Thump or Bang when moving through 2 corners only

[chadderuski]

Hi Everyone! I'm so close to being able to finally cut some chips with this machine, but I have an issue that I've spend days on trying to resolve.

I have a Bulkman 1000x1000mm machine mechanical kit, with my own 381oz stepper motors and the Gecko G540 running 48v. In Mach 3 I have Velocity is set to 2500mm and Acceleration to 250 ( I have tried a WIDE variety of settings here and they don't make a difference). This machine uses 1210 ball screws on the Y and X axis.

What I have checked:
- My table is level, the the rails and gantry are square and y-axis rails are parallel.
- I've loosened the ball screws from the gantry and z-axis to ensure my gantry runs smooth with no binding or in both Y and X.
- Linear rails and ball screws are well lubed with Super Lube 21036 Synthetic Grease (NLGI 2)
- I am using Uxcell 8mmx6.35mm Diaphragm Coupling Couplers, and swap them from the Z and X to see if one is binding but made no difference.
- I removed and remounted both steppers on the Y and A axis to ensure everything was tight.



The "THUD!" occurs only when rounding the left rear corner and right front corner of both the circle and square in the attached diagram. The right rear and front left corners transition smoothly with no change in sound. The THUD! is quite loud and you can feel it in the machine table and even the floor.

However, I can reproduce the THUDing if I manually jog the machine in Y and then use the keyboard to jog the X axis left and right. So something is not right, but I cannot for the life of me figure out what I need to fix.

I hope someone can help me get on the right track! Thank you!

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[joeavaerage]

Hi.
It sounds like the retainer rivets/screws of the diaphragm couplers are worn or loose. Any looseness will cause the holes of the diaphragm to wear out-of-round and thereafter the problem
will likely recur no matter how tight the rivets/screws.

Craig

[chadderuski]

Hi Craig,

The problem is not the couplers. I did check these and they are very snug.

I spent a lot of time going through the machine and did discover that one of the Y axis ball screws is bad, but this is not the problem either. I've ordered a replacement.

In the mean time, I also discovered that I was able to repeatably produce the issue by using the keyboard to jog the gantry in the Y direction, and then, while moving, hit either the left or right key. I can consistently get the "THUMP THUMP THUMP" each time I change direction of X.

So I'm wondering if it could be a bad driver in the G540 or a setting in Mach 3. Odd thing is I don't believe it's an acceleration issue. I can drop acceleration down to 50mm/s and still get the thumping.

If I jog normally X / Y or even XY by pressing two key at the same time, the machine doesn't do this.

I hope someone can shed some light on the issue...

Thanks!

[chadderuski]

Hello All... I've made some progress on the issue of the steppers making a pinking popping sound. This is somehow related to the HP Desktop I'm using with Mach 3. When I switch to my ye old 2002 Pentium Laptop with a parallel port, the pinking/popping is gone. Unfortunately, the laptop has a different problem in that it will constantly generate estops/limit stops even though it's just sitting idle... this doesn't happen on the desktop.

I did try setting pulse and signal delays on motor tuning, but this also had no affect.

Oh. and I did try the different modes in the bios for the parallel port with no change in behavior of the pinking/popping.

Still digging...