ACMO in 3D Printing: Balancing Safety, Performance, and Transparency

We appreciate the recent discussions surrounding safety in 3D printing, particularly concerning the use of 4-Acryloylmorpholine, also known as ACMO, initially brought to the forefront by Formlabs. Like others in the industry, we believe in addressing misinformation through education, allowing users to make informed decisions about their printing materials and processes. Our commitment extends beyond this discussion to include clear safety labeling on our products and ongoing education for our users on safe resin handling and cleaning practices.

Understanding ACMO

4-Acryloylmorpholine, or ACMO (CAS 5117-12-4), is a high-performance acrylate monomer widely used as a UV diluent in polymer formulations. In simpler terms, it makes formulations more workable and faster to cure.

Due to its exceptional properties - particularly its low viscosity and high curing efficiency - ACMO is prevalent in modern manufacturing. You likely interact with ACMO-processed products daily, from UV-printed packaging to adhesives in consumer electronics like smartwatches, and even in metal coatings and textiles.

ACMO in 3D Printing: Performance Benefits

In 3D printing applications, ACMO serves multiple valuable functions.

• It reduces resin viscosity and significantly accelerates print speeds.
• The significantly faster curing time thanks to ACMO not only improves productivity but also reduces energy consumption and print failure rates.

An example can be seen in our Siraya Tech Fast resin, which cures at 2.0s per 50µm layer on a common Saturn 3 Ultra, while Formlabs' Creator Grey ABS-Like resin needs about 7.5s for the same layer height. （Clicking the underlined link will take you to the print settings download page.）

Despite sometimes being portrayed as a "cheap" ingredient, ACMO actually commands a premium price - typically 3-4 times higher than other common 3D printing monomers such as Di-TMP TTA (previously DGPDA) and TPGDA.

The price of ACMO (N-Acryloylmorpholine, CAS number: 5117-12-4) varies depending on the supplier, purity, and quantity purchased. Based on Sigma-Aldrich's pricing for 97% purity ACMO with 1,000 ppm p-methoxyphenol as an inhibitor, the following prices are available:

(Please note that prices may fluctuate due to market conditions, supply availability, and order volume.)

Its presence in high-end industrial resins, such as Forward AM's (formerly BASF) ST45 (which holds ISO10993 biocompatibility certification and is used by industry leaders like Nexa3D and Stratasys), demonstrates its value in professional applications.

Safety Considerations

Like almost all materials used in 3D printing, resin with ACMO is a professional chemical and requires proper handling precautions whether it is used in a factory or at home. The safety protocols are:

• Avoid ingestion
• Protect eyes and skin
• Clean any contact areas promptly
• Ensure proper ventilation
• Use appropriate personal protective equipment

This means you should follow the above safety precautions regardless of whether the 3D printing resin you are using contains ACMO or not.

It's worth noting that in resin 3D printing, the cleaning alcohols often pose a more significant health risk than the printing materials themselves. Common cleaning solvents like isopropyl alcohol can be harmful if inhaled in an enclosed space. Proper ventilation and respiratory protection are essential during the cleaning process.

Addressing MSDS Concerns and Transparency

Following Formlabs' highlighting of the use of ACMO, we conducted a thorough examination of our materials and suppliers. It turned out that some of the oligomers we use for our resins have ACMO pre-mixed into them but not reported on the original MSDS. It is common for suppliers to add monomers to oligomers to lower viscosity and cost, and the amount is often considered trade secret for oligomer sellers. Only after much pressure did they share the details with us, and we found out that four of our resins are impacted. We have now updated the MSDS for Fast, Tenacious, Simple, and Build resins, which you can find here Siraya Tech MSDS.

Professional Tools Require Professional Care

As highlighted by Europe's REACH registration, ACMO is classified for professional use (EU ACMO statement). "Professional use" in this context means that users should be properly trained in handling these materials and working in an environment with appropriate safety measures in place, such as adequate ventilation.

While 3D printing has become increasingly accessible, it remains a professional tool - similar to power saws or spray painting equipment. Whether using resins with or without ACMO, proper safety protocols are essential, as all photopolymer resins contain chemicals that require careful handling.

Following manufacturer safety guidelines and maintaining proper protection measures will safeguard users not just from ACMO exposure but from all potential risks in the 3D printing process, including the more immediate concerns of cleaning solvent exposure.

A Call for Greater Transparency

We applaud Formlabs for bringing this issue forward. In our process to gain a deeper understanding of our supply chain, we also found that brands have been using "trade secret" and "proprietary" to block out the specific CAS numbers of the materials they use. ACMO is not the only material that can cause skin irritation and other potentially harmful effects if safety protocols are not followed. We should have greater transparency to know what materials are used. We call on the 3D printing industry to adopt greater transparency in MSDS reporting. Let's move towards a standard where MSDS sheets provide genuinely useful safety information, allowing users to understand the potential hazards of all components, whether they are ACMO or other chemicals.