Motors used on eary Ormerod? Duet support 2 motors on z?

Hi All,

By accident I have landed myself a tight time scale on getting notes back to work on upsizing the Ormerod at work! This is to increase the foot print to 300mm square (with a view to go larger), use an X-Y head and potentially one of the extrusion systems without a bowden cable.

Does anyone know the exact specification of stepper motor used on the early Ormerod 2 machines made by RepRap pro but distributed by RS? Alas my machine is at work and I'm at home!

Likewise can someone advise on how to wire two of the motors to the z-axis channel?

I'm still building a bill of materials for the upsizing. If I find the answers to the above in the mean time I will respond to this thread!

Thanks,

Wes.

I can see me making sure the remains of work's Ormerod are suitably recycled... ;-)

Found it! Downloading 2mB pictures from work over VPN is painful!

NEMA 17 JK42HS34 1334A

Step Angle: 1.8
Motor Length: 34mm
Current /phase: 1.33A
Resistance /phase: 2.1Ohm
Inductance: 2.5mH
Holding Torque: 2.2kg.cm
Wiring: 4 leads
Detent Torque: 120g.cm
Rotor Inertia: 34g.cm
Mass: 220g

Cool topic.

Would have liked to help but seems you beat me to it.

I would also like to know about transforming the ORMEROD into something more sturdy and with a larger build area.

Especially with duplicating the z axis motors.

If using an original Duet, connect the two Z motors in series. You may need to reduce the maximum Z speed a little unless you convert to 24V power - which is a good idea anyway because you will need more than double the bed heater power. Expect the two motors to get out of sync sometimes when you power off and on again.

If using a more recent Duet with 5 stepper drivers, connect them to separate drivers, then you can use the Z probe to auto level them.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Looking at the d-bot at the moment. It's on thingverse and ooznest do kits for the cut lengths of extrusions and a bundle of mechanical/motion parts. I'm going to prepare the builds to see how much filament it needs today and hopefully get the go ahead to progress with the project. Cost wise if using the steppers and Duet 0.6 from the 2014 Ormerod 2 the price looks to be around £500-600 without hunting around much on suppliers.

The steppers are shorter than the ones that can be included in the kit (1.68A NEMA 17) but I'm hoping for reasonable perfomance as the y axis doesn't have to drive the weight of the platform any more and the drive voltage has been doubled.

Thanks for the hint on the 24V through the Duet to feed the steppers and heaters. I've had a hunt around and seen many posts on this. Well worth dropping the current on the heater terminals. Alas with a 300W silicon 300*300 heater at 24V it'll still need an SSR as the 12.5A is over the 10A limit. Knowing the closed circuit faliure mode of the SSRs this would probably be a good time to invest in mechanical relays with suitably placed thermal fuses for the bed and hotend.

The Duet 0.6 can handle the 12.5A if you bypass the weak PCB trace with a wire link. Details on the duet3d.com forum. Avoid mechanical relays, they prevent you using PWM on the bed heater and using bang-bang control can cause Z banding.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Good to know about the 12.5A through the Duet. That simplifies things.

With regards the SSR I was a little unclear. I was intending to fit a thermal fuse in a an appropriate place and fit this in series with the relays coil (with reverse diode) direct to ground from a permanent live. I would then just break the feed to the heater on the switched side. This way if the temperature sensor looses contact/fails or the mosfet/ssr goes closed circuit it is a little more fail safe. Functionally the relays would close when the PSU is powered up and open when shut down. With enough poles you could send a logic level 'I'm ok' signal through spare poles. If you were to design more like industrial safety systems then this would be two relays with force guided contacts so if they welded shut you'd know about it. For the latter to work I guess I would need to investigate the GCode to power up and external PSU after checking the relays are in a safe state. If super paranoid I guess you could have a check every x number of layers, a brief interruption of the heaters may be worth the additional safety.

