Creating designs with traditional manufacturing in mind was already challenging by itself. Today’s designers now have to consider how to incorporate 3D printing and/or Direct Digital Manufacturing (DDM) into their designs. There is a desire to use a printed prototype part or assembly from a 3D printer, but the challenge comes from knowing where to start. So, I thought I would share some techniques to help get you thinking about DDM design.
The example above is a fairly simple prismatic part, machined very traditionally out of aluminum using a knee mill. I often look at parts like this and ask, “If I had to print this FDM what could I do to improve the design and reduce time in building and support removal?”
The first thing I would look for are any small, traditionally drilled holes, like the one you see in the cross section below (left). The second picture below shows the model processed in Catalyst. The small hole of the model (red) fills with support (blue) and can take a while to dissolve, especially when using SR-20 support material.
When looking at an inlet hole like this, I try to avoid using round cuts which require support, and design using “self-supporting angles.” Going back to the CAD model (left), I changed the inlet hole to be a 45 degree diamond hole (right), which fully eliminates the need for support. Catalyst proves that no support will be used for this and we pick up a huge time savings (right).
I reused this technique for the main hole as well. By adding a chamfer, whose length was equal to the slice height, I eliminated all the support material for the entire inlet, as seen below.
To tap; I built a diamond insert with a hole and printed the insert with the hole facing up. This allowed me to make a more accurate hole than printing on the vertices.
The traditional machined block (machined – left, CAD – right) at the top only allowed one inlet on the top of the part. This was most likely done to reduce the amount of machining required. However, using self-supporting angles on a printed part, we can create a hidden channel to connect three holes (right), which allows for superior air and fluid flow. This technique is definitely something we can’t do traditionally, without requiring an expensive subassembly.
From my CAD model, I drew a diamond on the front plane and used a revolve cut to make the hidden channel (left). I then patterned the original cut to create three inlets (middle). End users with Catalyst can use this technique to create features without support material, while drastically improving parts performance (right).
The Limitations of Stock
Another aspect of designing for traditional manufacturing was the need to consider stock to facilitate products, especially if it needs to be fabricated. One of the advantages of additive manufacturing is the ability to ignore limitations of stock. Traditionally, if I wanted to make a locator feature, like the one on the left, I would have to buy thicker stock, incurring more cost. Additive Manufacturing gives far more flexibility to produce simple features, like the one on the right, regardless of stock.
Recently, I wrote another post about Seam Control for FDM. This is another trick that will save post-processing time used sanding and filing a printed seam. Check out that post for further information.
Use Configurations to Manage Tolerances
No matter what Additive technology you use, managing tolerances is made easy by using configurations. Design the component as you want it in SOLIDWORKS, since you will use this design for shop floor drawings. With the desired design complete, then create a configuration that holds special features or tolerances that aid in 3D printing. Below is an example I used in the Seam Control post. The model on the left is designed in CAD how I want it. On the right shows an added special feature to be used for Addititive Manufacturing.
I also use configurations when blending FDM and laser cutting. For flat components like the one below, it is cheaper to laser cut stock rather than tie up a 3D printer, unless you don’t have a laser.
These are a few ideas that hopefully help you improve your prototyping and assist you if are considering Direct Digital Manufacturing.
Tags: Configurations, Insight, Catalyst, Direct Digital Manufacturing, Seam Control