Revolutionizing Orthopedic Implants: Automated Single‑Piece Workflows Cut Costs

Orthopedic implant companies face many challenges, but one of the biggest is inventory management. These companies (and the companies that manufacture the products they sell) must navigate how to produce a wide range of implant types, variants and sizes cost effectively, and then manage that inventory as it moves back and forth between warehouses and hospitals. This equates to high inventory requirements that can drain a company’s resources.

Mach Medical is an orthopedic implant contract manufacturer that was founded to address some of the challenges facing orthopedic implant OEMs, including inventory, using advanced manufacturing and automation.

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Inventory Control

By nature of their work, orthopedic implant companies generally carry 12 months of inventory to service customers, explains Dave Anderson, co-founder and business development leader at Mach Medical. “A product gets used in surgery and the hospital needs replenishment right away, or they may need six of the same size on the shelf in case they have two or three or four patients stacked up that day that are all going to need a knee for the left side in Size 5.”

Further complicating matters is that the inventory is always in motion. According to Mach Medical Co-Founder and General Manager Steve Rozow, orthopedic implants are kind of like shoes — they come in multiple types and sizes. When people want a new pair of shoes, they might go to a shoe store, which stocks each shoe style in multiple sizes for customers to try on. But patients who need orthopedic implants can’t go to a store to try different implants. The store (or a predetermined subset of it) needs to come to the patient in the hospital’s operating room. Surgeons have an idea of which size implant a patient will need before surgery, but they often have multiple options available in the operating room so they can choose the best fit at the time of the operation, or duplicates in case an implant gets contaminated. Then unused inventory gets sent back, and the used stock is replenished. “That inventory is constantly moving around and supporting surgeries, or maybe camped at a hospital, if the hospital is a high-volume hospital,” he says. At least 50% of the manufacturer’s inventory is either at a hospital or in transit at any given time. “In order for orthopedic manufacturers to add customers, a lot of times, they have to add that inventory footprint in order to serve those customers,” he continues.

The challenges of manufacturing families of parts make inventory management even more complex. “There are minimum order quantities associated with manufacturing that are driven largely by machine setup time,” Anderson says. “Let's say you take eight hours to set up a machine to run one SKU. You want to run as many of those parts as you can so you can get a decent per-unit cost before you tear the machine down.” But certain SKUs are used more often than others. For sizes that are on the larger and smaller ends of the bell curve of human sizes, if a manufacturer is “making 20 or 50 of an individual SKU, that might be five to 10 years’ worth of inventory,” he explains. “That's going to sit.”

Starting With Standardization

One way Mach Medical tackles these challenges is by standardizing production processes as much as possible. For example, instead of procuring different castings for different implants and sizes, the company starts with a more generic casting for each implant type. “There's virtually no tool development, and it's just off the shelf,” Rozow says. While this might mean implants spend more time on the machine and need more material removed than a more customized casting, the flexibility is worth the trade off. “If there's a design change, or the customer wants to tweak things here and there, it's usually a fairly simple program change,” he continues. “To accommodate that, we don't have to have tooling changes, which is where bigger costs add up.” He adds that as customers scale up implant production, Mach Medical can switch to a custom casting that’s more efficient to machine and more cost-effective.

Just as Mach Medical wants to reduce inventory of final products for its customers, it also works to keep its own inventory of castings and other raw materials lean. “We tend to keep pretty low inventories on those and have arrangements with those companies to flow that to us on a fairly tight, JIT-type basis,” Rozow says. Its facility in Columbia City, Indiana, is close enough to its raw material and casting suppliers that they can do “milk runs” twice a week to drop off the material Mach Medical needs for a few days at a time.

The raw material goes through an initial production process. Rozow says this typically includes two machining processes, inspection, cleaning and coating (which happens at Sites Medical, Mach Medical’s co-located sister company). At this point, the orthopedic implant is starting to take shape but is still incomplete. From this point, the company can turn the parts into multiple SKUs, such as different sizes or right and left versions. Then, as customers place orders, Mach Medical completes the implants through final machining operations where they’re cut to the correct size and shape, a cleaning process, inspection, finishing processes, and then a final cleaning.

This “flex lot sizing” system gives Mach Medical the best of both worlds: volumes that can make casting and heat treating more cost-effective, as well as flexibility to handle order volumes as low as one part. It also drastically shortens lead times for customers, from 20 weeks to three. Rozow says flex lot sizing and shorter lead times enable Mach Medical’s customers to reduce their warehouse inventory. “They can replenish on a shorter cycle, and they don't have to order those outliers as much,” he explains.

