How can I calculate the total cost of ownership of an industrial mixer, including energy, maintenance and cleaning expenditure?
The total cost of ownership, or TCO, of an industrial mixer comprises all direct and indirect costs over its entire lifecycle. This includes not only the purchase price and energy consumption, but also planning, installation, cleaning, maintenance, product losses, downtime, modernisation, decommissioning and residual value. For a robust comparison of two mixing concepts, all costs must be captured over the same period and discounted to a single present-day value.
The basic TCO formula, in plain-text notation, is:
TCO = CAPEX + Present Value of (OPEX + Cleaning + Maintenance + Downtime + Quality Costs + Decommissioning) − Present Value of Residual Value
CAPEX stands for the one-off investment costs. OPEX comprises the ongoing operating costs. The present value makes future costs comparable with costs at today's point in time. This corresponds to the basic idea of life-cycle costing: what matters is all costs from acquisition through operation and maintenance to decommissioning, not the purchase price alone.
Setting the scope of assessment
First, a consistent assessment period should be defined. For industrial mixers, ten, twelve or fifteen years are typical planning periods, for example. Both plants being compared must be assessed with the same assumptions: the same annual production volume, the same product range, the same number of batches, the same availability requirement, the same energy price, the same labour costs and the same quality targets.
A decision is then made on whether to calculate with real or nominal costs. In a real-terms view, future costs are stated without inflation and discounted with a real discount rate. In a nominal view, expected price increases for electricity, labour, water, cleaning chemicals, spare parts and disposal are taken into account and discounted with a nominal interest rate. Both variants are permissible, but must not be mixed with one another. ISO 15686-5 describes life-cycle costing as a systematic examination of the relevant cost flows across acquisition, operation and disposal; discounting brings costs incurred at different points in time onto a single comparable basis.
In addition to the total TCO figure, production-related metrics should also be calculated. Useful examples are cost per tonne of released product, cost per batch, cost per kilogram of solvent evaporated for vacuum mixer-dryers, downtime cost per hour, and contribution margin per available production hour. These metrics show more quickly where the greatest economic levers lie.
Capturing investment costs
Investment costs comprise more than just the price of the mixer. To be considered are the mixer itself, drive, gearbox, mixing tool, discharge device, control system, sensor technology and, where applicable, vacuum, heating, cooling or liquid-addition systems. In addition come transport, foundation, structural steelwork, lifting equipment, electrical installation, pipework, extraction, filters, dosing and weighing technology, protective devices, safety equipment, automation, integration into the process control system and, where applicable, necessary building work.
Factory acceptance testing, site acceptance testing, commissioning, process trials, training, documentation, qualification and validation also belong in the TCO assessment. In GMP- or ATEX-relevant applications, Design Qualification, Installation Qualification, Operational Qualification, cleaning validation, risk assessment, explosion-protection documentation and "as built" documents can be relevant cost items. These expenses are mostly one-off, but they reduce the risk of costly rework and protracted start-up problems after commissioning.
Assessing energy realistically
Energy costs should be based on the actual mean power drawn, not on the installed motor power. A mixer with 30 kilowatts of installed power does not automatically consume 30 kilowatt-hours per operating hour. What matters are the load profile, rotational speed, fill level, product condition, mixing time, batch count and idle times.
The simplified formula for the annual cost of the electrical drive energy, in plain-text notation, is:
K_Energy_Drive = P_mean × t_Operating × k_Electricity
Here, P_mean is the average actual power drawn, in kilowatts. t_Operating is the annual operating time in hours. k_Electricity is the electricity price in euros per kilowatt-hour. Where drive, frequency inverter and gearbox are considered separately, efficiencies and losses must be applied consistently. The most reliable approach is to record energy consumption during representative mixing cycles using an energy meter or via the control system.
For temperature-controlled mixers and vacuum mixer-dryers, drive energy alone is not sufficient. Heating and cooling energy, vacuum pump, condenser, temperature-control circuit, compressed air, blanketing gas, filter cleaning, control system, sensor technology and standby consumption must additionally be captured. For vacuum mixer-dryers, metrics such as kilowatt-hours per kilogram of water or solvent evaporated are additionally useful. For powder mixers, kilowatt-hours per tonne of released product and kilowatt-hours per batch are suitable metrics.
