投资公差是多少?

投资ment Casting Tolerances means the dimension range that can be met by investment casting. Its standard can be classified into 2 parts:Linear Tolerances几何公差.

几何公差 Linear Tolerances
平坦 平坦
Straightness Straightness, Length
并行性 圆角半径
圆度 平坦
Concentricity Concentricity
Hole Tolerance
弯曲的孔,内部半径和圆角 弯曲的孔,圆角半径

Linear tolerance

线性耐受通常应用于长度,同心性,圆角半径,孔,笔直,角半径,平坦和弯曲孔的投资铸件特征。

Each casting process’s linear tolerances are not the same. For example, the water glass lost wax casting can control general linear tolerances between CT7-CT8. The lost foam casting can meet CT8-CT9. But the silica sol casting tolerance is the most precise, it reaches CT5-CT6. Below is a list of liner tolerance standards for casting:

ISO8062(GB/T6414) CT4-CT8—Norminal dimension (mm) Linear dimension tolerance (ISO8062)
CT4 CT5 CT6 CT7 CT8
0 10 0.26 ±0.13 0.36 ±0.18 0.52 ±0.26 0.74 ±0.37 1 ±0.5
10 16 0.28 ±0.14 0.38 ±0.19 0.54 ±0.27 0.78 ±0.39 1.1 ±0.55
16 25 0.3 ±0.15 0.42 ±0.21 0.58 ±0.29 0.82 ±0.41 1.2 ±0.6
25 40 0.32 ±0.16 0.46 ±0.23 0.64 ±0.32 0.9 ±0.45 1.3 ±0.65
40 63 0.36 ±0.18 0.5 ±0.25 0.7 ±0.35 1 ±0.5 1.4 ±0.7
63 100 0.4 ±0.2 0.56 ±0.28 0.78 ±0.39 1.1 ±0.55 1.6 ±0.8
100 160 0.44 ±0.22 0.62 ±0.31 0.88 ±0.44 1.2 ±0.6 1.8 ±0.9
160 250 0.5 ±0.25 0.7 ±0.35 1 ±0.5 1.4 ±0.7 2 ±1
250 400 0.56 ±0.28 0.78 ±0.39 1.1 ±0.55 1.6 ±0.8 2.2 ±1.1
400 630 0.64 ±0.32 0.9 ±0.45 1.2 ±0.6 1.8 ±0.9 2.6 ±1.3

这是我们铸造厂中的衬里耐受性。

投资ment Casting Tolerance 1

几何公差

Geometric tolerancing is normally applied to the following features of investment casting: Flatness, Straightness, Parallelism, Roundness, Hole Tolerance, Curved Holes, Internal Radii and Fillets, and so on.

平坦

平坦tolerance is the total deviation accepted from a flat plane. The investment cast part’s surface must lie between the most flat plane and the plane which will affect the maximum deviation permitted.

在冷却过程中,蜡和金属在冷却过程中经历的体积收缩量将始终决定投资铸件的平坦程度。这种收缩通常位于质量的中心,被称为“菜”。这道菜可以由专业技术控制,但在某种程度上将始终存在。由于不同的配置和投资铸件合金,因此无法引用一般的平坦公差。

Straightness

People are always confused at the differences between straightness and flatness, as it seems so close. When it refers to the tolerance of straightness, the maximum tolerable diameter of the part’s divergence from a perfectly straight line will determine the straightness.

对于某些类型的投资铸件,直率可能是一个真正的问题。因为很容易弯曲一些相对较薄的短部分。根据我们的铸造经验,我们可能会检查设计零件是否可能弯曲,但是很难在生产前说弯曲范围。作为一个粗略的指南,恒定部分倾向于经历每英尺约0.024英寸的轴向弓。

并行性

When you see a blueprint that includes parallel prongs supported only at one end, it means a particular challenge for the completion of precise investment casting. Once there is a parallelism requirement for your part, our engineer in foundry will discuss this issue with you prior to production.

