[CNC_DL]

Hey Folks,

This is my first post on this site. I'm having some trouble with my new 3 Axis CNC from China and hoping to get some helpful feedback. Here is the issue:

Currently cutting a piece on the table where the machine keeps "loosing it's place" in the design. The Z and Y axis seem to know where they are but the X axis will lose it's place and start cutting the design in a different location. Once this happens the piece is ruined. I talked to the supplier and they seemed to think it's a problem with my GCode. If it were a problem with my GCode then why would it make this error in different places in the design? It seems like some other issue but can't seem to figure it out.

You can see from my attached photo what I mean. You can see where from one side the fine smoothing seemed to go ok then there is a line where it is no longer smooth because the machine is stops cutting the design in the correct place.

I stopped the machine once I noticed what it was doing. I moved it back to the 0,0,0 position per mach3. The problem is the 0,0,0 point is not where I set it originally.

Hoping for some help, fingers crossed!

[Jim Dawson]

I can't really tell from the picture what the part is supposed to look like.

But best guess is that you are losing steps, and that could be caused by:

(in no particular order)
Not enough motor
Cutting feed is too fast for the motors
Loose motor coupling
Bad stepper driver(s)
And probably some stuff I didn't think of

First tighten the motor couplings
Try an air cut and see of the 0,0,0 comes back to where it is supposed to.
Then try cutting again on a scrap piece.
If that doesn't work, try slowing down the feed rate.

[routalot]

Some good advice already.I would add a question or two;how big a machine?Do you have any previous CNC experience?What software was used to generate the toolpath and what cutting depth was specified?

The air cut is a good start and if it works out you can move on to a very light cut of a rectangular shape to see if the actual size turns out correct in all three dimensions.I suspect the root cause will be one of those things already mentioned.

[CNC_DL]

The cutting table on the machine is 24" X 36". I also have a 4 axis attachment and a 5 axis attachment. The software used for the Gcode was Aspire. I am brand new to CNC machines but I hire a tech who is fairly well experienced but he's not sure what the issue is either.

I'm still scratching my head on this one. I'm thinking maybe If i replaced the stepper and driver I could at least eliminate those as potential issues. I need to take the machine apart a bit to check the motor coupling but that is my next step. Either way, I'll be updating this thread to hopefully help the next guy.

[routalot]

From the Aspire software, what was the feed rate and depth of cut?I ask because one of the feed rate options is in mm/second and I have looked over a buddies shoulder as he used Vectric software and noticed that he had the feed rate per minute entered in the feed rate per second option box.You have to look quite carefully to be sure which option you have selected in the tool library.This would be the kind of error that might cause the problem if the number of steps required to execute the move cannot be generated fast enough.Even if this isn't the problem in this particular instance its worth looking so it can be eliminated.