The greatest energy saving often does not come from a more efficient motor alone. Frequently more important are a shorter validated mixing time, better heat transfer, less downtime, less unnecessary cleaning, and a high degree of residual discharge. A mixer that reproducibly reaches the target homogeneity in a short time and discharges almost completely can be more economical, despite a higher investment price, than a cheaper mixer with long cycles and high changeover losses.
Assessing cleaning in full
In multi-product plants, cleaning effort is frequently one of the largest TCO drivers. The direct cleaning costs comprise water, deionised water, WFI, alkaline agents, acids, surfactants, solvents, compressed air, energy for pumping and heating, energy for drying, wastewater treatment, neutralisation, disposal, filter changes, cleaning tools and labour.
The decisive indirect costs arise during the downtime. While cleaning, drying, visual inspection, release and, where applicable, analytical verification are taking place, the mixer is not available for production. The cleaning costs per product changeover should therefore be captured in full.
The simplified formula, in plain-text notation, is:
K_Cleaning_Changeover = K_Media + K_Energy + K_Labour + K_Disposal + K_Validation + K_Downtime
The annual cleaning costs are then obtained from:
K_Cleaning_annual = K_Cleaning_Changeover × Number_of_ProductChangeovers_per_Year
With frequent recipe changes, even a small reduction in cleaning duration can have a substantial economic effect. This is particularly relevant for allergens, active ingredients, flavourings, colours, fats, microbiologically critical products, and recipes with strict cross-contamination protection.
Design features have a considerable influence on these costs. They include low dead space, smooth and readily cleanable surfaces, extensive residual discharge, full accessibility, low-dead-space discharge devices, suitable seals, integrated wash lances, programmable CIP or WIP systems, and fast drying of the mixing chamber after wet cleaning. In the amixon® service profile, WaterDragon® is described as an automated system with rotating nozzles that can clean without spray shadows and accelerate drying with large volumes of air. The nozzle retracts from the mixing chamber after the cleaning cycle and closes tightly and free of dead space.
For regulated processes, the costs of cleaning evidence must also be taken into account. These include, for example, riboflavin tests, bioluminescence detection, swab tests, analytical methods, documentation, release, deviation management and, where applicable, repeat cleaning.
Planning maintenance and spare parts
Maintenance costs comprise preventive, condition-based and corrective measures. Direct costs are internal and external labour time, spare parts, consumables, lubricants, seals, bearings, mixing-tool parts, filters, sensors, measuring-equipment calibration, service contracts, inspections and documentation. Indirect costs arise from production interruption, restart, scrap, energy for start-up, and possible quality checks after the intervention.
A robust maintenance calculation should not rely solely on a blanket percentage of the purchase price. Such a figure can serve as an initial budget assumption, but must be supplemented by the specific design and application. Abrasive products, aggressive cleaning media, high temperatures, vacuum cycles, frequent product changes or heavy load changes can significantly increase maintenance costs. A low-maintenance design, good accessibility and a reduced number of product-near sealing and bearing points can, conversely, lower them.
For every critical component, the expected service life, part costs, replacement time, required qualification, number of replacements over the assessment period, and the downtime cost during replacement should be captured. A seal set with low material costs can become expensive if replacing it blocks the entire production line for many hours.
Spare-parts stockholding and obsolescence management also belong in the TCO. What should be held is not simply a large number of parts, but those with a long delivery time, high failure impact or complex replacement. Seals, bearings, filter elements, safety components, sensors, discharge parts, frequency inverters, PLC modules and specific mixing-tool parts should be assessed on a risk basis. Consignment warehouses can secure availability while limiting capital tie-up.
amixon® describes a wear-parts warehouse in Paderborn, as well as the ability to prepare planned maintenance deployments with a documented task list and parts provided as a precaution. Its own full control over production additionally supports the remanufacture of customer-specific components and compatible replacement solutions over a long plant service life.
