Many shops machine precisely, but few can even lift a 10-tonne part. Choosing a large part machining service therefore needs a special partner.
As a precision engineering and CNC manufacturer in Werl, Vulcanus machines heavy components up to 10 tonnes daily.
This guide shows the seven key criteria for choosing a supplier. It helps you avoid costly wrong decisions.
Key Takeaways
- Few shops have the machines, cranes and metrology for parts weighing several tonnes.
- Machine travel, table load and crane capacity matter more than the hourly rate alone.
- Every extra setup costs accuracy, so complete machining counts.
- Large parts need portable metrology rather than conventional measuring machines.
- Welding, stress relieving and machining from one source shorten routes and reduce risk.
What Counts as a Large Part?
There is no fixed limit. In practice, parts from around two metres long or several tonnes in weight count as large. At this size, parts no longer fit standard machining centres.
Typical Large Parts
- Machine beds, columns and frames
- Housings for gearboxes, pumps and presses
- Shafts, rotors and rolls
- Welded structures for crane and plant construction
- Plates, flanges and large-diameter rings
Typical Materials
- Structural steels and high-strength fine-grain steels
- Quenched and tempered steels such as 42CrMo4
- Grey cast iron and ductile iron
- Stainless and heat-resistant chromium-nickel steels
Material strongly affects cutting data, tooling cost and machining time. Our guide to CNC material selection covers the basics.
Our article on CNC machining for large parts gives an overview of processes, machine types and industries. This article focuses on choosing the right supplier.
Why Few Shops Machine Large Parts
Large machines are expensive and need a lot of floor space. Crane runways, foundations and experienced staff come on top. For many contract shops, this investment does not pay off.
With large parts, the first question is not precision. It is whether the part gets onto the table safely.
The result is a small market with limited capacity. That makes careful selection all the more important.
Large Part Machining Service: 7 Criteria for Choosing a Supplier
1. Machine Travel and Working Envelope
X, Y and Z travel determine the maximum part size. Height including the tool matters as much as length. Also check whether all faces can be reached without re-clamping.
Five-Axis or Angle Head
Five-axis machines and angle heads reach inclined faces and holes in a single setup. This saves time and improves positional accuracy. Our article on the 5-axis milling machine explains the benefits.
2. Table Load and Workpiece Weight
Every machine has a maximum table load. If your part is close to that limit, accuracy often suffers. Ask for the permitted load including workholding.
3. Cranes and Handling
A supplier needs cranes with sufficient capacity above the machine. Suitable lifting gear and trained staff matter just as much. Without them, parts get damaged and setups take long.
Clarify Logistics From the Start
- Delivery by truck and unloading on site
- Door and hall dimensions for transport
- Lifting points or lugs on the part
- Packaging and securing for the return trip
These points belong in the quote, not in the delivery week.
4. Clamping and Complete Machining
Large parts deform under their own weight. A well-planned support and clamping concept prevents distortion after unclamping. Every extra setup introduces new positional errors.
Fixtures for Large Parts
For series of large parts, dedicated fixtures pay off. They shorten alignment and ensure the same position for every part. For single parts, shops usually work with modular supports and clamps.
Horizontal machining centres with pallet changers machine several sides efficiently. Our article on vertical vs horizontal milling shows the differences.
5. Metrology for Large Parts
Conventional coordinate measuring machines are too small for many large parts. Portable measuring arms and laser trackers are used instead. They measure directly on the machine or in the hall.
Ask for inspection reports on functionally critical dimensions. Our article on precision measurement gives the background.
Watch the Temperature
Steel expands by around 12 microns per metre per degree. On a six-metre part, a five-degree difference already means almost 0.4 mm. Reputable shops therefore record the measuring temperature.
6. Welding, Stress Relieving and Machining From One Source
Many large parts are welded structures. They carry residual stresses that release during machining and distort the part. Stress relieving before finish machining prevents this.
Our article on heat treatment of metals explains more. If welding and machining sit with the same supplier, transports and coordination loops disappear.
7. Quality System and Experience
Certified quality management to ISO 9001 is the baseline. References with comparable size and material say even more. Our article on how to choose a CNC machining supplier lists further general criteria.
Direct Technical Contacts
With large parts, questions often arise during production, for example about stock allowance or datums. A direct line to the engineer avoids waiting time. Ask who will actually handle your project.
