Pfaff Industrial 918 Guide

ADJUSTMENT MANUAL
296-12-19 338/002
Instruction Manual engl. 06.18
918
938 U
938
938 U
This adjustment manual applies to machines
from the serial number 8 300 001 and
software version 0435/006 onwards.

Reprinting, reproduction and/or translation of PFAFF adjustment manuals (including parts
thereof) is only permitted with our prior agreement and citation of the source.
PFAFF Industriesysteme
und Maschinen GmbH
Hans-Geiger-Str. 12 - IG Nord
D-67661 Kaiserslautern

Table of Contents
Contents ..................................................................................Page
3
13 Adjustment ........................................................................................................................... 5
13.01 Tools, gauges and other accessories .................................................................................... 5
13.02 Abbreviations ......................................................................................................................... 5
13.03 Explanation of symbols.......................................................................................................... 5
13.04 Checking and adjustment aid................................................................................................. 6
13.05 Adjusting basic machine ........................................................................................................ 7
13.05.01 Compensation weight............................................................................................................ 7
13.05.02 Needle in needle hole centre (in sewing direction)................................................................ 8
13.05.03 Needle bar parallel guide ....................................................................................................... 9
13.05.04 Locking lever........................................................................................................................ 10
13.05.05 Zero stitch and zigzag stitch scale ....................................................................................... 11
13.05.06 Needle in needle hole centre (crossways to sewing direction) ........................................... 12
13.05.07 Zigzag stitch width............................................................................................................... 13
13.05.08 Zigzag stitch movement (only on the 918 and 938) ............................................................. 14
13.05.09 Needle hole symmetry - left, middle and right (only on the 918 and 938) ........................... 15
13.05.10 Multi-stitch movement (only on the 918U and 938U).......................................................... 16
13.05.11 Zigzag movement (only on the 918U and 938U).................................................................. 17
13.05.12 Target positioning device sensor (only on the 918U and 938U) .......................................... 18
13.05.13 Needle position adjusting lever............................................................................................ 19
13.05.14 Bottom feed dog zero position (with a closed gear box) ..................................................... 20
13.05.15 Bottom feed dog zero position (with an open gear box)...................................................... 21
13.05.16 Bottom feed dog sliding movement .................................................................................... 22
13.05.17 Bottom feed dog lifting movement .................................................................................... 23
13.05.18 Driving belt in the gear box.................................................................................................. 24
13.05.19 Hook bearing bracket .......................................................................................................... 25
13.05.20 Hook lubrication ................................................................................................................... 26
13.05.21 Pre-calibrating the needle height ......................................................................................... 27
13.05.22 Needle bar rise, hook-to-needle clearance and lower bobbin position finger ...................... 28
13.05.23 Readjusting needle height ................................................................................................... 29
13.05.24 Bobbin lifter position ........................................................................................................... 30
13.05.25 Bobbin lifter movement ....................................................................................................... 31
13.05.26 Bottom feed dog height ...................................................................................................... 32
13.05.27 Clearance between the presser foot and needle plate........................................................ 33
13.05.28 Presser foot pressure ......................................................................................................... 34
13.05.29 Needle thread tension release (in machines without -900/24)............................................. 35
13.05.30 Thread deflection bow ........................................................................................................ 36
13.05.31 Knee lever travel limit .......................................................................................................... 37
13.05.32 Knee lever backlash ............................................................................................................. 38
13.05.33 Bobbin winder...................................................................................................................... 39

Table of Contents
Contents ..................................................................................Page
4
13.06 Adjusting the under-edge trimmer -771//05 ........................................................................ 40
13.06.01 Neutral knife position .......................................................................................................... 40
13.06.02 Knife height ......................................................................................................................... 41
13.06.03 Knife position ....................................................................................................................... 42
13.06.04 Knife drive switch ................................................................................................................ 43
13.06.04 Workpiece protection guard ................................................................................................ 44
13.07 Adjusting thread trimmer -900/24 ....................................................................................... 45
13.07.01 Axial control cam position ................................................................................................... 45
13.07.02 Control cam (pre-calibrating) ................................................................................................ 46
13.07.03 Thread catcher position and test cut .................................................................................. 47
13.07.04 Control cam (recalibrating) .................................................................................................. 48
13.07.05 Needle thread tension release ............................................................................................ 49
13.07.06 Functional check of bobbin thread monitor -926/04 ............................................................ 50
13.08 Parameter settings ............................................................................................................. 50
13.09 Internet update of control CD ............................................................................................. 50
14 Circuit Diagrams 91-191 584-95 ....................................................................................... 51

