To print or machine? Produce by Additive or Traditional Manufacturing?
As Additive Manufacturing is gaining acceptance as a reliable alternative production technology we are facing this dilemma every day.
An important rule of thumb is here to assist us. According to it, for a part under question, the smaller the lot size and more complex the geometry is, the more likely 3D printing is the adequate production method.
In manufacturing facilities exists a family of custom auxiliary tools, which typically fall into this rule:
- Grippers in pick-and-place applications,
- Special pieces in automation lines,
- End-Of-Arm-Tooling for robotic applications,
- Holding fixtures for CMM measurements, etc.
All these custom tools are usually complex and are produced in batches of few pieces or usualy in just one piece.
Why 3D Print Jigs and Fixtures:
1. Device assembly consolidation into fewer pieces
Fixtures must follow the part surfaces, but usually in strange directions, those dictated by the production step that is used. For example, if we need a hole in an injection molded part, if the hole is in the opening direction, we will mold it, even if it is perpendicular to the opening direction, slides in the mold will form it. An additional post-molding process is only needed if hole direction is in strange angles not allowing the part to be ejected. Formation of features in irregular axis, is not only an issue for an injection molds. It is also difficult and costly to machine. Such complexities in traditional manufacturing (CNC machining), lead to a simplification of the components and towards a multipart assembly. Cost and lead time increases furthermore due to the necessary assembly features (Snap fits, threads with fasteners etc.), which must be incorporated into these parts.
On the other hand, in 3d printing, the whole assembly, might be consolidated into a single piece.
2. Lighter parts. Part 1: Plastic vs Aluminum or Steel
With 3D printing we have a wider range of materials to choose, compared to machinable plastic blanks. If, due to the application, there are no suitable plastic materials for machining, the much heavier aluminum or steel will be the only choice.
A typical example are grippers for automatic part pickers in injection molding of engineering thermoplastic materials. Grippers must be soft enough, to avoid damaging the products, but with high heat resistance to withstand the elevated temperature of the just ejected part.
Plastic materials for machining, hardly perform in the requested temperatures, but there is a wide choice of 3d printing materials for high heat applications.
3. Lighter parts. Part 2: Optimum design related to weight
Part design for 3d printing offers a much higher degree of freedom, allowing tailored made parts by using the smallest amount of material for the given specifications.
Producing parts comprised by trusses is easy in 3d printing and almost impossible in CNC machining.In metal 3D printing by Bound Metal Deposition, we can even provide parts with internal cavitation.
4. Lighter parts. Part 3: Infill
The most convenient way to produce light and strong parts is to transform all solid volumes into thin cell areas with internal trusses. This is extremely difficult in traditional manufacturing, but the standard method in 3d printed parts. Both from plastic or metal. These internal truces are the so called 'infill'.
It must be considered, that weight of grippers and end-of-arm-tooling cost money. Due to excess inertia, either the production line must be slowed down, or in case of robotic applications, bigger robots must be purchased.
5. Cut weeks from the development cycle.
3D printing is much faster than traditional manufacturing and it is important for these specific applications, as there is always the concern, to have all these parts in place, for the production to start. There are two important reasons that production velocity of 3d printing will offer a substantial improvement:
Finalization of auxiliary production tooling requires the pre-serial products. So construction usually starts after main tooling (injection molds, sheet metal or die-casting dies etc.) has been sampled, and there is always a time race for auxiliary devices to be completed before the end of the main tools corrections, but
delivering the production line, might require a few iterations of design, production and testing of the auxiliary tools. Time savings with 3d printing is thus multiplied.
6. Improved part manipulation by the 3d printed tools
It is not only that 3d printed parts might have extremely complex geometry, but also that this complexity is almost given for free!
In contrary with traditional manufacturing, manufacturing cost in 3d printing is loosely related to the part complexity.
So, designers, not only can take advantage of the design freedom in additive manufacturing, but also without fearing that complex shapes that improve parts function will not skyrocket the manufacturing cost. Optimum gripping geometries can be designed and easily manufactured.
7. Vacuum channels inside the body of the parts.
Except of the obvious cost savings, by creating a “plumbing” circuit inside the parts to deliver vacuum in suction caps there is also another benefit.
By eliminating the net of tubes, we avoid all tangle hazards.