01 -- How the Model Works
Most capacity estimates use a single nameplate CPH figure and one OEE factor. That approach fails on multi-machine lines because it does not account for placement share imbalance between machines, and it ignores the reflow oven as an independent constraint. This workbook models the line properly.
Utilisation-based output
Rather than outputting a single peak PCBs/hour figure, the workbook calculates required machine hours per product and compares the total against your net available hours per year. Products with different panelization and component counts consume very different amounts of line time, and this model makes that visible.
Per-product calculation
Each product in the mix table has its own PCBs per panel, components per PCB, double-sided flag, and panel length. Placer cycle time and oven cycle time are calculated separately per product. The workbook identifies the bottleneck machine per product and derives net PCBs per hour and required hours per year independently for each.
02 -- Section 1: Pick-and-Place Machine Table
Enter up to five machines. A typical line has one chip shooter for passives and a flexible placer for ICs and connectors. Enter at least one. The line cycle time is determined by the machine with the longest cycle time for its share of the placements.
Nameplate CPH
The theoretical maximum from the machine specification sheet, not your real-world speed. Use the published IPC-9850 or manufacturer figure. Real-world speed is accounted for by the Performance factor in the next column.
OEE Performance %
How fast this specific machine actually runs relative to its nameplate. Accounts for feeder misfeeds, head optimisation gaps, and program efficiency. Enter per machine because a chip shooter and a flexible placer rarely run at the same efficiency. Typical range 80–92%.
Placement Share %
What percentage of the board's total placements this machine handles. All machines must sum to exactly 100%. Cell E12 shows the running total and flags a warning if the sum is off. The workbook will not produce correct results if shares do not sum to 100%.
Line CT = MAX of all machine cycle times
Machine CT (s) = (placements x share% / 100) / (CPH x Performance% / 100) x 3600
The bottleneck machine is the one with the longest cycle time for its share of placements. This is product-specific. A chip shooter bottleneck on a passive-heavy board may become a flexible placer bottleneck on a connector-heavy board. The workbook calculates this per product row.
03 -- OEE: Three Components
Performance is entered per machine in the machine table. Availability and Quality remain line-level inputs because they affect the whole line equally.
Performance (per machine)
In the machine table. How fast each machine actually runs versus nameplate. Typical 80–92%. Different machines on the same line often have different Performance values.
Availability (line-level)
Planned uptime divided by available time. Unplanned breakdowns and preventive maintenance go here. Changeover is handled separately in section 3 and should not be included in Availability. Typical 75–90%.
Quality / FPY (line-level)
First-pass yield. Boards that fail and require rework consumed machine time for no productive output. Typical SMT line 95–99%.
Net PCBs/h = Mechanical PCBs/h x Availability% / 100 x Quality% / 100
04 -- Section 2: Reflow Oven
The oven is modelled as a separate throughput constraint independent of the placer. Tunnel length, dwell time, and load factor are line-level. Panel length is per-product because different assemblies may have different panel sizes.
Heated Tunnel Length
Enter the heated length only, not the overall oven length. Typical values: 5-zone approximately 180 cm, 7-zone approximately 250 cm, 10-zone approximately 360 cm. Always verify against your specific model datasheet.
Required Dwell Time
Total time the board must spend inside the heated tunnel per your paste datasheet. For SAC305 typical range is 240–300 seconds. This limits how fast the belt can run.
Oven Load Factor
How densely packed the belt is. 90% means a gap of 10% of panel length between panels. Below 85% risks collisions at the conveyor entry. Panel pitch = panel length / load factor.
Panel Length (per product)
Entered in the product mix table. The panel dimension in the direction of belt travel including any tooling frame. Each product can have a different panel length, which directly determines oven throughput for that product.
Oven CT (s) = (panel length / load factor) / (tunnel / dwell x 60) x 60
05 -- Section 3: Changeover & Planned Stops
Changeover time is a planned loss that sits outside OEE. The workbook subtracts it from gross available hours before any capacity calculation. This makes it visible as a separate number rather than buried inside Availability.
Full Changeovers / Week
Complete product changeovers per week: new stencil, full feeder swap, program change, first article inspection. On a short-run mixed line typically 4–10 per week.
