I designed a Celtic keychain with five colors: black matte for the body, gold for the border, white for the text, green for a clover, and red for a heart. Loaded it into Bambu Studio, assigned the filaments, and then stared at the AMS Lite's four slots.
Four slots. Five colors. Math doesn't work.
This is the story of how I tried three different approaches to solve that problem, learned some things about the A1's hardware limitations the hard way, and eventually got the print I wanted. The plan changed multiple times. That's how most of my projects go.
The Setup
The Bambu Lab A1 with AMS Lite is a great multi-color printer for the price. A great "print and forget" solution as long as you stay within the limit. The AMS Lite holds four spools and handles filament swaps automatically during a print. For most multi-color projects, four colors is plenty. But the moment you want a fifth, you hit a wall like I did.
My keychain design had five distinct colors, and the black matte body was the most filament-heavy by far. My instinct was to run the black as an external spool (mounted on the top of the printer) and use the AMS Lite's four slots for gold, white, green, and red.
The A1 doesn't support that. The firmware warns you not to use the external spool and AMS at the same time. But I figured I'd try anyway.
Attempt 1: The Y-Splitter (Failed) 🔀
I printed a Y-splitter, a small tube fitting that merges two filament paths into one feed line, which I added to one of the AMS ports on the printer. The idea was to run the external black spool through one arm of the Y and the AMS output through the other, both feeding into the printer's extruder.
Bambu warns against this, and now I know why. The AMS Lite doesn't just passively hold filament; it actively pushes and retracts it during color changes. When the AMS retracts one color to load another, it pulls filament backwards through the feed tube. With a Y-splitter in the line, that retraction force pushes filament back through the other arm of the Y, toward the external spool. The system gets confused, filament jams, and the print fails.
There's no check valve in a Y-splitter that would prevent this. The physics just don't work. If the black spool and the AMS colors never shared the same layer, I thought the timing might work out. It didn't. The AMS retracts aggressively between color changes regardless of what's on the current layer.
Verdict: Don't bother with a Y-splitter on the A1. The AMS Lite's retraction mechanism makes it incompatible.
The "Right" Answer: More Hardware 💸
The proper solution is the AMS Pro, which costs around $250 and supports chaining multiple units. You could run eight or more colors with the right setup. But the A1 doesn't support chaining two AMS Lites (that's an A1 limitation, not an AMS Lite limitation). So the upgrade path is specifically AMS Lite → AMS Pro, not AMS Lite + AMS Lite. This could be a business decision to push people to upgrade or an actual limitation of the software. Either way this was an expensive upgrade for the phase I am at.
I'll get there once the shop's keychain sales justify the investment. For now, I needed a workaround with the hardware I had.
Attempt 2: Manual Filament Pause (Worked, With a Gotcha) ⏯️
Bambu Studio lets you add a pause at a specific layer. The printer stops, you swap the filament manually, and the print resumes. This is the low-tech version of multi-color printing, and it works.
Here's how I set it up:
- Assign only 4 colors in Bambu Studio for the AMS slots (gold, white, green, red)
- Set the black body as one of the AMS slots temporarily so the slicer generates the correct toolpaths
- Find the layer where the body color ends and the detail colors begin using the layer slider in the preview
- Add a filament pause at that layer
- Before the print starts, load the black matte filament as the external spool
- When the printer pauses, swap from the external black spool to the AMS and let it handle the remaining four colors
The gotcha: I initially added the pause on the last layer of the black body. Wrong. The pause needs to be on the first layer where the new color starts. If you pause on the last layer of the previous color, the printer finishes that layer and then immediately starts the next one (with the wrong filament) before you can swap. One layer off, and you've got gold where black should be.
When adding a manual filament pause in Bambu Studio, place it on the layer where you want the new color to begin, not the last layer of the previous color. The pause triggers before that layer prints, giving you time to swap.
Attempt 3: Design Around the Constraint 🎨
While I was iterating on the pause approach, I stepped back and looked at the design itself. Did I actually need five colors? The red heart was the odd one out. If I dropped it and put a clover on both sides of the text instead, I'd have four colors: black matte body, gold border, white text, green clovers. Everything fits in the AMS Lite. No manual pause, no babysitting, no Y-splitter.
Honestly? It looked better. The symmetry of clovers on both sides balanced the design in a way that the clover-and-heart combo didn't. And the green clovers on black matte pop harder than I expected.