Not Just Milling: Turning and Drilling Large Parts
Large Turned Parts
Shafts, rolls and rings need lathes with a large swing diameter. For flat, large-diameter parts, vertical turning is the right choice. A supplier with both processes saves transport between shops.
Deep Holes
Large parts often have long bores for media or shafts. They require special tooling and stable processes. Our article on deep hole drilling on CNC machines explains the details.
Questions to Ask Every Supplier
- What maximum travel and table load do your machines have?
- What crane capacity is available above the machine?
- How many setups do you plan for my part?
- What metrology do you use for large parts?
- Do you handle welding and stress relieving yourself or through partners?
- Which comparable parts have you already made?
- How do you organise transport and packaging?
The answers quickly show whether a supplier is truly set up for large parts.
What Your RFQ Should Include
A complete enquiry avoids back-and-forth and produces a reliable quote.
- Drawing and 3D data with tolerances and datums
- Material and blank condition, such as cast, forged or welded
- Blank weight and dimensions
- Quantity and target delivery date
- Requirements for inspection, documentation and certificates
Realistic manufacturing tolerance matters too. Unnecessarily tight tolerances drive cost especially hard on large parts. If the blank is cast or welded, the machining allowance should be generous enough.
Have a specific large part? Send your drawing and blank data directly through our contact form.
How a Large Part Order Runs
- Enquiry and technical review: discuss drawing, blank and requirements
- Clamping and machining concept: plan supports, setups and tooling
- Blank preparation: cutting, welding and stress relieving where needed
- Milling and turning: roughing, intermediate measurement and finishing
- Final inspection and documentation: inspection report for all critical dimensions
- Packaging and transport: safe handover at your site
Comparing Costs Correctly
The Hourly Rate Is Not Everything
A low hourly rate looks attractive. But extra setups, rework or transport between suppliers quickly cost more. What counts is the total cost up to a ready-to-install part.
Items That Belong in the Comparison
- Programming, setup and machine time
- Fixtures and special tooling
- Heat treatment and any welding work
- Measurement, documentation and certificates
- Transport, packaging and handling
Our guide on how CNC quotes are calculated explains how a quote is built.
Plan Lead Times Realistically
Large machines are usually well utilised. Plan early and agree firm dates. For cast or forged blanks, their lead time comes on top.
Warning Signs When Choosing a Supplier
- No concrete figures on travel, table load or cranes
- No references of comparable size
- Measurement only with hand gauges instead of portable metrology
- Vague answers on welding, stress relieving and transport
- A quote for a complex large part without any questions
Large Part Machining at Vulcanus
Vulcanus-Stahl & Maschinenbau in Werl is built for heavy and large components. Welding, sawing, milling, turning and measuring are all under one roof.
- Milling: 4- and 5-axis, travels up to 4,500 x 1,200 x 1,800 mm, up to 10 tonnes
- Horizontal machining centre: with pallet changer for efficient multi-side machining
- Turning: up to Ø 1,200 mm and 4,500 mm length, vertical turning up to Ø 2,380 mm
- Welding: assemblies up to 10 tonnes to DIN EN 1090-2 EXC3 and DIN EN ISO 3834-2
- Metrology: tactile FARO measuring technology, also mobile at your site
- Quality: ISO 9001 quality management
All capacities in detail are on our CNC milling services page. Our guide to CNC contract manufacturing explains how we handle orders.
A Large Part Machining Service Is Only as Good as Its Setup
With large parts, machine, crane, clamping concept and metrology together decide the result. A supplier offering every step from one source reduces risk and total cost.
Ask the right questions before you place the order. The answers quickly reveal who truly masters large parts.
Looking for a supplier for parts up to 10 tonnes? Contact Vulcanus with your drawing and blank data for a reliable quote.
FAQ: Large Part Machining
When does a part count as a large part?
Usually from around two metres long or several tonnes in weight. At that point, standard machining centres are no longer enough.
What should I look for in a large part machining supplier?
Machine travel, table load, crane capacity, metrology and references. Whether welding and stress relieving come from one source also matters.
Why does the number of setups matter so much?
Every new setup introduces positional errors. Complete machining in as few setups as possible secures accuracy.
How are large parts measured?
With portable measuring arms or laser trackers directly at the machine. The measuring temperature should be recorded.
How much does large part machining cost?
It depends on size, material, tolerances and setups. Always compare total cost up to the ready-to-install part.
What documents do I need for a quote?
Drawing, 3D data, material, blank weight, quantity and delivery date. The more complete, the more accurate the quote.