Electric Melting Furnace Throughput: Calculate Real Output per Shift
Quick answer
Electric melting furnace throughput is not the capacity label multiplied by the number of hours in a shift. Calculate it from measured usable batch mass, complete heat-to-heat cycle time, casting yield, changeovers, and planned downtime. Validate the result with several normal production runs before promising delivery dates.
Use the throughput formula
For one furnace and one shift:
Saleable metal per shift = usable charge mass × completed cycles × casting yield
Where:
- Usable charge mass is the documented working load for the metal and process, not a brimful or universal kilogram claim.
- Completed cycles are the cycles that fit inside staffed operating time after setup, inspection, charging, heating, pouring, safe turnaround, and shutdown.
- Casting yield is saleable casting mass divided by charge mass. Sprues, runners, dross, spills, retained metal, and rejected parts do not count as saleable output.
If a workshop measures a 1.6 kg usable aluminum charge, completes four normal cycles, and records an 82% yield, the planning result is:
1.6 kg × 4 × 0.82 = 5.25 kg of saleable castings per shift
That is a hypothetical calculation, not a ToAuto performance claim. Your measured cycle must replace every example input.
Time the whole heat-to-heat cycle
A headline melt time usually covers only part of the job. Start the timer at the same defined state every time and stop it when the furnace is ready for the next equivalent charge. Record:
| Cycle element | What to measure |
|---|---|
| Pre-use inspection | Furnace, cord, crucible, tongs, mold, dry work zone |
| Charging | Sorting, weighing, and loading accepted metal |
| Heat-up and melt | Cold or warm start, metal, mass, geometry, voltage |
| Process hold | Only the justified time needed for the alloy and casting method |
| Lift and pour | Time from opening to controlled completion of the pour |
| Turnaround | Safe condition, inspection, and preparation for the next heat |
| Changeover | Crucible, alloy, mold, tooling, and documentation changes |
| End-of-shift shutdown | Supervised cooldown and required housekeeping |
The current ToAuto comparison page publishes different manufacturer melt-time ranges across furnace families, but those figures are not interchangeable production rates. The page itself distinguishes model, capacity, power, and heat source. Treat its times as dated manufacturer estimates until a revision-matched test reproduces the same conditions.
Capacity is not daily output
A capacity label answers only part of the question. Density changes the mass that fits a given crucible volume. Freeboard, tongs control, mold demand, and the furnace's documented working recommendation can reduce the usable charge. A larger crucible can also increase manual handling risk or create more metal than the mold system can accept.
Work backward from the casting:
- Add net part mass, gating, risers, test coupons, and a documented process allowance.
- Confirm the mold and pouring system can accept that mass.
- Select a crucible that provides controlled working space.
- Confirm the crucible fits the furnace and the lifting/pouring tools.
- Confirm the exact furnace revision is suitable for the alloy's required process temperature.
This mirrors a recurring community question: buyers struggle to translate a nominal crucible size into the number of ingots or castings they can actually pour. The defensible answer depends on the metal and working fill, not the label alone.
Find the real bottleneck
More furnace capacity does not automatically increase shipped output. The limiting step may be:
- mold preparation or burnout;
- alloy identification and charge preparation;
- one operator's safe lift-and-pour capacity;
- too few compatible crucibles;
- cooldown or inspection time;
- finishing, inspection, or rework;
- electrical supply or shared-circuit constraints;
- a lack of dry, ready molds when metal becomes available.
Industrial foundry examples show the same principle at a different scale: adding melting capacity can expose downstream constraints when molding and finishing cannot keep pace. A small shop should map the full flow before purchasing a larger furnace.
Build a planning range, not one perfect number
Use at least three scenarios:
| Scenario | Cycle input | Yield input | Appropriate use |
|---|---|---|---|
| Conservative | Slow normal cycle | Lower normal yield | Customer commitments |
| Expected | Median observed cycle | Median observed yield | Staffing and weekly plans |
| Stretch | Best repeatable cycle | Best repeatable yield | Improvement target only |
Exclude abnormal interruptions from the expected cycle only if you separately budget planned downtime. Do not erase failed heats. Categorize them so the plan reflects actual risk.
For a new furnace, begin with one supervised heat and a commissioning record. Do not schedule consecutive maximum-load cycles until the manual or manufacturer confirms the duty pattern and the workshop has demonstrated safe turnaround.
Frequently asked questions
How many melts can an electric furnace do per day?
Divide staffed production time by the measured complete heat-to-heat cycle, then round down and subtract changeovers, planned inspection, and shutdown time. A product-page melt estimate alone cannot answer the question.
Should I use the furnace's maximum kilogram rating?
No. Use a metal-specific working mass that leaves controlled pouring space and complies with the exact furnace and crucible documentation. Nominal kilograms are not universal across metals.
Does a warm furnace always make the next cycle faster?
It may change the cycle, but the effect must be measured and must not override duty limits, inspection needs, crucible condition, or safe operating procedure. Record cold-start and warm-cycle results separately.
Bottom line
Real electric melting furnace throughput is a measured process result. Buy or schedule around usable metal mass, full cycle time, yield, and the slowest downstream step—not a maximum capacity badge. The strongest ToAuto evidence would be a revision-matched, multi-cycle test log with energy, temperature, yield, and downtime fields.
