Missing Steps Poss TB6600 Fault

[neilricketts]

Hi, i know what you are saying but i am happy at 24v with the speed and that. it is just the missing steps that i think is being caused either through electrical noise which i will try changing the wiring first. However reading here and on other forum the tb6600 drivers are a common cause of lost steps and failing that is why i am asking about the other drivers as a possible replacement if i have to go down that route.

[Clive S]

Ok if you are happy so I won't mention it again but just let me say you will need all the power you can get using threaded rod. Turning the power up will help with lost steps.

[Neale]

My mk1 router, built from MDF, used M10 threaded rod as leadscrews. I used M752 drivers running off 68V. Never had a missed step, as far as I could tell. Had a lot of other structural problems, mind you... That was a bit OTT but I intended to re-use the electronics in a later version.

I'm still slightly unsure of the "missed step" assumption. Can you measure how much error there is after, say, 50 vigorous Z moves? 100 moves? Are the results consistent, or random? Change the speed and acceleration and try again? Before junking the drivers and replacing them with different cheap low-power drivers, it might be useful to get a better handle on the underlying problem. I might even swap a couple of drivers between axes and see if the problem follows the driver. Reroute the wires and see if anything changes. A bit of science is called for, carefully measuring and only changing one thing at a time, despite your obvious frustration! I found my Z problem when I was able to see that the error in microsteps after each height-setting operation was almost always equal to the number of direction changes during height setting, for example, and the error was independent of how far the axis travelled.

[neilricketts]

Hi Clive S thankyou and I do appreciate your advice its just I know of cnc machines running on 24v and m10 threaded bars with no missing steps. I will consider changing and increasing the psu voltage if necessary I want to explore all avenues. The machines I know of that run on 24v don't use the tb6600 drivers but they use gecko ones which at the moment are out of my price range as I am just a hobbiest. I will however keep your advice on hand increase that is the route I decide to go.

Cheers Neil

[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

[jagmeetk22]

Solution :-

It user P817 optocouplers which is low speed.
We need high speed optocoupler like 6n137.

Replace Direction and Pulse(Clock) optocoupler with 6n137 optocoupler then it will not miss an step.

Hi, i am new here and i am hoping you may be able to help me. I have built my own cnc router and it is working but i am losing steps on all of my axis. I have tried changing and making various designs of anti backlash nuts. I have also tried adjusting amp settings and step settings from 1/8 to 1/2 steps. It is more pronounced on z axis. when doing a project of a v carving i can end up being as much as 3.4mm above the work piece at the end. I am now beginning to suspect that my tb6600 drivers are at fault because when the machine is running the alarm light is continously flickering during the machine is running. I am wondering if this could be resulting in the loss of signal which is then resulting in lost steps. My machine is

4x Nema 23 stepper Motors bought second hand. (ebay)
4x TB6600 stepper drivers (ebay)
M10 x 1.5 Leadscrews
24v 10a DC PSU
5 axis breakout board (ebay)
Mach3 version 3.042
Dell Laptop with power management turned off running xp
Chinese Quiet 400w DC Spindle.

Cheers Neil