Tag Archives: injection mold design

Mold Design Consideration for Automated Molding

Injection molders today are using sophisticated, automated equipment aimed at molding high quality products with lean processes.  Automated auxiliary equipment is used to provide consistency in a process while reducing cycle times.  Each injection molder’s shop environment is different, and some equipment must be custom designed to work together.

 

An injection mold designer must be aware of the molding environment in which the mold will run, which includes the type of press, any auxiliary equipment used in the molding process and the location of tie bars and cooling lines.  This information is vital to a proper mold design to ensure that nothing will interfere with installation or operation of the mold.

Some Automated equipment that injection molders use are vacuum conveying systems, sprue pickers, robotic arms and conveyors, computerized quality inspection and rejection procedures, and automated packing procedures.

As any molder knows, reducing cycle time provides cost saving efficiencies that equate to increased profits to the bottom line.  Be sure to share with your mold designer any custom design requirements unique to your molding situation.  

Michiana Global Mold is experienced with the most challenging of mold designs requiring tight geometric tolerances with critical dimensions.  We construct molds used for any environment, with custom designed solutions provided with Unigraphics CAD/CAM Software, and Mold Flow Analysis if required.  

We are an ISO Registered mold making facility following a strict quality policy in all aspects of injection mold design and construction.  Michiana Global Mold has been a valuable supplier to many supply chains including to the Automotive industry for over 50 years.  We employ a highly knowledgeable and experienced staff, with skilled designers and journeyman mold makers.

Michiana Global Mold has in-depth knowledge designing and manufacturing injection molds that meet tight geometric tolerances.  Contact us today for a FREE design consultation and to learn how we can assist with all of your injection mold requirements.  

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Choose the Proper Gate Location in Injection Molds

The gate is the mechanism that allows the plastic resin to flow into the mold, and every plastic part design must take careful consideration of the type and the location of gates.  There are various styles of gating mechanisms typically used in injection molding, and each style will have an effect on the finished product.  The style of gating chosen can affect the visual appearance of the part, the likelihood of warping or sink marks, and proper packing to meet dimensional tolerances.

 

Avoid Defects from Gate Location

 

To avoid defects when processing, place your gate location at the heaviest cross section for maximum fill and packing to avoid sinks and voids.  Experienced mold designers will also know when to consider adding a second gate location, which may be necessary in complex geometrical shapes to obtain proper fill throughout the part.  

 

The location of the gate should allow for automatic or manual de-gating, designed with the minimal length of flow path to minimize visual flow marks.   In cold runner molds, the part is usually ejected attached to the runner and gate, de-gating removes the part from the runner system.  Some processes include automatic de-gating with robotic arms that grab the runner out of the mold separating it from the part or parts.  

 

Gates in Hot-Runner Tools

 

There are basically two types of gating systems used in hot-runner tools, where the plastic is injected directly into the cavity to avoid runners altogether.  In a hot-runner tool, the gate may be either a thermal (or hot-tip) gate, or a valve gate.  The hot-tip gate solidifies the resin at the tip nozzle immediately upon high pressure injection into the cavity, stopping the flow of plastic to the cavity.  

 

A valve gate is used when the plastic may not solidify completely upon injection, and therefore a valve slides over to cover the nozzle tip and stop the flow of resin.  Either type is effective and cost efficient when used properly in a hot-runner system mold.  

 

Michiana Global Mold is experienced with constructing cold and hot-runner tools, with various styles of gating mechanisms involved.  We are skilled with determining the optimum gate location for precision molds required to produce complex geometrical parts.

 

Michiana Global Mold has been exceeding customer expectation with high performing injection molds since 1964.  We have vast experience with all types of molds and mold base components. Contact us today for a FREE design consultation and to speak with one of our knowledgeable design engineers.  

 

Plastic Part Design to Avoid Sink and Warp

Plastic injection mold designers must consider the resin chosen for the part manufacturing when designing the mold as this plays a very important role in meeting part specifications.  One characteristic of the plastic material that requires careful consideration is the cooling rate compared to the geometry of the part.

 

What is Sink

This plays an important role in the likelihood of parts developing sinks or warps, and can have significant consequences on successfully molding parts with consistent results.  The cooling rate is extremely important because as the part begins to cool it will always begin at the mold surface and move inward, toward the center.  If the geometry of the part is such that the part is too thick, the center area of the part will not solidify quickly enough.  This center stays molten long enough for it to cause stress on the area already solidified, pulling downward towards the center and leaving a sink mark on the outer surface.  

