There is a compelling drive towards the use of additive manufacturing (AM) to manufacture mold tools. Here’s a look at one technology for micro mold tooling.

Jon Donner, CEO, Nanofabrica

As AM matures as a process not just for prototyping but for true production applications, there is an excitement about what the future may hold for manufacturing. Recently, there has been increased interest in using AM for the production of mold tools themselves, often called Direct Rapid Soft Tooling (DRST). DRST is well suited to scenarios when the goal is small series production where the cost of a traditionally manufactured tool is prohibitive, and the accommodation of design changes too hard or expensive.

The Nanofabrica process
The time and cost associated with the fabrication of conventional micro tooling for micro injection molding led Nanofabrica to assess the viability of creating AM produced DRST for short-run production parts and functional prototypes.

Nanofabrica’s AM process seen in the Terra 250 AM platform uses an ultra-high resolution Digital Light Processor (DLP) engine, achieving repeatable micron levels of resolution by combining the DLP engine with adaptive optics. In conjunction with an array of sensors, this allows for a closed feedback loop, which is at the heart of why the technology achieves high accuracy while remaining cost-effective as a manufacturing solution.

The trial results
In its recent experiments, the Terra 250 (which can achieve ultra-precise 1-micron resolution) succeeded in injecting PP, PE, and ABS into a 3D printed mold. Excellent surface finish was achieved with an Rz of 0.8-micron in the hardest direction, and an Rz of better than 0.1-micron in the Z plane.

In the initial experiments, the molds lasted for 20 shots with a molding pressure of 400 bar at 230°C. It took an hour to additively manufacture one mold at the cost of under $20. The materials were injected using an Arburg 35-ton machine.

Nanofabrica is fine-tuning the manufacture of its DRST through a combination of design optimization and improvements in materials. While the company is getting a good 20 shots off this preliminary testing, it is working on improving both the material (giving it much higher temperature resistance and strength) as well as the process (focusing on improving the impact pressure and stiffness of the printed soft tool) with the aim of handling tougher injection conditions and a larger array of injected materials. The aim is to last 1000 shots in the coming months accommodating temperatures of 350 degrees C and pressures of 800 bar.

This would unlock new business possibilities for mold makers and manufacturers who up until this point have been restricted to the use of long lead time and expensive traditionally manufactured mold tools for the achievement of any volume of molding, from prototype runs through to mass manufacture. The trials should stimulate the business case for a process chain that includes DRST, with a dramatically shorter lead time of about 2 hours from file to injected part and at costs reduced from thousands of dollars to tens.

Using the Terra 250 AM platform to produce DRST capable of manufacturing upwards of 1000 parts per tool opens up the possibility of small and even medium batch manufacturing. The platform is able to accommodate the manufacture of multiple small tools in each build, and so manufacturers can produce many replacement tools at low cost. In the future, for the cost of one aluminum precise mold which costs about $10K you could manufacture 500 soft molds on a Terra 250, leading to about 500K final parts through a faster process. In addition, each tool can be adapted as required, opening up the possibility of speed to first part out, and the ability to correct during the manufacturing process according to market and customer needs.

When AM produced DRST and traditional injection molding are compared, the savings in terms of product development time and cost are seen as compelling benefits for using AM. However, the fact that AM is relatively agnostic to complexity means that AM produced DRST could also stimulate innovation in product design and manufacture. AM can achieve geometries impossible using conventional processes, and as such is positioned as a key enabling technology driving the production of cutting-edge products as well as shortening the product development cycle. This is because it is quite often the case that product design updates are shelved by manufacturers due to the cost of new traditional molds.

The demand for AM produced DRST has been held back by perceptions that AM is limited in terms of surface finish, precision, accuracy, and repeatability and also in terms of the limited number of materials that can be processed. Nanofabrica’s AM process reaches micron-level resolution enabling high surface finish. When applied to manufacturing of mold tooling, it reduces the need to cut steel.

Nanofabrica
www.nano-fabrica.com

Author bio:

Jon Donner combines technical and business skills, and is now focused on making Nanofabrica an innovative and cost-effective solutions provider for manufacturers. Nanofabrica is Jon’s second startup, having earned his PhD in nano optics in the Romain Quidant Plasmonics group at ICFO Barcelona, Spain. Before his PhD, he earned a double degree at TAU (Tel-Aviv University) in physics and electrical engineering and worked in an electro-optics lab. jon@nano-fabrica.com.