@Steve_Popmarkov I figured out how to get CamBam to behave. Is this what you meant?
I had to adjust the Inner Tab Scale as documented here http://www.cambam.info/doc/plus/cam/HoldingTabs.htm
I have now managed to generate a path with a 6mm cut width, this results in a clearance cut first, then a 40% stepover to the second cut, then a final finishing pass for the last 10%. That should leave plenty of room for chips. I will test this run tomorrow.
Try flat tabs instead of “3d” triangular tabs the I’m assuming you are using a center cut endmill they often struggle with 3d tabs ball nose endmills are more suited to that task because of tool geometry
Good tip. I’m using a single flute up cut bit. I did try flat tabs too. Same issue. I think it might actually be resonance. Going to try some different tool stickout lengths and spindle speeds tomorrow.
@Ben_Delarre ,your chattering from first cut to final. That end mill is playing bumper cars at the end. Speed up. She’s getting board on the slow dive… when you break the bottom she’s catching the side and with the chatter is bouncing. You can double stack Al. This will assist with this as well. The bottom of the end mill will stay occupied the whole (hole :-)) time.
That slow dive goes away with triangle tabs. Still had the same issue thought but I an running at 500 feed rate. I know your files are going at 700 but when I tried that I had the same issue…wonder if my rpms are not the same? Have it at 250 (15000) on the dial. I guess the inverters aren’t super accurate?
@Brandon_Satterfield just tried the same again using the settings from your R7 file. I did the same as the ACME profile, 0.7mm doc, 600mm/min feed 5 plunge, spiral ramp inside profile. Again looked great till I got to the last pass, again the same issue. I tried varying the speed a bunch during the cut too to reduce chatter and couldn’t find any good sounding spots, all sounded worse than whats in the video above. I varied RPM from 13000 to 16000.
Any other ideas? I’m not sure I get what you mean about stacking up the Al, I don’t really have Al to waste as a spoilboard if thats what you mean?
I’ve had this issue before. In 1/2" thick material. Is that the thickness of plate your cutting?
Try slowing the plunge to a crawl. And since you have a single fluke it may grab once it hits the bottom or deflect once it finished cutting the triangle tabs, have you tried the straight plunge that cuts into the spoil board or cardboard. . The end mill dies not have the eight cutting edge on the bottom and coming off the the triangle cut. The end mill will struggle to cut thru the last cut. . Also check the backslash on the Z axis. It may have some slop in it and not pushing the end mill enough to cut thru
Your plugs look like 1/2" but the cut material looks like 1/4".
The issue is around the holding tabs correct? If you have 1/8" al, double stack it. If you don’t, use carpenters tape. The latter will remove the holding tab issue.
Another option will be to make the whole cut a pocket. No holding tabs.
I’ve had this same issue on the big mill, now I have to use a backer.
The plugs are definitely 1/4". And yeah the issue is around the holding tabs. I could indeed make this cut a pocket, but I can’t do that for the actual cutout pass which is the same operation essentially and has the same exact problem.
Hmm, so essentially give it an alu spoilboard for it to cut into on that last pass? Madness.
@Steve_Popmarkov plunge is already at a crawl, just 5mm/min. If you check the video above at 4:50 you can see where the issue first starts to occur. At this point we’re doing a cut around the outside of the plug, 0.4mm away from the outer wall. It does the plunge, and then as it accelerates into the arc after the plunge is complete it starts to chatter horrendously. Then on the second pass around we’re cutting the other side of the wall and the chatter gets worse, probably due to the rough surfaces made on the previous pass. I think this is probably just a resonance issue, but I’ve not yet been able to find a feed or spindle speed that stops it.
Yeah, exactly. If you keep the end of the end mill full it won’t allow for as much side load and hence deflection.
The reason I mention the pocket is because you won’t need the holding tabs.
Hmm interesting. Doesn’t that mean that we’re actually pushing way too fast then? Or perhaps actually cutting too shallow so that last 0.5mm pass hasnt got a high enough chipload?
Can you send me your file?
Yes, and if you can hold the cutout down with wood or screwdriver. And the new added alum or cardboard spoil board gives the enroll the extra room to cut thru the last pass. And try some wf-40 or Kingsford bbq lighter fluid as a cutting fiuild becarefl if you use the lighter fluid
@Ben_Delarre yeah a higher chip load could assist.
My calculator is telling me that at 600mm/min, 15000rpm spindle with a 4mm single flute I’ve got a chip load of 0.0015" that seems actually about right for a 4mm bit according to the charts I’ve found. Man, aluminum is so confusing.