The 20W Fiber Laser Dilemma: B6 vs B4
If you're running a small business and looking at fiber lasers, you've probably landed on two models from Commarker: the B6 20W and the B4 20W. They're both 20-watt fiber lasers. They both cost in the same ballpark. And they both target the same kind of user—someone who needs to engrave metals, mark plastics, or cut thin materials.
But here's the thing: they're not the same machine. Not even close in some ways. I've spent the last month comparing these two from a procurement perspective—not as an engineer, but as someone who manages budgets and tracks every dollar spent. I'm a procurement manager for a 12-person custom fabrication shop. I manage a $45,000 annual equipment budget. I've negotiated with 8 laser vendors in the past 6 years. And I built a cost comparison spreadsheet that I'm frankly a little embarrassed about the complexity of.
So let's break this down the only way that matters for a small business: what are you actually paying for, and what do you get in return?
Dimension 1: Upfront Cost vs. Total Cost of Ownership (TCO)
At first glance, the pricing gap is small. The B4 20W comes in around $2,200–$2,500. The B6 20W is roughly $2,800–$3,200. That $400–$700 delta feels manageable, but it's not the full story.
When I audited our 2023 spending on a similar procurement decision, I found that the "cheaper" option ended up costing us 22% more over 18 months because of add-ons and consumables. Let me explain what I mean for these two machines.
The B4 20W is the budget-oriented model. It's a solid entry-level fiber laser. The base unit includes the laser source, controller, and a basic worktable. But here's where it gets tricky: the standard lens is fixed focus. If you need to switch between different material thicknesses, you're looking at buying additional lenses. Those run $80–$150 each, depending on focal length.
The B6 20W is the upgrade model. The base price is higher, but it comes with a motorized Z-axis lift table. I'm not an engineer, so I can't speak to the motor quality. What I can tell you from a procurement perspective is: that lift table eliminates the need for manual focus adjustment and multiple lenses for most common materials. That alone can save you $200–$400 in accessories up front.
I wish I had tracked how many extra lens purchases we made before switching to a model with a lift table. What I can say anecdotally is that we bought three additional lenses in the first year for our older fixed-focus unit. That was around $320 I didn't anticipate.
The TCO verdict: While the B4 20W has a lower entry price, the B6 20W's included features (motorized Z-axis, better cooling, and a more robust build) make it the likely lower-cost choice over 2–3 years for anyone running more than 10 hours of engraving per week.
Dimension 2: Workflow Speed and Throughput
This is where the comparison gets really interesting—and honestly, a bit surprising.
Both machines use the same Raycus 20W fiber laser source. Both have roughly the same power output. So you'd think engraving speed would be identical. In theory, yes. In practice, not exactly.
The B4 20W is a more manual machine. You set the focus by adjusting the table height with a crank. For a batch of identical items, that's fine—you set it once and go. But if you're doing job shop work where every order is different—a batch of aluminum tags, then some stainless steel keychains, then some plastic panel overlays—you're spending 2–5 minutes per job change on manual focus adjustment.
The B6 20W has that motorized Z-axis I mentioned. In a job shop environment, that saved us an estimated 25–35 minutes per 8-hour shift. Put another way: the B6 can handle roughly 6–8 more jobs per day if you're switching materials frequently.
Don't hold me to this, but I'd estimate that translates to an additional $80–$120 in potential revenue per day for a shop charging typical per-job rates for metal engraving. That adds up fast. In Q2 2024, we ran a test comparing two similar machines with and without auto-focus. The machine with auto-focus processed 17% more orders in the same time window.
The throughput verdict: If you're running batch work (same item, high volume), the B4 20W is perfectly fine. If you're running diverse job shop work, the B6 20W's auto-focus pays for itself in increased throughput within 3–5 months.
Dimension 3: Build Quality and Longevity
I'm not a mechanical engineer, so I can't speak to the structural integrity in technical terms. What I can tell you from a procurement perspective is: the B6 20W uses a thicker steel frame and has noticeably better vibration damping when running at high speeds.
After tracking 40+ orders of similar equipment over 6 years in our procurement system, I've found that roughly 15% of our "budget overruns" on equipment came from premature wear on machines with thinner frames. The vibration causes minor misalignments over 12–18 months. It's not catastrophic, but it does require more frequent calibration and lens replacements.
The B4 20W's frame is adequate for light-duty use. For a hobbyist or a very small shop running under 20 hours per week, it'll likely serve well for 3–5 years. The B6 20W's frame is built for continuous use. For a shop running 40+ hours per week, the B6 is probably the better long-term investment.
The build quality verdict: The B4 20W is fine for low-volume use. The B6 20W is built for higher duty cycles. If you plan to scale, the B6 is the safer bet.
Dimension 4: Software and Ease of Use
Both machines use LightBurn-compatible controllers. That's a big win for both. LightBurn is widely considered the standard for laser engraving software, and having it on a fiber laser at this price point is great.
The difference is in the controller board. The B6 20W uses a newer generation board with slightly faster data processing. In practice, this means faster file transfers and smoother operation when running complex vector files. The B4 20W's controller is older but perfectly functional.
Looking back, I should have paid more attention to the controller specs when I bought our first laser. At the time, I figured "it runs LightBurn, what's the difference?" The difference is in how quickly the machine responds to commands, especially with complex vector files. The B6's newer board handles complex vectors noticeably better.
The software verdict: Both are LightBurn-compatible. The B6 has a slight edge with its newer controller. For simple text and basic graphics, you won't notice a difference. For intricate vector work, the B6 is smoother.
So Which One Should You Buy?
Here's my honest take, based on what I've seen across dozens of procurement decisions:
Get the Commarker B4 20W if:
- Your budget is strictly under $2,500 and you can't stretch.
- You do mostly batch work (same item, high volume) or very low volume runs.
- You're a startup or hobbyist running under 15 hours per week.
- You're comfortable with manual focus adjustment.
Get the Commarker B6 20W if:
- You can stretch your budget to around $3,000.
- You run a job shop with diverse materials and frequent changeovers.
- You plan to scale beyond 20 hours per week of operation.
- You value auto-focus convenience and higher throughput.
- You want the model that's likely to last longer with heavier use.
Even after choosing the B6 for our shop, I kept second-guessing. What if the B4 would have been good enough? The two weeks until delivery were stressful. Then the B6 arrived, I watched it auto-focus on a 0.1mm stainless steel shim, and I relaxed. It's a good machine.
But here's the thing: for a small shop just starting out, the B4 20W is not a bad choice. It's a solid entry-level fiber laser. The B6 is just a better fit if you anticipate growth or diverse workloads.
Prices shown are as of January 2025 based on quotes from Commarker and verified retailers. Verify current pricing before purchasing.
