In mechanical engineering, industry and technical trade, a large share of profit is not decided at the sale of the machine but over its entire lifetime -- in the spare-parts and service business. Depending on the segment, service accounts for 15 to 30 percent of revenue in German mechanical and plant engineering (VDMA), and spare parts are its most profitable building block. The average EBIT margin in industrial aftersales is around 25 percent versus about 10 percent in the new-machine business (McKinsey). A digital spare-parts catalog in the B2B shop lifts exactly this profit: it makes parts uniquely findable, shows live availability and customer-specific prices, attaches technical documentation to the item and enables round-the-clock self-ordering -- without asking sales. This guide shows what matters and why the real work sits in connecting the data.
Key takeaways
- Aftersales delivers an average EBIT margin of roughly 25 percent (McKinsey) versus about 10 percent for new machinery, with pure parts sales often above 30 percent gross margin (McKinsey). Service accounts for 15 to 30 percent of German machinery revenue (VDMA).
- A workable catalogue offers several routes to the same part: the OEM number plus superseded, successor and cross-reference numbers, entry by machine or serial number, an interactive exploded drawing, and attribute search by dimension, material or connection type.
- Stock level, lead time and the customer's own net price live in the ERP and are read per request rather than stored statically in the shop. An in-stock label that turns out to be wrong costs more credibility than an honestly stated delivery date.
- Data sheets, dimensional drawings, installation notes and certificates belong on the item page, fed from the PIM. They answer the fit question before the order is placed and cut back-and-forth queries, wrong orders and returns.
- Round-the-clock self-ordering does not remove inside sales, it redirects it: standard parts flow through unattended while freed-up time goes to advisory cases, large orders and new customers. B2B buyers now use around ten interaction channels per purchase journey (McKinsey).
- The real work sits in the interfaces: parts master with cross-references, stock per location, price determination, documents, and writing the order back into the ERP. A data audit before the technical connection exposes gaps that otherwise cause wrong orders.
Why Spare Parts Are the Most Profitable Revenue Driver
German mechanical and plant engineering generated revenue of around 254 billion euros in 2024 (VDMA) and employs over one million people (Statista). A substantial and disproportionately profitable part of this business only arises after the initial sale. Analyses across 30 industries show an average EBIT margin in aftersales of 25 percent -- more than double the roughly 10 percent in the new business (McKinsey). According to Deloitte, the operating margin in aftersales is on average about 2.5 times the margin from selling new equipment (Deloitte). Spare parts stand out in particular: pure parts sales often reach gross margins of over 30 percent (McKinsey).
The reason is structural. A machine sold once often stays in the field for ten, fifteen or more years and needs wear and spare parts over that time. This demand is more predictable and less price-elastic than the new business, because machine downtime is almost always more expensive than the part itself. Anyone who does not serve the supply for their installed base themselves leaves it to the free parts market -- and gives away both margin and customer contact. A digital spare-parts catalog is the channel through which manufacturers and technical trade keep this value creation in-house.
Key finding
What a Digital Spare-Parts Catalog Must Deliver
A spare-parts catalog in the B2B shop is more than an item list. It has to guide the technical buyer, the maintenance engineer and the service technician to the right part as fast as an experienced back office could on the phone -- only around the clock and without waiting. This matches buying behavior: according to Forrester, more than half of large B2B purchases are now handled through digital self-service channels (Forrester), and 97 percent of retail companies already run their own web shop as the most-used digital sales channel (Bitkom). Six capabilities decide whether a spare-parts catalog truly works.
Unique part identification
Via part number, machine and serial number, exploded drawing or category, the catalog leads reliably to exactly the right item -- without any risk of confusion.
Live availability
Current stock and delivery time arrive at the item in real time from the ERP. The customer sees before ordering whether and when it ships.
Customer-specific prices
Framework agreements, customer groups and volume prices are taken from the ERP. Each customer sees their personal net price instead of a list value.
Technical documentation
Data sheets, drawings, installation notes and certificates sit directly on the part. This reduces queries, wrong orders and returns.
24/7 self-ordering
The customer orders independently -- at night, on weekends or from an international plant. No waiting for a callback, no time-zone problem.
Reorder from history
Order lists, machine records and order history turn repeat purchases into a one-click action -- the most common case in the spare-parts business.
Unique Part Identification as the Foundation
The biggest hurdle in the spare-parts business is not the purchase but finding the right part. A maintenance engineer often knows only the machine, not the item number of the faulty component. A wrongly ordered part means a return, extended downtime and frustration. A good catalog therefore offers several paths to the same goal and merges them cleanly. The basis for this is structured, well-kept part data -- a topic closely linked to sound product data care and PIM quality.
- Direct search via the original part number (OEM) including old, successor and cross-reference numbers, so that outdated designations also lead to the current item.
- Entry via machine or serial number: the customer selects their equipment, the catalog shows only the matching spare parts -- no confusion across product ranges.
- Interactive exploded drawing: a click on the position in the drawing leads straight to the item with price and availability.
- Attribute and full-text search over technical features such as dimensions, material, power or connection type when the part number is unknown.
Only combining these paths makes the catalog robust. Offering only a part-number search loses every customer who does not know that number. Adding the machine assignment turns the installed base into a precise ordering assistant. Exactly here it is decided whether the customer orders themselves or reaches for the phone again.
