Hope you are all having a very happy Christmas (or whatever else you celebrate). Stay safe !!

A special THANK YOU to everybody at the DUET team for your incredible service both in the design and especially the support !!

I just finished a test print with 100% success. Thanks for the suggestions.
I think the major problem was that I never removed the gap from when I was printing both the model and support with pla. I had completely forgotten about this.
I also printed slower although I don't actually know which of the many speeds is used - I suspect it was 26 mm/sec for petg and pla at 40 mm/sec.
The petg and pla stuck together to a limited degree ... enough to hold everything together yet not so much as to make support removal difficult.

I only have two words ...... Woooooo Hoooooo !

If your offset values are zero, you are probing points that the Duet doesn't know about and you are then taking those probing points to adjust the mesh height. You are creating a bad height map and then applying it.
I don't understand how you can possibly expect any results but crap. You might as well work without any height map.
It's odd that you get stripes but before anyone can give you any suggestions about what is wrong, you MUST set things up properly !!!

Moderators .... could we please lock this thread and stop with the negativity please ?

This aught to be interesting: ) I got the popcorn, a glass of cool liquid and am ready for the entertainment

Another update - I have now printed three cover plates, the first one had some issues but the next two were perfect - I am very optimistic about the speed change.

Temperature was brought up as a potential issue for PETG. I dug out the details - Nozzle: 200 - 240 C, bed 75 - 85 C .... so I am right where I should be.

Thanks again to all that offered their input! To be honest, I could have stared at the settings til the cows come home and not seen that I had set it for higher than the recommended speed. I had been printing at that speed for quite some time. It's great to be able to bounce these kinds of things off the people in this forum because although it might stick out like a sore thumb to everybody else, sometimes it's difficult for the one staring at the problem to see the trees for the forest!

It is highly unlikely that the SSR has failed since it is not stuck in the 'on' position. It is way more likely that there is a wiring error.
Are you aware that the positive line will always be high no matter if the heater is on or off?
Simply wiring the negative to ground will cause all these issues.
Verify the ruting of the two control lines.

@Co3get, here is my heater section of config.g:

; Heaters

M308 S0 P"bedtemp" Y"thermistor" T100000 B4200 ; configure sensor 0 as thermistor on pin bedtemp
M308 S3 P"e2temp" Y"thermistor" A"bed sense 2" T100000 B4200 ; configure alternate or second bed heat sensor
M950 H0 C"bedheat" T0 ; create bed heater output on bedheat and map it to sensor 0
M140 H0 ; set bed heater to heater zero
M143 H0 S120 ; set temperature limit for heater 0 to 120C
M307 H0 B0 S1.00 ; disable bang-bang mode for the nozzle heater and set PWM limit
M308 S1 P"e0temp" Y"thermistor" T100000 B4200 ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1 ; create nozzle heater output on e0heat and map it to sensor 1
M143 H1 S280 ; set temperature limit for heater 1 to 280C
M307 H1 B0 S0.6 ; disable bang-bang mode for the nozzle heater and set PWM limit
M308 S2 P"e1temp" Y"thermistor" T100000 B4200 ; configure sensor 2 as thermistor on pin e0temp
M950 H2 C"e1heat" T2 ; create nozzle heater output on e0heat and map it to sensor 2
M143 H2 S280 ; set temperature limit for heater 2 to 280C
M307 H2 B0 S0.6 ; disable bang-bang mode for the nozzle heater and set PWM limit

It's been a while since I set that up so am not too sure what all was done.
I do know that in order to display the second bed temperature on the graph in DWC, you need to go into the 'Extra' bit of the 'tools and extra' pane and flip the 'show in graph' thingy.

Hope that helps.

Yes, middle of bed for the sensor, offset a bit to not be directly where the bed wires go into the heat pad. I don't think it makes much difference exactly where it is located as long as it is somewhere in the middle-ish.

