tekkydave

That's pretty much how my D-Bot is. The wheels are on diagonally opposite corners. With a heavy bed it's best to use 1mm pitch screws to avoid 'back-driving' when power is removed or z motor(s) de-energised. That's assuming 1 motor per screw. If just 1 motor with screws driven by belt/pulley arrangement then steeper screws may be ok. 

4 hours ago, adyj1 said:

Is there a list of supported dslrs anywhere? I couldn't find one... 

There is a List of supported cameras on the gphoto website.

Try oacapture on Linux. Also make sure you are using a USB3 socket & cable.

Indi can control DSLRs via gPhoto https://indilib.org/devices/ccds/gphoto.html

8 minutes ago, Gina said:

Too small I think.  Needs 70mm height.

They would need a printed 'cup' thingy to hold them and stop the whole printer just rolling. Could be printed to give the right height.

Have you considered tennis balls as feet? Would absorb some of the vibrations.

Looking good. Is there any tilt front/back in the bed at all or has spacing the z-carriage wheels solved that issue?

2 hours ago, Gina said:

I've considered using "Stall detection and sensorless homing" in the stepper motor instead of using endstops but it seems complicated and also not very reliable so I think I'll stick with microswitches.

I had it working and it seemed ok. I've gone back to using conventional optical endstops as it is quieter. Plus the resume on power fail doesn't work correctly with stall detection as it sets the axis zero to the nearest 4 full steps.

Soldering is ok as long as a good mechanical connection is made first. Be careful not to overheat the connectors though as the plastic melts easily on these connectors. I've destroyed a few myself trying to desolder connections. I would sleeve/heatshrink the connections after just in case.

Ha ha, don't worry I do that myself

17 minutes ago, Gina said:

Tried disabling CoreXY so that i could test the motors individually.  There is a problem with the RH motor (Drive 0) or X motion. The Y control moves the X carriage diagonally as expected.  That would indicate a RH motor problem yet that motor works with CoreXY mode.  I have confirmed that everything moved freely by hand.

Shouldn't drive 0 be connected to the LH motor? Not sure it would make any difference, though. Moving either motor by hand should move the carriage diagonally. Also check the order of the wires on the connectors. I had to switch the red & blue before using motors on the Duet which were wired for RAMPS. If you were using them on Duet before then probably ok.

Quite agree, Gina. My current D-Bot consumed most of my Prusa when I first built it.

I've used JST-SM Plugs & Sockets for extruder motor, hotend & part fans and JST-RCY for the hotend heater circuit.

19 hours ago, Gina said:

Yes, I remember that you did that Dave and if I find the bed is not held level enough I may go for your solution.  And yes, I shall be using a Duet control board.  I was originally planning on using 3 Z drive rods but with belt drive.  Decided it was too complicated and experiments with 4 rods on my Giant printer proved disastrous.  Three motors means an expensive add-on to the Duet so if I can get away with two motors I can save money.

EDIT :- For @tekkydaveChecked cost of Duex2 - £74-34.  This seems an inordinate cost just to add two stepper drivers.  Actually, really adding only one as the second extruder driver could be used for one of the Z drives.  If only Duet had provided 6 drivers instead of 5 it would have been covered.  Considering TMC2100 drivers cost about £8, spending £74 to obtain the same result does seem excessive.  I wonder if there's an alternative.  I can see the advantage of three Z motors.  I wonder if one could connect three motor coils in series like we do for two.

I got my Duex2 for £42.50 + vat (£51). At the time (Sept 2018) they had a special offer running.

14 hours ago, Gina said:

Yes, I remember that you did that Dave and if I find the bed is not held level enough I may go for your solution.  And yes, I shall be using a Duet control board.  I was originally planning on using 3 Z drive rods but with belt drive.  Decided it was too complicated and experiments with 4 rods on my Giant printer proved disastrous.  Three motors means an expensive add-on to the Duet so if I can get away with two motors I can save money.

EDIT :- For @tekkydaveChecked cost of Duex2 - £74-34.  This seems an inordinate cost just to add two stepper drivers.  Actually, really adding only one as the second extruder driver could be used for one of the Z drives.  If only Duet had provided 6 drivers instead of 5 it would have been covered.  Considering TMC2100 drivers cost about £8, spending £74 to obtain the same result does seem excessive.  I wonder if there's an alternative.  I can see the advantage of three Z motors.  I wonder if one could connect three motor coils in series like we do for two.

It's a good point but the Duex also adds lots of extra i/o which may or may not be useful. It has onboard 12v regulator which allows me to have a mix of 24v and 12v devices without resorting to buck converters etc.

I found by previous mistakes that it is best to use the screws to maintain the plane of the bed and the z-axis wheels just need to keep it constrained in the x-y plane. My first iteration of the D-Bot relied on the wheels to keep the bed level. They were not very good at it

+1 for the 1-start screws. Gives very fine z resolution.

I would strongly recommend having 3 leadscrews each driven by it's own motor. I use this method on my D-Bot and the bed is rock solid. If you are planning on using the Duet then get the Duex2 Or Duex5 expansion board to give you sufficient drivers.

You can also make the bed self-level itself

https://duet3d.dozuki.com/Wiki/Bed_levelling_using_multiple_independent_Z_motors.

I think that's due to insufficient part-cooling. Also when the layers are that small they dont set solid before the next one causing the deformation.

If you are using Slic3r look at the cooling options. You can make it slow down on small/short layers.

Duet say the cooling should be from the rear of the board but none of the components on my board get more than slightly warm to the touch.

My board cooling fan is an 80mm PC type fan and is always on. it's so quiet I have to look at it to check it is running.

It's one of These

Yes - lithium grease. You only need the tiniest amount.

That's the way I do it to get the z carriage level. I have extra adjusters on the corners of the heated bed for fine adjustment of the bed itself.

I've used the tracking number to redirect them to my address - I fancy some new ones

9 minutes ago, Gina said:

Here are a couple of diagrams - first the arrangement I have ATM and the second with just two wheels.

Will the 2 wheels be able to keep the XY frame constrained in the Y-plane. I wouldn't rely on the leadscrews to constrain the bed.