At a Glance

40K

Doors Per Week 

1M

Unique Product SKUs 

40+

Python Programs Owned 

3–5× 

Client Savings vs. Market 

The Situation : What We Set Out to Do, and What We Actually Did

Most manufacturing ERP transformations are more complex in execution versus in design. The scope that gets signed rarely reflects the full picture, because that picture only becomes visible once implementation is underway. 

OS Doors entered this engagement with a clear brief: SAP S/4HANA Public Cloud, manufacturing module, integration with an existing Python-based Manufacturing Execution System. Within four months, the brief turned into: full ownership of a 40+ program MES codebase controlling every machine in the factory. 

The resulting project took 24 months and encountered multiple layers of complexity: near-million product data at a scale SAP’s standard tools were not built for, a commercial standoff that required decommissioning the entire landscape and rebuilding it from scratch, a go-live performance issue, and a finance function that sought deeper operational integration.  

None of these are unusual in isolation. In combination, over 24 months, they test the quality of the relationship between client and partner more than they test the quality of the technology. This case study is organised around five strategic findings drawn from that test.

The Situation : What We Set Out to Do, and What We Actually Did

OS Doors is a PE-backed Irish manufacturer producing roughly 40,000 custom doors per week for contractors and builders. The manufacturing operation worked great. The financial infrastructure around it however needed operational integration to enable product-level cost tracking, consumption visibility, and precise margin measurement. The investor required granular margin data. SAP was selected to deliver end-to-end integration. 

Percipere was selected in late 2023 on the strength of being “ERP plus” – combining SAP delivery with intelligent automation and process mining. This became critical when scope expanded beyond ERP. 

Lesson 1 : “ERP ++” is not a pitch. It is a risk mitigation strategy.

At OS Doors, 40+ Python programs controlling factory operations – from nesting calculations to sanding and painting – had to be retrofitted from a Sage connector to SAP and aligned to process design. This is not SAP work strictly speaking. It is manufacturing automation intersecting with SAP.  The distinction matters enormously when you are choosing a partner. 

Percipere took ownership of this because it was built with intelligent automation and process engineering capability. This avoided a second procurement, a new team, and an unrecoverable loss of context mid-project.  

This is not unique to OS Doors by any means. Mid-market manufacturers run on production systems built over years, specific to their machines, their materials, their process logic. Those systems are rarely documented to a standard that survives the people who built them. When an ERP project begins to resolve the real integration requirements in detail, the scope that emerges can be quite different to the scope that was signed. 

This is not a risk that can be fully mitigated in design. It can only be managed through the depth of the partner. 

Three questions worth asking in Partner selection:  

1. Can the partner work with bespoke production code and automation beyond SAP? 
2. What is their track record when scope shifts materially mid-project? 
3. How does their commercial model handle scope evolution without stalling delivery? 

Lesson 2 : Data Migration is tricky always. Period.  

In complex manufacturing environments, data is a project in its own right – one with its own architecture, its own risks, and its own dependency on the client’s readiness to engage with data governance for the first time. 

OS Doors had close to one million product records. This was the result of a business model in which every contractor order for a customised door configuration creates a new SKU – one that may never be reused. The standard SAP migration templates were not built for this scale. 

Four constraints in combination

Four constraints defined the migration challenge:

1. SAP’s Migration Cockpit has a 100MB per-file upload limit. Percipere built a custom Python script to automatically split files into logically coherent, SAP-compliant chunks. 
2. SAP Public Cloud’s test data refresh feature cannot be reset to zero – a requirement SAP’s standard tooling does not accommodate without a paid service. 
3. OS Doors had no prior SAP data framework experience. Understanding how to structure and populate XML templates correctly was a prerequisite to any migration. Percipere guided multiple iterative cycles of upload, testing, and correction before the data quality was sufficient for meaningful testing. 
4. OS Doors could not test in subsets. Their volume and product variety meant that a meaningful test required a full-production scenario with accurate data – not a curated sample. Any contaminated data in the test system invalidated testing entirely. 

This resulted in a year-long migration effort involving custom tooling, iterative cycles, and ultimately a full system rebuild before accurate testing became possible. This was absorbed entirely by Percipere. The team had backups and a documented rebuild plan. The execution was clean. The cost to the client was zero.  

Lesson 3 : Go-Live is rarely the finish linetegic Takeaway

Every go-live carries some risk. Even with sufficient testing, production load will surface issues that testing cannot. 

At OS Doors, SAP was running queries against one central warehouse bin stock – filtering for specific products from a pool of millions – on every delivery transaction. With the volume OS Doors, each query carried significant computational weight. Delivery posting slowed. A backlog accumulated. Goods were leaving the factory floor; the ERP was not keeping pace. Invoicing stalled. 

The CFO tracked order-book-versus-invoicing daily. He could see the gap widening in real time.

How it was resolved 

Percipere raised a high-priority ticket with SAP for a system optimisation. SAP’s proposed fix – restructuring warehouse bins into virtual sub-bins to reduce query scope – was technically sound, but SAP would take a week to prototype, approve and deploy the hotfix.  

