Endmills and Router Bits, Oh My!

[Cartierusm]

Ok, so I've searched and I'm not sure what forum to post, but as I'm using a home built CNC router I figured I'd start here.

I noticed when cutting .125" deep, with a .125 overlap with a 1/4" router bit with a 1/4" shank I was getting some bit defelction, even running at 10 IPM. I don't remember too well because this was months ago, but I think I slowed it down even further and still got defelction.

I now use a 1/4" bit with a 1/2" shank and I don't get any defelection, it's also a high grade new bit.

So what I need to know and I'm sure a lot of us noob could use the knowledge as well are the specifics.

Even though YOUR machine can traverse at 120 IPM. What is a realistic cut speed and depth of cut and overlap of cut for different material. Also what bit.

So for plywood, hardwood, plexiglas and plastic. I would like to see a format something like: Plywood, 1/4" Router bit, 15 IPM, .125" depth of cut, .125 overlap, you know something like that. Of course add in if coolant is needed or even you standing over the part with a spray bottle, as in cutting plexiglas or plastic, if it's necessary.

Also when, aside from cutting metal, would an endmill be of use, if at all? I need to mill some plastic project boxes to make my Pendent Control and I don't want to buy another router bit when I have an 1/8" endmill already. If I can use an endmill should I run it at 22,000 RPMs? On that note, how does cutting speed and amount of material removed at a time correspond to professional CNC Mills work when they run at 10,000 RPM? I always wondered because I use a formula to figure out the RPMs on my Bridgeport to calculate rate of cut for bit size. I didn't think it had to do with the machine but just laws of physics with regard to a bit being able to remove material.

Anyway, any help would be appreciated.

[Khalid]

U didn't mention the spindle RPM, No of flutes....

[ger21]

I'm guessing your bit deflection was when cutting metal?

Anyway, what works on one machine might not work on another. A lot of variables come into play. I know of commercial routers that cut 3/4" depth in one pass, with a 1/4" diameter compression spiral, at 1000 ipm. I doubt that does you any good.

[Cartierusm]

Sorry, I am using a Porter Cable Router at 22,000 RPM 2 Flute. No Bit deflection was cutting plywood, I was inches from the piece as it was cutting, right up close I could see the bit flex. Could have been a cheap bit. I am now using a good bit.

[Cartierusm]

Ok, what did I learn today? Well I'm trying to mill a 3/16" piece of 5052 Aluminum, 10" x 8", for my Pendent Control. I started with Artcam and made the text a V carving centerline cut. I used a 60 degree 1/2" V router bit. It worked OK, but I had to use a 3M Roloc pad to debur the top so the letters looked better, not much work, but could be better. I plan on filling the letters in with paint so the text stands out. I was making .056 deep cuts in one pass. I started out with 5 IPM then turned it down to like 2 IPM and that seemed to make the walls of the letters smoother. What I decided after all I did today was that I need a bit specifically for milling aluminum. Maybe I'll use a 1/16" Ball Mill.

Then I proceeded to mill the through holes for the buttons and switches. I used a 1/2" endmill in the router. .032 passes for both steps and overlap. I don't know much about ramping so I left that at zero. Now I know. When making a straight cut down into aluminum with an endmill it shook the table and I could see my Z axis move, not good. I was going real slow .05 IPM for the depth feed rate. I ended up getting frustrated and jacked it up to .75 ipm and feed by hand. I basically had the G code move the bit into position and I then did a Feed Hold and then feed the bit in all the way through slowly and then started the program again so it could do it's circular patterns to make the size hole I programmed in. OH BTW I was testing on scrap with a router speed control but the torque drops off dramatically so I had to use it at full speed. So by this point the bit was hot and I was squirting it with coolant. I thought the bit was fried. After all the holes were machined I proceeded to do the final profile cut on the outer edge of the aluminum to round the corners and clean up the edge. It cut fine at 15 IPM....weird. So I figured it out. I don't need to go so slow and the bit was fine. Next time I will have to use ramp so the endmill is feed in while going in a circle, endmills don't do good going straight down even if they are center cutting bits.

