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What does it take to make a custom motocross part?

Billy Wight, President, Luxon MX

June 15, 2019

"How much for a customized ignition cover for my 2003 RM250? Can I get it by the weekend?"
- Potential Customer

We often receive requests for new products, custom products, or one-off products from our customers. Often, though, the customer is shocked at the price and the lead time. And it’s not just us, a quick scan of the online forums will often reveal posts of people looking to arrange a group buy, complaining about a companies price, or their refusal to make a custom part. So why is this? I'll shed some light on that and what it takes to create a new product.

Custom Part
Our KTM and Husqvarna one-piece top bar mount with integrated handguard and damper mounts.

I’ll be using our one-piece top bar mount and handguard mount as an example here. It’s fairly representative of a “typical” one-off part as far as size and complexity, though for more complex parts, the process is even more involved. This wasn't a part we had planned on offering originally, but was requested by a customer. Our customer approached us wanting to buy our KTM bar mounts, but he wanted to have handguard and damper mounts as well. Since this is fairly popular with off-road riders, we went ahead with it.

Step 1, Initial Design:

For any custom part or new product, we have to base the design on something, and that usually starts with measuring up a stock component for fitment and then making our desired changes. In this case, we already had geometry for standard bar mounts and the damper mount, we just needed to understand the geometry necessary to attach the handguards. For this we reverse engineered (worked backwards from finished product to a design) a competitor product and made a 3D CAD model (we use SolidWorks) of their handguard/bar mount. The reverse engineering process depends on how complex the part is. Sometimes it’s as simple as measuring with a caliper to get the necessary dimensions. Other times we have to use more advanced methods such as scanning, CMM probing, or optical techniques. Luckily in this case, a caliper and the probe head on our CNC machine were enough to accurately measure the part.

Using the reverse engineered part, it was fairly straight-forward to accurately locate the mounting holes for the handguards on our initial design. And with all the other required features are known (mount locations, bar clamp faces, etc.), it’s a matter of connecting them all together. For this we use our general engineering intuition to develop a design that is lightweight, strong, and manufacturable to wrap up the initial design.


Initial Design, what did it take?
  • In this case, the customer supplied us with the competitor part to measure, which was nice not having to buy one. But we still had to receive it and ship it back when we were done. So someone had to box it up, arrange and pay for shipping, and drop it off to be shipped. Not a whole lot of time and money, but all these little things add up and increase costs. $15 for shipping and about 1 hour of time.
  • Reverse engineering and CAD modeling of the competitor part, ~2 hours
  • Initial design of Luxon’s part, ~4 hours

Step 2, Analysis:

In general our competitor's products work, but often they can be too heavy, too flexy, not strong enough, or some combination of those. Our goal is to fix those issues and offer a higher performance alternative. One of the tools we use to flush out our designs is finite element analysis (FEA); a computer aided analysis tool to determine strength and stiffness of a part. Though FEA is becoming more mainstream, this To achieve accurate results, and in the end a good design, you really need a mechanical engineer with years of education and experience to do this work. Fortunately, I am one!

For these bar mounts we want to ensure they’re strong enough to withstand the normal tip-overs and bashing through branches without issue, but we don’t want them so strong that they create a huge lever arm in a crash and break something else more expensive, like your triple clamps. It’s a pretty delicate balance (see our bar mount blog for more information about that). We also want to keep them lightweight so you’re not bolting an anchor to your bike. Strong and lightweight don’t typically go together, which is where the analysis comes in. We are able to simulate crashes and forces applied to the mounts and see if they fail, all in the computer, before they’re even manufactured. We’ll run an analysis, review the results, revise the design accordingly, and repeat the process until we have a suitable design.

This all can be a lengthy process on something complex like a set of triple clamps. Luckily this part is fairly simple, so not a lot of design iterations were required. And we had the competitor parts available in CAD for a strength comparison from our earlier reverse engineering. This makes things easier as the strength of those parts and their performance on the bike is already known.

With the analysis runs and design iterations complete, all that's left are some small details; edge breaks, chamfers, small fillets, etc. to give our part a smooth and finished look and feel. Once complete, the final part design is ready for manufacturing. The CAD design and relevant design data is then archived in our data management system to track changes and revisions.


