Upgrading Mini Kossel to Duet electronics

I've tested the new 0.80m and also the newest 1.0 firmware, both of then seems working perfectly.

Pavel, thanks for the feedback. As the delta-specific work appears complete except for auto calibration, I will freeze the delta branch and do further development work on my dev branch, which now includes the delta support.

Edited 1 time(s). Last edit at 01/24/2015 04:37PM by dc42.

---

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].

Delta support is now a standard feature of my fork of RepRapFirmware, starting at version 1.00a, and available here [github.com].

In version 1.00b I have added support for IR Z probing on deltas for accurate height determination (M558 and G30 commands), however this is largely untested at present. Bed probing and compensation (G32 and M557 commands) is also implemented in theory, but completely untested. I will do further work on this when I have fitted an IR probe to my Mini Kossel.

I could add support for the mechanical switch Z probe of the Mini Kossel, however that would require implementing macros files to extend and retract the probe. So unless there is any demand from users for that support, I'll concentrate on the IR probe support. It should be possible to use FSRs in the bed supports in place of the IR probe, as all that is required by the software is an analog input that rises when the probe approaches or contacts the bed.

---

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].

Hi Dave, I have been relying on your kossel-to-duet blog and it has become my bible for this process, thank you! I have a bunch of parts on order so I'm still lining up my ducks. (or is that an American expression?)
You have suggested 0.9 degree motors but I have seen multiple comments that those and/or 1/32-step drivers are too fast.
I would think the Duet could easily keep up though, unless there is a limitation somewhere not related to the MCU speed or word size.

Quote
shadowphile
Hi Dave, I have been relying on your kossel-to-duet blog and it has become my bible for this process, thank you! I have a bunch of parts on order so I'm still lining up my ducks. (or is that an American expression?)
You have suggested 0.9 degree motors but I have seen multiple comments that those and/or 1/32-step drivers are too fast.
I would think the Duet could easily keep up though, unless there is a limitation somewhere not related to the MCU speed or word size.

0.9 deg motors or 1/32 microstepping would seriously stretch an Arduino Mega or similar atmega2560 electronics on a delta. But I expect the Duet to handle them adequately. At worst, travel speed might be limited to 200mm/sec instead of the 400mm/sec that I currently achieve with 1.8 deg motors and 80 microsteps/mm.

I ordered some new motors a few days ago (3 x 0.9deg JK42HM48-1684 for the towers, and a 1.8deg JK42HS34-1334 for the extruder). They are due for delivery tomorrow or Monday. So I will soon know for sure how fast the Duet can drive them. I also have some firmware efficiency improvements planned to improve the maximum speed.

---

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].

great!, I will await your report.
thanks

Quote
dc42

Quote
shadowphile
Hi Dave, I have been relying on your kossel-to-duet blog and it has become my bible for this process, thank you! I have a bunch of parts on order so I'm still lining up my ducks. (or is that an American expression?)
You have suggested 0.9 degree motors but I have seen multiple comments that those and/or 1/32-step drivers are too fast.
I would think the Duet could easily keep up though, unless there is a limitation somewhere not related to the MCU speed or word size.

0.9 deg motors or 1/32 microstepping would seriously stretch an Arduino Mega or similar atmega2560 electronics on a delta. But I expect the Duet to handle them adequately. At worst, travel speed might be limited to 200mm/sec instead of the 400mm/sec that I currently achieve with 1.8 deg motors and 80 microsteps/mm.

I ordered some new motors a few days ago (3 x 0.9deg JK42HM48-1684 for the towers, and a 1.8deg JK42HS34-1334 for the extruder). They are due for delivery tomorrow or Monday. So I will soon know for sure how fast the Duet can drive them. I also have some firmware efficiency improvements planned to improve the maximum speed.

Might I ask why you choose a smaller motor for the extruder?

Quote
Koenig
Might I ask why you choose a smaller motor for the extruder?

The 17HS19-1684S has too much torque for the geared extruder that came with my T3P3 Mini Kossel kit. To get the right amount of force (so that it the nozzle gets temporarily obstructed, it skips steps instead of grinding through the filament), I have to reduce the current to 400 to 500mA. However, this reduces the available extruder acceleration, because of the high rotor inertia of this long (48mm) motor. So I have a choice:

1. Keep the motor, but use a lower gear ratio, or even direct drive.

2. Keep the gearing as it is, but use a shorter motor with lower rotor inertia.

I chose (2) partly because it means that I can sell a set of 4 motors along with most of the parts from the Mini Kossel kit I started with. Also because the motor I chose is the same one used in my Ormerod printer, and I may copy the geared extruder design from that.

---

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].

Quote
dc42

Quote
Koenig
Might I ask why you choose a smaller motor for the extruder?

