Maintaining Linear Guides

Hi everyone. This post about maintaining the linear guides on your LongMill. We’ve had a couple of people report to us that they’ve had their Z-axis get stuck or become rough especially when they have been running over a long period of time.

I and another customer who has experienced this issue have been investigating the cause of this for a few weeks and doing more research to help customers prevent their linear guides from sticking.

I’ll just fill everyone in on our recommendation for maintaining your linear guides to ensure they work flawlessly for every cut. If you want to hear more about what we’ve done to look into linear guide maintenance, scroll down past this section to read more.

Maintaining your Linear Guides

Although the frequency of lubricating your linear guides may vary depending on the type of cutting you do and the frequency of use, we would recommend doing this procedure every 20-30 hours. However, if you experience any grinding noises or roughness in your gantry, we recommend doing this procedure more often.

  1. Wipe your linear guides with a clean cloth, paper towel, rag, or shop towel to remove any dust that may have accumulated on your linear guides. Move your Z-axis up and down if needed.
  2. Apply a liberal of machine oil or grease to your linear guides. Move your Z-axis up and down to ensure that the bearings inside have a chance to get coated Most general-purpose lubrication options should suffice. However, it is not recommended to use dry lubricants or anything with particulates such as graphite in the lubricant.

Here are some links to more into about lubrication:

  • https://www.thomsonlinear.com/en/support/tips/what-should-be-used-to-lubricate-linear-bearings
  • https://www.hiwin.com/pdf/lubricating_instructions.pdf

We believe that most general-purpose lubricants such as the 3 in 1 oil should suffice since the linear guides are used in a relatively low speed, low load application.

These instructions are now a part of our Machine Maintenance page on our Resources.

Jumping into our other findings

One of our customers had reported having their Z-axis linear bearings seize several times, and with the help of this customer, we have investigated the issues further. Initially, this had been a fairly uncommon issue, with only 3 tickets in our system pertaining to these parts as well as a small number of users reporting this issue on our Facebook group so it hadn’t been top of mind for us to investigate. However, I guess it’s better to sort potential problems out than let them sit and percolate forever.

Based on research, the main reason for failure for linear guides is lack of lubrication. This is what I suspect happens.

  • Linear guides get coated with dust from regular use. This dust either sticks to the lubricant already on the guides and either falls off taking lubricant with it, the guides push it off, or the user wipes off dust and lubricant.
  • The chance of the ball bearings in the guide seizing goes up either due to the resistance between the balls rubbing against each other or dust making their way into the guide

To replicate the issue I first cleaned all of the grease and debris from a spare ZX gantry using brake cleaner. This provided a situation where the linear guides would have no lubrication. Then the guides were coated in MDF dust and were moved back and forth.

Although I was not able to create a complete failure of the bearings, were was a noticeable increase in friction, and over a longer period, I suspect that the bearings would be able to be coaxed into seizing.

After this testing, I applied machine oil to the guides as discussed in the section above and the linear guide returned to its original smooth movement. I believe that cleaning and relubricating the linear guides can return seized linear guides back to life, and maintaining them should ensure smooth operation for the years to come.

I hope that adding this helps improve the LongMill’s reliability and ensure that everyone’s machine keeps chugging along great!