I’m struggling with X-axis grinding noise as it runs back and forth. There also is some noticeable metal dust along the linear gear rail.
I’ve completely removed and re-installed the gear rail making sure it is straight. I’ve also adjusted the tension bolt both very tight to loose - and all spots in between. It occasionly improves the sound but then it returns pretty quickly.
Any help would be appreciated.
-Andy
I noticed when I replaced my pinion gears the machine was noticeably quieter. Maybe its time. They are designed softer than the rack and are a wear item. The worn pinions will have a noticeable step in them where they make contact with the rack, making the overall diameter smaller. This would be the first thing I would check. I assume you checked the spring tension and the main pivot bolt of the stepper pinion assembly.
I also use a high pressure gear lubricant on my racks. It’s stinky and gets everywhere if you don’t protect what you don’t want it on. I use a thin piece of wood or cardboard to shield the spray. This is what we always used on our big machines with helical racks. Only need it every 100 hours or so.
Maybe check the grub screws on the aluminum belt gears. Or possibly the belt itself. Also check for any missing teeth in the pinion or rack. I don’t think it could be much more than that except the stepper bearings which is doubtful.
I found one of my old pinions. This doesn’t seem like much wear but it made a huge difference in noise level and cut quality. All of my cut edges had slight ripples to them. Like an oscillation.
Good news is you can replace the entire assembly for $200 if necessary.
https://www.avidcnc.com/pro-rack-and-pinion-drive-20-p-1388.html
Great advise! The machine is only 4 months old so wondering if I have the spring tension too loose or tight.
If the machine is so new I would guess it is just something loose. I would go through the assembly steps for the x axis drive. Take it apart and reassemble step by step in the Avid directions. You probably just missed a small step that has finally become a problem after vibration from use. It shouldn’t take more than an hour total to do it slowly double checking your work.
As far as the tension of the spring… Too loose and you get more backlash as the teeth are not fully engaged, too tight and you will prematurely wear the pinion from pressing it too hard into the rack. I don’t think this is the issue. Especially if you have tried it loose and tight. Just set it to the Avid spec. Finger tight, then 3 turns. You should be able to push the pinion off the rack by hand with a decent push on the Stepper/Pulley assembly. This is what my spring looks like. Notice the spacing between the coils. About 1/16" or 1mm. This is for reference so you know you are in the ballpark.
I have had the big pivot bolts loosen on me before. See pic. This will make the whole thing wonky if not tightened properly. Pay attention to the directions. It is very specific how these are set. Although looking at the new directions they may have changed/upgraded this on the newer machines. My machine is 2+ years old. It should be tight enough that there is no play if you try to move it in the direction of the bolt axis, but enough that it can freely pivot on the bearing and bushing.
Great that helps a bunch!
On the new assembly machine revision it has that tension bracket facing in do you have yours like that?
I’m only asking because I had mine reversed and it caused too much tension in a recent upgrade I did.
No, that part is good. Turns out the motor pully gear assembly had sliipped down. Problem solved!
Thanks again for your help. I took apart the motor and sure enough the motor pully gear had slipped down. Looks like a set screw wasn’t tightened. Re-did that and now we are smooth and quite again.
Awesome, good to hear. These machines are mechanically simple but well engineered. They do require an inspection from time to time though. The part I like is parts are relatively inexpensive compared to the industrial CNC options. I have been using our machine for a professional cabinet shop doing 1-2 high end kitchen jobs per month and it has been surprisingly great. So, just keep an eye out for loose parts and it should work for you for years.
