Automating the moldmaking process

Aug. 7, 2003
New software tools take the grunt work out of mold design and manufacturing.

   Managing Editor

Delcam's Die Wizard automatically finds a product model's split line and forms the two die halves.


PS-Moldmaker generates a 3D, solid-model assembly of the mold and tooling. The approach is said to reduce errors and speed production.


PS-Electrode software identifies areas where EDM electrodes are needed, generates the design, and selects the most suitable blank and holder from a catalog database.

Offshore competition is becoming a fact of life for tool and moldmakers. To compete with low-cost producers, established manufacturers have no choice but to improve efficiency, speed delivery, and offer more flexibility. It's not a hopeless battle, according to the experts, if companies are willing to change their approach to moldmaking and take advantage of the latest software tools.

One solution is automated moldmaking, a new approach to mold manufacturing that encompasses CAD-data transfer, design of core, cavity, mold, and EDM electrodes, and production of the final parts.

"Everyone talks about China's low labor costs," says Peter Dickin of Delcam plc, a supplier of product-development and manufacturing software based in Birmingham, England. "But the labor-cost content in a typical mold tool is probably less than 10%. If you can make your skilled people more productive and reduce waste by eliminating mistakes, you can easily overcome that 10%.

"Automation is about making people more skilled and more productive," says Dickin, not about putting moldmaking responsibilities in the hands of low-wage novices. "No software can turn unskilled people into skilled moldmakers. Rather, automation reduces the routine work and allows more time for creative work. It lets experienced workers design better molds and quote more business, and it eliminates repetitive work and reduces mistakes."

Streamlined design

Delcam has developed a range of software tools that integrates moldmaking processes from concept to completed part and automates the process wherever practical. Its PowerShape hybrid-modeler and PS-Moldmaker software, for instance, form a system for the automated design of plastic-injection molds. First off, it can import a variety of CAD models. "OEMs often insist on subcontractors using the same software that they do," says Dickin. "But OEMs don't seem to realize that these people work for a range of customers, in most cases, and it's financially unviable to have one set of software for each customer."

PowerShape's PS-Exchange program accepts a wide range of formats, including Catia, Pro-E, Unigraphics, and SolidWorks, and produces standard outputs that include Parasolid XT, IGES, and STEP. And because CAD models are often imperfect, it offers powerful data-repair tools, such as removing duplicate features, retrimming surfaces, fixing gaps, and adding draft. A Solid Watertight wizard links gaps without deleting faces and highlights problems that cannot be fixed automatically.

Unlike traditional methods, PS-Moldmaker streamlines design by generating a 3D assembly detailing all components in the mold. In conventional mold manufacture, on the other hand, one team typically handles 3D core and cavity design and produces parts on three-axis CNC machines, while a second team generates 2D drawings for tooling, plates, and pins for two-axis machining and assembly. "The problem is that two processes undertaken by separate groups inevitably means you've got a management challenge to make sure all the bits arrive for assembly at the same time," says Dickin. "And inevitably when working with 2D drawings there are going to be errors between the drawings and what you actually want."

Creating the entire design in 3D is a better approach for several reasons, he says. Instead of attempting to coordinate the workflow of two separate teams, one integrated team, if not one individual, creates the entire design using a single CAD system. This eliminates the delays of one group waiting on the other.

It can substantially reduce the time required to make a tool, in large part by eliminating mistakes, says Dickin. At the design stage, working in 3D may well take longer, but the increased reliability results in substantial time savings for the overall moldmaking process. "Instead of constantly having drawings with the wrong dimensions, holes in places that don't line up, parts that don't match when you try to assemble them, basically every part can be inspected against the 3D model as it's made," he says. "Problems are dealt with on the spot, so when it's time to assemble, it all fits. Not having to rework saves real time and money."

And designs improve, because the engineer can see all the components in position and simulate movements to ensure the tool works as intended, according to Jon Hunwick, a Delcam application engineer. "Moldmaker isn't simply positioning components in space, it is creating a set of assembly rules for how the components join together," he says. That lets the designer graphically test, for example, that there is sufficient clearance to remove the molded component from the tooling. "Which is comforting to know, rather than getting to the end of the project and discovering the part won't come out," he says.

A preview mode lets designers experiment with alternative layouts. There is no need to recreate the entire assembly with every addition or alteration to the design, or to complete the design before creating a solid model of any component.

Wizards at work

The first stage of PS-Moldmaker is the Die Wizard. It finds the split line of the product model, creates split and run-off surfaces to form the two die halves, and then dynamically separates the cavity, with the split surface, from the die blocks. The wizard creates flat areas in the corners of the block whenever possible to simplify alignment of guide pillars and bushings. And it can create multiple inserts for use within a single plate of a multicavity tool.