Monetising downtime
Downtime costs are frequently the most important, and at the same time the most frequently underestimated, TCO item. They consist of more than just a service technician's wage. Relevant factors are the lost contribution margin, ongoing fixed costs, personnel waiting time, scrap, rework, start-up material, energy for restarting, delayed deliveries, contractual penalties and, where applicable, the loss of customer orders.
The simplified formula, in plain-text notation, is:
K_Downtime = t_Downtime × CM_per_Hour + K_Scrap + K_Rework + K_Restart + K_ExpressLogistics
Here, t_Downtime is the duration of the downtime in hours. CM_per_Hour is the lost contribution margin per production hour. K_Scrap comprises the cost of product that can no longer be used. K_Rework describes additional costs for reprocessing or repeating a batch. K_Restart comprises energy, labour and product losses up to a stable process state. K_ExpressLogistics accounts for special transport or procurement costs in the event of a fault.
The contribution margin per hour must not be confused with revenue. What is decisive is the margin lost through the quantity of product not produced and not sold. Where sufficient stock, spare capacity or alternative production lines are available, the actual damage can be lower. At a bottleneck plant, however, it can be considerably higher.
Downtime should be recorded separately by cause: mechanical defect, electrical defect, sensor technology, software, cleaning, product changeover, missing raw materials, missing spare parts, quality deviation, operating error and external causes. Only this differentiation shows whether investments in better seals, automation, training, spare-parts kits, cleaning or remote support are actually economical.
Capturing product losses and quality
Product losses arise from incomplete discharge, scrap, faulty batches, start-up material, cleaning losses, rework, segregation during discharge, and possible cross-contamination. Particularly with high-value active ingredients, speciality chemicals, additives or recipes with expensive raw materials, the residual quantity in the mixer can be economically more significant than electricity consumption.
Calculate the value of the residual quantity per batch and multiply it by the annual batch count. Added to this are costs for flush material, cleaning media, disposal and, where applicable, the loss of the following batch in the event of contamination. Extensive residual discharge not only reduces direct product loss, but also shortens cleaning and product changeovers.
Quality costs comprise scrap, rework, additional analytics, delays, complaints and release losses. A cheap mixer with inadequate mixing quality or unstable discharge quality can thereby cause high follow-on costs. The demonstrated mixing quality across the entire discharge sequence therefore belongs in the TCO just as much as energy and maintenance.
Comparing costs on a present-value basis
For a comparison over several years, future costs should be discounted to today's value. The present-value formula, in plain-text notation, is:
PV_t = C_t / (1 + r)^t
Here, PV_t is the present value of a payment in year t. C_t is the payment or cost item in year t. r is the company's internal discount rate. t is the respective year within the assessment period.
The complete TCO formula, in plain-text notation, is:
TCO = CAPEX + Σ from t = 1 to n [ (K_Energy_t + K_Cleaning_t + K_Maintenance_t + K_Downtime_t + K_Quality_t + K_Other_t) / (1 + r)^t] − [ ResidualValue_n / (1 + r)^n]
CAPEX is the one-off investment cost. K_Energy_t is the energy cost in year t. K_Cleaning_t is the cleaning cost in year t. K_Maintenance_t is the maintenance and spare-parts cost in year t. K_Downtime_t is the downtime and restart cost in year t. K_Quality_t comprises scrap, rework, analytics and other quality-related costs. K_Other_t comprises, for example, licence costs, insurance, external inspections, training or other operating costs. ResidualValue_n is the expected residual value of the plant in the last assessment year n.
Where an alternative incurs higher initial costs but lower annual operating costs, the discounted savings should additionally be calculated. An investment is economically advantageous if the present value of its savings exceeds the additional investment. ISO 15686-5 and comparable life-cycle costing methods use this approach to make cost flows at different points in time comparable.
