I sell a lot of mobile printers that are destined to spend their lives mounted in a vehicle. The majority of them are 8.5″ wide thermal printers that are used to generate citations and reports for patrol officers from continuous roll thermal paper. I recently had a fairly large project for the same application that required a 4″ printer and following are some thoughts and observations on the Zebra RW 420 that was chosen for the task.
Speed.  Compared to industrial thermal label printers at speeds of up to 14 inches per second (IPS) the 3IPS print speed of the RW 420 may not sound very impressive. But, at approximately three times the speed of the 8.5″ model, it’s a noticeable improvement. Even if the form is slightly longer due to the reduced width, you’ll still end up ahead, and the forms are usually scaled so that you’re not printing twice as many pages.
RW 420 Havis Mount
Ruggedness.  It’s fairly obvious at first glance that the RW 420 is a much more rugged unit. This becomes more important for carried-use applications where a printer is more likely to be dropped or banged around a bit more. Similarly, IP Rating isn’t critical for use inside a vehicle. One side affect of the increased ruggedness of the Zebra printer is a much wider operating temperature. The 8.5″ printer is rated to operate between 41-95°F with a storage rating of 5-122°F.  Zebra rates the operational use of the RW 420 between -4-131°F and -22-149°F for storage.  That’s a pretty significant difference and one to be considered for long term reliability.  If you’re regularly storing outside of specs, it will affect the useful life of the printer.
RW 420 LEM Mount
Power source.  This is kind of a weak spot for the Zebra. I’m sure the engineering reasons are sound, but you can’t run the RW 420 with an empty battery well. For a permanent vehicle install, you will almost certainly want a battery eliminator that sits in as a permanent replacement for the battery. It’s going to cost about $65 more than a standard power supply that works with the battery but eventually the battery will need to be replaced, even if the printer is always connected to vehicle power. More annoyingly, (due to certification constraints) you can’t buy an RW 420 without a battery. I sincerely hope that this is something that’s addressed when the time comes for a product refresh.
Overall, the Zebra RW 420 makes a compelling case for a vehicle mounted printer.  The up-front cost difference from an 8.5″ thermal printer is far from negligible, but print speed, ruggedness and a more compact form factor should be enough to earn serious consideration in the decision making process. Feel free to contact me with your mobile printing questions.  Demo equipment is available for qualified projects.