Adjustment
5
13 Adjustment
Observe and comply with all instructions in the instruction manual's chapter
1 Safety! In particular make sure that all safety covers are installed again
correctly after making adjustments, see chapter 1.06 Hazard information in
the instruction manual!
Unless otherwise stated, the machine must be disconnected from the mains
before all adjustment work!
Risk of injury due to accidental machine start-up!
No screw clamp may be fastened to the needle bar with the PFAFF 918 and 938!
This may damage the special needle bar coating.
Notes on adjustment
All adjustments in this manual are based on a fully assembled machine and may only be
carried out by technical staff trained for this purpose. Machine covers, which have to be
removed and replaced to carry out checks and adjustments, are not mentioned in the text.
The order of the following chapters corresponds to the most logical work sequence for
machines that have to be completely adjusted. Both the preceding and following chapters
must be observed if only specific individual work steps are carried out. The screws and nuts
indicated in brackets ( ) are fastenings for machine parts, which must be loosened before
any adjustment and tightened again afterwards.
13.01 Tools, gauges and other accessories
O1 set of screwdrivers with blade widths from 2 to 10 mm
O1 set of wrenches with jaw widths from 7 to 14 mm
O1 set of Allen keys from 1.5 to 6 mm
O1 metal ruler, order no. 08-880 218-00
O1 feed dog setting gauge, order no. 61-111 651-33
O1 adjustment pin (5 mm diameter), order no. 13-030 341-05
O1 hook bearing bracket setting gauge, order no. 91-129 996-05
13.02 Abbreviations
t.d.c. = top dead centre
b.d.c. = bottom dead centre
13.03 Explanation of symbols
Activities to be performed or important information in this adjustment manual are
emphasised by symbols. The symbols used have the following meaning:
Note, information
Maintenance, repairs, adjustment, service work
(only to be carried out by technical staff)

Adjustment
6
Fig. 13 - 01
13.04 Checking and adjustment aid
It is possible to precisely locate the required needle bar positions through
insertion in holes 1 - 5.
OTurn the handwheel until the needle bar has almost reached the required position.
OPlace the adjustment pin in the corresponding hole provided and press it down.
OTurn the handwheel slightly back and forth until the adjustment pin engages in the crank
cutout behind the bearing plate, thus blocking the machine.
Hole 1 = 2.0 mm after bottom dead centre of the needle bar (2.0 after b.d.c.)
Hole 2 = top dead centre of the needle bar (t.d.c.)
Hole 3 = 0.25 mm after top dead centre of the needle bar (0.25 after t.d.c.)
Hole 4 = 1.0 mm after top dead centre of the needle bar (1.0 after t.d.c.)
Hole 5 = 4.0 mm after bottom dead centre of the needle bar (4.0 after b.d.c.)
4
2
5
1
3

Adjustment
7
Fig. 13 - 02
13.05 Adjusting basic machine
13.05.01 Compensation weight
OMove the needle bar to b.d.c.
OTurn the compensation weight 1 (screws 2) according to the rule.
1
2
Rule
When the needle bar is in b.d.c., the largest eccentricity of the compensation weight 1
should be in the top position.

Adjustment
8
13.05.02 Needle in needle hole centre (in sewing direction)
Rule
At zigzag stitch setting “0“ and the needle position setting “Middle”, the needle should
pierce the middle of the needle hole looking in the sewing direction.
OMove the needle bar to b.d.c.
OTurn the eccentric pin 1 (nut 2 and screw 3) according to the rule.
Fig. 13 - 03
2
1
3

Adjustment
9
13.05.03 Needle bar parallel guide
Rule
The guide bar 5 should be parallel to the needle bar.
OMove the needle bar to t.d.c. (hole 2).
OLoosen the screws 1 and 2 and the nut 3.
OPosition the largest eccentricity of the pin 4 to down.
OMove the cutout of the guide bar 5 until it abuts the eccentric pin 4, turn the eccentric
pin 4 according to the rule and tighten the nut 3.
OSlide the guide bar 5 down and up again up to the stop. The bushing 6 must not move
sideways (re-adjust the eccentric pin 4 if necessary).
OMove the guide bar 5 until it abuts the eccentric pin 4 and tighten the screws 1 and 2.
Fig. 13 - 04
1
3
4
2
5
1
3
4
6
2
5

Adjustment
10
0
1
2
6
5
3
4
Fig. 13 - 05
13.05.04 Locking lever
Rule
The zigzag stitch adjusting lever 3 should lock in any position.
OLoosen the screw 2.
OPress the locking lever 1 until it pushes up against the zigzag stitch adjusting lever 3.
OTurn the pivot pin 4 to the left until it stops.
ORelease the locking lever 1.
OThe locking lever 1 should be parallel to the zigzag stitch adjusting lever 3.
OTighten the screw 2.
1
3
2
4

Adjustment
11
Fig. 13 - 06
13.05.05 Zero stitch and zigzag stitch scale
Rule
At zigzag stitch setting “0“,
1. the needle bar should not move sideways when turning the handwheel,
2. the marking “0“ on scale 1 should match the marking 2.
OSet the needle position adjusting lever 4 to “Middle“ and loosen the screws 5 and 6.
OAllow the machine to run slowly and turn the zigzag stitch adjusting lever 3 to the right
until the needle bar no longer moves sideways.
OSwitch off the machine, move the screw 5 until it abuts on the right and tighten.
OLoosen the screws 7 and adjust the scale 1 according to rule 2.
OTighten the screws 7.
The screw 6 remain loosened for the subsequent adjustments.
1
23
4
5
6
7
7

