A machined part does not arrive at the next operation clean. It arrives coated in whatever the machine tool was running: cutting oil, way oil, hydraulic oil, sometimes all three, plus fine chips and the abrasive grit that came off the deburring bench. The drawing specifies a surface finish and a coating; it says nothing about the residue, so nobody owns the residue until the powder coat starts fisheying, the MIG weld starts poring, the adhesive refuses to wet out, or the coordinate measuring table starts leaving smears. That is usually the moment a washer appears on the capital request, and usually the moment the selection starts in the wrong place: by comparing machine brochures instead of defining the soil and the acceptance test. The questions below are the ones worth putting in front of any supplier before anyone mentions price.
1. What is actually on the part, and how did it get there?
Start with your own process, because no supplier can infer it from a part number.
- Oil type and additive package. Neat oils carrying extreme-pressure additives, such as chlorinated paraffins or sulfur-phosphorus packages, leave a tenacious film that resists alkaline attack. Semi-synthetic and synthetic coolants usually strip more easily, but they leave drying salts and biocide residues behind.
- Has the oil been heated? A film that has been through a thermal cycle, from hot chips, a hot tool, or a part left in a sun-loaded rack, polymerizes. Baked-on oil does not respond to the same chemistry or the same temperature as a fresh film, and a supplier who has only ever tested fresh soil will overpromise.
- What else is mixed in. Swarf, abrasive grit from deburring, way oil from the guideways, and any rust preventive applied downstream all change both the cleaning duty and the waste stream.
- Geometry. Blind holes, cross-drilled holes, threads, machined crevices and capillary gaps hold oil that a spray bar will never reach. As-cast surfaces behave quite differently from milled ones.
- Sequence. Are parts washed before or after deburring? Are they hot on arrival? Do they sit before washing, and for how long?
Then ask the supplier to state in writing which soil their machine was actually tested on. A datasheet that says "removes oil and grease" is not evidence about your coolant, your additive package and your dwell time.
2. What does "clean" mean, and who signs it off?
A machine cannot be judged against an undefined target, and a purchase order written without one will be argued about for years.
- Write the acceptance criterion before the order. The usual options are a water-break test on the machined surface, where a continuous water film must be held for a stated number of seconds; residual oil measured by weight; a wipe test using a fixed solvent over a fixed area; or a downstream proxy such as paint adhesion, salt-spray hours, weld porosity rate, or dye-penetrant results.
- Fix the sampling plan. Which part number, which lot, which face, how often, and what happens when a sample fails.
- Get quality engineering to agree the method now. A supplier who is confident in the machine will not object to a written protocol. A supplier who is guessing will keep the test vague.
3. Which cleaning mechanism suits this soil and this geometry?
Every mechanism has a working range and a failure mode. Ask each supplier to describe where their machine should not be used, and treat a refusal as information.
| Mechanism | Where it works | Where it gives up |
|---|---|---|
| Aqueous alkaline spray or walk-in washer | Repeatable part families, high throughput, chips flushed off open surfaces. | Blind holes and capillary gaps. Chemistry strength, bath contamination, rinse quality and drying all need managing. |
| Aqueous immersion with agitation or ultrasonics | Internal cavities, drilled and cross-drilled holes, complex geometry, because cavitation reaches where spray cannot. | Sump loading and bath contamination. Poor fit for free-flowing high-volume lines. |
| Solvent or vapor degreasing | Heavy oil films, fast turnaround, and processes that cannot tolerate water or a drying step. | Solvent handling, emission controls and unit cost. Thin synthetic residues can be less cooperative. |
| Hot water and high-pressure steam | Oil and grease films where heat does the work chemistry would otherwise do; in-place cleaning of machines, fixtures and floors; low-volume or high-mix work that cannot justify a fixed wash line. | Precision parts with oil held in blind holes. Not a substitute for a rinse-controlled aqueous line at production volume. |
If a hot-water or steam route is genuinely on the table, insist on the figures behind it: steam temperature at the outlet, working pressure, heating power, tank volume and material, water inlet requirements, and the duty cycle the machine is rated for. The listings under PowerDe's industrial steam cleaning equipment publish measured values rather than adjectives, and that is the standard to expect from anyone who reaches your shortlist.
4. What is the real throughput, including handling and drying?
- Takt, not brochure capacity. Parts per hour across your actual mix, including changeovers, rather than the single easiest part in the range.
- Loading and handling. Baskets, racks, fixtures or a hand lance; who loads them, how heavy a load is, and how far the operator walks each cycle.
