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Mold design goes solid.

Injection mold design is in the midst of a second computer revolution. The first one occurred when designers exchanged their drafting tables for CAD workstations. Now, mold designers are again changing the way they work, this time in response to the growing dominance of solids-based CAD software. With more and more plastic part design carried out wholly or partly in solids, mold designers must be able to work with solid models as a starting point. "Many mold designers today are on the brink of going to solids or going out of business," says Steven Alexander, president of Spectrum Mold Technologies, one of the sources of new design-automation software.

Pluses and minuses

Mold designers know that it's one thing to work with a solid part model and another thing to design an entire injection mold - from the parting surfaces of its cores and cavities to its myriad assembled parts - in solids. "Designing molds in solids can be cumbersome," says Alexander. He notes that it takes valuable time to create all the automation routines that let users build a finished mold assembly from a collection of mold-base and component geometries. And it takes extra time for the computer to process a solid model. "Working in solids can be resource intensive," agrees George Mallory, engineering v.p. at CAD supplier Rand Worldwide. Adding to the time burden is need to train many mold designers whose work styles are based on their tried-and-true 2-D CAD systems.

Nonetheless, solids do offer advantages, including the ability to enhance the visualization of complex mold assemblies. "Historically, mold-base selection has been a 2-D operation. You don't need 3-D to do this part of the job. But once you start putting in water lines and other components, you get into 3-D problems," explains Mallory.

What's more, the way solids ties together the many elements of a mold assembly - and sometimes the part model, too - can help users manage the all-too-common design revisions. Even designers who have reservations about solids concede that it has some value: "2-D is still more efficient for initial concept development, but 3-D can be efficient for production designing," says Feliks Veysman, R&D director for Mold Makers Inc. in Germantown, Wis.

The good news is that working with solids throughout the mold-design process, from part to mold design to machining code, has gotten much easier. Help for the solids-challenged comes in form of 15 new software products that automate the most repetitive aspects of injection mold design. "We do all the grunt work," says Bob Nofftle, president of Cimlogic, a supplier of mold-base software. The new products automate the design process to varying degrees, but many go as far as to enable creation of a solid mold assembly with just a few mouse clicks, Much of that added speed comes from the ability of most software to handle design revisions automatically or semi-automatically. The parametric and associative nature of the underlying solid modelers adds a kind of built-in intelligence. So changes made to one element of the mold design update the dimensions and locations of all the related elements. For example, re-sizing a mold plate will also update the size and location of all the holes, bushings, and other features associated with that plate. Changes also carry through to the bill of materials and production drawings, providing even greater time savings.

The new software also can reduce the level of expertise a mold designer needs to be productive in solids. "You do not have to be an expert in Pro/Engineer to design a mold in Pro/Mold," notes Craig Therrien, product manager for mold-design products at Parametric Technology. Unigraphics' new Mold Wizard software minimizes training requirements with step-by-step "wizards" to guide users though important design tasks, according to product manager Mike Rebrukh.

The new mold-design products run not as stand-alone packages but within the environment of specific CAD systems - whether as a third-party plug-in or a fully integrated component. "Keeping the same look and feel is a huge benefit for users," points out Joe Dunne of CAD vendor SolidWorks.

Solids-based mold-design software can be differentiated primarily by price and by the presence or absence of explicit automation tools for extracting core and cavity designs from a part model. On the high end in both price and functionality are products that automate the entire mold-design process in solids. They tend to feature explicit tools for creating core-and-cavity geometry, for applying shrinkage and different types of draft, and for creating the mold assembly.

Unigraphics' Rebrukh claims, "When I ask mold shops where all the time goes, they answer 'core and cavity design.'" That view is supported by John Levering, engineering director for Minco Tool & Mold Corp. in Dayton, Ohio. He reports that splitting the cores and cavity inserts on a complex part with over 5000 faces took just 4 hr with Unigraphics' MoldWizard, versus 30 hr without it.

Another class of solids mold-design software focuses only on the mold assembly, without offering automation tools for core-and-cavity work beyond the generic functionality of the CAD system. In other respects, this type of mold-base creation software can have just as many features and as much built-in design intelligence as high-end systems. Or, in some cases, it can have fewer capabilities and can function as a low-cost, plug-in solids library of mold bases and components.

