2.1 Machine Architectures
The choice of Pick-and-Place (PnP) architecture defines the DNA of your Surface Mount Technology (SMT) line, setting the fixed trade-off between raw speed (CPH), component flexibility, and capital investment (CapEx). You are essentially choosing how the machine manages the physics of movement, which dictates two major production variables: Takt Time and Changeover Efficiency.
2.1.1 The Two Core Architectures: Gantry vs. Turret
Modern high-speed placement machines primarily use one of two fundamental movement systems. Choosing between them determines your machine's optimal product mix.
Feature | Modular/Gantry Systems (Flexible Mounters) | Rotary/Turret Systems (Chipshooters) |
Motion System | X-Y gantry, moving over a stationary board. | Rotary head spins components past stationary vision. |
Placement Speed (CPH) | Moderate to High. (Up to 80k CPH per module) | Extremely High. (Often ≥ 100k CPH) in pure chip mode) |
Component Range | Excellent. Handles everything from 01005 to large, odd-form, heavy connectors, QFPs, and BGAs. | Limited. Best for small passives (01005 – 0603). Struggles with heavy/large ICs. |
Placement Accuracy | Superior. Uses linear encoders and dedicated Z-axis control. Essential for ≤ 0.4 mm pitch. | Good but generally lower for large components due to high speed/inertia. |
Changeover Time | Fast. Component swap is typically managed via smart feeders/cart changes. | Slow. Fixed feeder banks mean high cost/time for swapping parts not in the bank. |
CapEx/Flexibility | High CapEx initially, but excellent scalability (add modules/gantries) and flexibility (high-mix capability). | Lower CapEx per placement, but fixed capability and poor high-mix performance. |
Strategic Takeaway: If your EMS business is High-Mix/Low-Volume (HMLV) with frequent product changeovers, you want Flexible Modular/Gantry systems. If you run one board for weeks/months (High-Volume/Low-Mix), a Turret system is the most cost-effective way to get sheer speed on passives.
2.1.2 Line Topologies: Aligning the Flow to Your Mix
How you arrange the PnP machines in the line must match the board's component distribution and your required Takt Time.
1. Role Split (Chipshooter – Flexible)
- Setup: Chipshooter (PnP1) handles all high-volume passives, then the board moves to the Flexible Mounter (PnP2) for large/complex ICs.
- When it Wins: Boards dominated by thousands of small chips and relatively few large parts. This maximizes speed by pushing the fast work to the fastest machine.
- Watch-Out: If the flexible mounter becomes the bottleneck (Constraint), the chipshooter sits idle waiting. Requires disciplined load balancing (see below).
2. Tandem Split (Flexible A – Flexible B)
- Setup: Two flexible mounters of similar capability run in series, splitting the component count roughly 50/50
- When it Wins: The most common setup for HMLV. It simplifies feeder management (as parts can run on either machine), speeds up changeovers, and offers redundancy.
- Watch-Out: Requires symmetrical programming and near-perfect load balancing to avoid bottlenecking.
3. Dual-Lane / Parallel Processing
- Setup: The entire line (Printer, PnPs, Reflow) processes two PCBs simultaneously on two separate conveyor tracks, or the PnP machine internally handles two boards at once.
- When it Wins: Extremely short boards or highly aggressive Takt Time requirements where placement time is the constraint. Ideal for "pack-and-stack" products.
- Watch-Out: Requires twice the number of feeders or mirrored feeder setups for both lanes, significantly increasing kitting complexity and OpEx.
2.1.3 Load Balancing: Protecting Your Takt Time
The line Takt Time is always set by the slowest process step (the Bottleneck). In a PnP line, this is almost always the placement machine with the highest component count or the largest variety of parts.
- Measure and Compare: Use the machine's logging data (or a simulation tool) to calculate the placement time per board for each machine, excluding board travel time.
- Target 10% Symmetry: Your goal is for the cycle times of all PnP machines in the line to be within ± 10% of each other.
- The Fix: If PnP2 is 20% slower than PnP1, re-allocate the simplest, highest-count parts (e.g., 10kΩ resistors or common 100 nF caps) from PnP2 back to PnP1 until the times equalize.
- Protect the Constraint: Once balanced, treat the slowest machine (your current Takt constraint) as sacred. Never add more difficult parts or increase its feeder change frequency.
Uptime Rule: Maximize Permanent Feeder Banks. By keeping 80% of your common components (like 0402 passives) in fixed slots, you massively reduce the time and risk involved in every single changeover, cutting down on OpEx and kitting errors.
2.1.4 Strategic Feeder Management
Feeder capacity and changeover are the daily operational killers.
- Feeder Density: Gantry systems generally offer higher feeder capacity per machine footprint than older turret systems, allowing you to run boards with higher complexity (more unique part numbers).
- Smart Feeders: Invest in Intelligent Feeders. These communicate their Part ID (PN) and position back to the machine software, virtually eliminating the risk of mis-kitting (placing the wrong part).
- Kitting Carts: Use dedicated kitting carts or exchange trolleys so the feeders for the next job are prepared offline, allowing the changeover time to drop from hours to minutes.