This issue was a real drag!

During my weekend of upgrades a couple of weeks ago, I noticed that my engraving results had become totally unacceptable. I was sure it had to do with the upgrades I had made; I just couldn't find what it was. But yesterday, I started looking in a whole new direction and found the answer in an unexpected location.

Whenever you build your own laser, you are destined to run up against some issues you never expected, making resolution all that much more troublesome. When I recently installed a new laser tube, installed a 4 axis drive board, and upgraded the Y axis motor couplers, I never expected to have problems with the X-axis. But that is exactly what happened. Take a look at the tests below and notice how irregular the vertical sides of the letters are; sometimes wavy, sometimes angled. Something has certainly gone wrong.

The first and third lines are normal engraving. Lines 4 and 5 are unilateral engraving. And line 2 is outline (cut) mode. Notice a few things:
  • Even the outline (line 2) has some issues with the shapes of the 'C' and 'e' and the dot over the 3 'i's and the 'j'. 
  • The unilateral engraving is problematic as well. That is a sure sign that it is NOT backlash in the x axis.
  • The issues get progressively worse at one end (the right end). I did not notice this at the time, but it should have been a dead giveaway as to the real problem, which I will explain shortly.

Of the updates and new installs that I had just made, the only things that made sense were the BuildLog.net 4 axis drive card and the fact that I rearranged the layout of the electronics in the process.

If that theory were correct, I could only imagine that it was noise interference from a power supply or from the X axis motor itself, which now had a lot closer proximity to the controller and open air driver board. (My previous individual drives were all encased.)

I spent a lot of time tying to isolate the new drive board from the power supplies. I spent a lot of time tying to isolate the new drive board from the motors. I spent a lot of time tying to isolate the controller card from the new drive board and power supplies. I spent a lot of time tying to rearrange the whole electronics layout. Let's face it; I spent a lot of time - period.

At one point, I manually moved the laser head along the X axis and felt just the slightest wobble. Closer inspection showed that it was visibly noticeable as well, if I looked carefully. So I did what any good mechanic would do - I tightened it up. Guess what - the results were WORSE.

Testing revealed that the head, once snugged up to remove the wobble, was much harder to move, both manually and under power.Obviously, something was wrong with the mechanical movement of the laser head. There was significant drag in the X axis.

Time to tear it all apart and see what was going on. Watch the short video to see what I found.

Here is a static view of the results. Click on it to see it larger.

Notice that the final line, the test after the X axis drag problem was corrected, is very clean and has letter edges that are straight or consistently curved. I still have some additional testing to do, but believe the current results to be acceptable.

Lesson to be learned from this: Lazing produces an inherently dirty environment. We add air assist to keep the lenses clean. We add air extraction to remove as much of the airborne particles and fumes as possible. But it is still a dirty environment. Bottom line - check and clean all rollers, bearings, and rails often.

1 comment:

  1. Good find Tim. I have been cutting a lot of MDF lately and you should see the smoke that generates. It is really sticky as well. My laser has quite literally stuff up today and now I can't cut vectors at all without the beam wandering all over the place and not following the path. The LCD screen resets back to Chinese and when I press the LASER button the laser stays on and tries to burn a hole through the table. The random cut path is reproducible to the exact path so I don't know if it's the software or the hardware. I am going to buy the new 2012 one and send the old one back so Marco can test it himself. Sharp corners are rounded and the bottom of slots come out triangular instead of flat. Such is life on the laser path!
    keep up the good work on the Blog. I for one find it interesting.