I have made another of these parts. This time I tried 3mm depth of cut. It was OK. Also I tried using climb milling for the finishing pass, instead of conventional milling. It isn't much different. Also I put the coolant guard back on, so I could pour the coolant on quicker. I made a mistake with the program for this one and there is a gouge, see the second picture. The tool is very battered. It has only made 2 parts. I noticed it was a bit damaged after the first part, but it is a lot more damaged now. I will try reducing the feedrate from 300 to 200. I will use a new cutter now. Also, the later roughing cuts are leaving the material up to 0.1 too thick. I can't explain this yet, so I will try it again to see if it happens again.
4 comments:
us a dial-indicator to measure the runout of your spindle. It looks very much like bad spindle bearings, or if your machine is a very small one naybe the whole machine is bending. The only cure for that is a bigger/heavier machine!
Other variables you have to work with are the size of endmill and number of flutes, and your spin speed. What kind of coolant are you using? How fast are you spinning the tool? Oh, and are you working in metric or english units (i.e. what are the units on your feed rate?)
(I'm fairly inexperienced at this stuff myself, only started in machining months ago.)
andyw, It is a small machine. I get a good surface finish with softer material, like Delrin. I think you are right that I simply need a big machine.
Perry, I am using a 6mm 3-flute milling cutter, running at 7000 rpm, feedrate of 200 mm/min. The coolant is soluble oil borrowed from my dad, poured from a jug, see my next post with video!
7000 rpm seems about 2x too high under the circumstances, or so the rule of thumb I've been taught to work with would run a quarter inch end mill. Usually I run much slower than that still and only take 50 thou at a time (1.2mm)
I'm probably being much less agressive than you can be with much heavier cooling of course.
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