A practical worksheet
For a practical TCO calculation, every alternative should be assessed in the same table with the same assumptions. To be captured are machine price, peripherals, installation, FAT and SAT, commissioning, qualification, training, annual drive energy, heating and cooling energy, vacuum and compressed-air costs, annual cleaning costs, annual maintenance and service costs, annual spare-parts costs, spare-parts warehousing costs, product losses, scrap, rework, downtime by cause, software and automation costs, compliance and documentation costs, modernisation costs, decommissioning costs, and expected residual value.
Assumptions regarding production volume, batch count, shift model, energy price, labour cost rate, number of cleaning changeovers, contribution margin, downtime costs, discount rate and assessment period should additionally be documented. Run at least three scenarios: a realistic base scenario, a conservative scenario with higher energy and maintenance costs, and a risk scenario with longer delivery times or more unplanned failures. This sensitivity analysis shows which assumptions actually dominate the economics.
How amixon® assesses the energy efficiency, TCO and payback of an industrial mixer
The total cost of ownership of an industrial mixer is not determined by the purchase price alone. What is decisive is energy consumption, product loss, cleaning and changeover times, maintenance and spare parts, and the actual service life. On request, amixon® can prepare a comprehensive utility-value analysis and a product-specific TCO, ROI or payback assessment for investors. The basis for this is not blanket catalogue values, but measurements and process data from trials with the original product.
The relevant cost blocks
Over an assessment period of, for example, ten years, five blocks substantially determine the economic evaluation: energy, product loss, cleaning and changeover times, maintenance and spare parts, and depreciation over the actual service life. Additionally, costs for installation, commissioning, qualification, labour, cleaning media, downtime, scrap, rework, obsolescence management, modernisation and decommissioning can become relevant.
The simplified TCO view, in plain-text notation, is:
TCO = CAPEX + Present Value of (Energy + Product Loss + Cleaning + Changeover Time + Maintenance + Spare Parts + Downtime + Quality Costs + Modernisation + Decommissioning) − Present Value of Residual Value
CAPEX denotes the one-off investment costs. The present value makes future costs comparable with today's costs. For a robust comparison, different mixer concepts must be assessed over the same period, with the same production volume, the same product changeovers, the same quality targets and the same discount rate.
amixon® optimises the key TCO factors by design. Blanket figures in kilowatt-hours per tonne are, however, not credible, because the specific energy requirement depends on recipe, batch size, fill level, mixing time, rotational speed, moisture, flow behaviour, liquid addition and further process conditions. Energy consumption, mixing time, discharge, product changeover and cleaning effort are therefore determined in the pilot plant using the original product.
Energy: low-speed rather than power-intensive
The annual costs for the electrical drive energy can be approximated as follows:
K_Energy_Drive = P_mean × t_Operating × k_Electricity
P_mean is the average actual power drawn, in kilowatts. t_Operating is the annual operating time in hours. k_Electricity is the electricity price in euros per kilowatt-hour. What is decisive is the real mean power draw, not the installed motor power alone.
amixon® mixers operate with controlled three-dimensional product recirculation and comparatively low tool circumferential speeds from around 0.8 m/s. Energy input is not primarily achieved through high rotational speeds, throwing motion or heavy impact stress, but through recurring product circulation. This can limit mechanical load, wear and energy input.
The Gyraton® silo mixer GM can mix large batches of up to around 100 m³ slowly and with low current draw, provided the product and process task allow for it. The twin-shaft mixer HM generates superimposed product flows and can support fast distribution across the entire batch volume. With the KoneSlid® mixer KS, the required mixing quality — depending on recipe, fill level and target homogeneity — can be achieved after around 20 to 30 tool revolutions. The actually required mixing time, however, must always be determined in a trial with the original product.
Short and reproducible mixing times reduce the amount of energy per batch and at the same time increase throughput per unit of installed power. What is decisive is not the theoretically shortest mixing time, but a robust process window in which the target mixing quality is reliably achieved. An unnecessarily long mixing time increases energy demand, product stress and cycle time without delivering a corresponding quality gain.
For mixer-dryers and temperature-controlled apparatus, heating and cooling energy, vacuum, condensation, temperature-control circuit, compressed air, blanketing gas, filter cleaning and standby consumption must additionally be taken into account. For vacuum mixer-dryers, metrics such as kilowatt-hours per kilogram of water or solvent evaporated are particularly meaningful. The actual values are captured in the pilot-plant trial and transferred to the target size.