Changeover Duration
Average time per full changeover in minutes. A simple well-organised swap: 45–60 min. Complex changeover with fixture changes and full first article: 2–4 hours. Use your real average, not the best case.
Minor Stops Buffer
Small recurring stops per shift: feeder reloads, paste replenishment, stencil wipe cycles. Default 20 minutes per shift. They accumulate. Track your actual data if available.
Net hours/week = Gross hours - (changeovers x duration/60) - (minor stops/shift / 60 x shifts x days)
A line running 4 full changeovers at 90 minutes each loses 6 hours per week before OEE is applied. On a single-shift 40-hour week that is 15% of capacity gone before the first board is placed.
06 -- Section 5: Product Mix Table
Up to 8 products, each fully independent. Panelization and panel length are entered per product. The workbook calculates placer and oven cycle times separately for each and identifies which is the bottleneck.
PCBs per Panel
How many individual PCBs sit in one production panel. Enter 1 for single boards. Enter 6 for a 2x3 array. Affects placer cycle time: a 6-up panel has 6 times the placements per machine cycle as a single board but also produces 6 PCBs per cycle.
Components per PCB
Total SMT placements on one individual PCB, not per panel. The workbook multiplies by PCBs per panel automatically. Count all SMT placements including passives, ICs, and connectors.
Double-sided (0 or 1)
Enter 1 if the board requires two SMT passes. This doubles the effective machine time consumed per panel and halves PCB output per hour. The most common source of capacity planning errors on mixed assemblies. Enter 0 for single-sided.
Panel Length (cm)
Panel dimension in the direction of belt travel including any tooling frame or break-off tabs. Different products can have different panel sizes. This feeds directly into oven cycle time for this product.
07 -- Reading the RESULTS Sheet
A
Pick-and-Place Machines
Summary of your machine table: nameplate CPH, Performance %, effective CPH, and placement share per machine. Verify this reflects your actual configuration before reading capacity figures.
B
Changeover & Available Hours
Gross hours, changeover loss, minor stops loss, and net productive hours per week and per year. This is the real available time that all products compete for.
C
Per-Product Capacity Analysis
For each product: placer cycle time, oven cycle time, which is the bottleneck, net PCBs per hour, required hours per year, and percentage of net annual capacity consumed.
D
Net Capacity Summary
Net hours per year, total required hours, available headroom in hours, and total line utilisation as a single large percentage.
E
Line Status Verdict
One of three states based on total utilisation. Below 70% the line has comfortable headroom. 70–85% is achievable but tight. Above 85% the line is overloaded for the current shift model.
K–U
Hidden Helper Columns
Intermediate calculations per product: individual machine cycle times, line CT, oven CT, bottleneck CT, mechanical PCBs/h, net PCBs/h, required hours. Hidden for cleanliness. Unhide to audit the math.
FEASIBLE -- below 70%
HIGH LOAD -- 70–85%
OVERLOADED -- above 85%
08 -- Common Planning Mistakes
01
Placement shares that do not sum to 100%
If shares sum to 80%, 20% of placements are unaccounted for and cycle time is wrong. Cell E12 shows the running total and warns you. Do not proceed until it reads 100%.
02
Confusing panels with individual PCBs
Components per PCB means one board, not one panel. If running a 4-up panel with 150 components per board, enter 150 for components and 4 for PCBs per panel. The workbook multiplies them internally.
03
Forgetting double-sided assembly
A double-sided assembly goes through the line twice. Entering 0 when the board is double-sided doubles apparent capacity and halves required hours. If you produce a mix of single and double-sided boards, enter them as separate products.
04
Using nameplate CPH as actual speed
Nameplate CPH is measured under ideal lab conditions. The Performance OEE per machine adjusts for real conditions. If you leave Performance at 100%, capacity will be overstated by 15–25% on a typical SMT line.
05
Putting changeover inside Availability
Changeover is a planned, predictable loss. OEE Availability measures unplanned downtime. If you bury changeover inside Availability it compounds multiplicatively with other OEE losses and becomes invisible as a separate improvement target. Keep it in section 3.