69 yuan gram mohou: what the yellow-green resin actually buys you

Mohou.com lists this material at 69 yuan per gram, which puts it in the economical band of stereolithography resins. The color is yellow-green, and the vendor describes it as an ABS-class resin with precise, durable properties. In practice that means it cures harder and stronger than the standard white resin many shops run as a default, while giving up some toughness.

That trade-off matters more than the headline number. A part that survives a drop test in white resin may crack in the yellow-green grade, because toughness and hardness pull against each other in most photopolymers. Buy the material when you need stiffness and dimensional stability, not when you need impact resistance.

One more limit: SLA resins are not production plastics. They creep under sustained load, they are sensitive to UV, and they soften with heat. Treat any resin part as a short-life tool, not as a stand-in for ABS, PC, or POM in the field.

The unit is yuan per gram, not per part. A small bracket printed in 5 g of resin costs about 3.5 yuan in material, which is close to nothing. The same bracket in 200 g costs roughly 138 yuan. So the label tells you the material rate; the part geometry and the support structure tell you the real bill.

Support material, build orientation, and hollowing drive that gap. A tall, thin part with dense supports can consume 30-50% of its resin volume in structure that gets thrown away. A well-oriented, hollowed part wastes far less. If you are comparing quotes across suppliers, ask whether the quoted figure includes supports and post-curing.

There is a second cost question engineers usually skip. What is the hourly rate of the machine, and how long does your part occupy the build platform? On a full platform shared with other jobs, the material rate dominates. For a single large part that ties up the machine overnight, machine time dominates and the 69 yuan gram mohou rate stops being the deciding factor.

Pick the resin when the question is shape. Concept models, master patterns for a later mold, housings that only need to sit on a bench and show proportions, and fixtures that hold a sensor once during a build review. These parts do not carry load, do not see heat, and do not need a thread that survives repeated assembly.

Move to machining when the part has to answer a mechanical question. A bracket that must hold 40 N without flexing, a housing with a Ø6 H7 bore, a plate with 0-80 tapped holes, a heat sink that sits near a motor. Machined 6061-T6 or 7075 gives you the real modulus and the real thread strength, and ±0.005 mm on the features that mate.

There is a middle path that often beats both. Print the shell in resin to check the look and the cable routing, then machine only the load-bearing inserts and bond or screw them in. You get a fast visual and a real mechanical interface, and you skip the cost of machining the whole envelope.

Watch three signals that say the resin part has outlived its usefulness. The first is creep: a part that slowly bends under a constant spring load. The second is heat: anything above roughly 60 °C in service. The third is a tolerance stack that no longer closes after the third revision. At that point, more resin iterations just buy more scrap.

The step that decides your second-round cost is the file you send. A resin model exported as STL loses the feature intent: holes become faceted, thin walls get rounded, and a nominal Ø6 bore arrives at Ø5.8. Send the original CAD in STEP or Parasolid, plus a drawing for anything with a tolerance, thread callout, or surface finish.

Say which features are functional and which are cosmetic early. A block that looks like a housing to a machinist is a 40-minute job if the bores are clearance holes and a 4-hour job if two of them are bearing seats. That single sentence changes the quote more than the material choice does.

At GreatLight we run prototypes from one piece up to 10,000+ part runs on 127 high-precision CNC machines, including 16 simultaneous 5-axis centers and 16 mill-turn centers. Quotation and free DFM analysis come back within 12 hours, and production can start within 24 hours. Uploads stay confidential, and an NDA is available on request.

If the resin model was right and the part now needs to be metal, we can usually hold the same datums and add the tolerance the resin could not. That is the whole point of keeping the CAD clean through the early iterations.