When it comes to making a designed part, you have several choices: traditional machining, which covers a range of options; injection molding; and now additive manufacturing. Even more recently though, is the trend of combining metal fabrication and additive manufacturing to make parts. Jim Belosic, founder and CEO of SendCutSend, offers tips on combining these technologies for both prototypes and final parts.
SendCutSend is a high-tech cloud-based manufacturing company, specializing in the precision cutting of a variety of metals and aerospace materials. Jim often found himself in need of specialized materials in small quantities to finish his personal projects, but metal fabrication vendors were only willing or able to handle large orders. So, Jim saw an opportunity to create an on-demand laser cutting service, and that’s how he started SendCutSend. Jim has since discovered that many designers need to combine multiple types of manufacturing processes to make their prototypes or final parts.
MPF: How can a designer use both traditional subtractive and additive technologies together to make a part?
We really see that designers are combining both subtractive and additive in some really unique ways that we never expected to see. It’s a hybrid of the positive qualities of both techniques. You can take the strength and weldability, or machining ability of steel or aluminum, and then combine that with the absolutely unlimited design flexibility of additive manufacturing. For example, in a drone, you may need high strength in one area, and then it needs to mount to some kind of crazy camera mount or something with this really complex geometry. That’s where we see a combination of say 6061-T6 aluminum that has been overmolded with a 3D print so that it can mount like a camera gimbal or something like that.
MPF: You’re looking at a lot of overmolding options as a way of putting in the 3D printing aspect to things?
Yeah, we see overmolding, almost like a tab and slot approach or what we call a puzzle piece approach. It really depends on the capabilities of the additive process and how experimental the designer is willing to get. One of the best methods that we’ve seen is stopping mid-print and inserting the metal piece or the non-additive, and then continuing the print. There’s a risk of nozzle collisions and I think you have to plan your slices accurately, but it’s been highly successful because it allows robust hardware to be mounted. We’ve seen applications where people are using the inherent magnetism of steel in order to mount their 3D prints, or they’re perhaps embedding a Hall-effect sensor or something like that. I think we’ve just started to scratch the surface on what’s capable.
MPF: Is this combination of additive and traditional machining technologies for prototypes or only end-use parts?
Both. We’ve actually seen, I’d say, 95% of our customers start out with a prototype and after a couple of refinements, then we’ll go into production. So, we’ve created a single part for a single customer or 100 thousand parts for a single customer. It just depends on their end use. The limitation that we find is usually in the speed of the additive process. We can produce thousands and thousands of parts relatively quickly but to then 3D print, overmold, or puzzle piece them together can be prohibitive.
MPF: That’s always still a key issue with additive manufacturing. It’s not quite as fast as let’s say a stamping process.
Correct. The stamping is amazing as far as how many parts you can put out. However, the setup and initial investment is also kind of through the roof. So, just to get that stamping line going, like the first 500 pounds of material that come out, are going to be waste. What’s nice is, with the new fiber lasers that we run, our cutting speed is somewhere around 2000 inches per minute, depending on the material. And really our loading time, because of our software, is measured in seconds, not hours. It’s relatively easy for us to change materials, to change jobs and eliminate some of that downtime. But again, without multiple machines, the additive side tends to be the bottleneck.
MPF: Let’s go back to the materials portion of things. Whether an engineer is using something for a prototype or end use, what are the key issues regarding materials for these combination processes?
One design concern would be exposure to moisture. Even if it’s an overmolded process or it’s going to be fully embedded, if you use just mild steel, there is still the opportunity for rust to form over time. So, I highly recommend using stainless steel or aluminum for longevity. Another concern that we’ve seen, when trying to do overmolding, is the use of copper can yield some really unexpected results. During the 3D printing process, if you’re using a hot-melt adhesive or a hot-melt print, the copper can absorb so much of that heat, that it can have unexpected effects. Halfway through the printing process, all of a sudden, the bed will go super, super cold and that’s a massive problem.
Copper is incredibly conductive and it’ll steal heat away from anything. If you’ve ever tried to braze copper, the amount of heat that you can put into it is absolutely through the roof.
It’s going to take some trial and error and what we’ve seen is that every single additive machine handles heat a little bit differently or is sensitive to heat differently. We’re happy to provide some sample pieces so that people can try different techniques and see what’s going to work best for their particular application.
MPF: That takes us to the question of, what are some key design tips for projects that require multiple combinations of manufacturing methods in order to make the part either as a prototype or as an end-use?
