Printers & Thermal Paper

Start here, because it decides all four consumable choices and there is no partial credit.

Every media page in this range carries the same warning in capitals: NOT COMPATIBLE WITH MP-20 PRINTERS, or the reverse, and each one names the part to order instead. That is unusually helpful labelling and it exists because the mistake is evidently common.

What makes it worth reading twice is that the two paper rolls have identical published dimensions. Both the TDP-225 roll and the MP-20 roll are given as 2.25″ × 118 ft, 57 mm × 36 m. Same width, same length, different part numbers, and each declared incompatible with the other printer.

Identical dimensions with declared incompatibility usually means a difference the dimensions do not capture: core diameter, roll outside diameter, or which face of the paper carries the thermal coating. Any of those will stop a roll working in the wrong printer even though it physically fits the holder. The printers' own specifications show where they differ: the TDP-225 takes outside-wound media on a 1 to 1.5 in core, up to 5 in across, while the MP-20 is built around a 57 mm wide roll about 57 mm across.

The practical consequence: reorder by printer model and part number, never by measuring the roll. The measurement will tell you the two are the same, and it will be wrong.

This is the easier decision, and it comes down to where the printed weight ends up.

Paper rolls print continuous receipts and weight tickets: the document that goes with a delivery, into a file, or to a customer. Both printers take a 2.25 inch roll, and at $20 for five rolls the running cost is negligible.

Labels are die-cut and adhesive, at 2 × 2 inches, and they are what you want when the weight has to travel with the item: a bin label for counted stock, a pallet label, or a barcode a scanner picks up later. The TDP-225 is described as printing text and bar codes, so a label can carry a scannable part number alongside the weight.

The cost comparison is worth doing once, because the two label products are packaged very differently. The TDP-225 labels are one roll of 1,250 labels at $26, which is about 2.1 cents each. The MP-20 labels are five rolls of 280, so 1,400 labels at $45, or about 3.2 cents each.

That is a real difference at volume, and it is one of the few places in this catalog where the consumable cost, rather than the hardware cost, is the argument for a particular printer.

The TDP-225 has an RS-232 interface, and RS-232C is standard on every Transcell indicator. So in the common case the answer is that nothing extra is required: the port exists at both ends and the printer ships with its RS-232 cable and a 9 V adapter in the box.

Three situations change that. If the indicator's only serial port is already occupied by a PC or a remote display, you need a second RS-232 module. If the run is long, between buildings, or passes near large drives, you want the isolated version. And if the printer is driven from an MP-20 rather than a TDP-225, the lead is the DB9 to DIN cable, which is a different part.

The other thing worth deciding before ordering is the output mode. An indicator sends either on demand, when PRINT is pressed, or continuously. A printer wants demand mode; a remote display wants continuous. This is configured on the indicator rather than detected by the printer, so it is a setting to get right at commissioning rather than a fault to chase afterwards.

And if the ticket has to carry a timestamp, that is neither a printer feature nor a cable: it is the Time / Date / Print Formats firmware option on the indicator.

Both printers here are direct thermal, which is worth understanding because it has a real operational consequence.

Direct thermal printing uses chemically treated paper that darkens under heat. There is no ink and no ribbon, which is why the running cost is low and why there is nothing to replace but the media itself. The print head simply heats the paper where the image should be.

The trade is permanence. The same chemistry that responds to the print head also responds to heat, sunlight, friction and solvents. A ticket left on a dashboard in summer, a label on a drum in direct sun, or a receipt that meets a cleaning chemical will fade, sometimes to blank, and the timescale can be months rather than years.

The practical rules that follow are simple. Do not use a direct thermal print as the archive copy. If a weight ticket has to be kept for records, scan it, photograph it, or log the weight over the serial port at the same time it is printed. Store spare media in its packaging, away from heat and light, because unused rolls age too.

For a label that genuinely has to survive outdoors for years, direct thermal is the wrong technology and thermal transfer with a resin ribbon is the right one. That is a different class of printer, and worth saying so rather than selling media that will disappoint.

Worth asking, because a printer is often bought to solve a data problem it is not the best answer to.

If the weight has to reach shipping software, an ERP or a database, printing it and typing it back in is a slow, error-prone route. The same RS-232 port that drives the printer will drive a PC directly, and if the destination is a network application, a USB, Ethernet or Wi-Fi module puts the reading into software without paper in the middle.

A printer earns its place when the paper itself is the point: a ticket that travels with a delivery, a label a scanner reads later, a record a driver signs, or a legal-for-trade transaction where a printed weight is part of the paperwork.

The two are not exclusive, and the best installations often do both: print the ticket for the driver and log the weight to the system at the same time. That is exactly the case where a second serial port becomes worth its price, because one port drives the printer and the other feeds the software.