Bearings, Bushings and Belts

Most printers use a belt or wire to move the print heads left to right along their width or Y-axis, as it is technically referred to. Attached to this belt or wire is the carriage containing the print heads, which, in turn, travels along a guide rail with the assistance of attached bearings or bushings. Over time, the belt and bearings can wear and eventually cause all sorts of problems affecting the overall reliability of your printer, not to mention generate costly and unnecessary service calls. Fortunately, much of this can be mitigated by you without having to call in a technician or buy parts. A little attention and maintenance here can prolong or even prevent failure altogether.

Belts really are designed to last the life of the printer and many do; however, sometimes conditions arise that cause premature failure of the belt or wire, such as belt tension. Belt tension essentially is slack (or lack thereof) in the belt or wire that can cause premature wear and even breakage. If there is too much slack in the belt, the slack will cause abrasion against other parts, which will lead to belt failure. If the belt is too tight, it can create undo stress on the motor and also lead to premature failure or breakage.

When belts are replaced, their tension should be checked with a belt tension gauge. This tool measures the belt tension by testing resistance, which is commonly measured in kilograms, grams or pounds of force. Although this tension should remain at nominal levels during the life of the printer, they can be affected by many things, including the environment and heavy use. Head strikes can exacerbate belt and motor issues and typically are the cause of premature belt failures. Beyond reducing head strikes, however, maintaining the belt by ensuring proper tension can go a long way in reducing failure and is fairly easy to do.

Belt tension tools are used a lot in the automotive industry and available online. Although they can get very expensive for precision work, any inexpensive tension (or force) gauge up to 3,000 grams or seven to 10 pounds should do. If your printer uses a wire to move the carriage, consider a tension gauge that includes a hook on the end. Here is a link to an online supplier of tension gauges with hooks: http://tinyurl.com/kmnmq2.

For belt driven printers, I recommend a “bar” type tension gauge that works by simply pushing the gauge up against the belt to take force measurements. It is available online here: http://tinyurl.com/neqvg5.

As you begin making tension adjustments, keep checking to make sure that the belt or wire is centered on the pulley and does not drift or move positions when the carriage is moved from side to side. On some printers, this is caused by uneven tension between the top and bottom of the belt and adjustments should be made so that they have roughly equal tension along the width of the belt to mitigate this. Other printers will use guides in the pulley system, eliminating the need to ensure belt or wire alignment. Make sure that the belt or wire never touch the guide rail but not so tight that it does not somewhat flex. The belt or wire in most cases will flex slightly but not enough that it gives any slack.

Tip: When making tension adjustments, make sure that the carriage is centered in the middle of the printer and test the tension on both sides of the carriage.

As the belt moves the carriage, the bearings or bushings help facilitate smooth travel along the guide rail. When bearings or bushings are damaged or not lubricated, they cannot only exacerbateor even create belt and motor issues, they also can damage the guide rail. Motors and belts can be replaced with relative ease; guide rails are a different story and can cost quite a bit on some printers. Making sure the bearings, bushings and guide rails are clean and lubricated will go a long way in preventing costly service in the future. You can routinely lubricate these critical components on your printer at little or no cost. In fact, many printer manuals include cleaning and lubrication as part of a regular maintenance routine, and some even come with kits containing all the tools and supplies needed (see Image 1).

Lubricants are a dime a dozen. I prefer to use Nye oil, which is used by watchmakers to lubricate their moving parts. Also used for lubricating weapons, Nye oil is good for repetitive, high-speed environments and works great on printers. Check for Nye oil online at: http://tinyurl.com/n9hzpn.

Note: While most printers are lubricated with oils, some printers use grease. Grease is much thicker and does not mix well with Nye oil or other lubricants, for that matter. Confirm with your dealer or printer manufacturer. Checking for lubricant residue also can tell you if grease is being used, but if you're not sure, hold off until you are. If grease is being used, I recommend you use the same type of grease and source it through your dealer or printer manufacturer. Some printers will use both grease and oil, so keep that in mind, as well.

You also may need to remove most of the printer's covers to access the bushings and bearings. Once you have opened the printer and accessed the carriage, make sure to lubricate the guide rail and any bearings or bushings on the carriage, too (see Image 2). Don't use too much lubricant and never drop lubricant directly onto whatever you're lubing. Use an applicator or a cotton swab to rub the oil into bearings and a lint-free cloth or towel to apply oil to the guide rail. Make sure to wipe off any excess oil because too much oil will attract dirt and create buildup.

Tension Guide
Here is a quick belt and wire tension guide for some common printers that have been in use for a few years now:

NOTE: If your printer is still under warranty, I suggest you hold off making tension adjustments but be aware of what we have discussed.

Mutoh Falcon II (+ Falcon II Outdoor):
50” and 64” models should have 100 grams of tension plus/minus 10 grams.
87” models should have 90 grams of tension plus/minus 10 grams.

Keep in mind that Mutoh printers typically have steel belts that can snap if tightened too much. Belt tension is adjusted on the left and can be accessed once the left covers are removed (see image 3). It's important to note that when adjusting belt tension on a Mutoh printer always check to make sure the belt does not drift off the pulleys when the carriage is moved to the left or right. Make sure also to check the belt position on the right side, as well. Ensuring equal tension on both the top and bottom tension adjustment screws goes a long way in correctly aligning the belt on the pulleys.

Roland SC-545 & SC-300v:
Roland SC-545: These printers should have between 960 to 1,180 grams (or gf) of tension. Part number ST-001
Roland SC-300v: Wire tension on this model should be 4.5 to 5.5 pounds (2041 to 2494 grams). Part number ST-011

These Roland printers use a wire, instead of a belt. Wire tension is adjusted by first loosening several retaining screws on the pulley assembly, located on the left of the printer. Tension is controlled by two screws that can be adjusted by screwing in to increase tension or out to loosen tension (similar to the pulley and tension screws shown in image 3). Make sure you take a tension reading after each adjustment.

Roland sells tension gauges specifically for each printer model. You may be able to purchase this through your Roland dealer.

Mimaki JV3 Series:
Belt tension on these printers should be around 250 grams.

Mimaki uses primarily rubber belts, which should be free of slack or if pressed, should not flex more than 1.6 to 2 mm. Adjusting tension is done by loosening the retaining screws holding the motor assembly, repositioning the assembly and re-tightening the retaining screws. Test for proper tension and repeat.