Practical tip: build in cross-references from the start
Live Availability and Prices from the ERP
Two pieces of information decide conversion in a spare-parts purchase: is the part available, and what does it cost me specifically? Both values live in the ERP, not the shop. Stock changes with every pick, delivery time depends on procurement, and the price follows the framework agreement, customer group and order quantity. A catalog that works with outdated or flat values here loses trust -- a displayed 'available' that is wrong costs more credibility than an honest delivery time.
That is why ERP integration between shop and inventory management is the technical heart of a spare-parts catalog. Stock and delivery time are read from the ERP in real time or in short intervals, customer-specific prices are determined per request instead of stored statically in the shop. This way every logged-in customer sees their own net price, their conditions and the real stock. The clean implementation of these data flows is the focus of our integrations and interfaces.
A catalog is only as good as its data
Technical Documentation on the Item
Spare-parts buyers are technicians. Before ordering, they want to know whether the part fits, how it is installed and which standard it meets. When data sheet, dimensional drawing, installation note and certificate sit directly on the item, queries and wrong orders drop noticeably -- and sales is relieved of recurring standard enquiries. These documents usually come from the product information system (PIM), which maintains them centrally and hands them to the shop via the interface. For variant-rich assemblies the catalog can also be connected to a product configurator and guided selling that guides the right version instead of leaving customers to guess.
A spare part sells not on price but on the certainty that it is the right one. That certainty comes from documentation on the item -- not from a callback on the next business day.
24/7 Self-Ordering Without Asking Sales
The real efficiency gain lies in self-service. Today, a spare-parts order still runs in many companies via phone, email or fax: the customer describes the part, the back office identifies it, checks stock and price, sends a quote, the customer confirms. This process ties up sales capacity and costs hours to days. A digital catalog reverses it. According to McKinsey, B2B customers now use an average of ten interaction channels across the buying journey and expect, following the 'rule of thirds', one third each in-person contact, remote interaction and full self-service (McKinsey). The spare-parts purchase is the prime case for the third third -- standardized, recurring, technically unambiguous.
| Criterion | Manual ordering | Digital catalog |
|---|---|---|
| Part search | Description to the back office | Number, machine or drawing |
| Availability | Query required | Live from the ERP |
| Price information | Wait for a quote | Customer price shown instantly |
| Ordering window | Office hours | Around the clock, any time zone |
| Sales effort | High, per order | Low, only exceptions |
| Reorder | New enquiry | One click from history |
Sales does not disappear here, it is redirected. Instead of typing up standard orders, it handles advice-intensive cases, large orders and new customers. Recurring spare-parts orders run via quick order and order lists, while machine records and prices are bundled in the B2B customer portal with self-service. This lowers the effort per order while the number of processable orders rises.
From Data Silo to Live Catalog: the Integration Work
The interface of a spare-parts catalog is built in a few weeks. The real work -- and the value -- lies in bringing the spare-parts data from ERP and PIM into the shop live and correct. B2B online trade handled via websites, shops and marketplaces in Germany reached around 509 billion euros in 2024 (ECC Cologne) and already accounts for 12.1 percent of the total revenue of wholesalers and manufacturers (IFH Cologne); for 2025 a further 6.3 percent of growth is expected (ECC Cologne). At the same time, 78 percent of retail companies already sell via marketplaces (Bitkom), where 67 percent see rising price pressure from discount platforms (Bitkom). An own, data-sovereign spare-parts catalog is the answer -- but only if the data flows.
- Part master and structure: map item numbers, designations, cross-references and machine and assembly assignment from ERP and PIM cleanly into the shop data model.
- Stock and delivery time: live or interval synchronization of stock per location so that the displayed availability is reliable.
- Prices and conditions: determine customer-specific net and volume prices per request from the ERP instead of storing them statically.
- Documents and media: bind data sheets, drawings and certificates from the PIM to the right item.
- Order write-back: write the order triggered in the shop back into the ERP as a document, so that picking and invoicing are end-to-end.
This connection is our focus. We link Shopware Open Source via integrations and interfaces with ERP, PIM and accounting, so that the spare-parts catalog stays live and calculates correctly. To connect to the existing procurement systems of large customers, a punchout and OCI integration complements the catalog so that spare parts can also be ordered directly from the customer's purchasing system.
Risk of poor master data
In Four Steps to a Digital Spare-Parts Catalog
A spare-parts catalog does not emerge as a big bang but step by step along data quality. The following order has proven itself because it puts the foundation before the interface.
- Data audit: review part master, cross-references, machine assignment, documents and pricing logic and close gaps -- the basis for everything else.
- Build interfaces: connect ERP and PIM via robust integrations, bring stock, prices and documents into the shop live and set up the order write-back.
- Design catalog and search: build part search, machine entry, exploded drawing and item page with availability, price and documentation.
- Rollout and self-service: connect customers, activate order lists and machine records, focus sales on exceptions and continuously extend the catalog with parts and data.
Shopware Open Source is well suited as a foundation because it is open source, comes without license costs and adapts to B2B requirements such as customer-group prices, volume discounts and role permissions. In our individual Shopware development we build from it a spare-parts catalog that can be part of a complete B2B portal with self-service. Whether the catalog runs standalone or is embedded in a broader channel strategy is settled by the trade-off between own shop and marketplace -- the data-sovereign base remains the own catalog in both cases.
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