How they work

Though the software products differ in how much automation they offer, almost all of them involve roughly the same steps to produce a solid model of a mold assembly:

1) After creating or importing a 3-D part model, users create cores and cavities around that model, using either automated routines, generic CAD operations, or some combination of the two to arrive at the parting surfaces.

2) Following the core-and-cavity work, users pick a mold-base size in which the core/cavity inserts will fit. (Most systems can support direct impression of the core and cavity into the mold plates.) Depending on the software, the process will be all but automatic. Users typically have to enter some information through a drop-down menu or dialog box. All of today's mold-design software offers one or more libraries of solid geometry for mold bases and components from popular vendors. Much of the software also lets users work with custom base sizes.

3) Through a dialog or menu interface, users add all the tool's functional components - from gates, runners, ejection, cooling, and slides right down to individual screws, pins, and bushings. As these components are added, the mold-base software also creates the associated holes and features for those components, keeping track all the while of relations between features.

4) In conjunction with the CAD system, or though their own functionality, the mold-base packages generate four-view production drawings and an automatic bill of materials (BOM). These programs also set the stage for CNC code generation - whether through integration with the underlying CAD/CAM software or through an interface with third-party CAM packages.

5) Finally, this mold-design software works hand in hand with solids-based flow-analysis software capable of taking gates and runner systems into account. (Both C-Mold and Moldflow recently released solids-based flow packages. They will be discussed in next month's issue.)

The time saved by automating these steps can really add up. Take the example of a recent one-cavity tool designed in Autocad's Mechanical Desktop: Mold-base creation software from R&B Ltd. boiled down 272 CAD operations into just 16, a savings of 94%, according Dr. David Stelzer, R&B's research director. In general, the new solids software can shave at least 25% off the mold-design cycle, Stelzer estimates. Other vendors claim time savings of 25% to 70%.

Veysman notes that today's advanced mold-design software - such as the current Unigraphics or Pro/Moldesign releases - will allow an even more sophisticated work process. The user will first develop a preliminary mold design that includes a parting line, runners, gates, cooling, and ejection. This design will go out for customer approval, after which the preliminary design will be updated with the addition of a finalized parting line, drafts, and fillets.

What to look for

When it comes time to choose mold-design software, there are several factors to consider. Price is one of them - from $500 for a plug-in library to more than $15,000 for a high-end CAD system with integrated mold design.

Flexibility is another. "Everyone wants a one-button solution, but the system still has to be flexible," says Phil Brylowski, a Cimatron application engineer. For many mold designers, it's important to be able to design not only in solids but also in some combination of 2-D and 3-D surfaces and solids.

Flexibility also means ability to deal with both standard catalog parts and custom components and assemblies. Not all software supports all three methods for working with custom sizes - creating user-defined libraries, dimensioning each plate or component on the fly, or modifying the closest standard sizes from the library.

Associativity is key

Users should also consider the degree of associativity and design intelligence provided by different mold-design packages. All but the simplest of them can recognize at least some of the dimensional, positioning, and functional relationships between mold components and features. And all those mentioned here can update the BOM and production drawings.

But some software has more associativity than others. The most sophisticated mold-design software tends to be tightly integrated with its underlying CAD system and thus provides full associativity with the part model. In practical terms, that means that any changes to the part model - say, with the addition of a boss or change of draft angle - cause the mold design, BOM, production drawings, and even NC toolpaths to be updated automatically to reflect that change.

Therrien adds that a growing emphasis on concurrent part and tool design makes associativity with the part model more important than ever. "A lot of companies now use the tool design to finish designing the part," he says. "Good associativity makes it all possible and eliminates a huge amount of work downstream."

Guide to Solids-Based Software for Mold Design

Computer Aided Mold Design (CAMD)

R&B Ltd., Petah-Tikva, Israel (

CAMD currently exists in five variants for different CAD systems in which it runs. "The products are very similar," says marketing director George Berold, but some functionality depends on that of the underlying CAD system. As examples, he cites the way in which cores and cavities are split and the degree of associativity with the part model and machining packages.

