Mechanical Parts Design Guide
Limit part complexity and unnecessary features to reduce milling time—and production cost
Overall design guidelines
In view of the fact that many designers are not familiar with the rationality of processing and the cost control of products, we have produced this design guide.
Chamfers
The part of the default 3D model that is not chamfered or below C0.5 is processed with C0.1~0.5. Chamfers above C0.5 should be modeled in order to get a more accurate price.
Hanging holes
Since most of the surface treatment requires the lifting parts to be immersed in treatment fluids, such as white zinc plating (trivalent), various anodizing treatments, it is necessary to have holes on the model that can be used as lifting.
If there are no hoisting holes, it is recommended to model them in the following way, and the number of hoisting holes should be at least 2 or more
① Through-hole of Φ3.5 or more (general tolerance)
② M5 or more threaded holes
③ Waist-shaped hole of width 5 or more (general tolerance)
④ Shaped hole of width 3.5 or more (general tolerance)
Cavity and groove design guidelines
The recommended size of the inner R angle of the cavity groove is ≥R0.5, and the depth of the cavity groove should be within 4 times of the diameter of the milling cutter (the radius of the milling cutter used for processing the cavity groove must be ≤ the minimum width of R or ≤ cavity groove in the cavity).
Cavity slot shape
Considering the processing cost, the following shape combinations of cavity grooves should be designed first to obtain the most economical solution.
The cavity groove R angle needs to be modeled
When machining with a milling cutter, the trajectory of the milling cutter creates an R angle. Please model the R angle here.
The larger the R-angle, the larger the diameter of the end mill used, the shorter the machining time and the lower the cost.
In general, the minimum R-angle required for milling cutter machining of cavity slots is R0.5. If the R-angle is less than R0.5, a special machining process is required.
The R-angle of the cutter tip does not need to be modeled
Because the tip of the end mill actually has a very small R angle, the bottom of the cavity groove will theoretically produce a corresponding R angle, and this R angle should not be modeled. If the 3D model has an R-angle of the cutting edge, the machining direction cannot be determined correctly
Open cavity modeling
It is recommended to design a groove with two sides or a bottom through the cavity, and it can be machined with a milling cutter or wire EDM regardless of whether there is an inner R angle.
It is recommended to design the non-through-cavity groove with internal R3 or more.
(R0.5 or more can be machined by end mill, but considering the actual machining depth, it is recommended to design it as R3 or more.)
Modeling of closed cavities
For a closed cavity surrounded by 4 sides, the inner R is too small to be machined with a machining center (the cost of the machining center is relatively low), so try to model it with a large internal R angle.
| Cavity groove | Non-penetrating | Non-penetrating | transfixion | transfixion |
| Refer to inner R | Inner R≥R0.5 | Inner R<R0.5 | Inner R≥R0.5 | Inner R<R0.5 |
| Diagram |  |  |  |  |
| Processing method | Machining centers | Not recommended | Machining centers | Wire cutting |
When chamfering closed cavity slots, it is recommended that the chamfer be below C20. Chamfering above C20 requires a special tool, which increases the machining cost and is not recommended.
Chamfering of the mouth of the open cavity groove
When inverting the outer R angle on the cavity groove, the following shapes are not recommended and cannot be machined with end mills.
*For the shape shown on the left and middle of the figure below, after designing the inner R angle in the modeling stage, the chamfering cutter can be used to process the overall chamfering of the mouth.
*The size of the chamfer of the cavity notch is recommended to be below C20, and the chamfer above C20 needs to be processed with special tools, which will increase the processing cost (cannot be automatically quoted), except for the following special exceptions, it is not recommended.
Special case: For the unilateral chamfer shape shown on the right side of the figure below, an end mill can be used for chamfering, and one side can exceed C20.
Recommendations for the design of round holes
Holes with unspecified tolerances (general accuracy tolerances) are generally called “straight holes”.
Straight holes without precision requirements (drilling): Recommended hole diameter is Φ20mm or less, and recommended machining depth is 10 times the diameter of the drill.
Straight holes with a diameter of Φ20mm or less (milling cutter): The recommended machining depth is 4 times the diameter of the milling cutter.
