Honestly buy something uncoated like Datron’s micro carbide O-flutes I bet they cut longer and cleaner.and the’re very nicely polished.
Talked to a professor and your SFM was too low. What happens is in non rigid machines there is a sweetspot, too low and the point at which your chip is in a bit of a superposition of both liquid and solid causes the liquid part to begin to weld to the cutter. Too high and your tool will wear much faster as well. Basically you need less flutes because your IPT is going to be cut down by a factor of how many flutes you have eg if you go from 3 to 1 at the same feedrate your IPT will be 3 times as large.
It’s all a bunch of math, figure out the SFM you require for that grade of aluminum which is 800-1500 SFM and works out to rpm = 800-1500 x 3.82 /.25 = 12,224 - 22,920RPM
Then you take those figures and figure out how to get your ideal IPT or inches per tooth so you take 18000 multiply it by the reccomended IPT of 0.002 which gives you 36 ipm feedrate
Next based on the cut that you’re going to take you calculate actual feedrate based off radial engagement 50-100% of the cutter you use recommended feedrate less than that and it increases so at 35% stepover you run 5% faster, 30 10%,25 15%, 20 25%, 15 40%, 10 70%, 5 130%.
There is a bit more math to it than this when you use multi-flute endmills but single flute makes things easier.
From what I can see you were cutting too slow as you had 3 teeth and therefore you had about 1/3rd of the chipload you need and your little scraps of chip were so thin that they were melting in that moment in addition you were generating alot of heat in your tool.
(38.25/15000) = 0.00255 / 3 = 0,00085 IPT and reccomended is 0.002 so either you need to move at a speed your machine is not rigid enough for or you need to spin at a speed your spindle is not capable of leaving you with the last option less flutes.
Another important factor is spindle power. On a VFD for instance you have a somewhat linear horsepower to RPM and as your RPM lowers so does your Horsepower which means less removal which means more problems I assume this is the same with routers/universal motors.
Basically that 3 flute is just a finishing tool for you unless you want to wreck it or modify your machine to be more rigid and support higher feeds.
I also find the aluminum machining videos to be quite misleading as many of them use trochoidal toolpaths which aren’t reallly possible in CC. Ok maybe not impossible but you’d have to be crazy to draw the lines yourself somehow measure the stepover and give each little arc it’s feeds and speeds based off engagement etc. Not only that but each pass would have a pause and a spindle on off cycle which isn’t in Winstons videos indicating he’s using a postprocessor on a different program.
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Additionally these “bad” zones you don’t want to be in can be improved with the use of cutting fluids and micrograin carbides, smaller endmills, Polished finishes, etc.
Also the horsepower I mentioned, HP = MRR x mf
Aluminum mf is .3
MRR = IPM * WOC * DOC
this calculation is to ensure you have about a 6 cubic inches per minute removal rate per horsepower and this is why I run at full RPM because anything less I am getting less horsepower and therefore sub optimal cuts as my horsepower drops unless calculations to adjust are done.
@No_Soup_For_You: Thank you for this response. It is very helpful. It sounds as if the feeds-and-speeds in MeshCAM are not as good as they could be: I will adjust them manually from now on,
I would also start somewhere in the DoC range listed on carbide create and go up from there. The formula I gave you assumes utmost rigidity.
Datron make great tools and all but for new users who are very likely to make tool breaking mistakes during their learning journey. In my opinion it’s better to start with low cost tooling and stepping up after they are having success. Breaking high dollar endmills is beyond painful and there are several low cost single flute options available on various sites like Ebay and Amazon.
I started on a stock So3 with 6mm ebay single flutes after reading VinceFABs thread years ago.
it’s worth the read.
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