3D Printer Markforged Materials: How to Choose Without Repeating My $41K Mistake

If you're trying to decide which 3D printer Markforged sells is right for your shop, you're probably asking the wrong question. The machine is only half the equation. The material you choose, and the orientation you print it in, determines whether the part survives or fails.

I've been handling additive-manufacturing orders for eleven years. I've personally made (and documented) 21 significant mistakes, totaling roughly $41,000 in wasted budget. Now I maintain the pre-purchase checklist that keeps our team from repeating those errors. This guide is built around that checklist.

There is no universal best material. The right choice depends on what the part has to do, how hot it gets, and who has to approve it. Let me walk you through the three scenarios I see most often.

What changed in industrial 3D printing

The old belief that carbon fiber 3D printing is a hobbyist gimmick comes from an era when carbon fiber meant chopped dust mixed into PLA. That was true ten years ago. Today's industrial systems are different. Markforged machines print continuous carbon fiber, fiberglass, Kevlar, and metal alloys. What was best practice in 2020 may not apply in 2025. The fundamentals haven't changed, but the execution has transformed.

Another thing I had to unlearn: People think a more expensive printer makes stronger parts. Actually, it's the reverse. Printers cost more because they can process materials and control the process in a way that produces stronger parts. The machine doesn't create strength by itself. If you print a bracket in Onyx with no reinforcement and 20% infill, it will crack no matter how expensive the printer was. That was an expensive lesson.

In my first year, I made the classic rookie mistake: I approved 50 Onyx alignment blocks at 37% infill because a friend used that setting on toy parts. Every block shattered in a vise within a week. 50 parts, $1,150, straight to scrap. That's when I started choosing materials based on the load case, not the marketing sheet.

Choose the material based on the load case, not the marketing sheet.

Types of Materials for 3D Printers: The Only Three Buckets You Need

You will see hundreds of material names. In industrial practice, the types of materials for 3D printers that survive factory use fall into three buckets:

• Chopped-fiber thermoplastics – nylon or PA filled with short fibers. Good balance of toughness, chemical resistance, and cost. Example: Markforged Onyx.
• Continuous-fiber composites – strands of carbon, glass, or aramid laid into a thermoplastic matrix. Dramatically stiffer and stronger along the fiber path. Example: Onyx with continuous carbon fiber.
• Metal alloys – stainless, tool steel, and superalloys for tooling and end-use parts from metal printers.

Within each bucket, you choose a grade based on temperature and chemical exposure. Don't overcomplicate it.

Scenario A: Shop-floor fixtures, jigs, and alignment tools

If the part is a bracket, a jig, a fixture, or a quality-control gauge, start with Onyx. It's a chopped-carbon-fiber-filled nylon that handles continuous heat around 80°C — maybe a little more depending on the exact grade. Check the Markforged official website for current values; I don't trust my memory for anything that affects safety.

For a fixture that gets knocked around, use a high infill, not the 37% I used. I'd rather put the material in than explain why a tool failed. If the part needs to carry load across a long span, add continuous carbon fiber. The difference is way bigger than I expected. A straight Onyx bracket flexed; the same geometry with two fiber rings held until the table it was bolted to bent.

Onyx also doesn't have the layer-adhesion surprises of pure nylon. It's forgiving for first articles. But it's not magic. It won't survive a welding torch or a hot platen.

Scenario B: Metal tooling or low-volume metal parts

Use metal when the part has to survive ejection, stamping, vibration, or repeated clamping. Markforged metal systems print in alloys like 17-4 PH stainless, H13 tool steel, and other selected metals. We've printed injection-molding inserts that lasted hundreds of cycles without cracking. That doesn't mean every part is defect-free. We still inspect, test, and machine mating surfaces. But some parts simply can't be made from polymer.

The trigger for metal is simple: if the part gets hot enough to soften nylon, even briefly, polymer is the wrong answer. Another trigger is threads or sharp edges that polymer can't hold. In those cases, metal is the right answer.

But I've also learned when not to use metal 3D printing. Long thin shafts, large cylinders, or anything that needs tight tolerances all over is still better machined. Additive excels at complex shapes in small quantities. It doesn't exist to replace every CNC operation.

Scenario C: Structural frames that are really tube designs

This scenario catches a lot of people, including me. If your part is a frame, roll cage, or exoskeleton made from round or square tube, printing the whole thing is usually the wrong move. Tube is cheap, strong, and available. A good laser tube cutting Mendota Heights shop can notch, bend, and cut tubes to length faster than we can print the same structure. We send those frames out to a local job shop and then weld them.

(Should mention: we learned this after trying to print a full tube frame once. It took 26 hours and still snapped at a bolt hole.) Now we don't argue with geometry.

That's not a failure of 3D printing. It's using the right tool. The hybrid approach works best: laser-cut and welded tube for the frame, Markforged for the custom brackets, gussets, and mounts. Additive lets us match those connecting parts to the exact tube angles. It's faster than sourcing cast brackets and stronger than bent sheet metal.

Where Can I Buy HP 3D Printers?

I get asked 'Where can I buy HP 3D printers?' enough times that it deserves an answer. HP sells Multi Jet Fusion systems through its industrial sales team and certified resellers. They are production machines for polymer parts, especially PA12, and they're excellent when you need high throughput of medium-sized parts.

If your priority is continuous carbon fiber or metal, HP's material set is different. That's not a value judgment; it's a tool-fit question. But if you're producing thousands of clips, ducts, or housings per month, an HP system should be in the conversation. Just remember to price the whole cell: powder handling, depowdering, finishing, and safety equipment. The printer is only one line item.

How to Decide Which Scenario You're In

Here is the three-question flow I use with my team.

1. Is the overall shape a tube or frame? If yes, call a laser tube cutting shop first. Print only the mounts and brackets.
2. Does the part see heat, chemicals, or repeated impacts that would soften or crush polymer? If yes, go to metal.
3. Can the part be produced as a polymer fixture with a dense shell and reinforcement? If yes, use Onyx and add continuous carbon fiber around the load path.

If you're still not sure, do a small test: print one sample, put it in the actual work cell, and load it the way an operator will. Then check for deflection and cracking. That test has caught 47 potential errors for us in the past 18 months. It's cheaper than a full production run of the wrong part.

Bottom Line

Don't let anyone sell you a universal material answer. The right material, printer, and process depend on your scenario. The machine can't make that decision for you.

Before you buy anything, verify the current specs on the Markforged official website. And if someone tells you additive will completely replace machining or laser tube cutting, smile and walk away. It won't. It will make those tools better by printing the parts they can barely make.