Edit: In industrial systems the 'I'm ok!' signal is actually 'I'm safe'. In other words it would be closed circuit when the relays are open and the heaters disabled. This way if the relays failed the force guided contacts would hold the 'I'm safe' loop open. Likewise wiring breaks would also hold it open.

Edited 2 time(s). Last edit at 08/04/2017 03:10AM by WesBrooks.

Quote
dc42
... using bang-bang control can cause Z banding.

Do the older (2014ish) systems and firmware default to bang bang or PWM? The Ormerod suffered banding. I may have been too quick to blame the slight bend in the z-axis threaded rod!

Go ahead for the project granted!

I've ordered the printed parts to short cut some time. Not sure how long that would have taken to print but in ABS with the nuts and bolts for £100 on ebay. I'll be keeping a close total on spend so will keep it well logged.

The Ormerod is highly likely to live again, but may not be anytime in the next few months! All that I'm taking from it is the Duet, steppers, and power socket. May order a duplicate of the last to save disturbing it. For work the flexibility of direct or bowden as well as 1.75 and 3.00mm filament is all on the wish list.

You may like to consider an AC Silicon heater rather than a DC One you would need a relatively Cheap DC-AC SSR but you would have the flexibility to increase the power of the heater if you wish.

You can auto-level two Z motors that are in series. Fit a mechanical end-stop to the base of each Z-screw. Then to synchronise, reduce the drive current to the Z motors and drive to below zero. The motor of the first side to hit the end-stop will stall and skip steps until the other side is also at its end stop.

Dave

Project is progressing well. The machine frame and motions are built and I have temporary wiring in place to allow me to test things out. Waiting on a piece of tool plate for the elevator base. I've ordered parts to allow a pair of 24V force guided contact relays to cut the power to the heaters, and separated off the fans onto a separate PSU so that the hot end doesn't get really guey if the power is cut while the cartridge is still hot.

Three PSUs is a bit awkward - 5V, 24V (heaters / steppers), and 24V safety relays & fans. Guess I could have used a DC-DC from the safety / fan PSU to the 5V, but that's probably almost as much hassle as running an additional PSU. I avoided the old Ormerod 2 5V regulator as people said these get hot, and the on board regulator as there were reports of the duet regulator being electrically noisy.

Force guided contact relays to kill the mains to the heater/steppers is also overkill, but wanted to err on that side of things as it is likely to be a shared resource in an R&D environment.

I think a 3rd stepper and screw will be considered for levelling and ultimate rigidity, but I will take the detail of that conversation onto the Duet forum if I can't find information in their wiki.

Edit:
Multiple lead screw correction discussion on this forum.
...and wiki page that links to on the Duet wiki.
Duet fourm

Edited 1 time(s). Last edit at 09/05/2017 04:04AM by WesBrooks.

Current wiring diagram plans:

Sheet 1: Power distribution & heater / stepper safety cut out
Sheet 2: Duet 0.6 wiring for core X-Y

Don't play too much attention to the colours & notes! These aren't final diagrams and I'm not generally overly reliant on colours of wires other than specials like earth bonding / connections.

...after much faffing about I've decided to tie the negative side of the PSUs together, but not tie them to the ground. I'll be ensuring the frame is fully earth bonded and connected to the mains earth.

Edit: Earth bonding isn't essential here as there is no voltages on the machine above 24V. I've done this to reduce any charge build up and maybe electrical noise.

Edited 1 time(s). Last edit at 09/05/2017 03:36AM by WesBrooks.

It's alive! Minor wiring change as the force guided contact relay didn't change when using the normally closed contacts to power the reset button. Shame as it would have been a good self diagnostic. As it happened the relay just buzzed. I guess a small capacitor between the supply side of the reset button and the relay may just do the trick.

Anyway, the core x-y system is running. Done a orthoganal axis correction build and made a few more parts for the system. Got a long process ahead of improving the settings and build qualities, but initial build qualities are exceeding that of the ormerod - although I never put much effort into optimising that and the system is nearly double the cost!