1
00:00:07,620 --> 00:00:09,900
- Let's talk about the
Laser Printing Process.

2
00:00:09,900 --> 00:00:12,210
The laser printing process is broken down

3
00:00:12,210 --> 00:00:15,810
into several steps, let's
talk about each of those now.

4
00:00:15,810 --> 00:00:18,930
The first is the processing step.

5
00:00:18,930 --> 00:00:22,050
In the processing step,
this actually begins

6
00:00:22,050 --> 00:00:25,560
at the computer that
initiates the print job.

7
00:00:25,560 --> 00:00:27,540
The computer will calculate the data

8
00:00:27,540 --> 00:00:29,970
that needs to be printed, and then send

9
00:00:29,970 --> 00:00:33,030
that off to the printer
either as an entire print job

10
00:00:33,030 --> 00:00:36,420
or it will spool it one page at a time.

11
00:00:36,420 --> 00:00:39,720
Once it gets to the printer,
that data is recalculated

12
00:00:39,720 --> 00:00:44,100
and stored in RAM until
it's ready to print,

13
00:00:44,100 --> 00:00:46,230
so that's the processing stage.

14
00:00:46,230 --> 00:00:49,050
It's kind of a pre-stage
to the actual printing

15
00:00:49,050 --> 00:00:51,630
that happens in the laser printer.

16
00:00:51,630 --> 00:00:55,380
So there we have the processing stage.

17
00:00:55,380 --> 00:00:57,900
The next step is the charging step.

18
00:00:57,900 --> 00:01:01,350
In the charging step, a negative voltage

19
00:01:01,350 --> 00:01:04,290
is applied to the primary corona wire,

20
00:01:04,290 --> 00:01:08,400
that's a wire that sits on
the drum in the printer.

21
00:01:08,400 --> 00:01:12,550
So we'll label this,
the primary corona wire

22
00:01:19,260 --> 00:01:22,470
and that negative voltage
that is applied to that wire

23
00:01:22,470 --> 00:01:24,450
comes from the high voltage power supply

24
00:01:24,450 --> 00:01:27,120
within the printer, that
wire actually presses

25
00:01:27,120 --> 00:01:31,500
against the drum which is often

26
00:01:31,500 --> 00:01:33,870
inside of the toner cartridge.

27
00:01:33,870 --> 00:01:35,100
In fact, a lot of these pieces

28
00:01:35,100 --> 00:01:38,250
are inside the toner cartridge
on many laser printers.

29
00:01:38,250 --> 00:01:40,590
So in the charging
step, a negative voltage

30
00:01:40,590 --> 00:01:42,840
is applied to the primary corona wire

31
00:01:42,840 --> 00:01:45,630
which then passes through to the drum,

32
00:01:45,630 --> 00:01:48,270
so the drum now has a negative charge

33
00:01:48,270 --> 00:01:50,733
and that is the charging step.

34
00:01:52,410 --> 00:01:55,020
Next on the list is the exposing step.

35
00:01:55,020 --> 00:01:57,450
This is also known as the writing stage.

36
00:01:57,450 --> 00:02:00,300
In the writing step or exposing step,

37
00:02:00,300 --> 00:02:04,290
the laser is activated
and it shines its light

38
00:02:04,290 --> 00:02:06,930
on the drum as the drum spins.

39
00:02:06,930 --> 00:02:11,480
What this does is it applies
a lesser negative charge

40
00:02:11,480 --> 00:02:15,720
to the drum and that ultimately
is gonna be what creates

41
00:02:15,720 --> 00:02:20,640
the letters, those imaged
areas, those areas written

42
00:02:20,640 --> 00:02:21,750
by the laser.

43
00:02:21,750 --> 00:02:24,150
And by lesser negative charge, I'm saying,

44
00:02:24,150 --> 00:02:26,880
let's say this particular laser printer

45
00:02:26,880 --> 00:02:31,880
applied a negative charge of -600 volts DC

46
00:02:31,920 --> 00:02:33,900
to the primary corona wire.

47
00:02:33,900 --> 00:02:36,840
Well, when the laser shines on the drum,

48
00:02:36,840 --> 00:02:38,880
that area would be a lesser charge

49
00:02:38,880 --> 00:02:43,800
meaning, perhaps -100 volts DC.

50
00:02:43,800 --> 00:02:45,870
So it's actually a greater number

51
00:02:45,870 --> 00:02:48,810
but it's a lesser
negative charge than this.

52
00:02:48,810 --> 00:02:53,633
So, that is the exposing also
known as the writing stage.

53
00:02:56,190 --> 00:02:58,110
Next is the developing stage.

54
00:02:58,110 --> 00:03:00,180
In the developing stage,

55
00:03:00,180 --> 00:03:04,020
the toner is applied to the
drum and basically what happens

56
00:03:04,020 --> 00:03:06,750
is you have negatively charged toner,

57
00:03:06,750 --> 00:03:10,860
but it's a higher charge
than the areas of the drum

58
00:03:10,860 --> 00:03:13,200
that we're written to by the laser.

59
00:03:13,200 --> 00:03:16,530
And so the toner is applied
to the areas of the drum

60
00:03:16,530 --> 00:03:20,373
that we're written to, and
that is the developing step.

61
00:03:21,810 --> 00:03:23,910
The next step is the transferring step.

62
00:03:23,910 --> 00:03:25,500
In the transferring step,

63
00:03:25,500 --> 00:03:29,940
the toner is going to be
transferred over to the paper.

