DFMXpress Injection Molding Rules

Is your company equipped enough to design your plastic injection mold in an invariable environment?


It may sound hard. But SOLIDWORKS 3D CAD software allows us to design plastic injection molds with composite geometries. It provides a 3D workspace which showcases our final results before getting it for production. One can also validate the mechanical functionality of the molds and the components which in turn increases your productivity multi-fold.


SolidWorks can handle various CAD data and provides access to a range of add-on mold design and production applications. Cut down your mold design cycle, import and export various data formats and enhance your design communication with your customers, with the help of SolidWorks 3D CAD.


In continuation with our earlier blog posts, following are the injection molding rules-based checks:

• MINIMUM WALL THICKNESS: Walls which are too thin can cause filling problems and develop high molding stresses and also lead to structural failures and poor insulation characteristics. A minimum wall thickness of 2.0 mm is recommended

• MAXIMUM WALL THICKNESS: Avoid walls which are too thick to prevent cooling problems and defects such as sink marks and internal voids. Thick walls can also increase cycle time
  

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SOLIDWORKS DFMXpress – Mill Rules Overview

Are your manufacturability issues bringing down your profits?

If yes, then look no further. DFMXpress, an integrated feature in SolidWorks is engineered to guide the designer on the problems faced during the manufacturing process. It automates the design process through a set of rules-based checks thereby accelerating and improving the entire design through manufacturability procedure.

In our earlier article we discussed on the drilled hole checks functionality in DFMXpress. In this, we shall explain you in detail on the Mill rules.

MILL RULES

1. DEEP POCKETS AND SLOTS

Deep, narrow slots are difficult to machine. The long, slender end mills required to machine them are prone to chatter, which makes tighter tolerances difficult to achieve. Deep slots also make chip removal more difficult if the slot is blind.

Recommendations:

• Avoid long corners with long radii.
• Design milled areas so that the end mill length-to-diameter ratio is no greater than 3:1.

2. INACCESSIBLE FEATURES

Features should be easily accessible for machining in the required direction. Inaccessible features require special cutters or machining techniques.

3. SHARP INTERNAL CORNERS

Sharp inside corners cannot be achieved with traditional milling and require non-traditional machining processes such as electrical discharge machining (EDM).

Recommendations:

• When designing a three-edge inside corner, one of the inside edges must have the radius of the end mill. A generous corner radius can accommodate a larger milling cutter, which is preferred. Use the radii recommended by fabrication personnel to ensure that tools are easily obtained and maintained.
• If sharp corners cannot be avoided, drill a separate relief hole to allow a male ninety-degree corner to fit. Drill the hole first because drills cannot withstand significant side loading.

4. FILLETS ON OUTSIDE EDGES

For outside corners, chamfers are preferred to fillets. An outside fillet requires a form-relieved cutter and a precise setup, both of which are expensive. Blending of fillets into existing surfaces is expensive to manufacture, even with ball end mill.

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SOLIDWORKS DFMXpress – Drilled Hole Checks Overview

SOLIDWORKS DFMXpress – Drilled Hole Checks Overview

Designing is a crucial stage in a product’s life cycle. It is very important to detect and eliminate errors in the initial stages of design, since these errors will cause problems during manufacturing or increase production costs.

How good will it be, if SOLIDWORKS has an automated manufacturability validation tool?(DESIGN FOR MANUFACTURING)

The answer is Yes.

DFMXpress is an analysis tool that validates the manufacturability of parts. It helps in upstream validation of areas, which are difficult and expensive to manufacture. It also provides a mechanism for knowledge captures and employ for continuous betterment.

DFMXpress functionality includes:

• Drilled hole checks
• Milled feature checks
• Turned part checks
• Sheet metal checks
• Standard hole size checks
• Injection molding checks

In order to reduce tooling costs and for efficient manufacturing, there is a set of rules, to be followed, which the above functionalities carry.

Drill rules:

1. Hole diameter-to-depth ratio: For production, small diameter holes (less than 3.0 mm) and high depth-to-diameter ratios (greater than 2.75) are difficult and not recommended. Deeper, blind holes make chip removal difficult

2. Flat bottoms on holes: Blind holes should not be flat bottomed. While reaming, flat-bottomed holes cause problems. Standard twist drills should be used to generate cone-bottomed holes. The bottom angle should conform to the angle on standard drills

3. Perpendicular entry surfaces: The entry and exit surfaces of a drilled hole should be perpendicular to the hole axis. The drill tip might wander if the surface, which the tip contacts is not perpendicular to the drill axis. Exit burrs will be uneven around the circumference of the exit hole, which can make burr removal difficult

4. Holes that intersect internal cavities: Drilled holes should not intersect cavities. During machining, drills follow the path of least resistance when intersecting a cavity. The drill might wander when it reenters the material. If a hole must intersect a cavity, the drill axis should be outside the cavity

5. Partial holes: When a hole intersects a feature edge, at least 75% of the hole area should be within the material. Do not let the axis of the hole intersect an edge of the part or the drill might wander

6. Tolerance checks: Tolerances should be no tighter than necessary. Stringent tolerances might require special process parameters that are not within the natural capability of available machine tools

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