When it comes to additive manufacturing and rapid prototyping, there are basically two methods commonly used in the industry: FDM™ and PolyJet™.

FDM™ – or Fused Deposition Modeling™ – and PolyJet™ are two of the industry’s most advanced technologies for 3D printing equipment available on the market today. The capabilities offered by these two methods enable a wide range of activities, from budget-friendly modeling to large-scale, large-format production with bigger expenditure budgets.

Choosing between the two means understanding the various – and different – benefits each technology brings to the table.

Here’s a rundown of FDM™ versus PolyJet™ and which one may be more applicable to you based on your needs.

FDM™ Explained

This technology was developed in the 1980s by S. Scott Crump, and first came into commercial use in 1990. The terms ‘Fused Deposition Modeling™’ and ‘FDM™’ are both trademarked by Stratasys, our supplier and the maker of a wide range of 3D printing equipment.

With FDM™, thermoplastic filament is fed through a heated head and is sent out through high pressure as a fine thread of semi-molten plastic. The process entails taking this fine thread and using it to put down a continuous stream of material to form layers. The layering process is what eventually contributes to a finished product.

The process, as with virtually all 3D printing equipment, is controlled by a computer-aided manufacturing software package. The product is built from the bottom up. This produces products that are suitable for prototyping, modeling, and production.

PolyJet™ Explained

In contrast to FDM™, PolyJet™ uses a carriage that has at least four inkjet heads accompanied by UV lamps that travels over the work space and deposits tiny droplets of photopolymers. Photopolymers turn solid when exposed to UV light, hence the UV lamps. The carriage will print a thin layer of material that is built up, layer by layer, into a finished product (in a similar manner to FDM™).

As with FDM™, PolyJet™ processes are assisted by computer software and are suitable for products ranging from production-quality end products to models and prototypes. PolyJet™, since its inception, has become very popular with rapid prototyping.

Assessing the Strengths and Benefits of Each

Many facilities operate both a PolyJet™ system and a FDM™ system, to take advantage of each system’s strengths. But for those facilities that can only choose one or the other, it’s necessary to examine each system’s strengths to determine which can be most effective.

Build speed

Build speed is one factor that is often a priority (even though we believe it is a flawed performance measure). Assessing build speed is difficult because even though one system may have a slower build time, the number of required steps beyond the build phase are fewer, so it results in an overall faster completion time. PolyJet™ is faster than FDM™ at times, but this isn’t always the case.

Ease of use

Ease of use is also a primary factor, especially for lower-budget, desktop operations. Both systems offer simple material changeovers, easy setup, and simple file setup at the beginning of a process. FDM™ does offer one additional step (inserting a build sheet) in the setup phase, but that is a small difference.

Post-process stage

One area in which FDM™ and PolyJet™ differ is in the post-process stage of production. All you have to do to clean a PolyJet™ machine is to spray it with a water jet to remove the gel-like support material. With FDM™, a longer soak in a tank is required.

Operations with a low staffing level may prefer the fully-automated environment of a FDM™ program. For those who prefer quick turnaround, PolyJet™ may be the prime preference.

Budget concerns and cost

Additionally, budget may be a concern. PolyJet™ typically has higher operating expenses, so if budget is a main factor for you, FDM™ may be the best choice. Also, replacing build trays and extrusion nozzles with FDM™ is less expensive than replacing printheads with PolyJet™. Additionally, material costs are usually lower with FDM™.

Surface finish

If you want near-paint-ready surfaces that are almost good to go after they leave the printer, choose PolyJet™. FDM™ pieces often have layer lines and tool paths that can require either manual finishing or automated finishing to get ready to paint.

Feature Resolution

Some projects require high, fine resolution and fine detail. This is the strength of PolyJet™ systems, since they print in 600 x 600 dpi and 16-to-32-micron layers for a high standard of feature resolution. If creating fine-grained textures and very small features is a prime concern for you, PolyJet™ may be your best option.

Accuracy and stability

Accuracy for both FDM™ and PolyJet™ are similar, but when it comes to products being dimensionally stable under a load, FDM™ comes out on top. This can be crucial for production parts, which can make FDM™ a better choice.

Materials

Material choice is the biggest main difference between the two systems. PolyJet™ offers a deeper breadth of choice for materials (over 450 options with a wide range of rigidity, flexibility, strength, hues, and transparency) for superior product realism. FDM™, however, is better for thermoplastics that have higher functionality and durability.

Which 3D Printing Equipment Should You Choose?

Evaluate your needs and objectives in order to determine which system works best for you. What we’ve found is that most operations can benefit from both FDM™ and PolyJet™ in their facilities, so it eventually makes sense to eventually obtain both capabilities.

For help choosing the right 3D printing equipment for your purposes and goals, contact us and let us help you make the right choice.