From FDM 3D Printing to Injection Molding

May 5, 2024

How much does it actually cost to 3D print and when should you switch to injection molding?

Fused Deposition Modeling (FDM) is the preferred 3D printing method for fabricating products that are still in the early development stage and are likely to experience design changes, as FDM 3D printing can easily adapt to said changes while also being relatively low cost.

However, even when the design has finalized, some companies may still choose 3D printing as it has been shown to be effective with their product and is still able to meet the demand.

For in-house FDM fabrication of products, the retail price to customers might be broken down as follows:

Material Cost

  • Filament
    • Type: ABS, nylon, TPU, etc.
    • Weight used: Dependent on the product’s volume and complexity (PrintAWorld, 2021)
    • Sandpaper, paint, etc. (for post-processing, if applicable)

Machine Cost

  • Printing on Enders vs Prusas vs Ultimakers
  • Machine Depreciation: With every print, the value of the machine drops, and regular maintenance of the machine is required to prolong its useful lifetime

Overhead Cost

  • Labor: Machine/Print set up, monitoring/collection of print, post-process (sanding, painting, etc.)
  • Office Rental, utilities (electricity, etc.)
  • Building your product / R&D
  • Profit Margin
3D printing farm to increase production rate (O'Brien, 2022)

Though the retail price for consumers can be kept reasonable through 3D printing, it is not a sustainable option in the long term as it is time-consuming to print and manage prints. Even if more 3D printers were obtained to meet the demand, there would still be issues with lead time, and this would just mean more assets to maintain. It is important to note that not all 3D prints are perfect. Sometimes, a print may be defective and have to be disposed of after a whole day of printing.

The table below shows the amount of time taken to print a product using the FDM method:

FDM
Set-up time (initial) ~1-3 hours/printer
(Building the printer (if applicable), optimizing print settings, etc.)
Set-up time (fabrication) ~15-30 mins
(Slicing 3D model into STL, bed leveling, heating, etc.)
Fabrication Time (1 pc) 8 hours*
Fabrication Time (10000 pcs) ~666 days*

*Assuming no defective pieces

When such problems arise, injection molding is a preferred choice of manufacturing for those looking to meet growing demands and volume while reducing cost price.

Below are some consideration factors:

Volume

Production volume that can be achieved with injection molding (Image: Poulton, 2020)

Firstly, it is important to identify the level of demand for your product. This can be done by evaluating the number of orders per week or month, and how your 3D printers are performing in keeping up with demand. This data can also be used to predict how much volume will be needed in the next few months, as molds can take some time to fabricate depending on the complexity of the product.

FDM Injection molding
Set-up time (initial) ~1-3 hours/printer
(Building the printer (if applicable), optimizing print settings, etc.)
30 days
(Mold making and testing)
Set-up time (fabrication) ~15-30 mins
(Slicing 3D model into STL, bed leveling, heating, etc.)
~10-30 min
(Melting of pellet)
Fabrication Time (1 pc) 8 hours*

The table above outlines the differences in time at each stage of production for your product. If time is a limiting factor in your production, you may not have enough capacity to produce the volume you need.

Capital

The biggest cost that comes with injection molding is the creation of molds. The reason for this is because the molds have to be specifically designed and optimized for the fabrication of the product. More often than not, it takes multiple attempts and tests to get the mold right for injection molding, and that's something that's accounted for in its price.

The process of mold-making generally includes CNC machining, testing of the mold, and verifying that the product is made to specifications (Image: Product Development Experts ,u.d).

Therefore, having the funds for the initial set-up cost and volume to be able to commit to the production is therefore something to consider heavily.

Design

A perfectionist knows that there is always potential for improvement, so committing to a final design is a big deal. For injection molding, the design of the product cannot be changed until the end of the commitment period or until you have gotten a return on investment (ROI) from the mold, whichever comes first.

A mold is comprised of multiple cavities. Each individual product has its own unique cavity. (Image: Fast Radius, 2022)

The image above illustrates that there can be several cavities in a mold. However, these cavities don't have to be just for one design of your product; they can be a combination of different designs. For example, you might have 15 cavities in total split among 3 different designs in a single mold. Therefore, in order to streamline the production process, it is important to consider which designs are more likely to experience changes down the line. By grouping the designs that are more finalized together, and those that are still in the early stages of development onto another mold, we can avoid any disruptions to the production line. This would also allow those designs that are more final to make full use of its mold lifetime, while the other mold can be switched out for a new one once the ROI is fulfilled.

Another option you may want to consider before moving from FDM to injection molding, is fabricating your product with stereolithography (SLA) 3D printing. This can give you a better idea of the texture/finish of an injection molded product. Additionally, this may be useful if the design of your product has a functional element that is reliant on the nature of an FDM 3D print (eg. layer lines allowing for better fit).

SLA has a better print resolution that more closely resembles an injection molded product as compared to FDM. (Image: AllOnScale, 2021)

Closing Remarks

If you are considering injection molding because of the limitations of 3D printing, you must first ensure that there is sufficient demand to justify the investment in molds. You would also need to have enough capital to support production until you receive a return on your investment.

Injection molding is also a significant commitment, so it is important to have your product's design finalized before moving forward. You may also want to consider verifying your design with SLA 3D printing before injection molding.

At Factorem, we pride ourselves in being able to support a wide range of different manufacturing needs. Whether you are needing more 3D printing capacity, trying out SLA printing for the first time, or getting started on injection molding, we are here to help. If you would like to discuss your manufacturing needs with us, please don't hesitate to reach out to us at hello@factorem.co. ⭐