CAMD leaves the core-and-cavity work to the underlying CAD system. CAMD generates the entire mold-base layout while preserving the relations between all the mold elements. The whole process is semi-automatic, incorporating dialog boxes to guide users through the customization and detailing steps.

R&B currently offers mold-base and components libraries from D-M-E, Hasco, Futaba, National Tool, and PCS. CAMD currently runs under several CAD systems: MoldCreator for Autocad's Mechanical Desktop; MoldBase 3D for Cimatron IT; MoldDesign for Bentley's Modeler; MoldMaker for Matra Datavision's Euclid; and the new MoldWorks for SolidWorks.

Price: $3995 with one mold-component library. Additional libraries run $400-600 apiece.

Expert Mold Designer (XMD)

Cornerstone Technology, Windsor, Ont.

Once parting lines have been modeled in Cadkey, which serves as XMD's CAD package (other systems can also be used), XMD generates a complete 3-D mold assembly and draws it in four or more 2-D views. The assembly can also be converted to a solid via Cadkey's "Solidify" command. According to Cornerstone v.p. Paul Coleman, all components generated within XMD are fully associative across both 2-D drawings and 3-D models. Also, XMD places ejection and cooling with associativity to part data, Coleman adds. XMD also works with hybrid data. "It can handle everything from 2-D, wireframe, and surfaces to solids," says Coleman.

XMD currently includes a library of mold components from DM-E, National, DMS, PCS, and Progressive Components. A library of standard mold bases is due out this month. Expert Mold Maker, an add-on to XMD that will generate the NC code for each plate, is due later this year.

Price: $8500 without Cadkey (which adds $1995).

Mold Application

Rand Worldwide, Mississauga, Ont. (

Working in conjunction with Pro/Engineer, Mold Application creates an entire mold assembly, complete with parametric integration of all the components. Mold Application differs from other mold-base packages in that users do not have to manipulate solid geometry when creating the mold design. Instead, they work within Mold Application's separate graphical environment to configure and size the mold components in 2-D views. Upon completing the mold layout, users send the design to Pro/Engineer, where it is automatically built in solids. Though Mold Application keeps its distance from the CAD environment during the initial design steps, it does maintain full associativity between the solid part model and mold assemblies within Pro/Engineer, according to Rand engineering v.p. George Mallory. He adds that Mold Application's 2-D approach helps when designing on the fly by not eating up all your computer resources. "You tell Pro/E when it should crunch your design," he says.

Mold Application currently contains D-M-E and Hasco mold-base catalogs and can also support user-defined components. The software includes an on-line Design Advisor. Price: $3500.

Mold Expert

Cimatron Technology, Burlington, Ont. (

It consists of tools to automatically or manually create parting lines and parting surfaces from a solid part model. Cimatron also includes tools for producing electrode geometry and preparing it for CAM operations. According to application engineer Phil Brylowski, Cimatron will soon release a separate package called Quick Split, which performs rough core and cavity splits in just 4 or 5 sec. Brylowski says that Mold Expert's primary use will be for job quoting. For mold-base layout, Cimatron employs technology from R&B Ltd.


Unigraphics Solutions, St. Louis (

An add-on module to Unigraphics CAD, MoldWizard provides tools for automatic core-and-cavity creation - everything from automatic creation of parting lines and parting surfaces to drafting. Its automation capabilities extend to mold-assembly design. As an integrated system, MoldWizard provides associativity from part design all the way through NC toolpath generation. It also features a "wizard" interface that guides users through design steps.

MoldWizard's components libraries now include Hasco, Futaba, and D-M-E mold-base catalogs as well as a growing number of standard mold components. "Within a year, we'll be adding the catalogs of 12 or more suppliers," says product manager Mike Rebrukh. An upcoming release of MoldWizard is expected to add tools for designing cooling channels, ejectors, gates, runners, and EDM electrodes.

Price: $5900 as an add-on to UG/Designer or $15,000 for both.


Parametric Technology Corp. (PTC), Waltham, Mass. (

This granddaddy of CAD tools for mold design automates the building of cores and cavities from part models, as well as the detailing of mold bases. It recently underwent a major revision as part of the current release of its foundation CAD system, Pro/Engineer. According to product manager Craig Therrien, notable new features include a "skirt surface" function that automatically creates parting and shutoff surfaces from any user-defined parting line. Pro/Moldesign has also added more support for multi-cavity and family-tool layouts.

