Oki MICROLINE 421 Dot Matrix Printer - 570 cps Mono - 240 x 216 dpi
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OKI MICROLINE 421 Serial Impact Dot Matrix Printer

Product Details

The fast, rugged dedicated forms printer designed to perform in demanding environments.


Doing the job day after day.
The OKI® MICROLINE® 420 9-pin printer and its wide-carriage counterpart ML421 are a quantum leap forward in Impact printer performance. Engineered for dedicated forms printing in the most demanding point-of-sale, automa-tion and utility environments, ML420/421 printers are right at home in applications such as retail sales counters, medical facilities, automotive rental and repair shops, airline counters, financial departments and manufacturing sites. Their print speed and versatile paper handling make them ideal for the office, too.


Performance is built in.
The ML420/421 sport features that give them a strong edge over their predecessors as well as the competition:

  • 3-piece top cover provides easy access and unsurpassed break resistance
  • An internal cooling fan provides continuous airflow for the printhead—maximizing throughput productivity for long, unattended print jobs
  • Additional feed rollers provide precise forms handling and printed-character placement accuracy



Exceptional paper-handling versatility.
The ML420/421 have a zero-tear feature that accurately positions continuous forms for a clean tear at the perforation, which eliminates wasted stock. You also get perfect results with single sheets, index stock, labels and envelopes, too. All with-out jams or smears.


Value that goes the distance.
The OKI ML420/421 deliver the kind of productivity usually reserved for printers many times the price—starting with a super-fast print speed of 570 characters-per-second (in SuperSpeed Draft mode). Then there’s the rugged printhead—with its 200-million character life, powerful samarium cobalt magnets and stored-energy pins— delivering precise, sharp characters all the way through to the last page of a 6-part form. And the patented OKI closed-loop feedback system that assures character placement accuracy...


The OKI ML420/421: Just turn ‘em on and turn ‘em loose


Built to last, inside and out.
Field-proven reliability is just one reason OKI® MICROLINE® impact printers are the most widely-used in North America.1

The performance-optimized power supply of the ML420/421 has been enlarged to easily handle harsh printing conditions— and its energy management capabilities match power expenditures to print-job size, maximizing the life of the 9-pin printhead and other components. A long-lasting rack-and-pinion drive system ensures print quality longer than belt or cable systems. And the ergonomically-designed, impact-resistant chassis protects the ML420/421 from damage, even in the toughest working environments.


Performance that’s user-friendly. Controls are conveniently placed on the front panel for fast access. The automatic loading of continuous and cut stock makes every print job easier, and the design of the internal sheet separator enables easy loading of tractor-fed paper into the rear push tractor.


OKI has a reputation for quality and reliability no competing printer can claim—and backs it with 3 years of warranty coverage 2 and a network of authorized OKI Dealer Service Centers and Service Depots.


The reliable, affordable ML420/421 can work wonders in virtually any forms-handling application.


1 2002 NPD Intellect and Evans Research Market Share Data.
2 3-year standard warranty parts and labor/2-year printhead.


Print Speed And Quality
Super Speed Draft (cps)570   
High Speed Draft (cps)510   
Utility Speed (cps)380   
Near Letter Quality Speed (cps)95   
Letter Quality Speed (cps)N/A   
Number Of Colors1   
Maximum Graphics Resolution (dpi)240 x 216   
Fonts and Bar Codes
Resident Scalable FontsYes   
Resident Bar Code FontsYes (8 types)   
Paper Handling
No. Of  Copies6   
Automatic Paper Forms LoadingYes   
Short Tear OffYes   
Zero Tear OffYes   
Rear FeedYes   
Bottom FeedOptional   
Pin Feed PlatenN/A   
Top Pull TractorsOptional   
Push TractorsOptional   
Paper Feed Rate (inch per second)4.5   
Cut Sheet Feeder OptionOptional   
Roll Paper Stand OptionOptional   
Parallel InterfaceStandard   
Serial InterfaceOptional   
Number of Pins9   
Autogapping PrintheadNo   
Expanded Head GapYes   
Printhead Life (characters)400 million   
Memory Buffer Size128K   
Reliability/MTBF (hours)20,000   
Monthly Workload (pages)17,000   
Operating / Physical Specifications
Noise Level In Operating Mode (dBA)56   
Noise Level In Quiet Mode (dBA)52   
Ribbon Life (characters)7.5 million   
Power Voltage120v or 220v   
EPA Energy Star ComplianceYes   
Dimensions Of Narrow Carriage w/out Box
(W x D x H) (inches)
Dimensions Of Wide Carriage w/out Box
(W x D x H) (inches)
21.7 x 13.6 x 6.0   
Weight Of Narrow Carriage w/out Box (lb.)N/A   
Weight Of Wide Carriage w/out Box (lb.)21.2   
Additional Features
Front Panel Direct Access ControlsYes   
Front Panel Limited Function ModeYes   
Warranty3-year standard warranty parts and labor; 2-year printhead   
Toll Free Telephone Support (hours/days)24 / 7   
EmulationsEpson® FX, IBM® ProPrinter®, OKI MICROLINE   
OS CompatibilityWindows® XP, 2000, 98/95, 3.x and NT® 4.0; MS-DOS®   


Product Comparison


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General Information
The OKI wide-carriage counterpart ML421 is a quantum leap forward in Impact printer performance. Engineered for dedicated forms printing in the most demanding point-of-sale, automa-tion and utility environments, ML421 printers are right at home in applications such as retail sales counters, medical facilities, automotive rental and repair shops, airline counters, financial departments and manufacturing sites. Its print speed and versatile paper handling make it ideal for the office, too.

Technical Information
Print Color Capability:Monochrome
Maximum Mono Print Speed (cps):570
Maximum Print Resolution:240 x 216 dpi
Number of Pins:9-pin
Number of Columns:136

Standard Memory:128 KB

Parallel Port:Yes

Media Types & Handling
Media Type:Cut Sheet
Media Type:Single Sheet
Media Type:Multiple Part Form
Media Type:Continuous Form
Media Type:Index Stock
Media Type:Envelope
Media Type:Label
Media Size:Custom Size
Media Size:Letter - 8.50" x 11"
Media Handling:Push Tractor Rear
Media Handling:Friction Feed
Maximum Print Size:Letter - 8.50" x 11"

Fonts & Emulation
Language Emulation:Oki Microline
Language Emulation:IBM ProPrinter
Language Emulation:Epson FX

MTBF:20000 Hour
Duty Cycle:20000

Power Description
Power Source:AC Supply
Input Voltage:120 V AC
Operating Power Consumption:58 W

Physical Characteristics
Form Factor:Desktop
Weight (Approximate):21.20 lb

Additional Information:
  • Number Of Copies: 6
  • Front Panel Limited Function Mode
  • Front Panel Direct Access Controls
Certifications & Standards:
  • Energy Star
Platform Supported:PC
Energy Star:Yes
Environmentally Friendly:Yes
Environmental Certification:ENERGY STAR

Limited Warranty:3 Year

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Shipping Restrictions
  • This item cannot be shipped to PO Boxes.
  • This item can be shipped only within the U.S.

  • UPC: 051851450292 
  • Mfr's Part #: 62418801