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Oct 23,2026
Not "three men" because a salesman said so. Four drawings, four tables, and the arithmetic that produces 1.1 to 2.9 depending on what your shop actually does all day.
This is an illustrated explainer, so we will do it the way a shop floor does it: one drawing at a time, one number at a time, no adjectives. Everything below uses the same baseline, so you can substitute your own rates and re-run it in five minutes.
| Method | Clean rate | Operators tied up | Effective m²/h per operator | Man-hours for 300 m² | Labour $/m² |
|---|---|---|---|---|---|
| Angle grinder + wire wheel | 1.2-1.8 m²/h | 1 | 1.5 | 200 | $14.67 |
| Sandblasting (suction) | 7-9 m²/h | 2 | 5.0 | 60 | $4.40 |
| Chemical dip / gel | batch, 8 h dwell | 1 + handling | 6.0 | 50 | $3.67 |
| 500W pulsed laser | 12-14 m²/h | 1 | 10.0 | 30 | $2.20 |
Labour only. Media, chemicals, disposal, PPE and extraction are excluded here and priced in Figure 4.
Read the fourth column, not the second. The sandblaster is fast, but one man blasting needs a second man feeding media, moving parts and watching the hose - so 8 m²/h of machine becomes 5 m²/h of operator. The laser's 14 m²/h becomes 10 m²/h because one man can hold the head, watch the seam and step sideways without a helper.
Divide 10 by 1.5 and you get 6.7. That is the number the salesman is quoting, and it is real - for as long as the machine is lasing. It is also almost never what happens, because a machine only works while there is work in front of it. That is Figure 2.
| Step | Time for 100 m² | Share of the job | Who does it |
|---|---|---|---|
| Unload, position, clamp | 1.5 h | 11% | Operator |
| Masking, protecting machined faces | 0.8 h | 6% | Operator |
| Lasing (100 m² ÷ 13 m²/h) | 7.7 h | 58% | Operator |
| Repositioning, turning the part | 1.6 h | 12% | Operator |
| Inspection under light, touch-up | 0.9 h | 7% | Operator + QC |
| Filter change, nozzle clean, sweep | 0.8 h | 6% | Operator |
| Total | 13.3 h | 100% | 7.5 m²/h job rate |
58% of the paid hour is light on metal. The other 42% is the same handling, masking and inspection that the grinder team also does - and that is the single most important sentence in this article, because it explains why the replacement number is never the throughput ratio.
Ceiling one is throughput - how much faster the beam is than the tool it replaces. Ceiling two is utilisation: the share of the shift where a part is actually in front of the head. If your cleaning bay waits on welding, paint or a crane, that number is 40-60%, not 90%. Ceiling three is residual manual work - the corners, the deep pits, the edges that need blending, the threads that need taping. In practice that runs 15-30% and it does not disappear, it just gets cheaper per part.
| Shop type | Utilisation | Residual manual | Workers replaced | What limits it |
|---|---|---|---|---|
| Foundry / castings, cleaning is the bottleneck | 85% | 10% | 2.6-2.9 | Part size, crane time |
| Heavy fabrication, rust before paint | 60% | 20% | 1.9-2.2 | Painting line rhythm |
| Automotive / restoration, mixed substrates | 55% | 25% | 1.6-1.8 | Delicate panels, masking |
| Light fabrication, oil and weld discolouration | 30% | 30% | 1.0-1.1 | Cleaning is not the constraint |
That last row is the one that saves people money. If cleaning is 20 minutes of a four-hour build, the machine still pays - on quality, on consumable spend, on the fact that nobody has to grind a weld seam by hand at 6 pm. But it does not pay on headcount, and anyone selling it to you on headcount is selling you a story.
System cost: 500W unit $9,800 + extraction and filtration $3,900 = $13,700, FOB, before freight and duty. Consumables and filters add $1,180 a year. Now the three cases, each with a real shop behind it.
| Case | What actually happens | Annual cash effect | Payback |
|---|---|---|---|
| A. Hire avoided | One grinder retires, no replacement hired. Output held by the laser plus the remaining men. | +$41,800 1,900 h × $22 |
3.7 months |
| B. Overtime eliminated | Crew stays at 5, but Saturday overtime of 300 h/year disappears. | +$9,900 300 h × $33 |
16.6 months |
| B2. Redeployed, extra capacity sold | Nobody leaves. The bay takes 40% more work; contribution margin on the extra volume is $1,450/month. | +$17,400 | 9.4 months |
| C. Nothing changes | Machine installed, same crew, same volume, same hours. Cleaning is just nicer to do. | -$1,180 consumables only |
never |
Case C is not a strawman. It is the most common outcome when nobody is told what the freed hours are for.
Notice that Case A and Case C are the same machine, the same shop and the same throughput. The only difference is a decision made in the first week: whether the freed hours are converted into a payroll line, into shipped volume, or into nothing. A laser cleaner does not save labour. It removes labour content from a process, and then it is management's job to turn that into money.
Left to right: blasting needs a second man on media and handling; chemical needs racking, dwell time and waste treatment; laser is one man, one head, dry.You do not need our tables. You need a stopwatch, a tape measure and one honest week.
Step 1. Pick three parts you clean every week. Measure their surface area in m² - length × width × number of faces, ignoring what you never clean.
Step 2. Time the current method from picking up the tool to setting it down. Divide area by hours. That is your manual rate.
Step 3. Ask the operator how many minutes per shift are spent waiting for parts. Divide by 480. That is your utilisation, and it is usually lower than the owner believes.
Step 4. Multiply area per week by 46 weeks. That is your annual cleaning load.
Step 5. Run the formula in Figure 3 with a job rate of 7.5 m²/h. If the result is below 1.2, buy on quality and consumables. Above 1.8, buy on labour. Between them, buy on overtime and capacity.
If you send us three part photos and your current cleaning hours per week, we will run this arithmetic with your numbers and send back the table - including the cases where the answer is "do not buy yet". We would rather lose a machine sale than sell a payback that does not exist.
Photo + surface area + current hours per week is enough. We reply with the Figure 3 table filled in for your shop, plus a 90-second video of your material being cleaned at 500W.
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