Medical and laboratory equipment
In medical and laboratory equipment the drive is almost never working hard. It is working quietly, intermittently, for a decade, inside a program that has to document why it will keep working. The engineering problem is that none of the specifications that get compared describe that: continuous torque is barely used, rated life in hours is barely accumulated, and the numbers that decide the outcome are the stall torque into an occlusion, the mesh order that reaches a technologist's ear, the reversal error at the start of an aspirate, and the count of starts rather than the count of hours.
The clusters
Mechanisms that share a load model, not markets that share a trade show.
- Infusion, syringe and enteral pumps
- Pipetting and liquid handling
- Sample transport and diagnostic analyzers
- Pharmaceutical dispensing and metering
- Compact valves and pumping mechanisms
Each of these issues is a different physical quantity wearing the same word.
The middle column is what the issue actually is. The right column is where it gets decided, which is usually earlier than the motor selection.
| Issue | What it actually is | Where it is decided |
|---|---|---|
| Acoustic noise | A narrowband mesh tone coupled into a panel, not a loud motor. | Stage split and mounting, decided before the motor is chosen. |
| Intermittent life | A start count, not an hour count. Half a million cycles is often under fifty running hours. | The cycle definition, converted into starts, revolutions and RMS current. |
| Heat | Rarely a constraint on an intermittent drive, and the whole constraint on a holding one. | Whether the mechanism holds by self-locking or by current. |
| Current | The occlusion or jam detector on most of these mechanisms, and a weak one at high ratios. | The difference between free-running and loaded current, against the no-load pedestal. |
| Contamination risk | Brush debris, grease throw and wear particles from a source close to the fluid path or the sample. | Motor class and lubricant, both of which are configuration decisions. |
| Repeatability | Lost motion referred through the mechanism, not encoder counts referred through the ratio. | Approach direction, and where the feedback is mounted. |
| Long program life | Ten years of calendar with very little motion. Grease ages anyway. | A real-time life test, not a compressed one. |
| Change control | Which properties of the part the device file actually depends on. | A documented configuration with a revision, not a catalog listing. |
| Documented qualification | Evidence a device manufacturer can carry into its own design history file. | A qualification plan agreed before the first sample ships. |
Four roles, four different questions
A product page and a project record have to serve all four without becoming four separate websites. What each one needs before they will make contact is not the same information.
| Role | What it needs before contact | What it converts on |
|---|---|---|
| Mechanical engineer | Envelope, shaft and mounting, torque and speed at the real operating point, load model, life definition, noise. | A saved candidate, CAD, a drawing, or an application review. |
| Electrical or controls engineer | Voltage, current at the operating point, the torque-speed characteristic, driver requirements, feedback fit, thermal margin. | A curve, a calculation, or a feedback and control review. |
| Sourcing or procurement | Availability, sample status, minimum order, lead-time band, origin, cost drivers, and a second-source path. | A cross-reference, a supply-chain review, or a volume quotation. |
| Quality or reliability | Variation, life evidence, traceability, failure modes, and how change is controlled. | A failure analysis, a qualification plan, or a test report. |
The applications in this wedge
4 of the 10 pages in the library. Each one is a load model with the arithmetic shown.
Published configurations at or below 17 mm body diameter, which is the envelope band these mechanisms live in.
23 of 32 published configurations. Continuous output torque is calculated from the motor's rated torque through the ratio and the typical stage efficiency. The gearhead limit is a maximum, not an operating point, and 29 of 32 published configurations can stall above it.
| Configuration | Class | Diameter | Ratio | Rated output speed | Continuous output torque | Gearhead limit |
|---|---|---|---|---|---|---|
| MM-C0817-P02560-030A | Coreless brushed DC | 8 mm | 256:1 | 53.1 rpm | 22.3 mN·m | 80 mN·m |
| MM-C1017-P00311-060A | Coreless brushed DC | 10 mm | 31.12:1 | 366.3 rpm | 4.4 mN·m | 24.5 mN·m |
| MM-C1017-P10240-024A | Coreless brushed DC | 10 mm | 1024:1 | 8.7 rpm | 63.4 mN·m | 147 mN·m |
| MM-C1024-P00640-030A | Coreless brushed DC | 10 mm | 64:1 | 141.3 rpm | 40.3 mN·m | 98.1 mN·m |
| MM-C1025-P00311-030B | Coreless brushed DC | 10 mm | 31.12:1 | 334.2 rpm | 10.1 mN·m | 24.5 mN·m |
| MM-C1025-P02560-045B | Coreless brushed DC | 10 mm | 256:1 | 47.3 rpm | 57.2 mN·m | 147 mN·m |
| MM-C1213-S00523-030B | Coreless brushed DC | 12 mm | 52.25:1 | 216.3 rpm | 3.4 mN·m | 24.5 mN·m |
| MM-C1213-S01440-030B | Coreless brushed DC | 12 mm | 143.99:1 | 78.5 rpm | 8.3 mN·m | 24.5 mN·m |
| MM-C1219-S00523-045A | Coreless brushed DC | 12 mm | 52.25:1 | 136.1 rpm | 10 mN·m | 24.5 mN·m |
| MM-C1219-S00720-030B | Coreless brushed DC | 12 mm | 71.99:1 | 117.2 rpm | 9.3 mN·m | 24.5 mN·m |
| MM-C1226-S00523-060A | Coreless brushed DC | 12 mm | 52.25:1 | 130.1 rpm | 10.1 mN·m | 24.5 mN·m |
| MM-C1226-S01002-120A | Coreless brushed DC | 12 mm | 100.22:1 | 100.8 rpm | 9.3 mN·m | 24.5 mN·m |
| MM-C1321-P00191-060B | Coreless brushed DC | 13 mm | 19.13:1 | 404.6 rpm | 15.5 mN·m | 196 mN·m |
| MM-C1321-P03661-030A | Coreless brushed DC | 13 mm | 366.12:1 | 16.7 rpm | 120.8 mN·m | 294 mN·m |
| MM-C1329-P00191-120B | Coreless brushed DC | 13 mm | 19.13:1 | 417.7 rpm | 23.2 mN·m | 196 mN·m |
| MM-C1329-P00777-120C | Coreless brushed DC | 13 mm | 77.66:1 | 123.6 rpm | 113.4 mN·m | 294 mN·m |
| MM-C1626-P04552-240A | Coreless brushed DC | 16 mm | 455.19:1 | 23.5 rpm | 191.8 mN·m | 490 mN·m |
| MM-C1626-S00311-060B | Coreless brushed DC | 16 mm | 31.06:1 | 193.8 rpm | 12.1 mN·m | 29.4 mN·m |
| MM-C1636-P00203-060B | Coreless brushed DC | 16 mm | 20.25:1 | 269.1 rpm | 19.6 mN·m | 49 mN·m |
| MM-C1636-P04552-240A | Coreless brushed DC | 16 mm | 455.19:1 | 24.4 rpm | 191.8 mN·m | 490 mN·m |
| MM-C1726-P00203-060A | Coreless brushed DC | 17 mm | 20.25:1 | 297.8 rpm | 20 mN·m | 49 mN·m |
| MM-C1726-P01575-120A | Coreless brushed DC | 17 mm | 157.46:1 | 36.9 rpm | 150.2 mN·m | 392 mN·m |
| MM-C1736-P00292-240C | Coreless brushed DC | 17 mm | 29.16:1 | 192 rpm | 84.7 mN·m | 294 mN·m |
The reviews that apply here
One of these is usually the right first move. All of them return engineering, not a quotation.