Appearance
A European spindle manufacturer runs a TBT ML250 deep hole drilling machine producing coolant holes in shafts 20–50 mm diameter, 75–550 mm long. Cycle times vary from 3 to 30 minutes, keeping one operator tied to the machine. The manufacturer implements a Halter LoadAssistant robot cell with double-sided gripper and 176-position grid plate storage. The robot loads four shafts at a time via buffer stations. Average loading cycle: 3.5 minutes. The cell runs one attended shift plus an unattended night shift, doubling production capacity without adding labour.
Why Automate Deep Hole Drilling Workpiece Loading?
Deep hole drilling presents specific challenges for manual loading:
| Challenge | Impact | Automation Benefit |
|---|---|---|
| Long, varying cycle times | Operator idle time or absent during short cycles | Robot tends the machine continuously |
| Heavy workpieces | Manual handling fatigue, injury risk | Robot handles weight safely |
| Oil and coolant environment | Slippery floors, operator exposure | Robot works in the environment |
| High-value parts | Scrap from handling damage | Consistent, controlled handling |
| Multiple operations per part | Gundrill + ream + rifle (e.g., barrel cells) | Robot transfers between machines |
The primary motivation is typically not headcount reduction but machine utilisation improvement — ensuring the deep hole drilling machine runs during breaks, shift changes, and unattended periods.
Automation Methods
Comparison
| Method | Typical Payload | Workpiece Length | Flexibility | Relative Cost | Best For |
|---|---|---|---|---|---|
| 6-axis robot cell | 10–200 kg | Up to 1,000 mm | High | High | Mixed batches, multiple machines |
| Gantry loader | 50–500 kg | Up to 3,000 mm | Low–Moderate | Moderate | High volume, long shafts |
| Walking beam / conveyor | 10–100 kg | Up to 500 mm | Low | Low | High volume, identical parts |
| Pallet changer | 100–1,000 kg | Up to 2,000 mm | Low | Moderate | Heavy, large parts |
| Bar loader (automatic) | Up to 500 kg | Up to 6,000 mm | Very low | Low | Bar stock, continuous production |
Robot Cell (6-Axis)
The most flexible option. A 6-axis industrial robot (FANUC, KUKA, ABB, or similar) picks raw workpieces from a storage system, loads them into the deep hole drilling machine, and removes finished parts.
Key design elements:
- Gripper — double-sided or quick-change gripper for raw/finished parts
- Part storage — grid plates, pallets, or conveyor for raw and finished parts
- Buffer stations — pre-staging positions to decouple robot and machine cycles
- Safety system — light curtains, interlocks, and protective fencing
- Controller integration — robot communicates with the drilling machine PLC
Gantry Loader
A gantry system spans the machine working area and transfers workpieces along a linear axis. Suitable for long, heavy shafts where a robot's reach is insufficient.
Key considerations:
- Linear axis length must accommodate workpiece length plus clearance
- Gripper travels above the machine, requiring headroom
- Part storage is typically at one or both ends of the gantry
Integration with Existing Machines
Most deep hole drilling machines can be retrofitted for automated loading:
- Verify the machine has a standard interface for external loading (automatic chuck / steady rest open-close, cycle start signal)
- Install sensors to confirm workpiece presence and position before clamping
- Provide electrical and pneumatic connections for the gripper system
- Program the robot and machine controller handshake sequence
- Implement collision avoidance logic
Tip: The simplest retrofit path is to use the machine's existing M-code interface. Most deep hole drilling machines have spare M-functions that can control chuck open-close, steady rest retract, and cycle start. No machine control modification is needed — only the robot-to-machine handshake signals.
Cell Design Principles
Robot-to-Machine Handshake Sequence
- Machine completes cycle, spindle stops, tool retracts
- Robot signals "request load/unload"
- Machine confirms: spindle stopped, chuck open, steady rest retracted
- Robot removes finished part, places raw part
- Robot confirms: part seated, gripper clear
- Machine closes chuck, advances steady rest, starts cycle
- Robot moves finished part to output
Cycle Time Management
The most important design principle: decouple robot cycle time from machine cycle time.
