Injection molding press. (Image thanks to Proto Labs. )
When it comes to evaluating production processes, there’s a longstanding assumption that injection molding is really a high-cost method reserved for high-volume production runs.
However , as on- requirement manufacturing becomes more common, that assumption is now less accurate increasingly.
For low-volume production works or prototyping even, injection molding represents a flexible and reliable option. If you’re considering using injection molding for your next prototype or short run production, there are several points to consider.
Injection Molding Materials:
Compared to 3D printing, injection molding offers engineers a variety of material options.
“ We offer anything from polypropylene, to santoprene, to glass-filled nylon and LCP, ” said Tony Holtz, technical specialist at Proto Labs. “You may get several materials with varying degrees of fillers and additives such as for example glass, mineral and colorants along with some high heat- and creep-proof resins such as for example PEEK and Ultem. ”
Proto Labs preferred mold materials is aluminum because of its ability to be manufactured quick and cost-effectively. But sometimes it uses steel because of its tooling material because of molding constraints such as for example mold temperature. Materials such as PEEK or Ultem require higher molding temperatures than most thermoplastics, so steel is better suited for high-temp plastics. Aluminum molds are typically able to produce well over 10, 000 components at Proto Labs and so are maintained in-house through the entire full lifetime of the project.
“Aluminum is a superb heat dissipater, ” said Holtz. “It draws heat from the part rapidly and disperses it in to the atmosphere. We maintain consistent heating temps in our molds, without the same heating and cooling lines that take a lot of time and money with traditional injection molds. This does increase our period times compared to traditional molds slightly, however , based on part complexity and size. ”
Aluminum mold for a good optical liquid silicone rubber component. (Image thanks to Proto Labs. )
That being said, Proto Labs supplies a selection of engineering-grade materials also, many of the same components as high-volume molders. “We’re furthermore using liquid silicone rubber as a mold material, which is an elastic material with many benefits over thermoplastic elastomers and also clear polycarbonate or acrylic, ” said Holtz. “The most typical resins are ABS probably, polycarbonate acrylic and nylon components. We’ve greater than a hundred resins which are, and that’s in virtually any combination-so we would have eight nylons available, and colorants which are added to those aswell then. ”
Single-Cavity vs . Multi-Cavity Molds:
A crucial question for just about any engineer dealing with injection molding is whether to decide on a single-cavity or multi-cavity mold. The short response to this query is that the decision of mold type depends upon how many parts you have to make. However , there is absolutely no simple cut off stage beyond which multi-cavity molds tend to be more economically practical than single-cavity molds.
For example , suppose you will need 10, 000 parts.
“Single-cavity aluminum molds are good for well over 10, 000 parts, ” said Holtz. “Primarily, a few thousand parts is what people want to be using those for. The same technology can also produce multi-cavity tools, up to around 8 cavities, depending on the size and complexity of parts . ”
Injection molded part. (Image courtesy of Proto Labs. )
If you need to produce this many components all at one time, a multi-cavity mold could be your best bet then. But if that’s the full total number of parts you will need over a period of two years, then it could be better to choose the less-expensive single-cavity mold.
Another consideration is certainly whether you anticipate your production needs to crank up in the future.
Having questions like these explains part of the appeal of on-demand manufacturing. “ In our initial quote, we have the ability to show you what your single-cavity pricing is, what your multi-cavity pricing is, as well as the pricing structure for a part for your production run, ” said Holtz. “You could forecast-say easily, if you want 100, 000 parts-what amount of cavities will undoubtedly be most cost beneficial. If you focus on that single-cavity tool and recognize that you will need a multi-cavity mold, we’re likely to deduct that preliminary tooling cost from your own second multi-cavity mold, so long as the part geometry stays exactly the same. ”
Designing for Moldability:
If you’re planning to use injection molding to produce your parts, you’ll need to design them with moldability in mind. But where do you start?
“If customers are looking at injection molding as their end process, the first thing they need is the CAD style. Send us that CAD design now, than looking forward to weeks of redesigning in-house instead, ” said Holtz.
For instance, sharp corners can weaken components due to molded-in stress from resin movement. Similarly, slim edges restrict resin movement and can break up during gate trimming. These along with other problems can be anticipated before the injection molding process begins through proper mold flow analysis early along the way.
Reducing sharp corners improves portion strength. (Image courtesy of Proto Labs. )
“ We have a proprietary mold circulation simulation called ProtoFlow, ” Holtz commented. “It’s distinctive to our method of manufacturing molds. Some customers have their own mold flow analysis, so we’ll compare the two analyses to give them a better understanding of our processes. Ours tends to have a higher pressure of molding-that’s why we use our very own simulation slightly. ”
“We can offer an automated manufacturing review also, removing undercuts and cores so that you can decrease your manufacturing costs, ” said Holtz.
Injection Molding in On-Demand Production:
Flexibility is a key benefit of on-demand manufacturing. With regards to injection molding, which means doing a lot more than prototyping just. “We discuss on-demand manufacturing with regards to bridge tooling, end-of-existence planning and supply chain emergencies, ” said Holtz. “Depending on when you need it, some inventories never exceed a certain amount, so you can continue using the aluminum tooling. ”
Thermoplastic injection-molded part. (Image courtesy of Proto Labs. )
The traditional model for injection molding had customers own the tooling, but Proto Labs takes a different approach as part of its on-demand philosophy. “Proto Labs owns the tooling, but the customer owns the exclusive right to the parts, the geometry and that mold, ” said Holtz. “We don’t talk about customer tasks, parts or even molds without their consent publically. ”
For customers, this means devoid of to cover tool maintenance, upkeep and storage costs.
“Proto Labs will keep up with the tool for the entire life of the project, ” said Holtz. “If the mold wears, requirements or breaks to end up being re-polished, customers typically do not purchase that. We’re going to repair the tool, or even replace the mold for the customer, as long as they continue to order parts from the mold. ”
Two particular features of Proto Labs’ rapid injection molding make this possible. First, the use of soft tooling from aluminium allows for modifications that can’t be done easily with steel molds. 2nd, and more significantly, Proto Labs helps to keep all its mold making in-house.
“We have a lot more than 400 CNC machines manufacturing components and molds, and more than 200 injection molding presses globally, ” Holtz explained. “ As you machine is completing an purchase, the operator is relocating to the next press, configuring it and getting that one began while another operator finishes the prior one. ”
This is what allows on-demand manufacturers like Proto Labs the ability to mold parts within days.
“ You will get an injection mold starting at $1, 500 in 15 business days or less, ” said Holtz. “We work directly from a 3D CAD file and develop the mold around that. We have proprietary software that generates code for CNC machines. We’re CNC milling, applying EDM and hand- finishing aluminum blocks, which is our actual mold. We don’t integrate multi-plate molds, and cooling and heating lines like conventional injection molding businesses. We’re taking that which was once a complex procedure and simplifying it to create quality parts as quickly as possible. ”