A second wizard designs the cores and slides required when molding parts with undercuts. The Slide Wizard automatically extracts the core and attaches the slide mechanism, based on user-selected components. Once the design is complete, the software automatically redesigns the split line and run-off surfaces, with draft incorporated within the core and cavity plates to accommodate slide movements.

A Cooling Wizard adds water channels within the mold core or cavity. The user simply sketches the layout and the software warns when they impinge on the cavity, are too close to give sufficient wall thickness, or are too far from the molding to be effective.

PS-Moldmaker also lets users exit from the automated process at any stage, manually adjust the design within PowerShape, and then return to the automatic methods to complete the mold. This lets the designer override the automated solution when necessary, based on experience that the tool taking shape is not as practical or cost effective as it could be, Hunwick explains. The designer might change the orientation, or go back to the customer and suggest modifications that will reduce tooling costs.

"This is the area where automation has real benefits," says Hunwick. "Mold design tends to be about 5% inspiration, and the rest is just pure, mind-numbing routine work." No matter how skilled the designer, doing the same operation over and over again is bound to lead to mistakes, he says. Automation lets experienced designers focus their skills on complicated details, while the software handles the mundane, repetitive tasks. Users benefit from the speed and simplicity of the high level of automation and also produce exactly the results they want.

Whenever possible the software selects standard components from a catalog database that covers a range of suppliers. The software also suggests appropriate sizes for nonstandard components. Users can modify any of these recommendations and add new components to a personal catalog for future use.

Automated drafting of the mold assembly and individual components produces a complete, associative set of fully ballooned drawings. Bills of materials for various suppliers of standard components are generated and updated automatically as the design develops. This means components can be ordered as soon as they are specified, possibly even before the overall design has been finalized.

Mold-tool features are not merely geometry - they also contain manufacturing information. So once the overall mold design completes, models can be passed to Delcam's PowerMill machining software. It automatically creates drilling instructions for water channels and other holes, and milling programs for pockets and other features, for automatic machining.

Automated electrodes

When machining cannot easily produce small features, sharp corners, or textured finishes, toolmakers often turn to electrical discharge machining. EDM removes metal by rapid electrical discharges between an electrode and workpiece. When these two parts are brought together within a fraction of an inch, an electrical spark melts and vaporizes metal and gradually forms a cavity in the workpiece in the shape of the electrode. EDM can create shapes and indentations not possible with other machining methods, such as helical cavities and rectangular holes.

Delcam's PS-Electrode automates the design and production of electrodes for EDM systems. This opens the process to more widespread use, according to Chris Hewitson of EDM manufacturer Agie U.K., Chelmsley Wood, England.

"Recent developments have greatly simplified the EDM process," says Hewitson, "making it quicker and more accessible, and so boosting its popularity as a reliable high-performance manufacturing method. Even so, potential users were still being deterred by the difficulty of designing electrodes." PS-Electrode removes this barrier, he says, making the use of EDM more attractive to companies manufacturing tooling with high levels of detail.

The software identifies areas where electrodes are needed, generates the electrode design, and selects the most suitable blank and holder from its catalog database. The latest version of PS-Electrode also lets designers step out of the automatic process at any stage, manually make adjustments, and then return to the automatic operation, says Chris Jones, PowerShape project manager. It also lets users mirror or duplicate a design for other areas of the model, and then combine the different sections into a single electrode. Designers can also add features such as reinforcing ribs, alignment notches, or fillets to ensure a smooth transition away from the tool surface.

Designs can be transferred directly to the PowerMill CAM program for generating machining data for milling electrodes from blanks. PS-Electrode will rotate the blank into the most efficient orientation for machining to minimize material waste and cutting time. The software also incorporates Agie's recommended spark gaps for both roughing and finishing electrodes, based on the material and required surface finish, which are applied automatically to the geometry from the model.

"PS-Electrode automates the process in terms of recognizing the burn area and very quickly creating the electrode," says Jones. "The time savings in modeling and machine setup for milling the electrode quickly produces a return on the investment," he says, making EDM a more cost-effective process.

The latest version of PS-Electrode links to the Agievision controls used on Agie's EDM equipment. The software can directly program the controls, which makes the process faster and less error prone. Previous versions only produced a setup sheet for manual programming of the EDM machine. In addition, the software checks for collisions between tool or holder and the workpiece, and makes necessary adjustments.

"What we've developed, with Delcam, is an automated system that take CAD data all the way through to programming the EDM machine, producing parts with very limited opportunity for error," says Hewitson. "It's much quicker and more reliable than other methods, and also gives much greater flexibility to interrupt a job, run another, and then pick up where you left off."

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