hold the Y Axis ballnut housing to the Z-Axis that needed tightening, so that helped as I think there was some play in the Z-Axis "rolling" about the Z Axis if that makes sense.
I also hooked up a bottle of PC coolant to the airbrush "mister" (will look at something less expensive for the future) and although its a bit vicious compared with a true mist i.e. almost flood I figured too much was better than nothing.
So I ran a roughing job for an aluminium catch in the normal 6082 using 12000rpm and 1200 mm/min and a DoC of 1mm. This ran, but I need to refine my toolpaths or how I'm generating them in Vectric, as the machine romped through the initial slot, but I had neglected to notice the toolpath was using alternate climb and conventional along the Y-Axis.
Whilst there was no mishap like last time, the difference between a conventional path compared to a climb was night and day i.e. the climb milling threw the chips out (and this time the chips looked like nice shiny chips rather than welds :) ). The conventional paths didn't throw the chips as well but the machine grumbled through the material, in fact the "grumbling" was vibrating the whole workbench
I also have some strangeness in the toolpath where some long cuts were stepping along rather than smoothly running and resulted in not so much chatter marks but waves.....weird.
Here's some pics of my first completed run in aluminium - I would have videoed, but I was hovering over the feedhold and e-stop :-) Also bear in mind this is a roughing pass and the "chatters" you can see are where the conventional milling occurred. The gouge you can see at one end of the oval was the "weld" and crap from the previous attempt.
Anyway, I am going to play with the strategies in Vectric to see which one does the most climb milling, as that was just eating through the material with nearly no "noise" at all.
I also have a finishing pass to run on the job shown as well as the other side - I hope the tabs hold up.....
More to come
Chris you can set climb as an option in CUT3D. I use Vectric (VCarvePro, CUT3D, PhotoVCarve and also CamBam [Not Vectric]). Why I use the different ones, is a horses for courses item and I could not afford Aspire at that time (the ones I got hurt the budget enough though they are help increase earning a good bit). Drop me a message and will gladly help as able on Vectric. CamBam has some very useful ability if you are doing isolated 2.5/3D type work (I use it to help make chromatic harmonica combs and they are complex planes on the interior). I am very sound sensitive and Dean is correct in that once you get used to it you will know what sounds right.
It is looking really nice. If you are looking for vacuum tables I would look at Sorotec out of Germany as they are selling a really nice model from a US firm and they are well made. I am finishing building a wooden one that will do the job I need and be fit to my work area. If looking for a vacuum set up let me know. -Micheal
Last edited by m.marino; 06-10-2013 at 03:45 PM.Life is Live it
CAD software VIACAD Pro v9 (Beta testing x64) Also Aspire v8
CAM Software Aspire v8, PhotoVCarve, CamBam
Machine: Custom built see build log: http://www.mycncuk.com/threads/3661-...Second-machine
Work with Solid Surfaces, Acrylics, Woods, Foamboard.
BUILD LOG: Web Goblin cnc has begunBy Web Goblin in forum DIY Router Build LogsReplies: 147Last Post: 12-02-2012, 07:49 PM