[urbanimports02]

so i have been running the mill pretty hard and i am noticing that the head moves a lot while cutting. i was noticing steps on the surface of parts like the head is out of tram, but i just trammed it in. the steps are opposite each other on each side of the part as it is cutting ccw(digging in on the left when moving one way and digging in on the right when moving the other way), so i figured the head must be moving. i started the program and watched it and can see it move side to side relative to the collumn as it switches directions, and it is missing the insides of the part by .030" or so. this is mostly side to side, not so much front to back, but i noticed the head tram is off front to back, but the only way i can think to correct that is to shim with shim stock or something of that nature. anyway, it appears to move within the z linear bearings. i am running a 1/2" 3 flute carbide high helix em at .25" doc 45% stepover 4000rpm, 30ipm in aluminum, so pretty aggressive i think for this mill, just curious if anyone else is seeing this problem. i am cutting an oil pan for a kawasaki ninja zx10r about 10.5"x10.5" so the spindle runs for 35-40 minutes solid just for this first roughing, so i am letting it sit and cool before the next roughing opperation, and then finish passes. anyone experienced problems running this hard this long??
Jesse

[ihavenofish]

thats not a very agressive cut at all. ive done similar cuts in 304 stainless at 20ipm on the nm200. i can do the cut you mentioned on my nm-070 (with poor results due to bad z gibs).

that cut should only be exerting 20lbs of force, so the first thing id check is if i could see any play pushing on the head by hand. if you get slop, perhaps the bearings arent preloaded correctly - or theyve worn prematurely.

if its chatter thats inducing this error, try to adjust the feeds and speeds to his a sweet spot.

[urbanimports02]

fixed the head problem. it appears as though my mill was "assembled on friday" there are 4 bolts holding each of the 4 linear bearing blocks on, and 1 of mine only had 1 bolt which was loose as were the other 12 bolts. we are not talking a little loose, they were a few turns backed out. and no, the 3 missing bolts did not fall out, they would have been captured by the head, so they were never installed. i was thinking i was going to have to rig up my hoist and take down some of the enclosure and waste a day taking the head off, then it dawned on me, i have a cnc machine, so i brought the head down until it rested in the vise, then unbolted the 4 large bolts, and moved the table forward a bit then to the side to move the head out of the way and access the suspect bolts, added those bolts and tightened it all up. whole job took 40 minutes, and the head trammed in real nice, and it all seems to be tight as a drum now. i will be cutting 4 gsxr-1000 oil pans this weekend, so we will see how she does. its actually impressive how good my results were before, because on the last part i was doing when i really noticed how bad the head was moving, the finish and all was pretty decent, and you could see the head move left and right as it switched directions. should be real good now, and i can crank up the feeds and speeds to where they should be.

[ihavenofish]

wow, thats crazy. glad you got it fixed, i knew it had to be something screwy, but thats REALLY screwy (i made a punny).

[urbanimports02]

ya, screwy alright, thankfully they are m6x25mm socket heads, which i buy in boxes of 100 for my oil pump/pan that i build, so the fix was quick and quite easy.