Special thanks to Ryan Gardner(https://www.facebook.com/ryangardner5457/) and Simon Paul Roberts(https://www.facebook.com/simon.p.roberts.5) for their valuable input on this article.
In the resin 3D printing community, there comes a point where every enthusiast feels a bit "restrained" by off-the-shelf consumables. We’ve all been there: standard resins are glass-brittle, high-end engineering resins break the bank, and those beautiful specialty pigments are often a nightmare to dial in.
However, mixing resins is the "secret weapon" that allows seasoned makers to seize the initiative. It is a strategic move toward performance customization and cost-efficiency. This isn't just a penny-pinching tactic; it is a fascinating exploration of material science. Whether you are looking to save a failing batch or engineer a new material property, this guide is for the "alchemists" ready to master their own vats.
.Why We Mix
1) The Redemption Experiment:
It is painful to toss "zombie resins"—bottles that have sat for 18+ months, losing their reactivity and becoming prone to failure. By introducing 30%–50% high-quality engineering resin (such as ABS-like or specialized Tough resins), the fresh, high-performance monomers can effectively "repair" the degraded cross-linking network. This synergy restores structural integrity, transforming brittle waste into material tough enough to handle post-processing like power drilling and tapping.
2) Scaling Up Cost-Efficiency:
With the rise of large-format printers like the ApexMaker X1, which can swallow 4kg of resin in a single fill, the cost of "pure" premium resin becomes prohibitive. By blending expensive ABS-like 2.0 with a budget-friendly base resin at a 50/50 ratio, you can achieve a "sweet spot." When calibrated correctly, the resulting sharpness and impact resistance are virtually indistinguishable from the expensive original, drastically lowering the cost-per-print for massive projects.
3) The Rigidity of the Miniature:
For character designers, the greatest heartbreak is a fine detail snapping off. Adding just 20% Tough resin to your standard mix injects enough flexibility to prevent catastrophic fractures, ensuring your miniatures survive the "tabletop drop test."
.Experimental Insights: The Pathology of Expired Resin and the Effect of Mixing New Resin
By comparing tests between pure expired resin and expired resin mixed with new resin, the experimental data reveal the strong chemical remedial effect of the mixing approach.
1) Overcoming the Critical Shrinkage Crisis and Restoring Accuracy
Expired resin suffers from degradation of components controlling shrinkage (e.g., monomer stabilizers), causing severe linear shrinkage during curing due to drastic molecular rearrangement.
· Dimensional accuracy tests (50mm, 30mm, 10mm): Measurements of expired resin were 49.85mm, 29.89mm, and 9.88mm, with a maximum negative deviation of -0.15mm, which is critical for parts requiring nesting or assembly.
· Performance of mixing resin: After adding new resin, dimensional accuracy recovered to 49.95mm, 29.95mm, and 9.95mm, with deviations perfectly controlled within -0.05mm, achieving up to a 66% improvement in precision.
The effective chemical components in the new resin rebalanced the reaction rate, suppressing excessive shrinkage.
2) Restoring Crosslink Networks and Balancing Strength and Toughness
· Flexural Strength tests: Expired resin showed 63.75 MPa, while mixing resin increased to 66.975 MPa (approx. 5.1% improvement).
· Mechanical performance improvement: This increase indicates that the new resin supplements fresh photoinitiators and monomers, filling in break points and defects during curing of the expired resin, restoring the intermolecular crosslink network. This not only increases strength but also reduces brittleness, preventing the model from easily cracking.
3) Resolving the Exposure Paradox and Expanding Parameter Tolerance
Expired resin suffers from severe degradation of UV blockers, causing uncontrolled stray light scattering. Even with exposure reduced to 2.4s, failures with excess curing occurred, and the capability to form small structures was poor. Mixing with new resin suppresses stray light scattering and brings expired resin back from a "narrow unusable window" to a normal operational range.
.Graded Use and Handling Recommendations for Mixing Resin
Based on the data, the main hazard of expired resin is not whether it can print, but whether the printed objects are accurate and hard enough. Recommended strategies include:
1) Finding the “sweet spot” ratio and usage classification: If expired resin has no abnormal odor or severe clumping, mixing new and expired resin at a 1:1 or 1:2 (new:expired) ratio offers the best cost-performance. Functional parts (e.g., gears, enclosures, clips) should never use pure expired resin. Mixing resin is suitable for large coarse models, supports, or prototypes; high-precision figures and parts should use pure new resin.
2) Physical pre-processing: Prior to mixing, fully stir for to redistribute settled photoinitiators, and filter potential polymer particles if possible.
.Battle-Tested Formulas for Beginners
1) Mixing Ratio
Success in mixing requires more than just pouring; it requires the right proportions. Based on extensive community testing, these formulas have proven highly reliable:
· The All-Rounder (4:4:2 Ratio):
40% Standard + 40% ABS-like + 20% Tough resin. This is the "Goldilocks" blend—ideal for general-purpose printing where you need a balance of crisp detail and enough structural strength for functional parts.
· The Sharpness Specialist:
50% ABS-like + 50% High-Precision resin. The microscopic pigment particles in high-precision resins act as "UV blockers," preventing light bleed and pushing edge definition to its absolute physical limit.
· The Speed Demon:
50/50 Grey and Clear resin. This creates a semi-translucent matrix. The increased light penetration allows for deeper UV curing per layer, potentially slashing exposure times from 2.0s down to 1.7s or lower, accelerating your production workflow.
Handling old or expired resins in 3D printing can be challenging. Is mixing resin merely a "cost-saving hack," or does it have a scientific basis? This article combines quantitative experimental data and practical experience to provide a comprehensive analysis of the rejuvenating effect and practical techniques of mixing resin.
2) Other Details:
· Mixing resin is highly viscous; maintain an ambient temperature above 28°C. Use a heater if necessary.
· Employ ACF film for easy release, which allows a lower lift height and faster printing.
· Fully cure bottom layers due to the complexity of the resin components.
· Do not mix water-wash resins with alcohol-wash resins, as their chemical bases are incompatible.
· Prefer liquid dyes for coloring; solid powders may settle over time, leading to failures.
· Minor parameter adjustments are usually sufficient (within±0.2 s of exposure), but testing the RERF of the mixed resin with 3Drs Starship 1.3 s is recommended.
.Appendix
Expired Resin and New Resin Mixed in the ratio of 1:1
Test 1: Flexural Strength Testing
Test 2: Exposure Time Testing
Test 3: AmeraLabs Town