With about 90% certainty, I can say you have a dud thermistor. Another 5% goes to a bad connection someplace and the last 5% is phase of the moon related. Notice there is 0% chance of this being tuning related.
Why am I so certain? Because I happen to have had the exact same issue and struggled with it for quite some time before deciding to put a second thermistor on the build plate. I relegated the original thermistor that is buried in the heater to backup status and use the new thermistor as the thermistor 'in charge'.
I display both values in the temperature chart for kicks and the original one is still doing it's dance.
As a side benefit, the replacement is more accurate as it isn't buried in the heater.
A tuning related issue will show an undulating temperature but what you see here is sudden temperature spikes, instantaneous changes in temperature, that are not physically possible.
You might be able to tune it a bit, as you found out, to stop the safeties from kicking in or you might change the safety mechanism to be less sensitive. This can buy you some time to get a new thermistor in.

Chances are that your home switch is defective.
Printer tries to go 'home', switch is already closed/open/whatever and the Duet says 'I am here and now I need to go to the zero position which is 10 mm from the switch'
This will repeat forever.
I would suggest pulling the wires for the home switch and see what happens. If you get the same result, short the x home switch terminals at the board and see what happens.
If the action doesn't change then either the config.g file is set up incorrectly or there is something wrong with the Duet.

If you have a multi meter, pull the x home plug and throw the meter onto the cable connections and see if pressing and releasing the home switch has the expected results.

@stuartofmt, thanks - that worked
I will have to set up a camera on my test computer and see how it goes.

@stuartofmt, my bad, the second download added a '.1' instead of overwriting the initial download.
I got further but then ran into dependencies. I attempted to install everything you listed but some dependencies did not load (not found) .
The error is now a dependency error re module 'imutils'

@stuartofmt, the original link now works with the changed file name but I still get the error.
Now to be sure, this could be entirely my issue since I did not load any of the dependencies that you mentioned. However, the issue doesn't look like it is caused by dependencies .....!
Screenshot from 2021-06-21 14-29-51.png

@stuartofmt, I can now do the wget. Note that the documentation also refers to VideoStreamer instead of videostream (note also capitalization) in many places.
When I run videostream.py I get a syntax error on line 7.

@stuartofmt, could you double check the wget link that is shown in the readme file?

wget https://github.com/stuartofmt/VideoStreamer/raw/master/VideoStreamer.py

It is not working for me.

@stuartofmt, very cool, I will give it a try. Thanks!

@phaedrux, thank you !

I am setting up a Raspberry 3B+ to run the Duet3 main board.
Can the camera port on the 3B+ be used to stream video of the build plate or will that over-tax the SBC?
Is it possible to use any pins on the SBC that aren't used by the Duet to run pi controlled relays?

To lump both of the above questions together, is the SBC meant to only run the Duet or can I run other processes that one would normally run on a pi?

@djthuma, first up, you can't use Duet wifi and ethernet in the same sentence. They are two distinct products. If you have the boards already then you are (baring major effort) stuck with that board and it's manner of connecting to the world. My preference if I was in your shoes would be ethernet all the way - for cameras and the Duet boards.
I see no reason to deal with the bed heaters separately unless you already have them at hand and even then I would be tempted to somehow change she setup in such a manner that the Duet controls the heater.

This is just my 2 cents of course and hopefully somebody else will offer their opinion as well.

Edit: So let's suppose you already have the heaters on hand and they are independently controlled. Let's further assume that you want to run 100C bed heat. What you would do is set the external controller to lets say 130C. The Duet signal to turn on heat would go to an SSR and the external heat controller would be powered by the output of this SSR. You will obviously need a second thermal sensor to attach to the heat bed and feed that signal to the Duet. You then have a rather interesting safety feature in that the external controller will never let the bed exceed it's set temperature (130C in this case) but the Duet will control the bed temperature in normal operation. Since SSR's can fail in the 'on' mode, this setup gives you a really nice safety net.
Note that I am not familiar with the bed heater that comes with a Modix printer and for all I know it might have multiple sensors and heat zones in which case my ramblings are just ramblings that do not apply.
As always, talk to a qualified person whenever you deal with something that can kill you or burn down your place of business.

@fcwilt, cool, I had no idea!
Thanks!