I thought I had my speeds and feeds dialed in for HDPE. yesterday the cut was great, today it went down hill fast. Picture of the 1/8" 1 flute bit I'm using, supposed to be for plastic, and 3 sample pucks. Puck on the left, 13750 spindle speed, 1397 mm/min, DOC 1.5875 Puck in the center, 18800 spindle speed, 1746 mm/min, DOC 1.95 Puck on right, EXACT SAME SETTINGS AS PUCK ON LEFT??????????? These are all done using climb milling (left) however I noticed on my small holes this was causing the bottom of the hole to be egg shaped. my 7.9mm hole was measuring 7.2mm on top and 6.5mm on bottom. So I switched all none critical cuts to conventional milling (right) and left this outer cut climb milling. That's the only change I mad and now I can not get a clean cut. I changed the bit 5 times, I flipped back and forth between the climb and conventional milling. Played with the speeds and feeds, nothing I did got me back to the nice smooth finish pictured. All of a sudden I now have considerable chatter, assuming it was the bit I changed it and changed it again, and again, and again.... I put all the settings back to 1397 mm/min, doc 1.5875 and still get the puck on the right. My spindle is the new Router11, it is considerably loud anything above 4 on the dial and has a vibration at the top of the router. How can I test the run out? I checked the bit by rolling it on a sheet of glass. I can not detect any bend or defect, it rolls flat so I don't think the bit is bent, and not 5 of them. I just don't understand why it's not cutting good anymore. Did something come loose? I checked the machine, can't find anything that moves. I just don't know what else to check. I usually over look the obvious so I will kick myself if I wasted all day trying to figure this out and it's something simple.
Hows your chip evacuation? Those marks on the side remind me more of chips getting recut /melting to the side
Its the same for all 3 pucks, the chips extract fairly well but do pile in the last quarter. I have a loud chatter now, where I didn't have before cutting the other 2 good pucks.
Hold endmill and give it a wiggle. See what moves - tactile approach, can detect minute movements. Maybe something gone a little loose. Grubscrews on shaft couplers, etc
I can slightly twist the entire C beam from pulling on the end mill bit. Figured that was normal, maybe not? Don't see anything loose. Wheels are tight. I have been wondering if something has come loose. Just haven't found it yet. Could I be loosing steps? maybe I need to turn the current up a bit on the motors. Think that would give me an egg shaped puck.
Look to your router bit I had something similar. Amazon??? Was using on pine but very expensive New Zealand pine. Absolute crap. Blunt as ............ cannot remember the brand. Maybe Hozly. Personally on your puck I would use a 1/4 bit straight carbide more rigid than those 1/8 cutters. I normally use HQ Master straight cut 2 flute for my toys.
Wish I could, but I need a 3/16 cut. There is a inner ring and an outer ring, I'm trying to get them out of one piece of stock. The puck is just a practice piece.
I have had the best luck cutting HDPE with an endmill with two straight flutes at 2500mm/min and cutting depth of 1/2 the diameter of the endmill. 99% of the time, it works every time. I leave about 0.2-0.3 mm for a final full depth finishing cut.
I plan to give that a shot, but it just doesn't make sense. I cut about 10 of these test puck, perfectly. Mow suddenly I have a vibration.
I noticed you said your holes are smaller than expected. Measure your endmill. If they are cheap Chinese endmills, they will not be 1/8" inch - unless you are lucky. They are generally smaller. I have had them range from 3.11mm to 3.17mm. I have yet to have one come to me that is actually 3.175mm. I discovered this problem with the first aluminum plate I cut. My 5.1mm holes were not big enough for a 5 mm screw to go through. Now I measure each endmill and enter that into the tool database for the CAM so holes and parts come out the expected size. The reason the hole may be smaller on the bottom is the end mill is flexing during the cut. This is the reason for the roughing and finishing job. You can actually see a 1/8" endmill form a slight curve when cutting. It is amazing the difference of a 4mm endmill vs a 1/8" (3.175mm) will be for cutting. I only use a 1/8" when I desperately have to use it. When cutting aluminum with a 1/8" the holes during roughing are very rarely round for me due to the endmill flexing during the helical drilling operation. They become round during the finishing pass.
Thanks Giarc, I spaced out I could use a 4mm bit for this. I'll have to see if I can find some 4mm cutters. I am noticing some deflection at the bottom 20% of the HDPE. I have tried a finish pass, that helps a bit but still deflects. I have even used the Circular cut and checked the "repeat pass" and that helped a little also. They look round now but still smaller at the bottom 5mm than the top side. It also helps to use the Conventional milling rather than climb. I think the climb on inside holes causes the single flute bit to pull towards the center creating even more deflection. Using a 2 flute seems to negate that effect. The top side is the correct size now at least. At any rate, I'll have to chalk this up to "something was loose". I never found anything loose but while looking for the problem I notice the two top forward V-Wheels are grooved on the outer edge. (The machine is only a couple weeks old - is this normal?) I opened all the eccentric nuts and re-tightened them, making sure I turned them all the same direction. It seems the Router11 is a bit heavy for these wheels. Is there a kit to beef up the Z like the LEAD1515? I am getting a good cut once again but not quite as smooth as the first ones, but much better. I also noticed my ramp and plunge was a bit high, around 600 so I set those to 330. seemed to help a bit also. But the V wheels are concerning.
That does not look normal. Are they grooved on both sides of the wheel or just one? The Router11 should not be too heavy at all. People have run 2.2 Kw spindles on these machines which are much heavier. Is there by any chance a spacer missing in the wheels? That could explain the wear and the cutting issues.
Just grooved on the one side. Spacers are in there. I didn't think that was normal either, but not sure how it happened. I didn't find anything loose. I should probably replace them.
Looks to me like a plunge or other consistent heavy force, like tool deflection in the -Y direction, has pushed the entire gantry carriage up and out of the V-slots for an extended period of time. Unlikely to have been tight enough, the whole gantry should flex long before the wheels pop out. Would explain the egg-shaped parts if the long axis was in Y- your z-axis/gantry was rocking back and forth more than it should.
Do you have digital caliper? I would measure the wheel against the others maybe it was flawed a tad too big. And now its just broken in. Just wishing.
Posted this on another thread, but thought I would also post it here. Very informative. I've learned a lot in two weeks Who is Afraid of Tool Deflection? [2020: 4 Evils + The Cures]