I'd still like to do the red heart version. It's a nice design. But it means adding a manual filament pause, which adds labor to every print. When you're making one keychain for yourself, that's fine. When you're printing batches to sell, the pause step adds real cost. Every print that needs babysitting is a print you can't walk away from.
This is the version I'm printing now, and it's the practical choice for production. Four colors, fully automatic, no intervention. In the future, I might do a variant with a white border and red heart, a different four-color combination that gets the heart back without needing a fifth slot. That's the fun of designing within constraints: you don't just solve the problem once, you find multiple solutions.
Future Experiment: Pre-Printed Bases with a Jig 🧩
There's one more approach I haven't tried yet but want to: print the black base keychains ahead of time as a batch, then place them back on the print bed and run a second print with just the detail colors on top.
In theory, this unlocks unlimited colors across two prints without any hardware upgrades. Print a full bed of black bases in one run (fast, single color, no AMS needed). Then load the AMS with your four detail colors and print the top layers onto the pre-made bases. Five colors, six colors, however many you want, as long as no single layer needs more than four.
The challenge is alignment. You need each keychain positioned precisely on the bed so the second print lands in the right spot. Any misalignment and your letters are shifted, your border is off-center, or the layers don't bond cleanly.
The solution I want to test: print a jig. A tray with cutouts that hold each keychain in an exact, repeatable position. Drop the black bases into the jig, and X/Y alignment is solved mechanically. You'd only need to dial in the Z-offset so the second print starts at the right height. That reduces the problem from three variables to one.
If the jig approach works reliably, it could change the production math entirely. Batch the bases, batch the details, no manual pauses, no hardware upgrades, and full color freedom. I'll write a follow-up post when I test it.
For now, printing in one go with four colors is the safest approach. The constraint forced me to make a better keychain.
The Wall Settings Problem
The color count wasn't the only issue. My first successful multi-color print looked cheap. The body had fuzzy, uneven walls that made it feel like a rough draft, not a finished piece.
The problem was wall thickness. I'd set the walls to a thinner value across the entire print so the small details (letters, clover outlines) would resolve cleanly. Thin walls work for fine detail, but they produce visible layer lines and a rough texture on larger surfaces.
The fix: use different wall settings for different parts of the print. I reset the body to standard .4mm walls, which gave it clean, solid surfaces. Then I applied thinner walls only to the top detail layers where the letters and small features needed to connect. In Bambu Studio, you can do this by right-clicking specific objects or using per-object settings if your model has separate bodies.
The difference was immediate. The body went from "clearly 3D printed in a bad way" to smooth and solid. The letters on top still resolved their thin strokes. Two wall settings, one print.
The Spool Extension Side Quest
One more thing. The black matte filament I bought came on a smaller spool than standard. It didn't fit the A1's external spool holder. So before I could even start on the keychain, I had to 3D print a spool extension adapter.
This is a common 3D printing experience: you sit down to do one project and end up doing two because the first one requires a tool you don't have. I printed the adapter in leftover gray PLA, and it took about 40 minutes. Not a big deal, but it ate into the afternoon I'd planned for the keychain.
What I'd Do Differently
If I were starting this project over:
- Design for 4 colors from the start. Work within the AMS Lite's slot count. The constraint usually makes the design better, not worse.
- If you need a 5th color, use the manual pause. It works, but set the pause on the right layer (first layer of the new color) and be ready to swap quickly.
- Don't try the Y-splitter. The AMS retraction makes it fundamentally incompatible.
- Split your wall settings. Standard walls for the body, thinner walls for detail layers. Don't apply one setting to the whole print.
- Check your spool sizes before you start. Order filament on standard spools, or print an adapter in advance.
The finished keychain took three attempts and most of an afternoon. My original plan (Y-splitter, five colors, one shot) didn't survive first contact with the hardware. But each failed attempt taught me something, and the four-color version I ended up with, black body, gold border, white text, green clovers on both sides, is cleaner than the five-color design I started with. That's the one I'm selling at the shop.
That's the pattern with most maker projects. The plan changes. You adjust. Learn from mistakes and get better every time. The final version is better than what you originally imagined, because you learned things along the way that you couldn't have known at the start.
The Bigger Picture
The Bambu Lab A1 with AMS Lite is excellent for multi-color printing up to four colors. Beyond that, you're either upgrading to the AMS Pro or getting creative with manual swaps and design constraints. Both are valid approaches depending on your budget and patience.
If you're at Maker Pub, we can help you set up multi-color prints and figure out the filament strategy before you start. We've been through the trial and error so you don't have to repeat all of it. Some of it, maybe. That's part of making.