- Dirty-to-clean separation, and where the parts go the moment they leave the machine.
- Drying. A washed steel part standing in a humid shop can begin to flash-rust within hours. Ask how parts leave the machine: compressed-air blow-off, a heated final rinse, vacuum drying, an oven, and what happens to the water and oil sitting in drilled holes.
- Chip management. How swarf is captured, how often the sump or filter needs cleaning, and whether fines are separated before the drain. Metal fines are abrasive, and oily sludge is a waste stream with a price attached to it.
5. What does the site need to support it?
Utilities and drainage are where these projects stall, so treat them as part of the quotation rather than as installation detail.
- Power. Single-phase 220 V or three-phase, the connected load, and whether the existing distribution panel can carry it.
- Water. Inlet quality, softened feed for a steam generator, and consumption per cycle.
- Drain and oil-water separation. Washing machined parts sends oil and metal fines down the drain. Ask what separation is included as standard and what is quoted as an extra.
- Ventilation. Heated oil releases vapor and alkaline tanks release mist; both need extraction.
- Floor space, floor loading and clearance for maintenance access, not just for the footprint on the drawing.
- Operator safety. With high-temperature steam under pressure, ask which protections are fitted as standard: leakage protection, short-circuit protection, over-temperature and over-pressure cut-offs, water-shortage protection, and an insulated hose and trigger gun. Ask which of those are options.
6. What will it cost to run, not to buy?
Ask for a running-cost sheet in writing: energy per hour, water per cycle, detergent per cycle, bath life, filter and consumable replacement intervals, the service interval, and the disposal route and cost for spent chemistry and oily sludge. A process that uses no chemistry has a considerably simpler disposal story, which is often the deciding factor in a job shop whose work changes every week.
7. Can they prove it on your parts?
This is the most useful request in the list, and the one suppliers either welcome or quietly avoid.
- Send a sample of your dirtiest parts, as received rather than pre-cleaned, and ask for a documented trial: the parts before, the parameters used, and the result measured against the acceptance test from question two.
- Ask what the trial does not cover, such as production takt, mixed loads, bath ageing and long-run stability.
- Ask for reference installations on comparable soil and geometry, with permission to call them.
- Ask which items are wear parts, what they cost, and how long replacement takes to arrive.
- Ask what the warranty excludes, who commissions the machine and trains the operators, and what the response time is on a breakdown.
- Ask whether the machine can be reconfigured if your coolant changes. Coolant suppliers reformulate, and a washer specified against one product can be stranded by a switch nobody planned.
8. Read the specification for what the machine is specified for
A usable datasheet states measured values together with the conditions they were measured under, and it states the duty the machine is intended for. As an example of the level of detail to expect, the datasheet for the PowerDe HW02 fixed station unit lists 6 kW heating power, a 160 °C steam temperature, 0.8 MPa working pressure, an 80 L SUS304 tank, a tap-water inlet and 220 V supply, along with leakage, short-circuit, high-temperature, high-voltage and water-shortage protection.
Read the second half of that page as carefully as the numbers. That model is documented for vehicle exterior, interior and engine-compartment cleaning. Checking what a machine is actually specified for, rather than what it is technically capable of doing once, is how most of the expensive mistakes in this category get avoided.
9. When the catalogue is not the answer
Machining shops rarely match a catalogue entry. High-mix, low-volume work; oil on fixtures and machine tables as much as on parts; a layout with no space for a wash line; a coolant that appears in no datasheet. In those cases the practical route is a configured station, meaning a steam or hot-water unit combined with the correct lance, nozzle set, recovery and safety package, rather than an off-the-shelf washer. PowerDe lists customized steam cleaning equipment among its engineering services, covering industrial applications such as equipment cleaning and oil-pollution cleaning, which is the conversation to have when your soil and your layout do not fit a published model.
The short version to take into the meeting
- What is the soil exactly, and has it been heated?
- What is our acceptance test, and who signs it off?
- Which mechanism fits the soil and the geometry, and where does it fail?
- What is the takt, including loading and drying?
- Can the building support it: power, water, drain, separation, ventilation?
- What does it cost per hour to run, and what does the waste cost to dispose of?
- Will you test our parts against our test method?
- What is this machine actually specified for?
- If nothing standard fits, what would you configure, and how do we verify it before we pay?
The machine itself is the easy half of this decision. The soil, the acceptance test and the drying step are where the money is, and all three sit inside your own plant. Settle those first and the specification you send to suppliers writes itself, along with a shortlist that is short for the right reasons.
