The Effect of Binder on Bioceramic Surface Roughness when Milling using Ball Nose End Mill

Abstract

Nowadays, the increasing number of road accidents has led to a rise
since the accidents may result in permanent disability that often require
surgical intervention. As a purpose to replace bone, a type of bioceramic
which is hydroxyapatite (HAP) is chosen since it is a chemical substance
that has similar characteristics to the mineral found in human bone and
hard tissues. The water-soluble binder is used to make the substances
hold together which is PEG and PVA. Four (4) samples of hydroxyapatite
with different amounts of binder are made to examine the effects of
binders on the bioceramic mechanical properties. on bioceramic surface
roughness when milling using ball nose end mill. The sample is
prepared by using dry mixing and compaction method whereas the
ratio of PEG and PVA used are from 1% to 4% by weight. After
compaction, the samples are sintered in the furnace for a total of 22
hours with 2 hours of soaking period in which the heating and cooling
rate is 120 o C/hour. The temperature set for the soaking period is
1200 o C. The HAp sintered body is then machined by CNC milling
machine using ball nose end mill cutter with a constant machining
parameter of cutting speed, feed rate and depth of cut which is
27m/min, 40mm/rev and 0.1mm. Other than that, the sample
undergoes mechanical properties testing such as modulus of rupture,
vickers hardness, porosity and density. From the test, it is observed the
amount of binder used influences the mechanical properties and surface
roughness of the sample. Sample 4 which contains PEG 4 PVA 1 has the
highest yield strength, hardness value and surface roughness. Other
than that, the highest porosity obtained is sample 3 which contains PEG
3 PVA 2 and sample 4 has the highest density. In conclusion, the
hydroxyapatite (HAp) samples with different amounts of binder used
influence the sample compatibility and mechanical properties.