News from the product management: Selecting a naXture actuator for your actuation task – Unlatching
We are continuing our blog series to support our customers in selecting our actuators and added a new application: “Unlatching”.
Application task “unlatching” explained – step by step – from the analysis to the verification of the selection in the force-velocity map.
Requirements for the work task
Actuation task:
A latch is to be opened.
- With a force of 350N, a self-locking mechanism is disengaged and the mechanism is unlocked. The actuator then pushes the latch into an end position.
- The total stroke of 15mm is divided into three parts:
1. attaching the actuator to the mechanism (0.5mm),
2. unlatching (4mm) and 3. pushing into the end position (10.5mm). - The total procedure should be completed in 1.5 seconds, with 0.5 seconds available for unlatching.
Requirements:
- A force reserve is to be provided: 50% of the nominal force.
- Safety state is “Normally Retracted“: in powerless state, the actuator automatically returns to the start position.
Analyses of the actuation task
1. Creating a force-path diagram
2. Setting up the requirement for the positioning time
3. Determining the load data:
- Load: FApp = 350N
- Stroke: 15mm
| Operating point | Stroke s [mm] | Force F [N] | Stroke Δs [mm] | Time t [s] |
|---|---|---|---|---|
| 1 | 0 | 0 | – | – |
| 2 | 0,5 | 0 | 0,5 | – |
| 3 | 1,2 | 200 | 0,7 | – |
| 4 | 3 | 350 | 1,8 | – |
| 5 | 4,5 | 0 | 1,5 | 0,5 |
| 6 | 15 | 0 | 10,5 | 1,5 |
Calculation of the load data
4. Calculation of the mechanical work W[J]:
- W = F * s
| Work W [J] | |
|---|---|
| W1 | 0,07 |
| W2 | 0,63 |
| W3 | 0,18 |
| Summe | 0,88 |
During the unlatching process…
- a mechanical work Wtotal of 0,88J is applied.
- A mechanical power of aprox. 1,76W (0,88J/0,5s) is required.
Selecting the actuator
5. Determining the force FPmax to select the actuator
- During unlatching, a work of 0.88 J is applied over a stroke of 4mm.
For the first estimation of FPmax we can assume 0,88J/0,004m = 220N and a surcharge of 65% resulting in 363N. - Additionally, we can take into account the requirement for a force reserve of 50% of the nominal force: Fmax = 350N * 1,5 = 525N
The displayed „Best Match“ then results in:
| FPmax | Fmax | vPmax | vmax | Hub |
|---|---|---|---|---|
| 338,00 | 675,00 | 16,00 | 32,00 | 30 |
Downloading the technical information sheet
6. Download the technical information sheet of the actuator:
| FPmax | Fmax | vPmax | vmax | Hub |
|---|---|---|---|---|
| 338,00 | 675,00 | 16,00 | 32,00 | 30 |
Verification of the force-velocity map
7. Checking the requirements for the actuating speed:
- A preloaded spring should be used to retract the actuator in the powerless state:
FRe(s) = 10N + 3,334 N/mm*s - In order to determine the extension speed of the actuator at the respective operating points and thus the positioning times to be checked, the path-dependent restoring force FRe(s) must be superimposed.
- From the force-velocity diagram of the technical information sheet, the positioning speeds can then be obtained and the positioning times calculated:
| Operating point | Stroke s [mm] | Force F [N] | Velocity v [mm/s] | Stroke Δs [mm] | Time Δt [s] | Time abs. t [s] |
|---|---|---|---|---|---|---|
| 1 | 0 | 10 | 31,53 | – | – | 0 |
| 2 | 0,5 | 11,67 | 31,45 | 0,5 | 0,02 | 0,02 |
| 3 | 1,2 | 214 | 21,85 | 0,7 | 0,03 | 0,05 |
| 4 | 3 | 371,7 | 14,38 | 1,8 | 0,16 | 0,21 |
| 5 | 4,5 | 25 | 30,81 | 1,5 | 0,03 | 0,24 |
| 6 | 15 | 60 | 29,16 | 10,5 | 0,36 | 0,6 |
8. In addition, the actuating speed at an additional load of 50% of the nominal force is to be checked – the procedure is in accordance with the previously prepared calculations:
| Operating point | Stroke s [mm] | Force F [N] | Velocity v [mm/s] | Stroke Δs [mm] | Time Δt [s] | Time abs. t [s] |
|---|---|---|---|---|---|---|
| 1 | 0 | 10 | 31,53 | – | – | 0 |
| 2 | 0,5 | 11,67 | 31,45 | 0,5 | 0,02 | 0,02 |
| 3 | 1,2 | 214 | 21,85 | 0,7 | 0,03 | 0,05 |
| 4 | 3 | 546,67 | 6,08 | 1,8 | 0,38 | 0,43 |
| 5 | 4,5 | 25 | 30,81 | 1,5 | 0,03 | 0,46 |
| 6 | 15 | 60 | 29,16 | 10,5 | 0,36 | 0,82 |
9. Verification of the requirements:
- The actuator can provide the required forces:
Both for the nominal force and with the required reserve of +50%. - The required actuating times for unlocking and extending to the end position can be confirmed.
Even in the case of additional load, the operating velocity remains within the requirement.