 

Avoid Sink in Plastic Parts with This Rule of Thumb

 

Ribs are used to add strength to plastic parts in thin wall or critical areas, but can also cause sink marks on the exterior side of the part.  When designing plastic parts to avoid sink marks, remember the basic rule to keep the thickness of the rib somewhere around 60% the thickness of the wall.  Following this rule of thumb should help to avoid sink marks during the cooling process.  

 

What is Warp

 

If a plastic part design includes areas of uneven wall thickness, stress can develop during the cooling and solidifying stage.  If this stress is excessive, warps will occur where thinner sections solidify faster than thicker sections.  

 

Avoid Warp in Plastic Part Design

 

When undue stresses due to transitions in wall thickness occur, plastic part designers can combat this by using a ramp.  Designers also use gussets in corners of some geometric areas to help prevent warping.  

 

Michiana Global Mold is an injection mold design and construction company with extensive experience in designing precision tools for complex injection molded parts.  Our skilled designers have vast knowledge of injection molding with various resins, and designing a mold to avoid common pitfalls in manufacturing.  Contact us today for a FREE design consultation and to speak with one of our knowledgeable engineers.

Determine Proper Ejection Method for Injection Mold Design

Injection mold design includes design of the optimum ejection system to meet part specification.  While ejector pins are most commonly used, there are other methods of ejection systems that are required in specific situations.

Ejector pins are round, and used to extend into the cavity to push the part out during mold opening so that the parts fall out or are pulled out by a robot.  Pins are adequate in most situations, although some part designs require pins along with an alternative method, or a different method altogether.

 

Ejector blades can also be used for ejection if the part design requires it, and these have more of a rectangular geometry.  Ejector blades are often used in designs where a thin wall exists, thus an ejector pin may damage the part with force or pressure applied in a critical area.

 

Ejection sleeves are tubular, and are ideal in areas of raised surfaces.  These raised surfaces are designed to assist with assembly in some designs, for example a raised hole at the end of a vertical part would be referred to as a boss.  Ejection sleeves provide 360° surface around the boss for easy part ejection with these types of part designs.

 

A stripper plate is another type of ejection system that consists of an entirely separate moving plate, that is designed to strip the part or parts from the core of the mold.  These are ideal in situations where you need to keep parts and runners separate, and are utilized in three-plate tool.  

 

Michiana Global Mold is a leading global injection mold design and construction company, with extensive experience in all types of ejection systems.  Our skilled mold designers and journeyman mold makers have extensive knowledge and experience with various types of mold construction.  We construct prototype molds with sample parts, cold runner or hot runner tools, shuttle molds, insert cavities and all aspects of injection mold design including engineering changes.

 

Michiana Global Mold was established in Indiana in 1964, serving various industries and specializing in complex, precision tools for the Automotive industry.  We offer a partner company in China with offshore mold making capabilities.  Both facilities are registered to ISO 9001 and follow strict quality management systems.  Contact us today for a FREE design consultation and to speak with a skilled design engineer.  

Molded Part Surface Finish and Ejection Methods

Injection mold designers must always take into consideration the surface finish required of the finished molded part.  The ejection system in the mold that removes the solidified parts out of the mold cavity or cavities has great impact on the part’s surface finish.  The most common ejection system uses ejector pins which can leave marks on the part, often referred to as witness lines.  

 

An experienced mold designer will position ejector pins in order to place witness lines in an area acceptable to the part print.  The ejection system and ejector pins are housed in the B side of the mold, extending into the cavity during ejection then retracting back into the mold.   Restrictions on ejection must be apparent prior to mold design, if ejector pins cannot be used without damaging the part, lifters can be utilized for proper ejection.  

 

The injection mold design must correspond to the ejection pattern and stroke of the press.  Michiana Global Mold is an experienced injection mold maker with in-depth knowledge of designing various ejection systems to meet customer specifications.  We use CAD/CAM Unigraphics software to design and develop a layout for the ejection system prior to cutting steel.   

 

In some cases, ejection systems must be designed around robotic arms that reach into grab the parts upon ejection.  These robotic systems are called ‘sprue pickers’, as sprue is another term for the runner that is also ejected with the part.  Some ejection systems automatically separate parts and runners, so that they do not need to be separated later.  

