Dry Screw Vacuum Pump Housings
We machine dry screw pump housings for OEM and aftermarket buyers. Both bores are machined in one fixture, on one datum — that's what holds parallelism across a production run, not just on the first piece.
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In a dry screw vacuum pump, the fit between housing bore and rotor OD is one of the most important reasons that decides how the pump performs. A few 0.01 mm of extra clearance is enough to destroy the design number. Either the pump misses its rated ultimate, or the consumption power exceed.
Bore surface finish matters for the same reason: some shops can't reach the full bore length with the boring bar in one pass, so the housing has to come off the table and get flipped to finish the other half. That leaves a witness mark where the two passes meet — a small ridge sitting in the rotor's running path. Design clearance is already tight, and once the rotor reaches running temperature and grows into its operating diameter, that ridge is where it rubs.
Dowel pin holes are a feature buyers don't usually look at twice. On housings where the bore body and the end plate are separate parts, the dowels hold the end plate aligned to the bore. If the end plate sits a few 0.01 mm off, the rotor lands in the wrong place. The clearance you spec'd on the drawing isn't what's on the pump.
At SCPM, we machine these housings against the drawing and against what we've seen go wrong on pumps built with them. The part you receive will meet the print and won't be the reason the pump misses spec.
Test Orders
Try the machining before you pay for a casting pattern.
Option 1
Cast Prototype
The standard route when you're going to series production. A partner shop 3D-prints a foam pattern of the housing, cast it through a lost-foam process, then bring the casting back to our floor for final machining.
Option 2
Weld Prototype
We break the housing into sections, machine each piece from solid stock, and weld them into a housing. Machining and finishing process will be applied, and it is qualified for a final production.
Use when you want the first piece off the line to be the same part you'll ship in volume.
Use when you want to see our machining hit the print before paying for a casting pattern.
Once the fabricated pilot passes your incoming inspection, the next step is the casting pattern. By that point the machining risk is settled — what you're paying for is the production economics, not a gamble on whether the housing will hold spec.
Measurement & Inspection
What we measure these housings with.
Bore parallelism, dowel position, and seal-face geometry are inspected on every housing — not sampled. The instruments below are the ones the numbers on your inspection report come from.
| Instrument | Make / Model | Capacity | Used for |
|---|---|---|---|
| CMM | TODO confirm (e.g. Hexagon Global S) | TODO (e.g. 1,200 × 1,000 × 700 mm, MPE_E 1.6 µm) | Bore-to-bore parallelism, dowel positions, seal-recess geometry |
| Bore gauge | TODO confirm (e.g. Mitutoyo digital) | Ø50 – Ø600 mm (TODO confirm) | In-process bore Ø verification on every piece |
| Surface roughness tester | TODO confirm (e.g. Mitutoyo SJ-410) | Ra 0.05 – 10 µm | Bore Ra, end-face seal Ra |
| Hardness tester | TODO confirm | TODO confirm | Material verification on castings and weld zones |
Every housing ships with the dimensional report from these instruments — sampling rate, instrument serial, and operator on the report.
Series Production
What happens once you commit to a series order.
After the pilot passes, the casting workflow handles every piece in the batch. The fixture, the CAM program, and the inspection routine are all retained — what changes is the volume, not the process.
Same fixture, same program
The CAM program and workholding proven on the pilot are retained for every repeat batch. No re-validation, no relearning the part. Setup time on a repeat order is hours, not days.
First article every batch
Even on repeat orders, the first piece of each batch gets a full CMM report before the rest of the batch goes on the machine. If a casting lot drifts, we catch it on piece one.
In-process probing on every piece
Touch-probe cycles measure the actual bore after roughing so finish passes correct against real geometry, not nominal toolpath. The parallelism number that ships isn't the first piece's number, it's the batch's number.
Material traceability
Mill test certificates are retained per heat lot and shipped with the batch documentation. Castings carry the foundry's pour-record reference (TODO confirm).
Each batch ships with
- Full dimensional inspection report per piece (TODO confirm)
- Mill test certificate (MTC) per heat lot (TODO confirm)
- First article inspection report (FAI) per batch (TODO confirm)
- Anti-rust packaging and export-grade crate
- Typical batch lead time: TODO (e.g. 15 – 25 days)
Common Questions
Frequently asked
Can you machine housings from our castings?
Yes. Send us your casting drawing and the dimensional report from your foundry, and we will plan the machining route around the actual stock condition. We can also coordinate the casting through qualified partners if you only have a finish-machined drawing.
What sizes do you cover?
Small, medium, and large series — covering bore diameters from Ø150 mm up to Ø600 mm and housing lengths up to 2,000 mm. Outside that envelope, we will tell you honestly whether we can still help. (TODO: confirm range before publishing.)
Do you make screw rotors as well?
No. Rotor lobe profiles are proprietary IP that should stay with the pump OEM. Our scope is restricted to the housing and surrounding components — shafts when they are separate parts, end covers, bearing housings, mounting hardware.
How do you verify parallelism between the two bores?
On the machine, with the integrated touch probe before finish passes; off the machine, with bore gauges and CMM verification on critical features. The bore-to-bore parallelism number on every batch is reported in writing, not just inferred from the process. (TODO: confirm reporting practice before publishing.)
How we handle your drawings
Drawing-driven only. Always under NDA.
We sign your NDA before quoting, retain drawings only for the production cycle, and never use customer files as reference for any in-house product line.
Send us your drawing