If you’re in the mold-making or injection molding game, you know those little mold accessories—sprue pullers, ejector pins, gate sleeves, core pins, alignment pins, the tiny cleanup nozzles and vent inserts—aren’t just random parts. They make your whole mold run smoothly, and let’s be real, when mold shows up on these? Your production grinds to a halt, parts get defective, and you’re losing money left and right. I’ve been supplying mold accessories for over 12 years now, and I’ve lost count of how many customers called me panicking because a batch of bad parts came out, and their first thought was “did our pins go moldy?” Mold Accessories
Mold on mold accessories isn’t the same as that stuff on your bathroom grout, by the way. Those little parts are in a constant cycle of being exposed to resin fumes, condensation from cooling lines, tiny bits of leftover plastic, and if you store them wrong (or your mold is sitting idle for too long), moisture gets trapped in the gaps, between sleeves and pins, or in the tiny crevices of vent inserts. It’s a gross, fuzzy, sometimes smelly growth that doesn’t just make your parts look off—it eats at metal over time, causes corrosion, and throws off alignment when your ejector pins stick because mold is gunked up in their grooves.
First off, let’s get one thing straight: you can’t just wipe this off with a rag and call it a day. I see customers do this all the time, and by the next run, the mold’s back because they didn’t kill every spore, or they just spread it around. These parts have precision tolerances down to a thousandth of an inch, so you can’t use harsh, abrasive stuff that’ll scratch them, right? Scratches are mold magnets—spores get trapped in those tiny lines, and boom, it’s back in no time.
Let’s break this down by how bad the mold is, because you don’t need to do a deep clean on a new accessory that’s got a little surface dust and no visible mold.
Starting with light mold: that’s the faint, powdery white or light gray stuff you see on the surface of core pins or the outside of ejector sleeves, no deep gunk, no discoloration. This is the easiest to fix, and you can do it without taking the parts off your mold (but I’d recommend taking them off, just to be safe, so you don’t get debris in your cooling lines). What I tell my regulars is grab a lint-free microfiber cloth—no paper towels, those leave tiny fibers that get stuck—and a mild, pH-neutral cleaner. Wait, not dish soap! Most dish soaps have harsh chemicals that can strip any coatings on your accessories (you know, those nitrided or chrome plates that keep pins from wearing out). Grab something like a pH-balanced equipment cleaner, the kind made for industrial machinery, not household stuff. Spray a tiny bit on the cloth, wipe every surface, get into the gaps between the pin and its bushing by gently twisting the cloth around it (don’t force it—you don’t want to bend a core pin), then rinse with distilled water. Tap water has minerals that can leave residue, which is another mold trigger. Dry them immediately with a fresh microfiber cloth, then air-dry for 10 minutes just to make sure every last drop is gone. Then, if you’re storing them or putting them back, give them a light coat of rust inhibitor (the dry kind, not the oily stuff that attracts dust) to keep moisture away.
Now, moderate mold: that’s when it’s a bit thicker, maybe a dark gray or even light green spot, starting to get into the small crevices, maybe causing a little sticking when you move the pin. This is where you need something a bit more powerful, but still gentle enough not to ruin the precision. A lot of customers reach for bleach, but bleach is bad— it can pit metal, and if there’s any leftover, it’ll react with resin and ruin parts. What I recommend is a 50/50 mix of white vinegar and distilled water. Vinegar is acidic enough to kill mold spores, but not harsh like bleach. Put the mix in a small container, submerge the accessory for 15 to 20 minutes—don’t leave it longer, or the vinegar can start to etch soft metals like aluminum. After that, take it out, use a soft-bristle toothbrush (new, don’t use one that’s been used for teeth, gross) to gently scrub the gaps, the vent slots, the threading on gate sleeves. Don’t scrub too hard, though—you don’t want to scratch the vent holes, which are tiny, like half a millimeter wide usually. Once you scrub it all, rinse twice with distilled water, dry immediately, and then hit it with that same dry rust inhibitor. I had a customer last month who tried this on a set of ejector pins that had been sitting in a mold for 3 months, and he said they worked like new after—no sticking, no mold coming back in the next run.