Product loss and changeover time
Product losses and changeover times are frequently underestimated cost blocks. Every residual quantity in the mixing chamber is either a direct product loss, additional cleaning effort, potential carry-over into the following batch, or a combination of all three effects. With high-value active ingredients, speciality chemicals, functional additives or recipes with expensive raw materials, residual discharge can be economically more important than saving individual kilowatt-hours.
amixon® states residual discharge rates of up to around 99.98 percent for the AM and KS series. For ComDisc® discharge concepts, up to around 99.99 percent is stated. These figures are design target values, not a blanket guarantee for every product. The actually achievable discharge rate depends on particle size, bulk density, moisture, stickiness, electrostatic charge, surface condition, product build-up and discharge concept. It must therefore be verified with the original product.
The cost of product loss can be determined, in plain-text notation, as follows:
K_ProductLoss_annual = ResidualQuantity_per_Batch × Value_of_Product_per_kg × Number_of_Batches_per_Year
Costs for flush material, disposal, cleaning media and, where applicable, consequential damage from cross-contamination should additionally be taken into account. Extensive residual discharge not only reduces direct raw-material loss, but also the duration and complexity of cleaning and product changeovers.
The changeover costs per product changeover can be approximated as follows:
K_Changeover = K_CleaningMedia + K_Energy + K_Labour + K_Disposal + K_Validation + K_Downtime
The annual changeover costs are obtained from:
K_Changeover_annual = K_Changeover × Number_of_ProductChangeovers_per_Year
Low-dead-space, fully accessible mixing chambers, good residual discharge and optimised cleaning programmes shorten every cleaning cycle and increase the plant's productive time. This has a direct effect on overall equipment effectiveness.
WaterDragon® and cleaning
In multi-product plants, cleaning, drying, visual inspection, release and product changeover are frequently bigger TCO drivers than mechanical repairs. The costs comprise water, deionised water, WFI, alkaline agents, acids, surfactants, solvents, compressed air, energy for pumping and heating, energy for drying, wastewater treatment, neutralisation, filter changes, labour, cleaning validation and downtime.
The WaterDragon® system extends automated wet cleaning. It can work with programmable target-jet nozzles that apply water to defined areas of the mixing chamber, mixing tool, door areas and discharge in a targeted way. Cleaning positions, target areas, spray duration, spray pattern, water quantity and cleaning sequence can be adapted to product, apparatus geometry and changeover strategy.
A particular advantage lies in the drying concept. WaterDragon® can introduce large volumes of air into the mixing chamber. This allows even cold wash water to be removed quickly and almost completely after wet cleaning, without the mixing chamber first having to be heated. The wash nozzle retracts from the mixing chamber after the cleaning process and closes tightly and free of dead space. This allows cleaning and subsequent drying to be completed faster, which shortens the time until the next production-ready batch.
The actual duration depends on mixer design, water load, air routing, product range, residual-moisture requirement and cleaning strategy. The cleaning and drying performance must therefore be validated for the critical product changeover. In regulated processes, riboflavin tests, bioluminescence detection, swab tests, analytical verification, documentation and release can additionally be required.
Maintenance and service life
Maintenance costs consist of preventive, condition-based and corrective maintenance. These include internal and external labour time, inspections, seals, bearings, mixing-tool parts, filters, sensors, lubricants, calibrations, service contracts, spare parts, documentation and the cost of the respective downtime.
amixon® mixers are designed for low-maintenance operation. The mixing tool is mounted and driven only at the top. A lower shaft passage with product-contact seal and bearing is eliminated. This reduces the number of critical sealing and bearing points in the mixing chamber. The low-speed operation can reduce the dynamic load on the bearings, gearbox and mixing tool.
Large Clever-Cut® inspection doors provide access to the mixing chamber, mixing tool and discharge area. Visual inspections, cleaning inspections and many maintenance measures can be carried out without extensive dismantling. The OmgaSeal® design is described as permanently tight, technically dead-space-free, wet-cleanable and microbiologically controllable.