What I will do next time is use the v carveing bit and just make a centermark. Move the gantry out of the way and use a cordless drill by hand to predill the holes removing most of the material but not coming close to the edge. Then run the hole program and it will do fine. I have a bridgeport i'm going to convert once I become proficient at using the machine I built and see if I have any design flaws, so when that's done I use that for milling metal.

[ZipSnipe]

Sounds like your taking too much off. Plus its a router not a milling machine so when your cutting aluminum its not the same as wood, I would also have an airline attached near the spindle to blow chips out. Whats probably happening is the bit spinning so fast its gumming up the cutter and your feed seemed slow. When milling aluminum on the Bridgeport I,ll usually run the speed about 750rpm and I,m blasting air on it the whole time. When we run alum in the VMC's they get blasted with flood coolant especially when drilling and they usually mill at about 2-3000 rpm with a pretty quick feed. Of course these machines weigh tons. I assuming your using a router that would normally cut wood or plastic. I would definetly use air on alum at least and coolant when drilling. I tried to find the link to one of the milling cutter manufacturers, they have a whole pdf telling the correct speeds and feeds in relation to the materials, I,d check different cutter manufacturer websites and see if they have that chart.

[Cartierusm]

ZipSnipe, I agree. I have a bridgeport and know all about calculations. The problem is I'm not going to spend thousands on a spindle, so I'm gonna use the router until I convert my Bridgeport to CNC. 1/32" is not that much. Basically it was only when I was plunge cutting straight down with the endmill, when it was making circular patterns widening the hole and routeing the edge it was fine.

Question, what do most engravers use to make lettering? I'm trying to find a version of the 90 degree V router bit but for metal.

[bclark6716]

go to 2linc.com they have some very good 'V' bits for engraving metal.

Brian

[harryn]

You mentioned that you are doing about 0.050 in depth per pass. While I have very limited experience, what I have seen is that my brother's manual bridgeport clone mill can take off a lot of material in Al in one pass. On the other hand, I have seen the small hobby mills struggle to take off 0.020 in depth smoothly.

Just FWIW (which is not that much) a 1/4 in 2 flute end mill in a hobby style setup is probably good for depths of 0.010 - 0.020 inches and 5 - 10 inches of cut per minute without a lot of chattering and complaining. Even then, we could not always cut "sideways" at the same time we were cutting depth. (in other words, you could remove 0.010 in of material - either horizontally, or verticallly, but not at the same time. At least that is what I saw so far in my very limited experience.

[Cartierusm]

SWEET!! Success. Well I finally got it figured out. What I did was get some brand new high end solid carbide endmills and worked from there.

The text using a router V bit didn't come out great but I knew this wasn't the right bit for the job but since the letters are going to filled in with paint it didn't matter.

So I programmed the text, then I programmed for the V bit to make a center punch mark for the holes, then the program stops. I then moved the gantry out of the way and use a Makita and a 3/8" drill bit and predrilled all the holes, the smallest hole the router is going to cut is 1/2". Then I programmed the holes using RAMP. With the new program and carbide 1/4" endmill it worked perfect. I used the standard Ramp settings in Artcam and then specified .0625 step and .0625 for the overlap. I set 5 IPM for the Plunge and 10 IPM for the feed speed. This was good but I could have gone faster with the plunge. I didn't get so much as a vibration....wicked. Then I needed to profile cut the outside, this worked before, but I decided to add LEAD IN settings. I ran the profile cut with a carbide 1/2" endmill at 20 IPM and it ran perfect.

Thanks everyone for the help. I will post pics of the pendent control I made in a few days when the paint is dry.

P.S. Oh, BTW I ran the router at full speed and it worked fine.

[Cartierusm]

Well here are the pics of the finished, painted and wired pendent control.