KE-750_MAINTE.pdf - 第132页
- 129 - 7. TROUBLESHOOTING 7.1 Part Mount Part mount offset can be classified in an offset of XY, θ , or XY θ . And, it can also be classified by causes as follows: 1. Bond (adhesive) or cream solder 2. Mount program ent…
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memorizes the stop position at the start time but the deviation counter
reads 0.
(3) When LM628 analyzes the data above, and profile of the motor drive is
complete,① command voltage is gradually applied to the AC servo
driver. The AC servo driver then controls the rotation speed of the
motor according to the voltage being applied. (The range of the
command voltage is ±10 V.)
(4) The AC servo driver counts the number of pulses from the rotary
encoder (1 pulse = 10 µm), and detects (② speed detection) the
rotating speed of the motor. On the other hand, the counted pulse is
input to both the current position counter and the deviation counter
(DOWN side) of LM628. As a result, the reading of the current
position counter increases, and that of the deviation counter decreases.
(③ position detection)
(5) The deviation counter performs a computation, (command pulse) -
(position pulse), and when the Z axis approaches the target position
plus 5 mm, the command voltage goes near 0 V to decelerate the
motor. As a result, when the Z axis reaches at +5 mm position, the
deviation counter reads 0, and the command voltage is set 0 V to stop
the motor. The operation of stop and acceleration/deceleration may
largely change depending on the gain setting of the AC servo driver.
Therefore, an appropriate gain setting value must be found and set for
the system.
(6) When the motor stops, the absolute counter of LM628 reads the position
at the start plus 500.
As described above, in the semi-closed loop system, both the speed control
and the positioning control are performed together with the rotary encoder
directly coupled to the motor. Therefore, if there is a defect in the
mechanical system before the motor shaft (overload, loose screw, etc.), the
stop position of the ball screw may be offset even when the rotating position
of the motor is normal.
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7. TROUBLESHOOTING
7.1 Part Mount
Part mount offset can be classified in an offset of XY, θ, or XYθ. And, it can
also be classified by causes as follows:
1. Bond (adhesive) or cream solder
2. Mount program entered
3. Cramp state of the board on the board carriage
4. Mount head
5. Vacuum or blow pressure when mount
6. XY axes
7. MS parameters entered
1. Problems caused by dispenser or cream solder
The adhesive and cream solder are main causes of trouble. On a
double-sided tape, it is necessary to be mounted correctly.
Symptom Cause Remedy
There is an
offset in XY and
θ axes when
mounting using
adhesive. (In
particular, for
small-sized parts
such as
2125/3216
capacitors, Melf,
and SOT)
With adhesive, there is an offset mainly in
θ axis, and this is affected by the amount
and position of adhesive. In particular,
2125/3216 capacitors, Melf, and SOT are
affected by the amount of adhesive. For
capacitors, the body is raised with respect
to its edges, and if little adhesive is applied
the body does not touch the adhesive. In
addition to this, if adhesive displacement
occurs, it is fixed by 1 point, and the part is
largely affected. This applies also to
SOT. The body is raised with respect to
the leads. Melf is likely to roll because of
its shape, and it can be largely affected by
the amount of adhesive.
In general, the amount of adhesive
increases, a stable mount is performed.
Check that there is no adhesive
displacement on the board to which
the adhesive is applied, using
position tracking. For the amount
of adhesive, check on the board
which the parts are mounted so that
the adhesive adequately touches
the parts. If there is problem with
the placement and amount of
adhesive, make corrections on the
application conditions of the
dispenser for the specific part type,
or for all part types.
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Symptom Cause Remedy
There is an
offset among XY
and θ when
mounting using
adhesive. (In
particular, for
medium-size
parts such as
aluminum
electrolytic
capacitors,
tantalum
capacitors, and
trimmers)
Medium-sized tall parts such as aluminum
electrolytic capacitors, tantalum
capacitors, and trimmers are likely to roll.
And, this is also affected by warp and size
of the board. Warp of the board when
mounting is a repulsion force of Z upward
movement, resulting in an offset. The
offset is mainly found in θ axis.
It is better to apply much adhesive.
On the mounter, install a backup pin
under the board around where the
parts are mounted to prevent board
warp. If this is not effective
enough, change the lift up speed to
medium or low after mounting.
There is an
offset in XY and
θ axis when
placement on
cream solder.
(When this
occurs with all
parts.)
For cream soldering, different from the
case of adhesive, there is little effect with
printing offset because of wide pat.
However, for soldering, leaving time and
viscosity after printing largely affect the
performance. The conditions of the
leaving time and the viscosity cannot be
the same because of the difference in type
of the solder, humidity of the leaving time,
and environmental conditions.
Check that the solder is dried out
before mounting.
There is an
offset in XY and
θ axis when
placement on
cream solder.
(In particular,
medium-sized
parts such as
aluminum
electrolytic
capacitors,
tantalum
capacitors, and
trimmers.)
This is also affected by dry soldering.
However, in this case, the same as the
adhesive, thickness and size of the board
affect the performance. Warp of the
board when mounting is a repulsion force
of Z upward movement, resulting in an
offset. In some case, it jumps.
Install a backup pin under the board
around where the parts are
mounted to prevent board warp. If
this is not effective enough, change
the lift up speed to medium or low
after mounting.