Cutting Forces
In this lab we studied the relationship of the cutting variables to the cutting forces. The tools used for this lab were: lathe, centerline mount, tool force dynamometer, single cutting edge tool, strobe light, thin walled aluminum tube mounted in chuck, profilometer, and micrometer.
Measurements of the inner and outer diameter of the aluminum tube were taken and the r.p.m. of the lathe was verified by using a strobe light. The r.p.m. of the lathe was found to be approximately 11 r.p.m. higher than what the settings said that the lathe would be running at.
Two different types of tests were done to measure the cutting force and tangential force on the cutting tool. The first test consisted of keeping the feed set the same and changing the velocity of the lathe. Four different speeds were used for this test. The velocities ranged from 90 to 330 r.p.m. and the feed was held constant at .0051 inches.
The second test consisted of varying the feed and keeping the velocity the same. Five different feed rates were used for this test. The feed rates varied from .0012 to .0102 inches and the velocity was held constant at 140 r.p.m.. The depth of the cut was the same for both tests and was measured at .491 inches.
The chips that resulted from changing the variables were different in thickness and texture. The side of the chip that was in contact with the tool was smoother and had a brighter finish than the other side. The chips from the faster feed rates had jagged edges and had a rougher surface than the chips from the slower feed rates. The chips also coiled differently when they came off of the tool. The thinner chips from the slower feed rates coiled tighter than the thicker chips from the faster feeds.
The graphs below show the different affects on the forces by the variables of velocity and feed rate. The tangential force increases rapidly in comparison to the force required for cutting. The increase in velocity did increase the two forces but very little in comparison to the effect of increasing the feed rate.
For the graph of the cutting forces vs. the feed rate click here.
For the graph of the cutting forces vs. the velocity, click here.
The material removal rate, estimated cutting forces, calculated HPu, horsepowers required for each cut and
correction factors c can be seen below.
