Missing Steps Poss TB6600 Fault

[neilricketts]

Hi, Neale the missing steps on the z axis is after doing a v carving of a Harley Davidson eagle plaque for example the bit will have raised above the work piece by anything from 1mm to 3.6mm. It is not consistent. I have tried switching drivers from other axis. Changing stepper motors from other axis. I have also changed from 1/8 step to 1/4 stepping, I have tried lowering and raising the amperage settings on the driver. I have also tried slowing the ipm to just 5 with acceleration to 5 and it still raises up from the work piece. I have made numerous different anti backlash nuts and my current design is spring loaded. The only thing that I notice is the alarm led is constantly flickering on and off on the driver when it is changing direction. However all the drivers do this on all of the axis and I do lose steps on my axis just not as much as the axis which is the hard working one.

If I do just normal cutting for example 2d cuts I don't have a problem only when there is a lot of up down movements. At first I thought I may have been my nut but not so sure now.

cheers neil

[m_c]

Do the axes always drift in the same direction?

If so, my first suggestions would be to try inverting the direction and/or step active high/low.
When the direction changes, the driver requires that the direction signal is changed at a certain point before the step signal. If it doesn't, the driver can move one step pulse in the wrong direction before changing to the correct direction. Over the course of many moves, this can lead to axis drift in a constant direction.

One possible test for noise problems, is too only move 2 axes, with the other remaining stationary (ideally against a DTI, or mark the coupler so you can see movement easier), and see if the stationary axis moves any. Also try with the spindle running, as they can also produce noise which can cause phantom steps.

[neilricketts]

Hi I have just tried setting the step active to low as suggested on the first page and ran my Harley Davidson plaque twice. This time the bit was above the work piece by 1.5mm. The second time it was 1.25mm above the work piece with no changes between each run. This has been the most consistent each time I have run the job. In the past it has been as high as 3.6mm above the work piece. If I set the direction to low it changes it so that up is down and down is up so I have left the low setting off on the direction for the time being. The suggestion of just moving 2 axis to see if the third axis moves is one of the first things I tried when I first built the machine and there was no movement. It also does not make a difference if the spindle is on or not.

I would welcome any other suggestions to try to solve this problem

cheers neil

[magicniner]

All my early experiments involved cheap TBxxxx drivers, my experiences with their reliability, sensitivity to noise and generally less-than-rock-solid performance led me to give them all away and use better drivers.
It would have been cheaper to start with better drivers from reliable suppliers, it's a learning and growing experience ;-)

[neilricketts]

Hi, I want to thank everyone who has given me advice on this forum. It looks like I have solved my problem. This morning I swapped the usb cable that goes from my breakout board to a 5v phone charger. Instead I placed the usb cable into the usb port of the laptop I am using. Then I altered the stepping settings from 1/4 to 1/16 on the z axis driver and kept the other 3 drivers at 1/4 stepping. Altered the ipm to suit the new stepping on z axis and ran a job and it was perfect no lost steps, no bit raising or lowering below the work piece. So to make sure I ran off 4 different projects this afternoon all perfect. Hooray.

So a big thankyou to everyone who responded to my post.

Cheers Neil