PDA

View Full Version : Need Help! Z axis strange behavior



Carlos Salaff
07-19-2015, 01:02 PM
Hi guys,

This is my first post in this forum.

I have a CRP-2448 machine with Nema23 motors and Gecko drive. I use Meshcam V5 and Mach 3.

I bought the machine second-hand a couple years back, but have rebuilt nearly everything at this point. I have milled several pieces of foam, but have always had a problem--steps in the piece and generally erratic Z-axis behavior.

I have completely disassembled and reassembled the z-axis to check for mechanical issues(none that I could see) and lowered the Accel/Vel values to see if the stepper motors were missing steps. That minimized the issue, but the issue remained.

The last time I tried to run mill, it made tiny steps, got slightly lower in Z as it cut, then decided to plunge straight down into my table... I attached a photo. 287230 I have reached out to Cory at CNCRouterParts, who has always been helpful, but also wanted to reach out to the collective wisdom on this forum

Have any of you had experience with this issue? Any help diagnosing the situation would be most helpful.

Thanks!
Carlos

ahren
07-19-2015, 08:07 PM
Carlos,

I would check your Delrin ACME nut to make sure it isn't un-threading from the aluminum body that holds it. I'm assuming this is the style of nut you have, but the machine is used so it could be something else. If it is loose, you should re-tighten the plastic nut all the way into the aluminum body, and tighten the jam nut on the back side. On newer (post 2013ish) versions of the nut there is also a cross-drilled set screw hole as a sort of belt and suspenders to keep the nut from un-threading, and if you have this you should tighten it as well.

The issue could also be electronic in nature. Especially if you have a G540 based system, these are very susceptible to overheating, and often need some sort of auxiliary cooling even if they are not in an enclosure. It could also be PC related, especially if you are running with a direct parallel port connection rather than a motion controller like the Ethernet Smoothstepper.

Either way, call us tomorrow and Cory or I can hep you out.

Ahren
CNCRouterParts (http://www.cncrouterparts.com)

Carlos Salaff
07-19-2015, 08:37 PM
Carlos,

I would check your Delrin ACME nut to make sure it isn't un-threading from the aluminum body that holds it. I'm assuming this is the style of nut you have, but the machine is used so it could be something else. If it is loose, you should re-tighten the plastic nut all the way into the aluminum body, and tighten the jam nut on the back side. On newer (post 2013ish) versions of the nut there is also a cross-drilled set screw hole as a sort of belt and suspenders to keep the nut from un-threading, and if you have this you should tighten it as well.

The issue could also be electronic in nature. Especially if you have a G540 based system, these are very susceptible to overheating, and often need some sort of auxiliary cooling even if they are not in an enclosure. It could also be PC related, especially if you are running with a direct parallel port connection rather than a motion controller like the Ethernet Smoothstepper.

Either way, call us tomorrow and Cory or I can hep you out.

Ahren
CNCRouterParts (http://www.cncrouterparts.com)

Hi Ahren, thanks for chiming in! I actually just disassembled and reassembled the Z-axis to inspect the assembly. I took photos of the Delrin bushing and housing upon "teardown". I inspected the bushing assembly and it seemed OK to me. The threaded rod moved securely through the threads, and I didn't see any damaging wear. That said, perhaps I missed something. Here are some photos FWIW:287246287248287250287252287254

The PC was bought new, and I am running through a parallel port. Not sure if the G540 has adequate cooling, but the fan keeps it lukewarm to the touch. I also sent Cory G code for the lastest file that went bezerk. All that said, I'll call you tomorrow, and look forward to getting to the bottom of it.

Thanks again,
Carlos

Carlos Salaff
07-20-2015, 01:31 PM
For any who may be encountering similar issues,

I just spoke with Cory of CNCRouterparts. As it appears that I do not have a mechanical issue, he advised that I may be experiencing problems stemming from my PC. I learned that many PC's have problems smoothly sending data to the G540 during milling operations. This is usually due to interruptions from other running functions on the PC. To that end I will try using the Ethernet Smoothstepper in conjunction with my setup. This will help to "smoothly" send signals to my G540 while milling. Hopefully that will get rid of the issues I'm experiencing. At the very least I know it will rule out a possibility. I will report back after running with the smoothstepper.

It must also be said that I greatly appreciate Cory and Ahren's customer support.

Carlos Salaff
08-03-2015, 12:13 PM
I just wanted to update anyone who may be experiencing issues like mine. I have since installed an Ethernet Smoothstepper that I purchased from CNCRouterParts. This has eliminated all of the steps and erratic movement from before. I was previously running Mach3 off of my PC with Windows 7. The other change I made was to unplug my internet connection. Not sure if that helped eliminate interference too. It should be noted that Cory and Ahren's customer service has been outstanding.

If you can't tell, I am pretty thrilled to have my machine working properly, as it was a nightmare before.

I have had one more incident where the bit dove into the table. Before it happened I heard a "click" sound--which leads me to believe something mechanical bound up, making things go haywire. I am milling a lot of foam material, and I think some foam possibly got into the works. Since then, I've been alongside with a vacuum, pulling away the foam chips, and have had no problems since.

Dennis Bohlke
08-03-2015, 12:42 PM
Milling foam can create high static charges that can discharge with an arcing voltage.

I have seen ion generators placed in the work chamber of machines to reduce the static charges.