If the robot must load and unload during machine idle time, the loading sequence is on the critical path. Strategies to minimise idle time:
| Strategy | How It Works | Idle Time Reduction |
|---|---|---|
| Double gripper | Robot carries raw part in one gripper, finished in other — swap in one motion | 50–70% |
| Buffer staging | Robot pre-stages raw parts at buffer stations while machine runs | 80–90% |
| Batch loading | Robot loads multiple parts into buffer, machine pulls them one by one | 90%+ |
| Dual-station workholding | Machine has two spindles — robot loads one while the other cuts | 95%+ |
The Halter cell at Ott-Jakob uses buffer staging with four-part batch loading, achieving a 3.5-minute average load cycle with most of the loading happening while the machine is cutting.
Gripper Design
| Workpiece Type | Gripper Type | Notes |
|---|---|---|
| Cylindrical shafts (consistent OD) | V-jaw gripper with serrated pads | Self-centering, accommodates diameter variation |
| Cylindrical shafts (varying OD) | Three-jaw concentric gripper | Centres the part regardless of diameter |
| Stepped shafts | Custom-contoured gripper fingers | Matches the workpiece profile |
| Blind bore parts | Internal expanding mandrel | Grips from the bore |
| Finished surfaces | Soft jaws or rubber pads | Protects surface finish |
Storage System Design
| System | Capacity | Suitable For |
|---|---|---|
| Grid plate | 50–200 positions | Shafts up to 600 mm, small to medium batches |
| Pallet stacker | 10–50 pallets | Larger parts, mixed production |
| Conveyor | Continuous | High volume, single part family |
| Magazine / tube | 20–100 pieces | Bar stock, short parts |
Case Studies
Case 1: Ott-Jakob / Halter — TBT ML250 Robot Cell
| Detail | Description |
|---|---|
| Machine | TBT ML250 deep hole drilling machine |
| Workpiece | Spindle coolant holes, 20–50 mm diameter, 75–550 mm long |
| Robot | Halter LoadAssistant Universal Premium 35 |
| Storage | 176-position + 88-position grid plates |
| Gripper | Double-sided end effector with custom fingers |
| Loading strategy | 4-part batch with buffer stations |
| Load cycle | 3.5 minutes (being optimised) |
| Results | One attended shift + unattended shift, doubled capacity |
Case 2: Mollart / FANUC — 3-Machine Barrel Cell
| Detail | Description |
|---|---|
| Machines | 3 deep hole drilling machines |
| Workpiece | Hydraulic transmission shafts, 384 mm deep holes |
| Robot | FANUC M-20iD/25 on gantry rail |
| Control | FANUC Series 35i-Model B multi-path CNC |
| Result | 90%+ uptime efficiency, 0.2 mm positional accuracy |
Case 3: TBT / Glumann — ML500 Automated Shaft Line
| Detail | Description |
|---|---|
| Machine | TBT ML500 with BTA/STS drilling |
| Workpiece | Shafts 80–140 mm diameter, 500–2,000 mm long |
| Loading | Two-level chain conveyor + two-armed gantry |
| Control | Fully integrated into machine CNC |
| Operation | Operator enters only length, diameter, and depth |
Case 4: UNISIG — Flexible Automation Platform
| Detail | Description |
|---|---|
| Approach | Modular automation (robot, gantry, conveyor, pallet changer) |
| Applications | Aerospace landing gear, rifle barrels, automotive shafts |
| Integration | Single supplier for machine + automation |
ROI Analysis
Typical Costs
| Component | Cost Range |
|---|---|
| 6-axis robot cell (complete) | £60,000–150,000 |
| Gantry loader system | £40,000–100,000 |
| Conveyor / walking beam | £15,000–40,000 |
| Integration engineering | £10,000–30,000 |
| Safety system | £5,000–20,000 |
| Tooling / grippers | £5,000–20,000 |
| Total (typical robot cell) | £80,000–250,000 |
Typical Savings
| Saving Source | Annual Value |
|---|---|
| Labour — one operator per shift | £30,000–50,000 |
| Labour — unattended shift (same operator runs 2 machines) | £25,000–40,000 |
| Machine utilisation increase (20–40% more cutting time) | £15,000–50,000 |
| Reduced handling damage / scrap | £2,000–10,000 |
Payback Period
| Scenario | Typical Payback |
|---|---|
| 1 machine, 2 shifts, robot replaces 1 operator | 18–30 months |
| 1 machine, 3 shifts (lights-out), robot enables +1 shift | 12–18 months |
| 2 machines, 1 robot tending both | 10–16 months |
| 3+ machines, automated transfer line | 8–14 months |
Warning: Do not underestimate the cost of integration and commissioning. The robot hardware is typically 40–50% of the total project cost. Programming, sensors, safety system, and commissioning account for the remaining 50–60%. A £100,000 robot may represent a £200,000+ total project.