At this stage of development, our biggest advice is experiment. We’re always really happy to see how these projects come out and we want to learn more, too. So, we have engineers in-house that are playing with these things every single day, but when it comes to our customers, we always love to offer sponsorships or discount codes or gift cards or whatever. If they’re going to work on something, I want to be part of that process. If you’re going to do one material, just talk to us, talk to our application engineers, and let’s send you five materials to try and let’s see what works best. I’m hoping that in a few months or a year, we’ll have some better guidelines on how to design, but right now it’s like every single time we do something it’s kind of new and maybe has a positive quality and a negative quality.
MPF: I think designers would love to experiment, but I think the first question they’re going to ask is, okay, what’s the cost of having to experiment?
For sure. We kind of have a hard stop with a minimum order of, of $29, because we offer free shipping, it’s free, FedEx two-day shipping. So a single part could be $29, but oftentimes because of our pricing model, you can fit 10 or 15 parts and it’s still 29 bucks.
Pricing goes way down with quantity. At larger quantities we’re as low as 50 to 45 cents apart depending on the material and what the geometry looks like. That being said, additive alone, as far as filament use, as far as time and everything. If you can add part of your structure with subtractive machining, then it can save a ton of time and a ton of money.
We’ve had customers who are creating parts with a large footprint, but the only part that needed to be 3D printed was maybe a couple of cubic inches. So, we can provide them with, say this big chunk of aluminum that’s a foot long and 18 inches wide, with all this geometry cut out of it. Then, they can add their little widget on the end. It saves them days and days of machine time. So, the cost ends up being negligible.
MPF: Do you offer advice or consulting to guide an engineer in that? When they present you with a design to you, can you kind of work with them through, well maybe this part ought to be machined and then this part ought to be additive?
Oh yeah, for sure. We have five or six application engineers on staff that just work with customers all day. We also treat our own facility as a lab, kind of like a hobby shop, where we’re always making our own projects and experimenting too. So, we’re not exactly experts, but we may have some experience that we can provide.
MPF: Well, you’re taking advantage of additive’s ability to people to fail faster and get to a winning design that much quicker.
For sure; that an amazing way of putting it. Sometimes with traditional three-axis or five-axis milling, the cost can be so prohibitive or the part just may not be able to be made because of the geometry, I think that keeps people from making their project a reality. We really want to eliminate that. Our goal is: even if you have to make a couple of compromises, at least we’re enabling you to get something out there so that you can hopefully get it on the shelves.
There are so many different filaments and additives and processes coming out on a daily basis sintering and all the different metal powders and all this stuff is coming out. I think it’s always going to be experimentation, but that’s kind of what we love, if we didn’t experiment anymore, I think, this job would get really boring.
MPF: How often are you seeing projects that require both machining or 3D printing or instead of maybe the word require would benefit from both types or multiple types?
I would say on a daily basis, for sure. We have a lot of customers that make drones and robotics and automation, they’re an automation industry. Almost daily, we see something with some specific geometry that we go, “Oh, I bet that this is going to be part of additive process as a secondary process.” Sometimes we’ll reach out to that customer and say, “Hey, keep us posted on how this works” or, “Let us know what you need.” Oftentimes, because of our automation, orders come through, and if they’re green-lit, they get packed up and we don’t get to see them. But on the chance that we can go down on the production line and see something and go, “Oh, this looks like it’s a puzzle piece where it’s going to get fit into a 3D print.” It really piques our curiosity so, we love to stay in touch with those customers and kind of collaborate.
One of the things that’s been really interesting to us lately is the combination of taking our metals plus additive, and then adding one more step, which would be welding. And it scares people because you don’t want to add a bunch of welding heat near an additive process, but we’ve been experimenting with some of the cooling techniques that welders use in order to keep the heat-affected zone minimalized. It’s been kind of cool. We’ve seen some robotics applications where the entire chassis is a welded structure, but they need to add a 3D print somewhere in a very robust method. They’ll overprint the 3D onto the metal, but then leave out what we call a tongue or a tab, that’s a couple inches long that can then be welded. During the welding process, you keep it cool with like wet clay, wet fiberglass, something like that to keep the heat from migrating. It’s been a really cool way of mounting a 3D print. It’s welding your 3D print onto something, I think the possibilities are going to be really, really cool.
With adhesives, you can go really far, but sometimes good old welding is the way to go. Especially because you can engineer against it much easier than some of the modern adhesives.
For more information, go SendCutSend.com.