Analysis, what did it take?
  • Finite element analysis initial setup and run, results evaluation, Luxon and competitor part, ~3 hours of time.
  • A few design iterations (design changes and analysis runs) to arrive at the final design, ~2 hours

Step 3, CNC Programming and Setup:

Now it’s time to make the part. Just put material in the CNC machine and the finished part comes out, right? This is a common misconception, there's a lot more to it than that! We must first think about how we’re going to machine the part. How do we hold it? What positions do we need to hold it in? What tools do we need? These questions are answered in the CAM (computer aided manufacturing) programming stage. We think about how the part will be oriented and held, then program the CNC machine’s toolpaths on the computer. This part has four set-ups to fully machine the part. That means we have to load the material in the machine, run the program and make our cuts, pull it out, re-orient it, put it back in, make the next cuts, etc., four separate times to arrive at the fully machined part. We need to think about these four different orientations and program the cuts for each one.

We also need to select the cutting tools necessary to make the part. In the case of this bar mount, we used 16 different tools to fully machine the part – 1 face mill, 4 drills, 2 taps, 2 roughing endmills, 5 finishing endmills, a chamfer mill, and an engraving tool. All these tools need to be loaded into the CNC machine, programmed with appropriate tool numbers and specifications, and accurately measured for height offsets. Since this is a fairly simple part, there were no specialty tools needed to manufacture it, just “basic” machining tools that we have on-hand. For some parts we have to special order custom-made tooling to machine them.

Next we need to get the material and prepare the blank stock pieces for machining. Depending on the part size and how many we need, we might have the right material laying around. For something this large, though, and at a reasonable quantity, we’ll probably need to go buy material. Depending on the part geometry, it’s often more time effective to buy a full twelve-foot length of material as it’s unlikely the metal shop will have the right chunk of stock laying around. In this case, though, I lucked out and found material in the remnant bins. The starting stock for six parts weighed in at about 33 lbs. With the finished parts weighing in at only 0.54 lbs. each, that’s a lot of material to cut away. Over 90% of it!

The material is brought back to the shop, and cut on the horizontal bandsaw into blanks for machining. In this case we’re making just five total parts. You’ll notice there are six blanks, though. That’s because one is a setup part. Unless the design is very simple, it's likely something will go wrong along the way. It’s usually something minor, but still big enough to scrap the part; that’s what the setup part is for. It’s the sacrificial part for those minor screw-ups so the CNC program and setup are fixed before machining the other five parts.


CNC Programming and Setup, what did it take?
  • CNC Programming time, ~3 hours
  • Material, ~$100 and 1 hour to go get it and bring it back
  • CNC setup (machine and tooling, material cutting) time, ~1 hour
  • Tooling and consumables: We use about $900 worth of tooling (not including the holders, tools only), to make this part, and these tools eventually wear out. They’re good for a lot of parts, but it’s something to think about. It’s also worth thinking about general wear and tear and upkeep on the machinery – the CNC machine, the air compressor, band saws, and anything the has wear items, consumables, or needs maintenance. It doesn’t cost much on a per-part basis, but it’s thousands of dollars at the end of the year.

Step 4 CNC Machining:

Now we machine the part; each setup programmed in the last step is set up and run to create the actual parts. Every part is different, but as mentioned earlier, our example part has four setups:


Step 4a, Machining the First Setup:
CNC Setup

The first setup is relatively straight forward since the material is nice and rectangular. We can clamp the material directly in a “standard” vice and start machining. The material has to be located, so the machine knows where it is, though. For this we probe its position and install a vice stop such that the material can be loaded in the same spot every time. The first machining setup removes most of the material and the part starts to take shape.


Step 4b, Machining the Second Setup:
CNC Setup

For the second setup things get a little more difficult. We need to hold on to the part in the vice, but it’s no longer a nice rectangle. For this we have to machine a set of “soft-jaws”, which are aluminum vice jaws cut to the shape of the part they’re holding. We’re essentially making a whole new part just to hold on to the part we intend on making. After machining the second setup the part really starts to take shape as most all the material we don’t want has been removed.


Step 4c/d, Machining the Third and Fourth Setups:
CNC Setup Fixture

Similar to the last setup, we need to make yet another part (a fixture) just to hold on to the bar mounts we’re making. In this case the mount face and bolt holes are at odd angles relative to the bar mount, which makes this fixture much more complicated than the last one. Of course this takes time to design the fixture and machine it; this particular fixture took three setups to machine itself, almost as many as the part we're making!