Automating Single-Piece Workflow

As Mach Medical’s strategy relies on getting parts to customers quickly, automation and lights-out machining is key. However, any automation system the company implements needs to be able to handle production of smaller batches of parts so as not to overwhelm customers (or itself) with inventory. “We can set up an economic order size of 20 or 50 femurs that are all the same SKU and automate that all day long. That's pretty straightforward,” Rozow says. “But when you load up with one of SKU X, five of SKU Y and three of SKU Z, that's where the behind-the-scenes software advantage of Flexxbotics comes into play because it accommodates single-piece flow.”

Mach Medical’s Flexxbotics cell automates initial processing of the partially finished implants into final products — final machining, inspection and a cleaning process. With Mach Medical’s varying and potentially small lot sizes, the company needed assurance that the cell was grabbing the correct part and loading the corresponding programs for that part. “We've got to protect against our machine and CMM crashing,” Rozow says. Flexxbotics provides a platform that enables all of the components of the cell to communicate with each other, including a vision system. A Universal Robots cobot grabs a part off a staging rack and brings it to the vision system, which confirms via a code on the part that the machine tool has the correct tools and program. After machining on an Okuma five-axis machine, the robot brings the part to an ultrasonic cleaning station for in-process cleaning. Then the robot brings the part back to the vision system, which uses the arbor to confirm the part before moving it to the CMM for inspection. If the CMM detects a nonconformance, it moves that part to one of six spots on a staging rack dedicated to nonconforming parts. If that area fills up, the cell shuts down and notifies an operator. Six slots for nonconforming parts may not seem like a lot, but Rozow actually sees this as overkill given the company’s non-conformance rate is less than 1%.

Despite the wide variety of SKUs that run across the cell, Mach Medical has standardized other components in the cell. “The robot is pretty agnostic to anything we bring in there, because of the standardized tooling,” Rozow says. The parts are held on fixtures with a common interface the robot uses to move them through the cell.

Standardization also extends to cutting tools, though Rozow says this is trickier. The company starts with a standardized tooling package for the machine tool but occasionally needs to add specialized tooling for complex features. Because tooling is such a cost-driver, Mach Medical continuously works to optimize tool life. It uses Pareto analysis on manually collected tool life data to determine the next priority for optimization. Flexxbotics also increases tool life, keeps part quality consistent and reduces scrap by facilitating closed-loop adjustment of cutting parameters based on inspection data from the CMM. “If we've got tool wear going on or that kind of thing, it's getting adjusted in real time,” he says.

Mach Medical is still working on proving out and stabilizing its process before expanding unattended machining. Right now, the cell is set up to run for 36 hours, but the company plans to set up a larger shelving system that will enable it to run for longer stretches. “The other thing we'll do is we'll add another machine in,” Rozow says. “Once we have that confidence, we'll slide a machine over.” A third machine could also be added to the cell in the future. The company is also planning to implement automation in more upstream processes, such as the production of partially finished implants.

Not only is this cell enabling flex lot sizing, but it also helps Mach Medical to hold tight tolerances repeatably. According to Rozow, customers generally allow for a 1-mm tolerance, but the company uses less than 25% of that. He believes the company is likely merely ahead of the curve with these tolerances though, and as surgeons switch from manual to more precise and consistent robotic bone prep, tolerances for implants will need to tighten.

Shoulders, Knees and Toes

Mach Medical is initially focusing on knee and ankle implants but is planning to extend this production model to other types of implants, such as hips, spine components or even tibias, which Rozow says come in even more variants than other types of implants and would likely require extremely low quantity or single-piece orders.

The Flexxbotics cell is a step toward Mach Medical’s ultimate goal of creating a just-in-time production model for orthopedic implants. “We can take an order in and deliver it within three weeks. Well, that's usually within the surgery scheduling window for a patient,” Anderson points out. Further advancements in pre-operative planning software would enable physicians or physicians’ assistants to determine which size implants the patient is likely to need, so Mach Medical can make those parts and ship them to the hospital in time for the surgery. Even if the manufacturer ships multiple implants (several different size options or duplicates in case of contamination, for example), Anderson believes this could enable implant companies to reduce their inventories by 85%. “That's hundreds of millions of dollars a year in savings,” he says.