64
00:03:29,940 --> 00:03:33,510
What happens is, the paper
now enters the printer itself

65
00:03:33,510 --> 00:03:35,940
and it does this through
some entrance rollers

66
00:03:35,940 --> 00:03:38,100
that help guide it in.

67
00:03:38,100 --> 00:03:40,773
So this is our paper here, my dotted line,

68
00:03:42,510 --> 00:03:47,370
and on most laser printers,
the paper passes through

69
00:03:47,370 --> 00:03:51,720
between the drum and what's known as

70
00:03:51,720 --> 00:03:53,853
the transfer corona wire,

71
00:03:56,130 --> 00:04:00,923
the transfer corona wire is
applied a positive charge

72
00:04:03,030 --> 00:04:05,640
and that's important because
the paper presses right up

73
00:04:05,640 --> 00:04:09,510
against it, as opposed to
pressing up against the drum.

74
00:04:09,510 --> 00:04:11,220
So your paper's going right against

75
00:04:11,220 --> 00:04:12,960
the transfer corona wire,

76
00:04:12,960 --> 00:04:14,670
so this gets a positive charge

77
00:04:14,670 --> 00:04:16,590
and the paper gets a positive charge.

78
00:04:16,590 --> 00:04:19,260
Now remember, the toner that's on the drum

79
00:04:19,260 --> 00:04:22,860
has a negative charge and
when it comes to voltages,

80
00:04:22,860 --> 00:04:27,860
opposites attract, so the
toner is applied to the paper

81
00:04:27,870 --> 00:04:31,170
and then it passes on into the next step.

82
00:04:31,170 --> 00:04:33,543
So that is the transferring step.

83
00:04:34,530 --> 00:04:38,820
Next, the paper's gonna go
past a static eliminator strip.

84
00:04:38,820 --> 00:04:40,980
You wanna remove the static from the paper

85
00:04:40,980 --> 00:04:43,500
because so much voltage
has been applied to it

86
00:04:43,500 --> 00:04:45,180
and if you don't remove that,

87
00:04:45,180 --> 00:04:47,340
the toner could just go flying anywhere.

88
00:04:47,340 --> 00:04:49,590
So this static eliminator
strip's gonna remove

89
00:04:49,590 --> 00:04:52,290
that excess voltage from the paper.

90
00:04:52,290 --> 00:04:54,750
Now the next step is the fusing step.

91
00:04:54,750 --> 00:04:58,680
In the fusing step, the toner
is compressed onto the paper

92
00:04:58,680 --> 00:05:02,100
with heat, making it somewhat permanent.

93
00:05:02,100 --> 00:05:05,550
So the paper's gonna pass
through a fusing assembly

94
00:05:05,550 --> 00:05:08,400
and these are rollers that
are gonna press the toner

95
00:05:08,400 --> 00:05:11,430
on there and heat up that paper

96
00:05:11,430 --> 00:05:14,370
to about 400 degrees Fahrenheit.

97
00:05:14,370 --> 00:05:17,280
So in the fusing assembly,
that toner becomes permanent

98
00:05:17,280 --> 00:05:21,270
on paper going through the fusing rollers

99
00:05:21,270 --> 00:05:24,630
and a lot of heat is applied
to make it permanent.

100
00:05:24,630 --> 00:05:25,930
So that's the fusing step.

101
00:05:26,970 --> 00:05:28,770
The last step is the cleaning step,

102
00:05:28,770 --> 00:05:31,110
this is just cleaning up the printer.

103
00:05:31,110 --> 00:05:35,730
In the cleaning step, you have
some excess toner on the drum

104
00:05:35,730 --> 00:05:38,130
and the drum keeps spinning
and that's scraped off

105
00:05:38,130 --> 00:05:41,340
by a rubber blade and that just falls into

106
00:05:41,340 --> 00:05:43,590
a little toner receptacle.

107
00:05:43,590 --> 00:05:47,760
Also there's an erasing
lamp and that shines a light

108
00:05:47,760 --> 00:05:50,970
on the drum so that it can bring

109
00:05:50,970 --> 00:05:53,490
the drum down to zero volts.

110
00:05:53,490 --> 00:05:56,040
So everything is basically now reset

111
00:05:56,040 --> 00:05:59,220
and the printer is for the next print job.

112
00:05:59,220 --> 00:06:01,890
And that is the cleaning step,

113
00:06:01,890 --> 00:06:04,860
so we have the processing step,

114
00:06:04,860 --> 00:06:08,220
the charging step, the exposing step,

115
00:06:08,220 --> 00:06:12,960
which is also known as
writing, the developing step,

116
00:06:12,960 --> 00:06:15,510
the transferring step,
which is really important,

117
00:06:15,510 --> 00:06:18,390
that's when the toner is
transferred to the paper

118
00:06:18,390 --> 00:06:22,080
because the toner has a negative charge,

119
00:06:22,080 --> 00:06:24,060
the paper has a positive charge

120
00:06:24,060 --> 00:06:26,190
which came from the transfer corona wire,

121
00:06:26,190 --> 00:06:29,613
remember, opposites attract
when it comes to voltages,

122
00:06:30,480 --> 00:06:34,500
the fusing step, where
we had that 400 degrees

123
00:06:34,500 --> 00:06:37,230
and the pressure of the pressure rollers,

124
00:06:37,230 --> 00:06:38,700
and then finally the cleaning step

125
00:06:38,700 --> 00:06:42,240
where the printer's cleaned
up and everything is set anew

126
00:06:42,240 --> 00:06:44,280
for the next print job.

127
00:06:44,280 --> 00:06:46,683
So that's it for the
laser printing process.