Can metal 3D printing reduce the scrap rate in mold production?

一, The waste problem in traditional mould making: the double problem of wasting materials and losing efficiency
The "subtractive processing" approach is used in traditional mould making. This means that materials are slowly removed through a series of steps, such as turning, milling, planing, and grinding, until the desired shape is reached. There are three key structural problems with this process path:
Low rate of material use: For example, when making die-casting moulds for automotive engine cylinder heads, typical methods require processing the whole steel ingot into a mould, which can take up to 70% of the material away. Based on numbers from one company, their mould workshop uses 1200 tonnes of steel per year. Of that, 840 tonnes is turned into garbage and just 360 tonnes is turned into useful items.
It takes 12 to 15 steps to go from preparing the raw materials to delivering the end product. Making one set of moulds might take up to 2 to 3 months. The battery pack mould development project for a particular new energy vehicle company has been pushed back by eight months since it had to be redone several times. This has cost the company more than 20 million yuan.
Difficult structural limits: It is hard to make moulds with complicated characteristics like conformal cooling channels and lightweight lattice structures using traditional methods. In order to make pattern block moulds, a certain tyre business needs to break down the whole tyre into more than 20 sections and work on each one independently before putting them all together. Not only does this raise the waste rate, but it also makes the mould less accurate.
二, The breakthrough of metal 3D printing: a paradigm shift from "subtractive" to "additive"
Metal 3D printing builds three-dimensional objects by stacking metal powders or wires on top of each other, which entirely goes against the way things are usually done. It also shows three main benefits for waste management:
1. A big jump in the rate of material use: from 30% to 90%
When making complex structures like mould cavities and cooling channels by hand, a lot of machining allowance is needed, which leads to a lot of wasted material. 3D printing technology directly drives manufacturing using CAD models, and it only uses as much material as the pieces themselves. Using SLM technology, a particular company made an aluminium alloy electric drive shell mould that uses 92% of the material instead of the 35% that standard methods use. This saves 180 kilogrammes of aluminium alloy material every set of moulds.
More importantly, 3D printing makes "topology optimisation" design possible, which can use less material while still being strong. A certain aviation company used topology optimisation to make a titanium alloy wing support mould that is 30% lighter and uses 45% less material while still performing the same way.
2. The ability to make complicated structures: getting rid of the fundamental source of waste
A common use case for 3D printing to cut down on waste is the conformal cooling channel, which is hard to work with using traditional methods. By building spiral and biomimetic dendritic cooling channels inside the mould that fit the shape of the product perfectly, the cooling efficiency can be boosted by more than three times. A certain company made a die-casting mould for the battery tray of new energy vehicles. It uses a 3D printed conformal water circuit, which cuts the cooling cycle from 45 seconds to 18 seconds, raises the product qualification rate from 92% to 99.5%, and saves 12 tonnes of steel waste by cutting down on the number of trial moulds.
The capacity to make 3D printed lattice structures is also important in the realm of lightweight design. A specific company made an injection mould for electric tools. By making a hollow hexagonal lattice structure in the area that doesn't carry weight, the mold's weight was cut by 25%, the amount of material used was cut by 30%, and the time it took to cool down was cut by 15% since it could hold less heat.
3. Quick iteration verification: cut down on the amount of trash produced during trial production
To make a traditional mould, you have to go through several rounds of trial production modification cycles, and each trial production creates a lot of waste. A vehicle business was working on a new dashboard mould for a new car model, but the first three rounds of trial moulds had to be thrown away because of design flaws. This created 45 tonnes of waste. The "design print test" cycle can happen quickly with 3D printing technology. After one company started using this technique, the mould creation cycle went from 6 months to 6 weeks, the number of mould trials went from 5 to 2, and the waste rate went down by 70%.
三, Technological advances and cooperation between industries: speeding up the development of 3D printing waste management
3D printing offers a lot of promise for waste management, but it still has to get beyond three big problems before it can be used on a broad scale:
Material innovation: It's important to make specialised powder materials that are cheap and work well. A certain company made nano tungsten carbide reinforced H13 steel powder that made the mould harder (HRC 60) while keeping its toughness. This cut material prices by 40% compared to imported products.
Standardising processes: It is very important to set up a single library of printing parameters and a quality control system. A company produced the automated support generation program e-stage for Metal+, which can cut down on the use of support materials by 35% and raise the powder recovery rate to 98%.
Collaboration in the industrial chain: Equipment makers, material suppliers, and mould makers need to work together to make a complete solution that includes "hardware, materials, and services." A company has released the UM600MT equipment, which has a forming size of 400mm × 600mm × 500mm. This size is big enough to print huge car moulds. The process database that supports it has more than 200 material properties that are often used.