Then there’s severe mold: that’s the fuzzy, thick, maybe slimy stuff, often with a bad smell, that’s gotten into deep grooves, or even started causing light corrosion on the metal. This is the big one, because if you leave this, you might have to replace the accessory, so you want to get it right the first time. Here, you can use a food-grade hydrogen peroxide solution—3% is fine, no need for the stronger stuff. Submerge the accessory in the peroxide for 30 to 45 minutes. Peroxide kills mold and bacteria without leaving a chemical residue like bleach, so it’s safe. If the mold is really bad, you can gently agitate the container while it’s submerged, but don’t shake it hard enough to bend anything. After the soak, use a nylon bristle brush (even softer than the toothbrush, so you don’t scratch) to get into all the hard-to-reach spots—vent holes, under the head of a core pin, inside the bushing. For tiny vents that a brush can’t get into, use a can of compressed air (the kind you use for keyboards, just hold it upright so no liquid comes out) to blow out any gunk. Rinse three times with distilled water, dry with lint-free cloths, then blow compressed air through all the holes and crevices to make sure no water’s left. A pro tip here: once it’s totally dry, wrap each accessory individually in acid-free tissue paper before storing it. Regular tissue paper has acid that can cause corrosion over time, especially on polished or coated parts.
Now, the biggest mistake I see is people cleaning the mold accessories but not fixing the root problem, so mold comes back a week later. Let’s talk prevention, because that’s way easier than cleaning. First, if your mold is going to be idle for more than a week, strip all the accessories, clean them thoroughly, and store them in a dry, temperature-controlled cabinet. Don’t leave them on the mold while it’s sitting—condensation will build up overnight, even if you think it’s dry. Second, after every production run, do a quick wipe-down of all accessories while they’re still warm (warm metal doesn’t hold moisture like cold metal does). A lot of customers wait until the mold is completely cooled, and that’s when moisture starts to form. Third, check your cooling lines—if there’s a leak or a line that’s not draining properly, that’s a constant source of moisture, which feeds mold. Fourth, never use cloths that have been used on other parts of the mold for cleaning accessories—you’ll just spread spores around.
Wait, and what about those really small accessories? Like vent inserts, or tiny sprue pullers that are almost too small to hold. For those, I use cotton swabs dipped in vinegar or peroxide, depending on the mold level, to get into the tiny gaps. Just make sure the cotton swab is lint-free, so no fibers get stuck in the vents—those will clog up and cause defective parts, which is the last thing you want. A customer told me last week he tried a regular cotton swab and got a fiber stuck in a vent, which made a whole batch of parts get tiny holes, so avoid that.
Also, let’s address the question I get all the time: “can I use ultrasonic cleaner for mold accessories?” Yes, but only if you do it right. Ultrasonic cleaners are great, because the vibration gets into tiny crevices you can’t reach, but if you put accessories in there too long, or use the wrong solution, you can damage the precision. I’d recommend using the mild pH-neutral cleaner for light to moderate mold, run it on low power for 5 to 10 minutes. For severe mold, use the hydrogen peroxide, and run it for no more than 15 minutes. Take them out immediately when the cycle ends, because if they sit in the ultrasonic solution after it’s done, residue can build up. And always rinse them well after, no exceptions.
Now, if you’re dealing with mold that’s gotten so bad that even after cleaning, the accessory is pitted, or the tolerances are off—don’t panic. Sometimes it’s not worth the risk, and that’s where I come in. I supply high-quality, precision mold accessories, and if you let me know what part you need, I can get it to you fast, so you don’t have to shut down production. I’ve seen too many customers try to save a few bucks by cleaning a badly corroded accessory, only to have it break mid-run and cost them thousands in downtime.
At the end of the day, mold on mold accessories is just part of the game, but it’s preventable and easy to clean if you do it right. The key is not to wait until it’s a big mess, don’t use harsh stuff that ruins your parts, and fix the moisture issues that cause it in the first place. If you’re not sure if you’re cleaning your accessories the right way, or if you need replacement parts because yours are too far gone, hit me up. I know how important your production is, and I’m here to help you keep those mold accessories running smooth, no mold, no defects, no downtime.
Transparent PET Crystal Cover Mold References:
- Mold Making & Design Magazine. (2021). "Proper Maintenance of Mold Components to Extend Service Life". Industrial Press Inc.
- Occupational Safety and Health Administration (OSHA). (2020). "Mold Remediation in Workplace Settings". U.S. Department of Labor.
- Society of Plastics Engineers (SPE). (2019). "Injection Mold Maintenance Best Practices". SPE Plastics Engineering Publications.
- ASTM International. (2018). "Standard Guide for Molded Part and Mold Component Cleaning". ASTM International.
Taizhou Leizhen Mold Co., Ltd.
Address: No.8828, Changtang Industrial Zone, Beicheng Street, Huangyan District, Taizhou City, Zhejiang Province
E-mail: ningleizhen@gmail.com
WebSite: https://www.leizhenmold.com/