For abrasive products, Hardox materials, carbide-containing protective weld overlays or ceramic coatings can be used. These measures are intended to increase the service life of the mixing tools and limit maintenance costs with heavy or highly abrasive powders.
The maintenance costs per year can be represented in simplified form, in plain-text notation, as:
K_Maintenance_annual = K_Inspection + K_WearParts + K_SpareParts + K_Labour + K_ServiceContract + K_Downtime_Maintenance
A pure percentage of the purchase price can serve as a rough budget assumption, but it does not replace product-specific planning. Abrasive products, aggressive cleaning media, high temperatures, vacuum cycles and frequent product changes can significantly increase maintenance costs. Good accessibility, a reduced number of critical sealing points and long service life reduce them.
According to the company, many amixon® machines have been in daily use for more than 30 years. The actual service life, however, depends on product type, abrasiveness, process load, cleaning, maintenance quality and modernisation strategy. Retrofits and modernisation can extend the service life and avoid replacement investments.
Robust figures instead of catalogue values
A credible ROI or payback calculation is based on measured process data. In the amixon® pilot plant, mixing time, energy consumption, residual discharge, cleanability, changeover time, product protection, heat transfer and reproducibility can be captured with the original product. This data is documented and can serve as the basis for designing the target plant as well as for the economic assessment.
On request, amixon® can prepare a comprehensive utility-value analysis for investors. It can jointly assess technical and economic criteria, such as mixing quality, product protection, energy consumption, cleaning duration, residual discharge, maintenance-friendliness, spare-parts availability, hygienic design, degree of automation, documentation, validatability, flexibility for new recipes, and expected service life.
Calculating downtime costs is particularly important here. In plain-text notation, it reads:
K_Downtime = t_Downtime × CM_per_Hour + K_Scrap + K_Rework + K_Restart + K_ExpressLogistics
t_Downtime is the duration of the downtime in hours. CM_per_Hour is the lost contribution margin per production hour. K_Scrap comprises product that can no longer be used. K_Rework describes costs for reprocessing or repeating a batch. K_Restart comprises energy, labour and product losses up to a stable process state. K_ExpressLogistics contains additional costs for urgent spare parts or special transport.
Downtime should be recorded separately by cause: mechanical defect, electrical defect, sensor technology, software, cleaning, product changeover, missing spare parts, quality deviation, operating error or external causes. Only then can it be established whether the most economically sensible measure is better cleaning, more spare-parts stockholding, a retrofit, training, predictive maintenance, or a changed process approach.
Run reproducibly and documented
Mixing programmes can be stored as complete PLC recipes. These contain mixing times, rotational frequencies, fill levels, dosing sequences, liquid additions, temperature profiles, pressure or vacuum level, post-mixing time and discharge sequence. Every batch can thereby be run with the same released parameters.
An ERP connection and barcode scanners can link recipe, raw-material batch, process values, operator interventions, cleaning status and batch release. This data basis supports batch traceability, OEE evaluation, root-cause analysis, maintenance planning and validation in regulated environments.
Remote support can shorten diagnosis time where alarm history, PLC status, HMI messages, drive data, temperature, torque and further process values are available in structured form. It must, however, be implemented via a secure OT concept with segmented networks, encrypted communication, individual accounts, multi-factor authentication, role-based permissions, time-limited operator release, and complete audit logs. The BSI explicitly recommends these protective measures for industrial remote maintenance.
Qualifiable and documented
For regulated environments, amixon® can design the plant on the basis of a User Requirement Specification and provide support with DQ, IQ and OQ. Documentation and design can be oriented to EU-GMP and FDA 21 CFR Part 11. Depending on the project, EHEDG, FDA hygiene guidelines, 3-A Sanitary Standards, USDA, GMP, ATEX and ASME can additionally be taken into account.
These services are relevant to the TCO because they can reduce risks from subsequent qualification, delays in release, additional cleaning checks or costly adaptations after commissioning. Responsibility for process validation, product release and the operator's quality system, however, remains with the operator.