I was unexpectedly contacted at October last year by the PCBWay - a Chinese manufacturer providing PCBs, milling, 3D printing and similar stuff - that they have found my blog and are willing to sponsor my next project. I was pleasantly surprised as I thought almost nobody reads my webpage (I keep it as a hobby and to document stuff I spent a lot of time looking for solution and the others might be interested in), so why not to use the opportunity, right?
A disclaimer: I was offered a sponsorship, but I try to keep this blogpost honest and describe the process of ordering CNC machining at PCBWay from start to finish as it really happened, there's no attempt to polish anything to make it look better than it really is...
What to make
I've used SeeedStudio and JLCPCB in the past, but I've had not prior experience with the PCBWay, although I was aware of their existence as I was looking for fab house that could make a cooper core PCBs with direct thermal path - the JLCPCB can do it, but only with OSP finish and very limited subset of other options, the PCBWay let's you select a completely custom setup (cooper thicknes, all kinds of solder pads finishes, thicknesses, colors,...) although it's not suitable for runs of just few boards due to a higher pricing.
At the time I've received the email, I've been working on another version of my caving headlamp (mk.I, mk.II), but it was not in a state when I would be willing to commit into ordering a bunch of expensive cooper core boards as the HW was not really finished and tested, but I was slowly finishing the lamp housing. The previous versions were a simple round shaped, easy to make at home, but the new version is quite complex and requires a decent precision for all parts to fit just right without squeezing them or having them too loose.
I've made several lamp body prototypes on the 3d printers to get the dimensions just right, it was pretty painful process. The lenses are using the body as a holder and must be positioned precisely to match the LED focal point, the lamp has two PCBs, the upper one also serves as a lens secondary holder, so lot of fine tuning here too and getting the lamp holder just right is a long story for another blogpost.
Preparing the order
The original lamp design was quite complex, with all the nice fillets everywhere, radii at the bottoms of the cooling fins, sharp corners, deep and precise pockets,... To summary - a very expensive to manufacture. I've spent quite a lot of time optimizing the design to reduce the cost. There's not much resources online on this, but the PCBWay has a nice manual online on the basics.
Both the PCBWay and JLCPCB have an online quoting system that calculates rough price from the step file - quite nice for rough estimates and partially usable for price fine tuning. From my experience, the JLCPCB tends to react better on smaller design changes like removing fillets or reducing depth of a pocket, the PCBWay is bit more crude, so it's harder to misuse it for price optimizations. Anyway, I've managed to reduce the JLCPCB price estimate from roughly 450 to 340 USD per 10 pieces, mostly by:
- replacing all fillets with simple 45 degrees chamfers
- increased corner radii in deep pockets
- removed all the useless chamfers inside the cooling fins
The price difference between original and optimized design on the PCBWay online quoting tool was much smaller, like few dollars. What was quite interesting, the estimated price of the very complex lamp body with all the threads from all sides, deep pockets, and stuff was 27 USD per part and the lamp lid which is just a piece of thin aluminum machined with few holes made from the single side was estimated at 26 USD. Clearly the online quoting tool is very rough.
Ordering
Ordering is easy, just upload step files from any 3D design software, if you need threads or anything else, add a 2D drawing, select material, surface finish and few other details and you are good to go.
The lamp body had several threads, few features with tighter tolerances (mostly just moving the tolerance window from +- something to -0 +2x something for mating surfaces) and one H7 hole for press fitting the button, everything noted in the drawing. For the surface finish, I've selected bead blasting and anodizing as the bead blasted surface looks much better than shiny one which shows all the scratches and imperfections...
After placing the order (no payment yet) I needed to wait like a day or so for engineering review. I was quite curious about the final prices as all the simple parts were priced almost exactly the same as the very complex lamp body.
When the review came, I was positively surprised, the prices of the simple parts were cut in half and the body price remained. All the other vendors I have tried offered like 25% higher price for the lamp body than PCBWay. The prices for the round parts were still quite high for my liking as I could make these at home on my lathe, so I've removed these parts from the order.
As I was offered a sponsorship for my next project, I've contacted the PCBWay with my order ID and they've added a coupon to my account which partially covered the cost. Additionally when the coupon was deducted from the order, not only the order price was reduced, but also the subsequent costs like duty, tax, bank handling fee (something the PCBWay charges you when paying with credit card if I understand it correctly), DTP service fee (for handling duty and tax for you),... Just to illustrate the cost added above the parts price, here's the final order (without coupon):
After applying the coupon, the shipping and DTP service fee stayed the same, but the Bank handling fee (whatever it is) and tax/duty dropped significantly.
Manufacturing
You can see the order timing on the attached image. It took slightly over a week from placing the order to manufacture the lamp body, then it got completely stuck. A message like Order surge, your order may be delayed appeared next to the order and nothing happened for almost a month. I've contacted the support to see what's going on. The response was almost immediate with expected finish date in about a week and question if that's ok.
The next day, another email came with photo of the already manufactured part and question regarding the dimensions. One of the holes was required to be in H7 tolerance, which for 14.5 mm hole diameter is -0, + 0.018mm. The engineer from PCBWay was asking if it's ok if the hole is slightly out of specs and sent a photo of the part and digital caliper placed in the hole. Well, I expected a bit more, the hole was 0,05mm larger than required, more than twice the tolerance range, measured with a tool that has precision around 0,02 or even worse - worse measuring precision than the maximum hole tolerance. This might have been partially my problem as I haven't checked the checkbox with increased required precision when ordering, but I kind of expected the engineering review to catch such issues before manufacturing...
Anyway, this was not a critical issue as I still didn't have the counterpart intended for this hole manufactured, so I could compensate for that issue. What kind of hit me from the photo attached to the email from the support was the color. I expected nice red color, but the actual look was more into the purple, maybe a bit orangeish. The support was nice, I've asked about the color and they've immediately sent me more photos and even a video. I guess I could have just asked and they would strip the anodizing and redo it to my liking, but I was kind of tired of waiting already, so I've agreed with the current state and they've sent the order immediately.
The DHL shipping was quite fast, the parcel basically arrived within 4 days where 2 days were a weekend.
Results
The machined parts are quite nice, no sharp corners, no machining marks (blasting helps), the anodizing looks ok, the color is not a clean red, but it's usable. The order arrived quite well packed, everything neatly wrapped in a foam material in a way that all parts were separated from each other.
Conclusion
Pros:
- Cheapest out of other Chinese vendors I've found for the complex lamp body
- Nice machining quality and surface finish
- Very good and fast support
Cons
- Online quoting tool is not very precise, expect big price changes after placing the order
- Double check the critical tolerances with support to avoid surprises later
- If precise color finish is required, work with the support before placing the order on details
