CNC Contract Manufacturing – Precision Parts to Drawing, from One-Off to Series
You have a drawing or a CAD model and you need a manufacturing partner who still delivers when tolerances are tight and materials are difficult. Bonsack Präzisionstechnik has been producing milled parts, 5-axis milled parts, turned parts and EDM components on a contract basis in Brotterode-Trusetal since 1992 — from the one-off part through small batches to automated series production.
We assess feasibility and get back to you promptly.
What CNC contract manufacturing
means at Bonsack
You define the design, we take care of the complete manufacturing process — programming, machining, finishing, inspection and packaging. You need no machines of your own, no in-house machining capacity and no staff for production planning.
The difference between suppliers rarely lies in whether a part can be made. It lies in whether it can be made reproducibly to the required accuracy — on the tenth batch exactly as on the first. That is precisely what our production is built for.
We work as an extended workbench for machine builders, plant engineers and technology companies that buy in precision components rather than machining them themselves — as a primary supplier just as readily as a second source alongside an existing one.
Our manufacturing processes at a glance
CNC milling and 5-axis simultaneous machining
Complex geometries, free-form surfaces, undercuts and deep cavities in few set-ups.
CNC turning and turn-mill parts
Rotationally symmetrical components, completed in a single set-up with driven tools and counter spindle.
Wire and die-sinking EDM
The finest contours, internal corners without a radius, carbide and hardened materials.
Toolmaking and spare parts service
Stamping and forming tools, mould making, spare parts for equipment in service.
| Parameter | Value |
|---|---|
| CNC machines in total | 20 – 12 machining centres, 2 turning centres, 6 EDM machines |
| Of those with 5-axis simultaneous kinematics | 9 |
| Travel, precision milling (X/Y/Z) | 705 × 425 × 610 mm |
| Travel, large-part machining (X/Y/Z) | 2,100 × 1,800 × 1,250 mm |
| Max. workpiece weight | 8 tonnes |
| Max. spindle speed | 20,000 rpm |
| Repeatability | under 3 µm |
| Turning diameter | up to Ø 230 mm, spindle bore 67 mm |
| Automated manufacturing | 4 robot cells, 228 pallet positions |
| Metrology room | Zeiss CONTURA G4, measuring uncertainty 2.0 + L/350 µm |
| Achievable tolerances | 1–5 µm on relevant features |
| Smallest components | under 1 gram |
The smallest part that leaves our production weighs less than a gram. At the other end stands the Deckel Maho DMU 210P: workpieces up to 2,100 × 1,800 × 1,250 mm and up to eight tonnes. Both run in the same production, under the same process control.
Four machining centres work inside robot cells – three EROWA systems and one Indunorm installation – with 228 pallet positions in total. Once the process parameters are dialled in, they keep producing overnight and at weekends without an operator.
Materials:
from aluminium to Inconel
The real difference shows in the materials that others turn down.
We machine titanium, Inconel, Hastelloy, Invar and Kovar — alloys that conduct heat poorly, tend to work-harden and wear tools quickly. Added to that is the hard machining of hardened parts by hard milling and finishing, plus the EDM of carbide wherever a milling cutter can no longer reach.
Naturally we also produce from aluminium, stainless steel, structural steel, copper, brass and engineering plastics. That is simply not the reason customers come to us.
Tolerances, metrology and documentation
On relevant features we achieve tolerances of 1 to 5 µm — depending on geometry, material and process. That is not a one-off result under ideal conditions, but the range in which we work series-capably.
The machine side for this: five of our Fehlmann machining centres hold a repeatability of under 3 µm, with spindle speeds up to 20,000 rpm. Added to that are stable clamping concepts with defined datum faces, consistent temperature control, process-capable CAM strategies and tool management that records wear before it reaches the component.
The documentation side: our metrology room houses a Zeiss CONTURA G4 with a scanning VAST XXT probe and a measuring uncertainty of 2.0 + L/350 µm — for components up to 1,200 × 1,800 × 800 mm. Supplemented by a Zeiss DURA MAX with surface roughness measurement, an optical measuring projector from Keyence and around 500 fit and thread gauges.
Inspection is tactile and optical, with a documented inspection report. On request we supply inspection records per batch or per component. Batches and programs are traceable; batch and serial numbers can be applied directly to the component by QR or Data Matrix code. Our quality management is certified to ISO 9001.
For UHV and cleanroom-compatible components, ultrasonic cleaning completes the process chain — cleaned and packed particle-free.
How working together unfolds
As a second source and during capacity peaks
Not every enquiry starts from scratch. Often the point is to secure a component that currently comes from a single source — or to absorb a peak that the established supplier can no longer cover.
We are set up for both. We take over existing drawing revisions, work our way into your existing inspection specifications and supply a first article with a complete inspection report that you can hold against your reference. Whether that becomes a permanent second source or a one-off call-off is your decision.
Framework agreements, call-off orders and stockholding
For recurring components, the individual purchase order is rarely the most economical solution. We work with framework agreements and call-off orders: you secure quantity and price over a period, but call off only what you actually need.
On request we take over stockholding on a Kanban basis. Programs, fixtures and inspection specifications stay archived — even a repeat order years later runs with the same parameters as the first batch.
Industries we manufacture for
Automotive
Precision parts and components for the vehicles of tomorrow.
Aerospace
Lightweight design, quality and safety for demanding applications in the air and in space.
Medical technology
High-precision manufacturing for life-critical medical systems.
Optics, Laser & Photonics
Components for light-based technologies at the highest precision.
Semiconductor industry
Manufacturing technology for the most complex structures in microelectronics.
Mechanical engineering
Mechanical precision parts for plant and special-purpose machinery.
Defence
Robust, reliable manufacturing for safety-critical applications.
Research
Flexible manufacturing solutions for prototypes, laboratories and test rigs.
Consumer & Food
Precision for hygienic processes.
Ultra-high vacuum industry
Precise components for extreme conditions
Frequently asked questions about CNC contract manufacturing
What is your minimum quantity?
From a quantity of 1. We produce single parts mainly as a prototype, sample or pilot run – that is, when a series will grow out of them later. We lay out parameters and the clamping strategy to be series-capable right from the first part, so that repeat orders run with identical values, even years later.
Up to what quantity does contract manufacturing with you make sense?
There is no fixed upper limit. What matters is the cycle time per component: from around 10 parts we produce automatically, and from about 50 pieces the robot cell with unattended pallet loading pays off. Beyond that, series production runs automated in 24/7 operation.
What documents do you need for a quotation?
A dimensioned drawing or a 3D model, the material, the quantity and your target date. Inspection specifications and surface requirements help us to cost it correctly straight away.
How quickly will I get a quotation?
Between 2 and 10 days, depending on project size and on external purchases (surface treatment, material, special bought-in parts where applicable).
What tolerances are achievable?
Depending on geometry and material, 1 to 5 µm on the relevant features.
Do you also machine titanium or Inconel?
Yes. Titanium, Inconel, Hastelloy, Invar and Kovar are part of our standard range, as is the machining of hardened parts.
Can you step in as a second source?
Yes. We take over existing drawing revisions and inspection specifications and supply a first article with an inspection report for comparison.
Do you deliver ready to install?
Yes — including deburring, finishing, defined surface roughness values, cleaning and, on request, particle-free packaging.