The 17HS19-1684S has too much torque for the geared extruder that came with my T3P3 Mini Kossel kit. To get the right amount of force (so that it the nozzle gets temporarily obstructed, it skips steps instead of grinding through the filament), I have to reduce the current to 400 to 500mA. However, this reduces the available extruder acceleration, because of the high rotor inertia of this long (48mm) motor. So I have a choice:

1. Keep the motor, but use a lower gear ratio, or even direct drive.

2. Keep the gearing as it is, but use a shorter motor with lower rotor inertia.

I chose (2) partly because it means that I can sell a set of 4 motors along with most of the parts from the Mini Kossel kit I started with. Also because the motor I chose is the same one used in my Ormerod printer, and I may copy the geared extruder design from that.

OK!

I was just curious.

Do you mind sharing where you got your motors from?

I have thoughts about upgrading my kossel to 0.9 steppers, have been waiting to hear your thoughts about it though.

Not sure I can wait any longer, I have an itch in my tinkering-finger....

Yesterday I had to replace the extruder drive. The hex bolt head was rotating in the large gear. I then found that it was impossible to repair, because of the superglue used to lock the hobbed insert to the bolt. So I have decided I don't like that design.

For now I have removed one of the extruder drives from my Ormerod and printed a bracket to mount it on the Kossel. It uses a smaller and cheaper motor, and I think the 3:1 gear ratio is a better compromise between torque and acceleration than the 5:1 of the original. I have found the spring loaded variant of the Ormerod extruder drive very reliable. So in the longer term I plan to adapt this version of the Ormerod extruder drive for the Kossel, which basically just means removing the mounting hook.

The 0.9deg motors I bought are JK42HM48-1684 and the extruder motor is JK42HS34-1334, both from Etang Electronics which sells on ebay UK. Total cost was £50.80 + VAT. These motors don't have flats on the shafts, so I ground flats on them. Also, they have flying leads instead of connectors.

I subsequently discovered [www.omc-stepperonline.com] which sells the 17HM19-1684S. This is the 0.9deg version of the motor I was originally using and would probably be my preferred choice if I hadn't bought the other ones. From the picture, it looks like it does have a flat. The 17HS13-1334S looks to be a suitable choice for the extruder drive. The prices are low and it looks like they ship direct from China, so delivery may take a while.

---

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].

Quote
dc42

Quote
shadowphile
Hi Dave, I have been relying on your kossel-to-duet blog and it has become my bible for this process, thank you! I have a bunch of parts on order so I'm still lining up my ducks. (or is that an American expression?)
You have suggested 0.9 degree motors but I have seen multiple comments that those and/or 1/32-step drivers are too fast.
I would think the Duet could easily keep up though, unless there is a limitation somewhere not related to the MCU speed or word size.

0.9 deg motors or 1/32 microstepping would seriously stretch an Arduino Mega or similar atmega2560 electronics on a delta. But I expect the Duet to handle them adequately. At worst, travel speed might be limited to 200mm/sec instead of the 400mm/sec that I currently achieve with 1.8 deg motors and 80 microsteps/mm.

I ordered some new motors a few days ago (3 x 0.9deg JK42HM48-1684 for the towers, and a 1.8deg JK42HS34-1334 for the extruder). They are due for delivery tomorrow or Monday. So I will soon know for sure how fast the Duet can drive them. I also have some firmware efficiency improvements planned to improve the maximum speed.

Dave

Do youu think that these 0.9 steppers would be suitable also could you post you Mount for the Ormerod Extruder please think I am going to go that route then just need to find the right 24V Heater/fan

Doug

Those steppers should be OK but are not ideal because the rated current (2A) is rather high. In my blog I linked to some motors from Etang Electronics (ebay UK supplier) which are rated at 1.67A and so a better match for the electronics.

Etang also sells these 24V 40mmx10mm fans [www.ebay.co.uk]. I got the 24V 30W heaters (to convert my E3Dv6 to 24V) here [www.ebay.co.uk] or you can get them from E3D.

I'll post the Ormerod extruder mount on thingyverse later this evening.

I now have a printed combined mains inlet & Duet mounting panel too.

Edited 2 time(s). Last edit at 08/10/2015 01:01PM by dc42.

---

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].

Dave

Thanks for the info.

I have ordered the ones from ETANG that you used £1 per motor just wasn't worth the hassle.

I have a 24V LED supply already so should be good to go for the next Delta (will be a smaller one geared up for finer prints)

Will be interested in your Duet mount as well.

Doug

I've published the extruder mounting plate at [www.thingiverse.com]. The 3rd iteration of the mains inlet + Duet mounting plate is currently printing, and if it is a success I will upload that one too.

---

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].