Various processes are available for the production of plastic parts. For small-series injection molding, we use aluminium tools, which can be used to produce hundreds to tens of thousands of plastic parts. Additive manufacturing using 3D printing can be suitable for the flexible and fast production of a small number of plastic parts or plastic prototypes.
But what happens when you combine the two? 3D-printed mold inserts are hotly debated. It almost sounds too good to be true: instead of high initial manufacturing costs for an aluminum tool, the right mold insert simply has to be produced in the 3D printer and the plastic parts can be manufactured at low cost. Does it really work? How profitable can the production of plastic parts with a mold from a 3D printer be?
We were so interested in this question that we realized a test project. Using the example of a bearing holder for the Knapsack bag, we wanted to find out which process is the most efficient: small series injection molding with aluminum tools? Plastic parts from the 3D printer? Or "the best" of both worlds, manufacturing with a tool produced in a 3D printer?
In our field test, we wanted to find out exactly: Which process costs how much? From what quantity of parts does 3D printer production make sense? Does manufacturing a tool using a 3D printer save costs and time? For what purposes is small series injection molding with conventional aluminium tool inserts relevant?
- The alignment of the insert in the 3D printer is of great importance, e.g. for the flatness of the inserts.
- The inserts must be re-tempered. There is a risk of warping here!
- The Accura HPC material has sometimes delivered the best results in terms of surface hardness, accuracy and thermal resistance. Difficulties arise during reworking. Only high-quality diamond files are suitable as tools. Wet processing is not possible as the material "swells" on contact with water.
- The contour of the SLA inserts must be very precise in order to be inserted into the mold frame without any problems and to ensure a clean touch pattern.
- The edge stability of the plastic insert is not as high as that of an aluminum insert.
- The additively manufactured tool is not yet finished after the printing process.
- The processing of original materials is possible with restrictions.
- Materials should be used that can be processed with low injection pressures and do not require high processing temperatures, e.g. PP, PE, ABS, ASA, POM, etc. E.g. PP, PE, ABS, ASA, POM etc.
- The contour of the component should be "simple" rather than complex. Simple "open/close molds" are required to avoid breakable moving mold elements.
- The injection molding process usually has to be adapted to the tool material - not primarily to the injection molded plastic to be processed!
- With predominantly low injection and holding pressures, it must be assumed that the full mechanical strength values of the materials will not be achieved.
- The long cooling times required can lead to the thermoplastic degenerating during this long dwell time in the screw of the injection molding machine.
- The maximum output quantity is very limited compared to aluminum tool inserts (~ 100 shots).
Our field test has shown that The production of plastic parts with an additively manufactured tool insert can be the right solution for certain requirements and a small number of parts. The possible use of original materials is a major advantage, especially in comparison to additively manufactured plastic parts from the 3D printer.
However, there are clear disadvantages compared to conventional small series injection molding with aluminum tools:
- significantly longer production time per plastic part
- Start-up necessary with 50-70 components that cannot be used
- after the start-up, it is possible that the 3D printing tool can no longer be used
- significantly shorter operating time of the 3D printing tool
- practically no profitability due to equally high initial costs and production times
In our test, the break-even point was 1,250 parts. From this part quantity, small series injection molding with aluminum tools was more profitable than additive manufacturing in 3D printing. The tool insert from the 3D printer was no longer usable after approx. 60 parts - and this at almost identical costs and production times compared to the aluminum tool. In economic terms, it was therefore not possible to break even with the use of 3D tools.
In our experience, it is therefore worthwhile relying directly on the production of injection molded parts with aluminum tools, as the aluminum tool lasted significantly longer than the mold insert from the 3D printer. After its production, many more steps are required to convert it into a functional tool.
Would you like to know whether a tool from the 3D printer is worthwhile for the realization of your project, whether you should rely on small series injection moulding with conventional aluminium tools or whether additive manufacturing is an option? Get in touch with us!