铸铁平台精度修复方法
时间：2016/1/25 8:54:36
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一般通过刮研来恢复铸铁平台的精度。所谓“刮研”，是刮削和研磨两个工序的结合。即平面刮削——研磨显示，再平面刮削——再研磨显示，如此往复，交替循环，不断运作。使铸铁平板的表面粗糙度值和形位误差逐步降低；接触精度、几何精度在运作中逐步提高，直到达到规定要求为止。
1、刀迹成形与受力分析
钳工在刮研铸铁平板操作时，将平面刮刀刀柄顶住胯骨，双手握住刀具，使平面刮刀与铸铁平板被刮表面形成一定的切削角度并对刀头施加压力，使平面刮刀刀刃吃紧平面。这时当人的胯骨和腰部给刀柄以推力，使刀刃切入铸铁平板金属表面并使刀刃在深入向前中切去研磨的黑点，然后将双手压力立即转换提升力，把刀头快速提起离开铸铁平板表面。完成了挖掘式的刀迹成形切削过程，并刮去一层极薄的金属刀迹运作有3种方法，即直推法、直推加扭转法、左右扭转法。直推法产生长方块、三角块。表面呈现微波形，表面质量较差，适宜粗刮；直推加扭转法产生反“6”块、正“6”块形，表面呈细微波形，表面质量光滑适宜细刮。左右扭转法产生正鳞块、反鳞块、燕翼块、燕身块等，表面呈细曲纹波形，表面质量光亮光滑，宜精刮或刮花（图2所示）。从刮削过程看，刮削是合力作用的过程，操作熟练程度决定了刮削质量的优劣。
2、黑点规律
研具与铸铁平板经过研磨以后，凸起部分的铸铁平板表面显示的全是黑点，黑点分亮点、浓黑点、淡黑点。这些黑点在刮研中是一个变量。经过连续的交替循环不断地运作不断地刮研，黑点由稀少变稠密，由不均匀分布变为均匀分布。黑点的演变过程，也是表面光洁度、表面接触精度、表面几何精度逐步提高的过程。
对研磨显示出来的黑点要区分对待。对于浓黑点刮削的刀迹大小应同按粗、细、精3个阶段规定大小刮削，其刀迹方向应同方向排列，逐步刮削到黑点全数刮完。经研磨显示后，第二遍以交错方向刮削也将黑点全数刮完。必须指出，每轮刮削，刀迹必须交错，否则将影响表面光洁度。在刮削中对黑点按亮、浓、淡在用力上应有轻重之分，对亮点、大浓黑点用力要大，对大多数的浓黑点用力要适中，对淡黑点，则保留不刮，待下轮显示后变黑时再刮，必须强调指出，对于分布在铸铁平板平面边缘、角落的亮点。因隐布稀少，极易为人眼所忽略，极易漏刮。因为漏刮点在研磨时往往顶起研磨平板，妨碍黑点的正常显示，会形成黑点越刮越少的现象。
3、刮研3阶段
在刮研全过程中，一般都要经历粗刮、细刮、精刮3个阶段。
粗刮阶段：粗刮的首要任务应先解决形位误差问题。比如车床溜板燕尾导轨的两端平行度，如不先解决好，留到粗刮好后再解决平行度，不但费工费时而且延误工期。粗刮刀迹要宽大、要大刀阔斧地进行。对每个点只刮一次不刮第二次。刀迹方向是同方向顺次排列，每轮变换一次。经过反复循环不断刮研，黑点由稀少变稠密，由不均匀分布至均匀分布，当任意刮方（25mm×25mm）达到4～6点时，表面粗糙度达到Ra2.5～Ra3.2时即告粗刮阶段中止。
细刮阶段：细刮在粗刮基础上进行。细刮的任务主要解决表面质量问题，即接触精度、几何精度（平面度达到0.01mm/500mm2）、表面粗糙度（Ra1.6～Ra3.2），同时还要兼顾到形位误差。细刮的刀迹宽为6～8mm，长10～12mm，刀迹建议采用直推加扭转法，正“6”块反“6”块刀迹较好，当任意刮方达到10～12点时细刮阶段即告中止。
精刮阶段：精刮是在细刮基础上进行的，精刮的任务是进行提高刮研表面质量，兼顾、核定形位误差。精刮要磨好平面刮刀，要锋利，落刀要稳要轻，特别要避免刀角划伤表面，精刮刀迹宽5～７mm，甚至更窄更短，视刮削平面大小而变化。刀迹建议采用左扭转法或右扭转法，刮削时用力宜小，刮花则例外。当黑点增加到每任意方20～25点时，即精刮结束，其铸铁平板平面度应为0.01mm/500mm2以下，表面粗糙度为Ra0.8～Ra1.6。
Cast iron platform precision repair method
The accuracy of the cast iron platform is
generally restored by scraping.The so-called "scraping" is a
combination of two processes of scraping and grinding. That is, plane scraping
- grinding display, then plane scraping - re-grinding display, so
reciprocating, alternating cycle, continuous operation. The surface roughness
value and shape error of the cast iron plate are gradually reduced; the contact
accuracy and geometric accuracy are gradually increased during operation until
the specified requirements are met.