Implementation Challenges
| Challenge | Impact | Mitigation |
|---|---|---|
| Workpiece variation | Gripper design complexity | Use adjustable or quick-change grippers |
| Coolant / chip environment | Sensor contamination, gripper slip | Use sealed sensors, textured gripper pads |
| Machine interface compatibility | Communication failures | Use standard fieldbus (Profinet, EtherCAT) |
| Collision risk during loading | Machine damage, part scrap | Redundant position sensors, force monitoring |
| Cycle time matching | Machine idle waiting for robot | Buffer staging, double gripper |
| Long setup for batch changes | Robot reprogramming time | Offline programming, quick-change gripper |
| Safety validation | Delayed commissioning | Engage safety integrator early |
| Operator acceptance | Resistance to automation | Involve operators in design, training programme |
Troubleshooting
| Problem | Likely Cause | Correction |
|---|---|---|
| Robot cannot pick part repeatably | Storage position tolerance too loose | Calibrate storage positions, use vision or force sensing |
| Gripper slips on oily workpiece | Gripper pad material wrong | Replace pads with high-friction material (urethane, ceramic) |
| Machine waits for robot at cycle start | Buffer stations empty | Verify robot scheduling logic, increase buffer size |
| Robot crashes into machine during load | Position offset after maintenance | Re-teach loading positions after any machine alignment work |
| Part not seated in chuck | Chip on locating surface | Add air blow-off at loading station |
| Scratches on finished bore | Gripper damage | Inspect gripper pads, replace if worn |
| Robot stops with no error | Safety interlock tripped | Check all safety gates, light curtains, and emergency stops |
| Communication timeout | PLC handshake signal lost | Check fieldbus connection, verify signal timing |
FAQ
Why automate workpiece loading for deep hole drilling?
The primary benefit is machine utilisation — automated loading enables unattended operation during breaks, shift changes, and night shifts, increasing cutting time by 30–100%.
What automation options are available for deep hole drilling?
Robot cells (most flexible), gantry loaders (long shafts), walking beam conveyors (high volume), pallet changers (heavy parts), and bar loaders (bar stock).
Can existing deep hole drilling machines be retrofitted for robotic loading?
Yes — most machines can be retrofitted using spare M-code interfaces for chuck open-close, steady rest retract, and cycle start. No machine control modification is typically needed.
How long does it take to implement a robot loading cell?
Typical project timeline: 12–20 weeks from order to production. Design 4–6 weeks, build 6–8 weeks, integration and commissioning 2–6 weeks.
How much does a robot loading cell cost for a deep hole drilling machine?
Total project cost (robot, safety system, integration, tooling): £80,000–250,000. The robot itself is 40–50% of this.
What is the typical payback period?
12–30 months depending on the number of shifts and utilisation improvement. Multi-machine cells pay back faster than single-machine cells.
Can one robot tend multiple deep hole drilling machines?
Yes — robots mounted on gantry rails can serve 2–4 machines. The Mollart/FANUC cell demonstrates this configuration with 3 machines.
What gripper type is best for cylindrical shafts?
Double-sided V-jaw grippers with serrated or urethane pads are standard for shafts. The double-sided design allows the robot to pick a raw part and remove a finished part in one motion.
How does the robot and machine communicate?
Typically through digital I/O handshake signals or fieldbus (Profinet, EtherCAT). The robot requests load/unload, the machine confirms safe state, the robot loads, and the machine starts.
Is unattended (lights-out) deep hole drilling feasible with robotic loading?
Yes — the Ott-Jakob cell at TBT runs unattended shifts regularly. Requirements: reliable chip evacuation, tool monitoring, coolant level monitoring, and collision detection.
Summary
Robotic and automated workpiece loading for deep hole drilling machines is a proven technology that delivers substantial productivity gains:
- Methods — 6-axis robot cells (most flexible), gantry loaders (long shafts), walking beam conveyors (high volume), pallet changers (heavy parts)
- Cell design — double grippers, buffer staging, and batch loading minimise machine idle time
- Integration — most machines can be retrofitted via spare M-code interfaces without control modification
- ROI — 12–30 month payback typical; multi-machine cells pay back faster
- Unattended operation — proven in production, requires reliable chip evacuation and tool monitoring
- The spindle manufacturer in the opening scenario doubled production capacity by adding a robot cell that runs one attended shift plus one unattended night shift, without adding labour