Precision hole design recommendations
Precision holes with a diameter of ≤ Φ20mm are generally reamer finishing, and the recommended processing depth is 5 times the diameter of the hole diameter. The diameter of > Φ20mm is generally processed by milling cutter and boring cutter, and the recommended processing depth is within 80mm.
Straight holes can be made by double-clicking the hole specification on the 3D setting screen to add tolerances, and the surface roughness Ra1.6 (Rz6.3) can be set on the side of the hole.
Design recommendations for threaded holes
The recommended effective thread depth of the coarse/fine thread hole is generally within 3 times the nominal diameter
Recommended Round Hole Shapes
It is recommended that the width of the waist hole is greater than 1mm, and the depth of the waist hole should be within 4 times the diameter of the milling cutter (the diameter of the milling cutter used for processing the waist hole must be ≤ the width of the waist hole,)
The waist hole can be double-clicked on the hole specification in the 3D setting interface to add a fit tolerance, and the surface roughness Ra1.6 (Rz6.3) can be set on the side of the hole.
The orifice is chamfered with a C or R angle
It is recommended that the chamfer of the hole and waist hole is below C20, and the chamfer above C20 needs to be processed with special tools, which will increase the processing cost (it cannot be automatically quoted), so it is not recommended.
It is not recommended that special tools be used to process the holes of holes and waist holes, which will increase the processing cost (automatic quotation is not possible).
C-angle or R-angle is chamfered in the step hole
It is not recommended to chamfer the C angle or R angle on the step surface of the hole and waist hole, if the chamfer is necessary and the C angle/R angle exceeds 0.5, special tools are needed for processing, which will greatly increase the processing cost.
The bottom hole of the precision hole or threaded hole is drilling, and the drill taper bevel angle (118°) will be used for modeling with the punching command, which can be recognized by this service.
In 3D design, the thin walls of the design parts are often ignored because of the large screen display ratio.
When the local wall thickness of a part is below the limit value, it may cause the actual product to be damaged or the shape feature to be deformed.
If your design exceeds the limit conditions, this service will have relevant prompts on the 3D setting interface. If you insist on inquiring according to the original design, you need to arrange a manual quotation correspondence.
Thin-walled conditions between Straight Holes, Precision Holes, Threaded Holes, and other shape features
The thin-walled limit between Straight Holes, Precision Holes, and other shape features
| diameter | φ2mm or more φ5mm or less | More than φ5mm |
| Thin-walled limit | 0.8mm | 1.0mm |
The thin-walled limit between the Threaded Hole and other shape features
| diameter | M2 or above M5 or less | M6 or above M10 or less | M12 and above |
| Thin-walled limit | 0.8mm | 1.0mm | 1.5mm |
The thin-walled limit between the Threaded Sleeve and other shape features
| diameter | M2 or above M5 or less | M6 or above M10 or less | M12 |
| Thin-walled limit | 2.0mm | 3.1mm | 3.9mm |
Thin-walled conditions between the “counterbore” and other shapes
| Diameter (D, d) | φ2 or more φ5 or less | More than φ5 |
| Thin-walled limit | 0.8mm | 1.0mm |
Thin-walled conditions between the bottom surface of the counterbore and other shapes
| Diameter (D, d) | φ3 or more φ6 or less | More than φ6 |
| Thin-walled limit | 0.8mm | 1.0mm |
Thin-walled conditions between the Hole Bottom and other shape features
| Thin-walled limit | 2.0mm |
The limit of the thin wall between the “waist hole” and other shape elements
| Thin-walled limit | 1.0mm |
The limit of thin-walled Cavities and other shape features
| Thin-walled limit | 1.0mm |
In general, this service uses 3D CAD data for manufacturing, but in the following cases, the shape of the model and the finished product may differ.
Inner corner, outer corner
If the inner and outer angles of the modeling are clear or C0.5 or less, C0.1~C0.5 will actually be used for machining.
The bottom hole of a blind hole
machcncmaster will automatically determine the most reasonable processing method according to the characteristics and tolerances of the hole. As a result, some blind holes have a flat bottom and the finished product may have a cone bottom (118°) or vice versa.