Meanwhile, Percipere team stepped in to manage transaction flow and bridge the gap between order book and invoicing to ensure business continuity until the perform fix was available from SAP.  

“These guys went the extra mile, burned the midnight oil to enable business continuity. That’s why we are comfortable.” 

- OS Doors stakeholder, following backlog clearance 

Percipere-isms 

• Post-go-live performance issues can damage a relationship and how partners handle it make all the difference. Percipere’s consistent position is to acknowledge issues and redirect to resolution.  
• Hotfix management on live systems requires more caution than pre-live environments. The instinct to deploy quickly is understandable; the risk of disrupting a live operation is not recoverable. Holding that line is important

Lesson 4 : Finance and Operations are not naturally connected.  

The Finance Controller’s remit historically operated downstream: invoicing, general ledger, month-end close. The upstream sequence – production, dispatch, delivery – fed into his world, but remained opaque.  

The contracted SAP Analytics Cloud reporting track was not ready at this point. So, Percipere built an order-versus-invoice report directly in S/4HANA. Within two weeks the CFO could see £1.2M on the order book, £600K invoiced, and – critically – drill into the £400K gap to understand its composition. Stuck in delivery. Not posted from production. Not yet manufactured. Each answer pointed to a different person and a different action. For the first time, a financial metric was directly connected to an operational cause. 

Post go-live, Percipere also created department-level process maps linking business processes to SAP transactions. These gave the Finance Controller something he had not previously had: a working picture of the full chain his function depended on. 

“By looking at all these documentations and the interaction that we have had, I learned more about the business than I had learned in the past four years.” –

Finance Controller, OS Doors 

Lesson 5: Leadership alignment does not guarantee user 

Leadership at OS Doors were engaged throughout. The majority of end users had learned to operate the legacy system over years of practice. They lacked familiarity with SAP,  and could not communicate difficulties due to language barriers.  

During hyper-care, Percipere had people on-site throughout the critical period to act as interpreter between what the ground floor was experiencing and what the leadership team was receiving as reports.   

Percipere’s senior teams right upto the Founders, were on continuous calls with both the on-site team and client stakeholders throughout hyper-care. The visible involvement of senior leadership gave the client assurance that the firm was invested in the outcome, not managing the situation from a distance.

What Kind of Organisation Should Read This?

PE-backed manufacturers at the start of an ERP project When private equity invests in a manufacturing business and demands stronger financial reporting, a common tension emerges: operations see ERP as finance’s project, finance struggles to grasp operations, and the CFO must bridge the gap. OS Doors exemplifies this dynamic. If your organisation fits this pattern, the costing, change management, and reporting sections of this case study will resonate will be directly relevant.

Manufacturers with bespoke production systems Many mid-market manufacturers run proprietary production software tuned to their machines and processes. When they move to SAP, integration is always a live issue. The OS Doors MES story is a useful lens for any organisation in that position.

Businesses with high-volume, high-variety product data If your product master runs into six figures, hits SAP Public Cloud file size limits or your business generates product records faster than it retires them, this case study is worth a full read.

Finance leaders seeking operational visibility If you are a CFO or Finance Director whose invoicing lags the order book, the cause is usually upstream. This case study shows why that gap exists and how ERP, process documentation, and closer finance-operations alignment can close it.

Organisations in or approaching a manufacturing ERP go-live The go-live and hyper-care sections of this case study apply to almost any manufacturing implementation in its final phase. They surface hard questions about volume-test ownership, hotfix governance on live systems, and the need for on-site change management during hyper-care.

Closing : What Holds an Engagement Together 

The OS Doors project tested every dimension of a complex manufacturing transformation. Scope doubled. A critical developer left mid-project. A full system rebuild. A go-live performance issue. Organisational learning curve. Each of those challenges were the kind of complexity that only reveals itself once you are inside it. Complications will arise – the key questions is what the partner does when they do. 

Percipere treated those moments as problems to be solved within the relationship they had built. That approach is what delivered a go-live in January 2026 and a Finance team that understood their business better than they had ever before.  

“This was not a straightforward project. The scope changed, the timeline extended, and there were moments that tested everyone involved. What I can say is that Percipere stayed the course and we got there. The business now has financial visibility at a product level that simply did not exist before. That was the goal.”

CFO, OS Doors

About Percipere 

Percipere is a business transformation consultancy delivering SAP implementations, intelligent automation, and process intelligence for mid-market and enterprise organisations. 

The firm works across the full transformation lifecycle – from design through to go-live and operational change – with a focus on delivering outcomes that hold.www.percipere.com 

About OS Doors 

OS Doors is an Irish manufacturer of kitchen and bedroom doors, producing approximately 40,000 units per week across a highly automated production environment. 

Backed by Rubicon Group, the company completed its migration to SAP S/4HANA Public Cloud in January 2026, establishing product-level financial visibility for the first time

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