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Double acting pneumatic cylinders

rodless, with roller guide, series VL1

The rodless cylinders of the VL1 series are particularly useful where there is no space for a standard cylinder. The piston rod does not extend from the cylinder. Thanks to their maximum stroke of up to 6 meters, they can also be used in applications where the use of a conventional cylinder would be impossible. This series uses the proven two-strip principle. The VL1 series includes roller guides on steel guide rails. The carriage can be equipped with a locking unit as an accessory.

Technical information

Technical data

Working pressure	0,6 MPa
Min. pressure	0,3 MPa
Max. pressure	1,0 MPa
Temp. range	-20^oC to +80^oC
Working medium	modified compressed air
Carriage speed	min. 20 mm.s^-1 max. 2 m.s^-1

Piston dia.	25	40	50
Force at 0,6 MPa [N]	250	640	1050
Connection	G1/8"	G3/8"	G3/8"
Length of adjustable cushioning [mm]	25	41,5	52
Max. stroke [mm]	6000	6000	6000
Stroke tolerance [mm]	+3,2	+3,2	+3,2

For long-term and trouble-free operation, we recommend:
1) speed maximum 1 m.s^-1
2) use a hydraulic shock absorber if the efficiency of the internal cushioning approaches the limit value
3) if the cylinder is used vertically, the cushioning capacity is reduced by 40%
4) maintain a correct and constant lubrication

The pneumatic sealing is achieved through an axial elastomer stripseal reinforced with Kevlar. This system guarantees dimensional stability even with high speeds. The external protection seal consists of a thermoplastic stripseal reinforced with Kevlar.

Weights

Piston dia.	25	40	50
Base weight (0mm) with medium carriage [kg]	2,10	6,34	10,85
Base weight (0mm) with long carriage [kg]	2,86	8,96	15,37
Weight of 100 mm of stroke [kg]	0,300	0,670	1,020

Construction / materials

caps: die-cast aluminium
tube: anodized aluminium
piston: aluminium
guide: ball bearings, steel guide rails
piston guide slide: acetalic resin
sealings: NBR

Permissible static load and stress

Cylinder force F	Static load			Static moment
Cylinder force F	P1	P2	P3	M1	M2	M3

Piston dia.	F [N] at 0,6 MPa	Medium carriage						Long carriage
Piston dia.	F [N] at 0,6 MPa	P1 [N]	P2 [N]	P3 [N]	M1 [Nm]	M2 [Nm]	M3 [Nm]	P1 [N]	P2 [N]	P3 [N]	M1 [Nm]	M2 [Nm]	M3 [Nm]
25	250	700	700	700	34	17	34	1000	1000	1000	63	25	63
40	640	1100	1100	1100	120	46	120	1600	1600	1600	230	69	230
50	1050	1500	1500	1500	170	85	170	2000	2000	2000	310	110	310

A moment is the product of the load (N) and the arm (m), i.e the distance between the centre of gravity of the load and the longitudinal axis of the piston. Please note that in dynamic conditions, the load must be reduced due to effects associated with the speed. Calculation of permissible dynamic stress and verification of internal damping efficiency can be found below.

Examination and verification of internal cushioning

In a system with moving masses, as in the case of rodless cylinders, it is essential to control the dissipation of the system’s kinetc energy as it is brought to a stop. First of all, it is necessary to establish and verify the most suitable method for cushioning the system, in order to avoid the moving mass (carriage with load) striking against the end-caps and compromising the life of the cylinder.

If the point corresponding to a given load and speed lies beneath the appropriate curve, the cushioning is able to absorb the kinetic energy of the system. Vice versa if the point lies above the curve, the cushioning is not able to absorbe the kinetic energy. In that case you must:
a) decrease the load and mantain the translation speed
b) decrease the speed and mantain the load
c) select a cylinder with a bigger bore or with twin chambers
d) use external hydtŕaulic shock absorber

Attention: if the cylinder is mounted vertically, the damping efficiency is reduced by 40%.

Dynamic load capacity

Procedure for determining the permissible values for dynamic stress:

determine the KRV coefficient according to the speed

multiply the permissible values for static stress by the KRV coefficient and the value calculated in this way is the maximum permissible value for dynamic stress

Example - verification of the suitability of the cylinder with a misaligned load in vertical position

In this example, we will check the suitability of a VL1 series cylinder with a roller guide with a piston diameter of 40 mm with a medium carriage. We will move a load of 50N, which is at a distance B3 from the vertical axis of the cylinder. The transverse distance of the load from the axis of the cylinder B1 is 110 mm (see example for series S1).

P2 = 50 N
V = 1 m.s^-1
b1 = 110 mm

b3 = 200 mm

Verification of the cushioning capacity
The graph for verifying the efficiency of the internal cushioning shows that for a moving value of 5 kg (50 N) and a speed of 1 m.s^-1, the point is under the curve for a diameter of 40 mm. However, when the cylinder is positioned vertically, the damping efficiency is reduced by 40%. This means that the internal cushioning will not be able to absorb the energy and safely stop the carriage with the mass. It is necessary to use a hydraulic shock absorber, reduce the speed or load.

Calculation and verification of the dynamic load capacity
From the graph for the permissible dynamic load, we determine the value of the KRV coefficient. For a speed of 1 m.s^-1 and the VL1 series, the value of KRV = 0,27. The value of the permissible dynamic stress CD is the product of the KRV coefficient and the permissible static load CM.
CD = CM · KRV = 1100 · 0,27 = 297 N
Since the load P (50 N) is less than the calculated value of CD (297 N), the selected cylinder is suitable for use.

Calculation of dynamic torque
In order to calculate the torques M1, M2 and M3 that act on the carriage, we must calculate the force generated by the load during acceleration and deceleration. We therefore determine the deceleration „a“ at the speed V and the damping length L and the dynamic force F.

Ø	L [mm]
16	16,5
25	25
32	32,5
40	41,5
50	52

a = v²/(2 * L * 10^-3) = 1²/(2 * 41,5 * 10^-3) = 12 m.s^-2

The dynamic force F will then be

F = (P * a)/9,81 = (50 * 12)/9,81 = 61 N

The toquues are then given by the relations:
MD1 = F · b1 = 61 · 110 = 6710 Nmm = 6,7 Nm
MD3 = F · b3 = 61 · 200 = 12200 Nmm = 12,2 Nm
Since the permissible torque value M1 (170 Nm) is greater than the calculated value MD1 (6,7 Nm) and the permissible torque value M3 (170 Nm) is greater than the calculated value MD3 (12,2 Nm), the selected cylinder is suitable for use.

See also other examples given for the S1 series and S5 series rodless cylinders.

Carriage adjustment of cylinder series VL1

If the load is not centered on the carriage, the carriage‘s roller guide must be adjusted. The following illustrations show the 3 most common off-center loading patterns and each illustration shows which screws need to be adjusted. The arrows indicate the screws to be adjusted, based on the position of the load (P). Turn the screw (A) according to the load. Put a drop of Loctite 242 onto the screw (B) and tighten it all the way down. Finally loosen both screws by 90°.