July 20, 2021

Roundtable Roundup: Multi Jet Fusion

By Rachel Hunt

We recently hosted a customer roundtable on leveraging 3D printing for end-use production. Listeners got a behind-the-scenes look at how tech startup, OVR Technology, used HP Multi Jet Fusion 3D printing to reduce development time on its R&D product roadmap.

The roundtable featured Erik Cooper, head of design at OVR, along with guests Eric Utley, 3D printing applications engineer here at Protolabs and Lee Dockstader, HP's director of vertical market development. If you missed it, no worries. You can check it out here.

Multi Jet Fusion (MJF) is an industrial 3D printing process that produces functional nylon components, and OVR selected this technology to prototype and produce end-use parts on their OX1 device. Check out the full story and podcast.

We received so many thought provoking questions about MJF during the roundtable. Below is a roundup.

MJF parts

Multi Jet Fusion Print Speed

Q: How long does it take to print a full 15 in. x 11.2 in. x 15 in. bed?

A: 8-9 hours at 8-9 sec. per layer, translating to approximately 1 in. per hour. This print speed provides strong economic justification for low-volume, high-complexity mixed run builds or builds of personalized unique parts. It doesn’t matter if you are making 1 part or 100 in the print bed, the speed remains constant. Making good use of space in the machine helps with part cost.

Q: How do lead times and costs compare between traditional 3D printing and MJF?

A: MJF is the most economical process we currently offer. The lead times are comparable to other techs we offer like SLA or SLS.

Multi Jet Fusion Materials

Q: What is the highest temp material you have available? My application is in an automotive exhaust application.

A: The highest temp we offer for MJF is PA 12, but we offer higher-temp materials in SLS and SLA such as a mineral-filled nylon and PC-like advanced high-temp material (Accura 5530).

Q: Do you have thermoset materials that can be used for 3D printing? They must be UL-approved.

A: MJF materials are thermoplastics, but we do offer 3D printed thermoset materials in SLA (unfortunately none are UL rated). We do have UL-rated injection molded material options for you.

Q: Do you have ESD-safe and higher-heat polymers available?

A: We currently do not have an ESD-safe option for 3D printing but we do have a high-temp mineral-filled nylon we offer in SLS.

Q: We are looking for material alternatives to HP Nylon 12 to allow us to have more flexibility in a sporting good part. What other materials allow for more flex and high-cycle spring qualities—similar to the materials used for heels/soles in shoes?

A: We offer more flexible materials in SLS. Our PA 11 Black and the TPU we offer in SLS is more flexible than the two nylons we offer in MJF.

MJF quality control
MJF typically offers a tolerance of +-0.012 in.

Multi Jet Fusion Design

Q: How does this method of 3D printing handle overhangs and support material?

A: A primary strength of the technology is that allows for design freedom. The powder itself acts as the support structure, so design is not constrained by overhangs or support structures. Just remember, you must stay within confines of printer, within min. feature size, and be sure to consider ways to combat material warpage (add radii, uniform wall thickness, etc.).

Q: How do tolerances compare between MJF and injection molding?

A: MJF is typically +-0.012 in. and molding for Protolabs is +-0.003 in. plus material shrink rate.

Q: What is the minimum gap that needs to be present between multiple overhanging layers?

A: Gaps typically need to be about 0.020 in. to not seal shut.

Q: What is the thinnest I could go if looking to make a 1mm plastic mesh?

A: The minimum feature size for MJF is 0.5mm. For a mesh I would go a bit thicker so that it is structural as a mesh designed right at the min. feature size can be very fragile. A 1mm size should work well.

Multi Jet Fusion Mechanical Properties

Q: On HP’s thermal inkjet, what is the layer strength (Z-axis) vs XY strength?

A: In general, the MJF tech is very isotropic, but is slightly weaker in Z than XY. The tensile numbers we represent on our data sheets are in Z and are the weaker numbers you should see in a given part.

MJF color dying
We can apply custom dying and custom painting to your MJF parts.

Multi Jet Fusion Secondary Operations

Q: How well does this process lend itself to supporting heat-staked inserts versus traditional molded parts?

A: This is another strength of the technology—the strength of parts. Parts will behave like molded parts when staking, and we do it daily! We have even electroplated these parts. It takes well to secondary processes.

Q: Are there different color options?

A: We only offer black, but HP offers MJF printers that can print in full color. HP has a color version of the production printer. It uses color agents instead of black agents on the outside skin of the parts.

Q: What are the options for custom coloring for MJF? Can dyes be custom colored or would they need to be painted?

A: Our standard process is to dye parts black. We can apply custom dying and custom painting to your MJF parts. For example, if wanting a dyed yellow part, a bright yellow would be hard to achieve. Expect a more Dijon mustard yellow. We have found that MJF does take matte paint very well. And, of course, HP does offer color production printers.

Q: Is the vapor polished part you're demonstrating also painted?

A: None of the parts are painted, but MJF parts do take matte paint well.

Q: How recently has the vapor polishing/smoothing process been applied to 3D-printed parts?

A: We do not yet offer this in the U.S. but do offer it in Europe. The technology itself has been around for a couple years.

Q: Does annealing for improved properties play into MJF printing?

A: We do not anneal whole parts and could see some warp risk, but it could be theoretically possible. We do anneal living hinges commonly to improve their cycle count.

MJF build
MJF is an industrial 3D printing tech that brings precision and repeatability to each build.

Multi Jet Fusion Applications

Q: Is MJF print technology seen as the most mature and capable for end-use production parts?

A: Absolutely. MJF is the leading 3DP technology for low-volume production plastic parts. It’s an ultra-versatile nylon material. The part finish off the printer is production quality and there are no layer lines. It prints faster than SLS, making it a very economical printing option for end-use part production.

Q: Are there any specific areas of consumer products that you see the most active in using MJF for end-use production, not just rapid prototyping?

A: Consumer products span many areas (phone cases, action figures, etc.). We see MJF being used for medical devices and drones. Also on the rise are customized orthopedics prosthetics—insoles, ankle braces, prosthetic socket mountings, scoliosis bracing, hand bracing, etc. 

Future of Multi Jet Fusion

Q: Do you see MJF technology working itself down to the consumer printers, kind of like FDM printers?

A: Our lowest cost machine is around $100,000, and in the end-use part powder bed laser sintering technology, this cost can be considered at the consumer level. Basically, at this price, you are getting color for free. 

Q: What are you most excited about for the future of additive?

A: The needle is constantly moving. MJF has really moved in the past few years—new materials, colors, texture options, etc. The pace of innovation speeds up with technologies like MJF. It offers the ability to decentralize manufacturing. Mass customization and flexibility are invaluable. As 3D printing design ramps, there’s no going back with all of the trained engineers out there.

Want to read up on some more frequently asked questions? Check out our FAQ page.