Advanced Application Overview: FDM For Composite Tooling
Recently, Cimetrix had the pleasure of hosting the Composites group from Stratasys to present a workshop on leveraging Stratasys technology for composite tooling. Today, we are sharing a recent post by Ross Jones, one of the members of the composites team. Continue reading for a brief overview on how to best leverage Strasys' Fused Deposition Modelling (FDM) technology for composite tooling applications.
FDM composite tooling offers distinct advantages over traditionally manufactured tooling; an FDM tools can have complex, highly functional designs that are tailored to the manufacturing process, whilst boasting superior cost and lead-time when compared to traditional methods. In general, the design process for FDM tooling is primarily driven by the process parameters for the final composite part (cure cycle, pressure, bagging approach, etc.), as well as the machine being utilized. Tools can theoretically be created on any Stratasys FDM printer; however, Cimetrix utilizes ULTEM1010, available on both the Fortus 450mc and 900mc 3D Printers (as well as some legacy Fortus machines), to ensure our tools have optimal strength and temperature resistance. Material selection is primarily determined by the cure cycle of the given application, while pressures and bagging approach will impact the design style and construction.
Typically, FDM tooling is designed in one of two major styles, shell style and sparse style (see below). That said, FDM composite tooling is not limited to these two styles — designs can be as complex, as simple, or as functionally oriented as the application requires.
Shell style tools typically require less material and build faster than their sparse style counterparts. Additionally shell style is often utilized when envelope bagging is preferred or desired. Sparse style tool design uses the basis of the shell tool, but reinforces it with an internal fill pattern, or essentially a support structure. Sparse style tools are typically used when surface bagging is preferred and/or tool rigidity is required. In high pressure and high temperature situations, tools may be printed with a solid interior fill to ensure tool longevity.
Regardless of the general tool style, designers should strive to minimize material use while optimizing print time and quality for the desired application. Keep in mind, however, that when tool longevity is desired, overbuilding the tools will help ensure that desired tool performance is received. Below we have summarized some key tips when considering leverageing FDM for composite tooling.
1. Print the least amount of material possible.
Design the tool for the intended use. Repair and development tooling, quite often, does not require the robust construction that production tooling requires.
Design from the composite laminate rather than an existing tool. This helps to reduce excessive bagging area. Typically, FDM tooling only requires 2-3” beyond the EOP for bagging materials.
When leveraging envelope bagging, using shell-style tool designs help to minimize material use over sparse style tooling
When edge bagging sparse style tools, printing with open ends and large air gaps, up to 2”, can reduce material use and improve air flow during the cure cycle
2. Use self-supporting angles to minimize the amount of support material required, Figure 3. Overhanging features require support material, which significantly extends build times while also increasing material use. Remember, Stratasys FDM printers can mainain self supporting angles of 43 degrees - use this to your advantage when designing tools to minimize material cost and print time.
3. Orient the tool such that the layup surface is printed in a vertical orientation and requires the least amount of support material The vertical orientation typically produces the best surface finish by minimizing stair-stepping, to maximizes surface quality and minimize the amount of post-processing work.
Comparing 3 build orientations for the same shell style tool; option 1 optimizes print time at the expense of surface finish, whilst option 3 optimizes surface finish and support material consumption.
4. Utilize larger layer thicknesses, aka – slice heights (0.013 and 0.020 inch). Larger slice heights dramatically reduce print time and allow for less dense support structures in sparse style tool designs. This can significantly reduce cost with very little impact on finishing work (depending on build orientation – refer to tip 3 above).
5. Avoid ultra-fine features such as scribe lines and rosettes. These features, typically just 0.005 inch in depth, do not print reliably even at the finer slice heights. Alternatively, a secondary trim tool can be designed and utilized for post-processing operations.
At Cimetrix, we have over 23 years experience providing Canada's aerospace and automotive leaders with cutting-edge additive manufacturing solutions for custom tooling applications. Today's post is a very brief overview of some main considerations to take when leveraging additive manufaturing for composite tooling, taken from our Composite Tooling Application Guide. For a copy of the complete applicaiton guide, or to speak with our Applications Specialists for a consultation, please do not hesitate to get in touch with our team!