帮我小小译一下Tool deflection compensation

帮我小小译一下Tool deflection compensation
Tool deflection compensation
In straight surface or constant curvature surface
machining,both average normal cutting force and average
surface error due to cutter deflection are constant.
Compensation can be achieved rather trivially by moving
the nominal tool path towards the machining surface by an
estimated amount of offset based on predetermined surface
error [16,25].In the case of machining curved geometries,
both cutting forces and surface error vary continuously
along the path of cut depending on workpiece curvature.
Therefore,the compensation scheme is not straightforward
and has been addressed in this section.
Fig.3 shows an instance of tool path with and without
compensation.Due to cutting force-induced tool deflections,
some amount of material will be left on the desired
surface (surface error) as shown in Fig.3a.In this case the
resulted milled profile (actual profile) will be different from
the desired profile and the error depends on many factors
such as cutting conditions,tool material,tool overhang,
etc.In order to reduce the error between actual and desired
profiles,one can offset the tool towards machined surface
by an amount which depends on local surface error.In
other words compensated tool path is a variable offset
curve of ideal tool path.It is necessary to compute amount
of offset or compensation along the entire path of cut.One
way to compute the compensation path is to offset the ideal
path locally by an amount exactly equal to predicted
surface error at that point but in opposite direction.This
simple scheme will not work due to highly nonlinear nature
of process geometry–cutting force relation as well as force–deflection relation.An iterative process needs to be
adopted for compensation to arrive at generated surface
which is within tolerances of desired surface.
The iterative process of tool path compensation is
shown in Fig.4.Ideal position of tool is programmed
tool position without considering the deflection and the
actual tool position is deflected tool position.In the next
iteration tool is offset by an amount equal to surface error
but in the opposite direction as shown in the figure.For
this new position of tool process geometry,cutting forces
and surface error are recomputed.The process is repeated
till the resulting surface error is within the prescribed
tolerance limit.This compensation is done at every feed
station along the entire tool path.The compensation
procedure steps can be formulated as an algorithm as
shown below:
1.decompose the ideal tool path into N feed per tooth
stations;
2.set I ¼ 1:1:N;

仪器误差调整与纠正
在进行直线,平面或者弯曲面加工当中,一般的垂直切割以及切割片引起的表平面误差通常是恒定不变的.可以通过预估表平面误差量,然后将垂直切割片位置按照这个量适当调整,对这种误差予以纠正和调整[16,25].在进行弯曲工件的切割加工时,切割力度和表平面误差是沿着切割线的变化而逐渐变化的,而切割线同时又受到加工工件自身曲率的影响.因此,之前的纠偏方法无法直接应用到该类工件的加工当中.本节内容则讨论了该类工件的纠偏方法.
图表3所示为进行过纠偏操作和未进行过纠偏操作的切割线实例比较.如图表3a所示,通过力引导型切割片的纠偏操作,在工件的切割表面以外会留下额外的一些材料(即表平面误差).用这种方法磨铣出来的表面(即当前的实际表面)会与预期所要达到的最终成形表面有所不同.这种不同是由多种因素所造成的,如切割条件,工具所使用的材料,工具的悬吊等因素.为减少实际表面与预期成形表面之间的误差,我们可以适当的使工具与加工件表面保持一定距离,这个距离通常根据表平面误差值决定.换句话说,切割线路不可避免的会与预期线路存在一定的偏移.所以有必要对偏移量或者纠偏量进行计算.对该偏移量的计算,其中一种方法是将局部的预期切割线路按照估计的表面误差量提前进行反向偏移.然而在几何外形与切割力以及切割力与挠度关系非线性化太明显的加工过程当中,这种方法就不太适用了.此时我们需要有一个如图表4所示的,能够对实际平面进行实时误差纠正的方法,以保证最终达到预期成形效果.理想的加工工具所处位置应当在不考虑误差影响的前提下,将其放置于设计位置,实际所处位置应当是进行过纠偏后的位置,如图表所示,实时纠偏工具总的反向偏移量应当等于表平面误差值.因为在这种几何加工过程当中,工具所处的新位置、切割力度和表平面误差都得到了重新计算,而且在不断重复,直至最终的表平面误差达低于允许误差为止.这种纠偏方式是沿着切割线路上的每个点一路进行下去的.纠偏过程和步骤可归结为以下计算公式：
1.将理想切割线路分解为N点/齿距.
2.设I ¼ 1:1:N;