It is difficult to maintain parallelism of these prongs because of volumetric shrinkage of the supporting structure. Yoke holes can also deform substantially as they reach ambient temperature. Careful design adjustment for volumetric shrinkage is critical to achieving an accurate part. These workpieces benefit from more extensive tooling and finishing.

圆度

真圆和给定圆周之间的径向差将定义圆度。旋转零件360°后,我们可以通过读取总指标来测试圆度。检查圆度的另一种方法是在最大条件和最小条件之间取得一半的差异。建议使用后一种方法,因为它花费的时间更少,而且更有效。

我们通过圆形部分的最小半径和最大半径来测量圆度。我们的检查过程将严格控制零件的圆度,并将挑选出偏用公差外的零件。

Concentricity

Concentricity is checked by two cylindrical surfaces sharing a common point or axis as their center. The extent of eccentricity is determined by the dimensional difference in the location of one center with respect to the other. The center of a bore to the outside diameter of a part will be concentric within .003″ for each 1/2″ of wall thickness.

Hole Tolerance

孔公差是铸孔的必要圆度。孔的周围金属必须对称以提供适当的拟合和/或间隙。这对于将铸件(如车轮轴)组合在一起,以确保其将其紧密贴合而不会振动而非常重要。更长的孔会经历更多的内部凹度,因此内部孔直径大于开口的直径。我们需要更加关心以满足指定的孔公差。

孔耐受性将是内部收缩的好处,对于最大1/2英寸的直径,孔间隙可能在+/- .003英寸内,这提供了准确的形状和拟合度。

弯曲的孔,内部半径和圆角

Preformed ceramic cores or a soluble wax can create curved holes. The normal hole tolerance will be doubled to take the curvature into account and all dimensions’ tolerance will be multiplied by two. We cannot size these holes so we provide a diameter tolerance of +/- .005.” For internal radii and fillets, as it is hard to control and inspect, when designed, they should be as wide as possible.

The below part is ourTechnical Data For Design ReferenceStandard

1.线性公差(mm)

尺寸(mm) ≤10 10~25 25 ~50 50~75 75 ~100 100 ~150 150~200 200 ~250 >250
Normal (mm) ±0.15 ±0.25 ±0.35 ±0.50 ±0.65 ±1.00 ±1.50 ±1.80 ±1.00%
Premium (mm) ±0.10 ±0.15 ±0.25 ±0.40 ±0.50 ±0.75 ±1.00 ±1.20 ±0.60%

2.对平坦,直度,圆度的耐受性

Dimension(mm) 0~25 25 ~50 50 ~100 100 ~150
公差(毫米) 0.2 0.4 0.6 0.8

3. Surface Roughness (Ra/μm)

Ra6.3~3.2

4. Limit Dimension for Casting Hole and Slots

Diameter of Hole(φmm) 孔的长度或直径(L/D)
φ2~φ3 L / D ≤ 1
φ4~φ7 L / D≤ 2
≥φ8 L / D ≤ 2.5
φ2~φ3 L / D ≤ 2
φ4~φ7 L / D≤ 4
≥φ8 l /d≤5

5.尺寸和重量范围

项目 最大限度 Min Best
概述尺寸(mm) 1000×300×300 20×10×10 <150×100×100
Weight (Kg) 40 0.015 0.2~5
最小壁厚(mm) 1.0 5~15

6.结构设计的建议

The factor effects the Tolerance

Tolerances may be affected by a number of factors.

Mold temperature wax or plastic temperature injection pressure
mold or shell composition back up sand 射击温度
rate of cooling 零件在“树”上的位置 热处理温度

Al thought there is a tolerance standard in investment casting industry, it may still vary from foundry to foundry, as some may be specialized in thin wall small parts, and others could be more professional in larger parts. Also the equipment may also has a certain effect on the casting tolerances.