Casting CoCr frameworks has worked for orthodontic labs for decades, but it’s a process with a lot of hands between the wax pattern and the finished appliance, and every one of those hands introduces variation. Metal 3D printing removes most of that variation. Once a lab’s workflow is dialed in, a CoCr expander, lingual arch, or removable partial denture (RPD) framework comes off the printer closer to design intent than casting can consistently deliver, with less labor per case.
The catch is that “dialed in” takes real setup work: the right powder, the right printer configuration, and a heat-treatment step that doesn’t get skipped. Here’s the full workflow, end to end, built around the equipment combination many labs are standardizing on: the HBD 150D FLEX Dual Laser, TopCore CoCr 10-30 μm powder, a Nabertherm N 7/H furnace for heat treatment, and a Retsch sieve shaker for powder reclaim.
Step 1: CAD Design & File Preparation
Every case starts the same way it would for casting: intraoral scan or model scan, CAD design of the appliance in your orthodontic design software, and export as an STL. From there, the workflow diverges from a milling or casting pathway.
- Orientation matters more than it does for resin. CoCr parts need to be oriented to minimize overhangs and reduce support density on functional surfaces (clasps, occlusal rests, connector bars) while still supporting thin sections through the build.
- Support structure design is a separate skill. Under-supported thin wires and clasps warp or fail mid-print. Over-supported parts take longer to finish and risk marring the surface during removal. Most labs build a support library for recurring geometries (Hawley clasps, Adams clasps, expander screws) rather than designing supports from scratch every case.
- Nest multiple cases per build. The dual-laser configuration on the HBD 150D FLEX is built for this: two galvanometer scanners work the build plate in parallel, so nesting several ortho appliances into one plate cuts total production time significantly compared to a single-laser machine running the same job.
Step 2: Powder Handling and Particle Size
This is the step labs moving from casting most often underestimate, and it’s where TopCore CoCr 10-30 μm powder earns its place in the workflow.
Particle size distribution directly determines layer density and surface finish. A tighter distribution in the 10 to 30 micron range packs more consistently in each powder layer, which means fewer voids, more predictable melt pools, and a smoother as-built surface that needs less finishing work afterward. Wider or inconsistent particle size distributions are where labs run into porosity and inconsistent mechanical properties, especially in thin clasp and wire sections that carry real functional load in the mouth.
Two habits protect that particle size distribution over time:
- Sieve every reclaimed batch before reuse. Run recovered powder through a Retsch sieve shaker to remove partially sintered particles and contamination before it goes back into the printer’s hopper. Skipping this step is the single most common way labs let particle size distribution drift out of spec without noticing until a print starts failing.
- Don’t over-blend reclaimed and virgin powder indefinitely. Track how many print cycles a given powder lot has gone through. Reused powder that’s been through the sieve multiple times gradually shifts in particle shape and flowability, so most labs cap reuse cycles and refresh with a percentage of virgin TopCore CoCr powder on a set schedule.
Step 3: Printing on the HBD 150D FLEX Dual Laser
With the file prepared and the powder qualified, the actual print is the most automated part of the workflow. The HBD 150D FLEX’s independent atmosphere purification system keeps oxygen levels low enough for a clean CoCr melt without opening the chamber between builds, and the dual-laser setup means orthodontic labs printing multiple small appliances per plate get meaningfully faster turnaround than a comparable single-laser system.
A few practical notes for orthodontic-specific builds:
- Thin wire sections (retainer clasps, expander arms) benefit from slightly reduced layer thickness compared to bulkier denture framework parts, even on the same machine and powder.
- Keep a documented parameter set per part geometry category rather than a single universal profile. A lingual arch and an RPD framework don’t melt the same way even in identical powder.
- Log every build (powder lot, parameters, plate layout) so a failed print can actually be diagnosed instead of just rerun blind.
Step 4: Heat Treatment and Stress Relief
This step is not optional, and it’s the one step most likely to get rushed under deadline pressure. As-printed CoCr carries internal stress from the rapid heating and cooling cycles inherent to laser melting. Skipping heat treatment, or cutting the cycle short, leaves that stress in the part, which shows up later as distortion, unpredictable spring-back in clasps, or reduced fatigue life exactly where a wire flexes every time a patient removes an appliance.
A Nabertherm N 7/H furnace (or an equivalent chamber furnace rated for CoCr stress-relief temperatures) runs the parts through a controlled heating ramp, hold, and cooling cycle before the plate is cut. This is what converts an as-printed part into one with the mechanical properties orthodontic appliances actually need in the mouth.
Step 5: Cutting, Support Removal & Finishing
Once heat-treated, parts are cut from the build plate, supports are removed, and the surface goes through the same finishing sequence a casting lab already knows: sandblasting, and polishing to a clinical finish. Because the as-printed surface from a well-tuned powder and parameter set starts closer to final geometry than a cast part, finishing time per case typically drops once a lab’s process is stable.
Test Printing: Ortho Appliances vs. Removables
Before moving a new powder lot, parameter set, or build layout into full production, run a small qualification batch across both major case types your lab handles:
- Orthodontic appliances (expanders, lingual arches, clasps): these are dominated by thin wire sections and functional spring behavior, so qualification prints should specifically check for warping after heat treatment and clasp spring-back under load.
- Removable partial denture (RPD) frameworks: these combine thin clasps with bulkier connector bars and rest seats in the same part, so qualification prints should check fit against the model, connector rigidity, and surface finish across both thick and thin sections of the same build.
Running both categories through a qualification build, rather than assuming a parameter set validated on one case type transfers directly to the other, is the fastest way to catch a mismatch before it reaches a patient.
Common Mistakes Labs Make Moving From Casting
- Treating heat treatment as optional on tight deadlines. It isn’t. Build the furnace cycle into your turnaround time from day one.
- Reusing powder indefinitely without sieving. Particle size drift is invisible until a print fails.
- Using one support strategy for every case. Thin wires and bulky frameworks need different support densities.
- Skipping a documented parameter log. Without one, every failed print is a mystery instead of a lesson.
FAQ
Why does particle size distribution matter so much for CoCr printing? Tighter particle size distribution packs more densely and consistently in each powder layer, which reduces porosity and gives more predictable mechanical properties, especially in thin, load-bearing sections like clasps and wires.
Can I skip heat treatment if the part looks fine as-printed? No. Internal stress from the printing process isn’t visible on inspection. It shows up later as warping or reduced fatigue life, particularly in appliances that flex repeatedly, like retainer and expander clasps.
How many times can reclaimed CoCr powder be reused? It depends on your specific powder and furnace parameters, but most labs cap reuse cycles and periodically refresh the batch with virgin TopCore CoCr powder rather than reusing indefinitely.
Thinking about moving your ortho and RPD production from casting to metal 3D printing? Talk to our team about building a setup around the HBD 150D FLEX Dual Laser and TopCore CoCr powder sized to your case volume.