Adjustment
12
13.05.06 Needle in needle hole centre (crossways to sewing direction)
Rule
At zigzag stitch setting “0“ and the needle position setting “Middle“, the needle should
pierce the middle of the needle hole looking crossways to the sewing direction.
OTurn the eccentric pin 1 (nut 2) according to the rule.
Fig. 13 - 07
1
2

Adjustment
13
Fig. 13 - 08
13.05.07 Zigzag stitch width
Rule
At the largest zigzag stitch setting, the marking 1 should match the largest zigzag stitch
indication on the scale 2.
OTurn the zigzag stitch adjusting lever 3 according to the rule.
OMove the screw 4 to the top and tighten.
Should the machine be fitted with a needle plate that has a smaller needle hole
than the zigzag stitch width on the scale, the zigzag stitch limit must be set
according to the needle hole width of the needle plate.
4
1
2
3

Adjustment
14
Fig. 13 - 09
13.05.08 Zigzag stitch movement (only on the 918 and 938)
Rule
If the needle bar is in t.d.c. (adjustment hole “2“) coming from the right bottom dead
centre, the needle bar should not move sideways when moving the zigzag stitch
adjusting lever back and forth.
OMove the needle bar to t.d.c. coming from the right bottom dead centre and insert the
adjusting pin into hole “2“ of the bearing plate (block machine).
OTurn the zigzag eccentric 1 (screws 2) according to the rule. Make sure that the zigzag
eccentric 1 protrudes about 5 mm from the right inner side of the cast wall.
OPull the adjusting pin out of the bearing plate.
21
5 mm
4
2
5
1
3

Adjustment
15
Fig. 13 - 10
13.05.09 Needle hole symmetry - left, middle and right (only on the 918 and 938)
Rule
At zigzag stitch setting “0“, the needle puncture position should be in the middle of the
needle hole.
At the largest zigzag stitch setting, the needle hole should be the same distance from the
middle puncture position on the left and right.
OLet the needle pierce paper in the required zigzag stitch settings.
OAdjust the zigzag eccentric 1 (screws 2) - without turning it - according to the rule.
21

Adjustment
16
13.05.10 Multi-stitch movement (only on the 918U and 938U)
Rule
1. If the needle is in the right-hand puncture position in b.d.c., the cutout 5 of the control
cam 3 should be level and point backwards.
2. The sideways movement of the needle bar should end when the needle punctures the
workpiece (carry out a check at the largest zigzag setting).
OPosition the setting wheel 1 to multi-stitch.
OSet the zigzag adjusting lever 2 to “Largest zigzag stitch“.
OTurn the control cam 3 (screws 4) according to the rule.
Fig. 13 - 11
43
2
1
5

Adjustment
17
2
13.05.11 Zigzag movement (only on the 918U and 938U)
Rule
If the needle bar is in t.d.c. (hole 2)coming from the right b.d.c., the needle bar should
not move sideways when moving the zigzag stitch adjusting lever 4 back and forth.
OPosition the setting wheel 1 to zigzag.
OTurn the zigzag stitch eccentric 2 (screw 3) according to the rule.
Fig. 13 - 12
3
4
1
4
2
5
1
3

Adjustment
18
Fig. 13 - 13
13.05.12 Target positioning device sensor (only on the 918U and 938U)
Rule
There should be a clearance of 0.2 - 0.3 mm between the sensor 1 and the control cam 3.
OAdjust the sensor 1 (screws 2) according to the rule.
1
3
2

Adjustment
19
13.05.13 Needle position adjusting lever
OLoosen the screws 1 and 2.
OSet the needle position adjusting lever 3 to “Middle“ and the zigzag stitch adjusting
lever 4 to the largest zigzag.
OPlace a piece of paper under the presser foot and pierce on the left and right with the
needle.
OSet the zigzag stitch adjusting lever 4 to “0“ and slide the needle position adjusting lever 3
to the right and left until the needle is positioned over each of the previously punctured
holes.
OMove the screw 1 until it abuts in the left needle position and the screw 2 until it abuts in
the right needle position and tighten.
Rule
The left and right deflection of the needle should be the same size at both the largest
zigzag stitch setting and the left or right needle position.
Fig. 13 - 14
2
1
4
3

Adjustment
20
Fig. 13 - 15
13.05.14 Bottom feed dog zero position (with a closed gear box)
Rule
The bottom feed dog should not move when turning the handwheel with stitch length
regulation “0“.
OLoosen the screw 1.
OPlace the open-ended wrench (SW 27)on the spring tension ring 2 and use it to hold the
regulating shaft 3 tightly.
OWhilst continuously turning the handwheel, turn the open-ended wrench on the spring
tension ring 2 according to the rule.
OMove the adjusting crank 4 until it abuts the circlip 5 on the casting and tighten the
screw 1.
OCarry out a check according to the rule.
1
2
5
4
3