Compensating For Thermal Effects - Parker 406LXR Series Product Manual

406LXR Series Product Manual
These are mounting surfaces or other items which produce a thermal change that effect the
temperature of the 406LXR base (i.e. Machine base with motors or other heat generating devices that
heat the mounting surface and thus thermally effect the 406LXR base).
Motor Heating From 406LXR
Since the 406LXR uses a servo motor as its drive, it produces no heat unless there is motion, or a
force being generated. In low duty cycle applications heat generation is low, however as duty cycles
increase, temperature of the 406LXR will increase, causing thermal expansion of the base. With very
high duty cycles these temperatures can reach temperatures as high as 30° C above ambient.

Compensating for Thermal Effects

How much you will have to compensate for the above thermal effects depend on the application
requirements for accuracy. If your accuracy requirements are high, you either need to control base
temperature or program a thermal compensation factor into your motion program. Controlling the base
temperature is the best method. However, this means controlling the ambient temperature by removing
all heat/cold generators from the area and operating at very low duty cycles. Compensation is the
other way of achieving accuracy without sacrificing performance. In this case the system must be
exercised through its normal operating cycle. The temperature of the base should be measured and
recorded from the beginning (cold) until the base becomes thermally stable. This base temperature
should be used in a compensation equation. Below is the fundamental thermal compensation
equation:
(
= −
C I I
d d d
=
C Corrected
d
=
I Incrementa
d
=
δ Thermal
T
=
ΔT Temperatur
Example :
Base Temperatur
Required move
=
C 100mm
d
In this move the commanded move should be 26.4 microns less (100mm – 99.9736mm) than the
desired move. This will compensate for the thermal expansion of the scale.
This is a simple linear correction factor and can be programmed in to most servo controllers using
variables for the position commands.
)

  
T
T
displaceme nt (mm)
l displaceme nt (mm)
Expansion (0.000022 mm/mm/
e Differenti al from 20

e of 32 C
100mm

 =
- (100mm 12 C)
T

C)

C
99.9736mm
33
Chapter 4 - Performance
Parker Hannifin Corporation
EMN Automation - Parker
Irwin, Pennsylvania