 

Whatever your part design, surface finish, or ejection system is required, Michiana Global Mold will design and construct a superior mold with flawless ejection for the specified part surface finish.  We are an ISO registered mold making company with an offshore mold making partner in China.  Contact us today for a FREE design consultation and to speak with a skilled mold engineer.

Design Plastic Injection Molds to Press Specifications

A plastic injection mold designer must consider many factors when designing injection molds, including the press the mold will run in.  Knowing the press specifications is very important in order for the mold to operate properly, and most efficiently during injection molding production.  

Vertical Press Clamping System

The orientation of the clamping system is of course a very important consideration, as this determines whether the mold will open horizontally or vertically.  A vertical molding press is used in over-molding production, also called insert molding because the molten plastic is molded around an object.  An example would be an electrical wiring harness with plastic molded around a portion of it, clamps or even something like knives where the handle is molded around the metal.  

The insert in a vertical molding press can be either steel or even plastic.  A vertical press requires molds for the top and bottom, as a vertical molding press has a rotary table which holds at least two bottom (B) sides of the mold, while the top half (A) half comes down to close on the bottom half molding the part.  

There is usually one top half, and at least two or more bottom sides to the mold, so that when the A side is molding the part on the back of the table, another B side is in front of an operator or a robot loading an insert into the open mold.  Once molded, a robot or operator can unload the over-molded part from the mold, prior to loading new inserts into it.   Constructing molds for a vertical molding press is quite different than for a horizontal molding press, even though the concept is the same.  

Horizontal Molding Press

The most common type of injection molding operation is in a horizontal press, requiring an A side and B side, closing together on a horizontal plane to mold the parts.  When the horizontal mold opens for ejection, parts usually fall into a bin below or are grabbed by a robot and taken to an inspection area.  Most horizontal molding operations do not require an operator at the press, as the vertical over-molding jobs do without automated equipment.   

Horizontal molding presses are very efficient and non-labor intensive, with a top-quality high-performing injection mold, a horizontal molding operation can run for hours in a lights out environment.  

Regardless of whether the mold is for a vertical or horizontal press, the placement of water fittings and hoses is of the utmost importance in designing the tool.  The clamping pressure and press tonnage are also very relevant specifications, in order for the mold designer to calculate the pressure of the molding operation while also considering the material chosen and how it will flow into critical areas.  

Michiana Global Mold has decades of experience designing tools for various plastic injection molding environments, meeting tight tolerances with high performing, precision custom injection molds.  Download a FREE copy of our book “Design Considerations for Different Molds” for more information.

Michiana Global Mold has decades of experience designing and building precision custom injection molds for various industries. Contact us today to speak with one of our knowledgeable engineers for a FREE design consultation on your mold building requirements.  We can custom design molds for your applications, regardless of your molding environment.

Mold Design Considerations for Thermoplastic Resins

The most common type of polymer used in injection molding is thermoplastic resins.  There are many different types of resins with various properties to meet part specifications for functionality.  When designing injection molds, the engineer must take into consideration all properties of the resin specified for the produce including adhesion, elasticity, resistance to high temperatures, shrink rate, resistance to corrosives, and desired finish whether matte or polished.

 

The cooling and shrink rate are of the utmost importance, as some parts with a high shrink rate will need the cavity designed accordingly so the finished product will cool and shrink within specifications.  Cooling rate is also important for ejection, as the resin must completely solidify prior to mold ejection.

When an injection molded part has a critical functionality, mold flow analysis may be helpful in determining resin flow into tight geometric areas.  Mold flow analysis clearly shows with computer aided simulation how the resin will flow as determined from its properties.  Predicting how thermoplastic resin will flow in the mold and cavities prior to cutting steel can be a valuable tool in avoiding costly mistakes.  Conducting the proper advanced quality planning with mold flow analysis can greatly improve lead times.  

Most journeyman mold makers will already possess the knowledge of hos particular resins flow just from experience.  A skilled design engineer with experience in manufacturing molds will have the knowledge to design the tool to produce a part to print specifications, with the chosen resin properties playing a huge role in tool design.

At Michiana Global Mold, we have been providing high quality precision molds for over 60 years, possessing more than 500 years of combined experience.  Our staff of highly skilled design engineers and journeymen mold makers are the best in the business with vast experience in various thermoplastic resins.

Contact Michiana Global Mold today to speak with one of our skilled and experienced mold designers to learn how we can assist you with your injection mold requirement.  We are an ISO9001:2015 Registered mold making company with vast experience constructing custom, precision injection molds for various industries.