The bar mount is bolted to this fixture and aligned by its outer perimeter for consistency, which allows the final two machining setups to be performed, creating the handguard attachment features.


CNC Machining, what did it take?
  • CNC Run time, total of 56 minutes per part, including handling and machine time (let’s just call it an hour for simplicity). This is mostly automated so no one has to stand around that whole time except for the first part to ensure it all goes as planned. So actual time spent by the programmer standing at the machine is about 2 hours for these six parts.
  • Program revisions – remember that setup part? We likely have to make minor revisions to the program, reload it into the machine, and get back to cutting. It’s not a huge amount of time, probably about 30 minutes unless something went really wrong!
  • Fixtures:
    • Soft jaws are about $30, but we might be able to use them for a couple different parts before throwing them away. Let’s call that $15. And they’re fairly simple, so design, programming, setup, and cut time for those is about 1.5 hours.
    • The custom fixture for setups 3 and 4 is a bit more complex. The material for that cost about $25, but it was three setups to machine plus programming and design time. That took about 3 hours total.

Step 5, Finishing:

The freshly machined part usually has a few sharp burrs from the cutting process; for these parts we tumble them to remove those burrs and achieve a consistent surface finish. The tumbler uses hard plastic/ceramic “stones” to smooth over surface inconsistencies. Once tumbled, the parts are sent out for anodize. Anodizing is a controlled oxidization process that creates a thin, hard, protective layer over the part. This layer can be dyed different colors and for this part we went with black to match our other bar mount components.


Finishing, what did it take?
  • It takes about 30 minutes to an hour to tumble the parts, but it’s pretty hands-off aside from loading and unloading parts. They do need to be washed and dried after tumbling, though, so it’s about 30 minutes total operator time to do this.
  • Then the parts must be individually wrapped and boxed up, then taken to anodize. Once complete we have to go pick them up. This is about an hour of time to do all that, plus the actual anodize cost is about $150. If we’re lucky we can throw these in with another batch that we have waiting for anodize, but often the timing just doesn’t work out and we have to do a special run. Such was the case here.

The Finished Part:

The Finished Part

So that’s it, right? Well no, now we just have finished parts on the shelf, there’s still more to go...

Some parts have special features or complex installation so we have to create and supply user manuals or installation instructions. Fortunately for this part, it is similar enough to our non-handguard bar mounts, so most of the installation instructions carried over and this only took about an hour to write up.

We also need some good photos of the part. There’s a solid hour of work to take quality photos and edit them for the website and marketing materials. Once photos are sorted out, we need to get a web page up, which takes about another hour to write up and integrate with our e-commerce and inventory management system.

Now the part in stock and ready to sell, but no one knows we have it. I won’t go into all the details, but we need to make social media posts, forum posts, send out an email to our subscribers, etc. to spread the word. We might consider putting out an advertisement, and of course that costs money as well. It doesn’t sound like much, but it’s all time that adds up quick, and someone has to do it.


Adding up the Time and Expenses

OK, now we're done. So how much did this take all together? Adding up the expenses listed throughout this process we come to $305. And that doesn’t include any wear items, tooling, etc. We’ll just ignore those for simplicity, but they exist nonetheless.

More important than the money spent, we also have to account for the time spent in getting this done. Most of the processes detailed above are performed by a mechanical engineer, a CNC programmer, or a web developer/graphics designer. These are not low paying positions, and for this example consider each of these costs us about $60 per hour all said and done with wages, taxes, and various other employee overhead. Some of the processes can be done by lower paying positions, particularly material loading, dropping parts off for anodize, etc. That makes a lot of sense in production, but for this first batch of parts these tasks will just be done by the higher paid guys as it doesn’t make sense to get someone else involved for only five parts. So, totaling up the time involved, we have 28.5 hours. At $60/hour, that comes to $1,710.

In total, that’s over $2,000 to bring this part to market. And at $179.95 retail, we need to sell about 15 of these just to break even! (Before someone complains about my math, remember that we only made five parts for that $2k.) On top of that, this whole process took a bit over a month to complete. So if you’re asking for a custom part, this is why you’re likely to get a response with a high cost, a minimum order, a long lead time, or simply “no” for an answer. But don't let that discourage you; you might have a great idea or want a part with enough demand to justify the process. It never hurts to ask!

Have an idea or need something custom? Contact us to discuss the details.

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Seth:

Very cool explanation. most people don't consider perishable tooling and everything else you mentioned.

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