1、Tool path forming and force analysis
When the fitter is working on the cast iron
plate, the flat scraper handle is placed against the tibia, and the cutter is
held by both hands, so that the plane scraper and the cast iron plate are cut
to a certain cutting angle and pressure is applied to the cutter head, so that
the flat scraper blade is tightly flat. . At this time, when the human shinbone
and the waist give the shank a thrust, the cutting edge cuts into the metal
surface of the cast iron plate and the blade cuts the black point of the
grinding in the deep forward direction, and then the pressure of the hands is
immediately converted into the lifting force, and the blade is quickly lifted.
Leave the cast iron plate surface. The excavation-type cutting process is
completed, and a very thin metal blade is scraped off. There are three methods,
namely, direct push method, direct push plus twist method, and left and right
twist method. The straight push method produces long squares and triangular
blocks. The surface is micro-waveform, the surface quality is poor, suitable
for rough scraping; the direct push plus twist method produces
anti-"6" block, positive "6" block shape, the surface is
fine waveform, the surface quality is smooth and suitable for fine scraping.
The left and right torsion method produces positive scales, anti-scales,
swallow wing blocks, swallow body blocks, etc. The surface has a fine curved
waveform, and the surface quality is bright and smooth, which should be finely
scraped or scratched (shown in Figure 2). From the scraping process, scraping
is the process of synergy, and the proficiency of the operation determines the
quality of the scraping.
2、black dot law
After the lap and the cast iron plate are
ground, the surface of the cast iron plate on the convex part is all black
spots, and the black dots are bright, dark, and black. These black spots are a
variable in scraping. After successive alternating cycles, the black spots are
dilute from dense to dense, and from uneven distribution to uniform
distribution. The evolution of black spots is also a process of gradually
improving surface finish, surface contact accuracy, and surface geometric accuracy.
The black spots displayed by the grinding
should be treated differently. For the thick black point scraping, the size of
the knife should be scraped according to the size specified in the coarse, fine
and fine stages. The direction of the tool path should be arranged in the same
direction, and the scraping should be scraped until the black spots are
completely scraped. After the grinding is displayed, the second pass is scraped
in the staggered direction and the black spots are also completely scraped. It
must be pointed out that for each round of scraping, the marks must be
staggered, otherwise the surface finish will be affected. In the scraping, the
black points should be light, thick, and light, and should be light and heavy.
For the bright spots and large dark spots, the force should be large. For most
of the dark spots, the force should be moderate. For the dark spots, keep it.
Do not scrape, wait until the next round shows black and then scrape. It must
be emphasized that for the bright spots distributed on the edge and corner of
the plane of the cast iron plate. Because the hidden cloth is rare, it is
easily overlooked by the human eye and is extremely easy to slip. Because the
scratch point often pushes up the grinding plate during grinding, hindering the
normal display of the black spots, the phenomenon that the black spots are less
scratched.
3、scraping 3 stages
In the whole process of scraping, it is
generally necessary to undergo three stages of rough scraping, fine scraping
and fine scraping.
Rough scraping stage: The primary task of
rough scraping should first solve the problem of shape and position error. For
example, the parallelism of the two ends of the lathe tail of the lathe slide,
if not solved first, to solve the parallelism after the rough scraping, not
only labor and time and delay the construction period. The rough scraper should
be large and must be carried out drastically. Only scratch once for each point
and do not scrape the second time. The direction of the tool path is arranged
in the same direction in sequence, and each round is changed once. After
repeated cycles of continuous scraping, the black spots become dense from rare
to dense, from uneven distribution to uniform distribution. When any scraping
square (25mm × 25mm) reaches 4-6 points, the surface roughness reaches Ra2.5～Ra3.2. That is to say, the rough
scraping stage is suspended.
Fine scraping stage: Fine scraping is
carried out on a rough scraping basis. The task of fine scraping mainly solves
the surface quality problem, namely contact precision, geometric precision (flatness
of 0.01mm/500mm2), surface roughness (Ra1.6~Ra3.2), and also takes into account
the shape and position error. The blade width of the fine scraping is 6~8mm and
the length is 10~12mm. It is recommended to use the straight push and twist
method. The "6" block is opposite to the "6" block. When
the scraping reaches 10~12 points The fine scraping phase is aborted.
Fine scraping stage: Fine scraping is
carried out on the basis of fine scraping. The task of fine scraping is to
improve the surface quality of scraping, and to balance and verify the shape
and position errors. Fine scraping should be ground flat scraper, to be sharp,
the knife should be stable and light, especially to avoid scratching the
surface of the knife corner, the fine scraping knife width is 5 ~ 7mm, even
narrower and shorter, depending on the size of the scraping plane. It is
recommended to use the left torsion method or the right torsion method. The
force should be small when scraping, except for scratching. When the black
point is increased to 20 to 25 points per arbitrary side, that is, the finish
is finished, the flatness of the cast iron plate should be 0.01 mm/500 mm 2 or
less, and the surface roughness is Ra 0.8 to Ra 1.6.
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