OKI Microline ML5591: Setup, Drivers, Ink and Common Problems

Is the OKI Microline ML5591 right for you?

A 24-pin wide-carriage Microline built for heavy continuous-forms work, the ML5591 prints 136 columns and handles up to six-part sets, which makes it the standard choice for logistics, manufacturing and government forms. Its 24-pin head produces far more readable text than the 9-pin models, at the cost of a higher purchase price. Ribbon life is long, but faded output across the whole page almost always means the ribbon rather than the head.

Best for: Logistics and manufacturing sites printing wide multi-part forms

Setting up the OKI Microline ML5591

Choose the emulation on the panel to match your host system — Epson LQ or IBM Proprinter are the usual options for ERP and warehouse software. Set the top of form and the paper-thickness lever for the form set you use, and save the settings to the printer menu so they survive a power cycle. For network use, fit the optional Ethernet interface and add the printer by IP; otherwise connect by USB and use a Generic / Text Only driver for line-mode output.

1. Unbox and prepare. Remove every piece of shipping tape and packing material, install the ink cartridges, and load paper in the tray.
2. Join your Wi-Fi. Keep the printer close to the router for setup. Most printers only connect to the 2.4GHz band, so if your router broadcasts one merged network name you may need to split the bands temporarily. See our Wi-Fi guide if it will not join.
3. Install the setup app. Use OKI's official app rather than a driver you found on a search result — third-party driver sites are the most common source of printer malware.
4. Add the printer. On Windows 11: Settings › Bluetooth & devices › Printers & scanners › Add device. On macOS: System Settings › Printers & Scanners › Add Printer.
5. Print a test page and run a scan if this is an all-in-one, so you find any problem now rather than when you are in a hurry.

Ink, toner and supplies

The OKI Microline ML5591 uses the following consumables. Match the number exactly when you buy: the same printer family often uses several different cartridge numbers by region.

• OKI ML5590/5591 black ribbon cartridge (approx. 10 million characters)

High-yield (XL) versions almost always cost less per page if you print regularly. On third-party ink and toner, read our honest assessment first, and note that some manufacturers push firmware that rejects non-original chips.

Full specifications