For creating mold assemblies, the new release of Pro/Moldesign also has a menu-driven mold-base selection tool in which users create fully associative mold assemblies. "Everything points back to the part model," says Therrien. Pro/Moldesign also works in conjunction with more detailed mold-base creation tools from other vendors (see Mold Application and Spectrum Mold). PTC parts libraries currently include mold bases and components from D-M-E (inch and metric versions), Hasco, Futaba, National Tool, and DMS.

Price: $16,000 for a complete package - $5995 for Pro/Engineer plus $9995 for the tool-design option that contains Pro/Moldesign.


SolidPartners, Livermore, Calif. (

Intended for SolidWorks CAD, this parametric mold-base library has D-M-E's A and B Series and PCS's A Series.

Price: $649.

SPECtrum Mold

Spectrum Mold Technologies, Spring Lake Park, Minn. (

Running as a menu-retrievable database for Pro/Engineer, SPECtrum Mold takes over after cores and cavities have been split and extracted using the Pro/Mold module. Spectrum president Steve Alexander says the program is more than a database: It's a full-fledged design tool with built-in relations that allow automatic sizing, re-sizing, and placement of mold components.

Its standard mold-base catalog includes D-M-E's A, B, X, and T Series. It also has component catalogs from D-M-E, Progressive Components, National Tool, and Superior. Its large library of nonstandard mold components and assembly applications includes custom ejection, unscrewing assemblies, slide assemblies, hot-sprue and runner assemblies, and D-M-E toggle-lock assemblies. It also supports three-piece mold-base housings (separate rails) and offers some Kona manifolds.

Price: $2500 for the first license and $350 apiece thereafter.


Cimlogic Inc., Nashua, N.H. (

Running within the SolidWorks CAD environment, Toolbox/MB automatically creates mold bases as parametric assemblies based on user input of vendor, style, size, and plate thickness, Toolbox/MB automatically sizes and locates holes and other basic features and components - including core pins, ejector pins, dowel pins, locating rings and bushings. According to president Bob Nofftle, the basic mold assembly can be completed with just four picks in a dialog box. Additional tools help users add support pillars and ejection.

The mold-base library currently contains D-M-E's A and B Series, as well as bases from Superior, PCS, and Progressive Components. The Hasco catalog will be added this year.

Price: $995.


Missler Topcad Canada, Bellefeuille, Que. (

Integrated with Missler's TopSolid CAD/CAM program, TopMold provides automated tools generating cores, cavities, and complete mold assemblies - all in an associative environment that connects the part model, mold assembly, BOM, and NO toolpaths.

According to sales manager Jean Ruby, TopMold's knowledge-based system has intelligence that goes beyond dimensional and location relations. He says Topmold will, for example, determine the torque needed for slides and check the efficiency of cooling-line paths. The latest release adds ability to work with surface data and new tools for creating runner systems and multi-cavity layouts. Its libraries now include D-M-E and Hasco mold bases and Stark components. Topmold also supports user-defined custom libraries.

Price: $12,000, including the foundation CAD system.


Vero International Software, Mt. Morris, III. (

Once cores and cavities have been separated within Vero's VISI-CAD system, the VISI-Mould module takes over to create the mold assembly. VISI-Mould pairs a database of solid mold parts with intelligence to recognize the relation of features. According to v.p. Jack Thompson, all the geometry is "associative and parametric" from the original part model all the way through mold-base assembly and CAM stages. Libraries currently contain mold bases and/or components from Hasco, D-M-E, PCS, and Superior. Users can also build custom catalogs in Microsoft Access.

Price: $7000 to $10,000, (including VISI-CAD), depending on number of libraries.
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Title Annotation:use of computer-aided design; includes related articles
Comment:Mold design goes solid.(includes related articles)(use of computer-aided design)
Author:Ogando, Joseph
Publication:Plastics Technology
Geographic Code:1USA
Date:Aug 1, 1999
Previous Article:PP engineering alloys branch out into molding, extrusion, thermoforming.
Next Article:Keep it dry: optimize moisture barrier in PE films.

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