Page 13 - 《橡塑技术与装备》英文版2025年12月

SPECIAL AND COMPREHENSIVE REVIEW

rigidity. As a result, the straightness and parallelism of the barrels with large length specifications, and the difficulty in
machined double holes often exceed the tolerance range, ensuring the perpendicularity between the plane and the inner
posing a major challenge in the machining process. hole. To address these issues, a series of measures need to be
Secondly, the machining of double holes requires two taken for improvement and optimization to enhance processing
clamping operations, which inherently increases the risk of accuracy and efficiency, and reduce the rate of rework.
machining errors due to multiple clamping. Especially when
the double holes are prone to forming an "eight" shape after 2 Innovative solutions
grinding, it further increases the difficulty of machining. In (1) During the machining process of the double holes in
addition, the perpendicularity between the double holes and the barrel, due to the issues of low efficiency and difficulty in
the plane is required to reach 0.03 mm, which is particularly ensuring quality in the original grinding process, we decided
challenging under existing machining conditions. to try changing the machining process from grinding to boring
Thirdly, the surface roughness of the double holes is (i.e., "replacing grinding with boring") (see Figure 4). The
also an indicator that requires special attention. In practical original intention of this change is to improve machining
machining, it is not easy to achieve a surface roughness efficiency and hopefully solve some quality issues in the
standard within Ra0.8 μm, especially in cases where the barrel grinding process.
length is long and the material hardness is high.
Fourthly, when the length specification of barrel-type
parts exceeds 1,200 mm, the machining difficulty will further
increase. Due to the limited machining range of the vertical
lathe, for barrels with a large length, it is necessary to adjust the
position of the vertical lathe and realign for machining, which
not only increases the machining difficulty but also prolongs
the machining cycle. The grinding time for each barrel may
exceed 40 hours, which will undoubtedly have a significant
impact on the final assembly timeline of the product.
Figure 4 CNC boring machine machining
Finally, to ensure the perpendicularity between the plane
and the inner hole of the barrel, the barrel plane needs to be After experimentation, we found that the surface
processed on a surface grinder. However, before processing, it roughness of ordinary boring tools cannot reach the Ra0.8 μm
is necessary to align the barrel's double holes according to their required by the drawings when boring large-diameter inner
straightness and roundness on a machining center machine tool, holes. This is mainly due to the friction and heat accumulation
and mill the grinding reference for the surface grinder. During between the tool and the workpiece during the boring process.
this process, due to the tendency of the barrel's double holes to To improve this situation, we tried using a light tool for
form an "eight" shape after grinding, there may be errors in the
inner hole machining, hoping to achieve the required surface
alignment reference, which requires multiple calibrations and roughness through fine cutting.
corrections using a three-coordinate measuring machine in the However, due to the influence of the barrel material
subsequent steps. The entire processing process is cumbersome and working conditions, the effect of light-cutting machining
and time-consuming, seriously affecting the processing cycle is also unsatisfactory. The oxide scale generated during the
and product quality. quenching and tempering process of the barrel and the cold
In summary, the difficulties in the double-hole grinding work hardening phenomenon occurring during the machining
process of the barrel mainly include insufficient spindle rigidity, of alloy barrels both increase the difficulty of machining. These
error accumulation caused by multiple clamping, difficulty phenomena not only lead to severe wear of the cutting blade
in controlling surface roughness, the difficulty in processing during machining but also require the hardness of the cutting

Vol.51，2025 ·7·