[ZS6HDV]

Just a quick update on my progress:

I picked up the printed parts from Quentin on Saturday, and spent most of my free hours since assembling the printer.

Status at the moment – I should be finishing up the wiring tonight and start testing movement, homing etc. The extruder is still completely missing (need some extra vitamins).

As it stands:

A more complete build record is posted at http://reprapramblings.blogspot.com

Regards
Hein

[ZS6HDV]

Your English is fine! As I understand it, the stepper driver ICs generally used in RepRap printers are current drivers, and the stepper motor voltage is not important. The drivers are running off a high voltage (relative to the stepper max voltage) and controls current.

The higher the current rating, the stronger the motor is (maximum torque). A free running stepper motor will automatically use less current than a straining one (that is, one that is under load).

Hein

[ZS6HDV]

Quentin

How did you adjust the speed of calculations to arrive at the limit of 500 calcs per second before the Arduino ran out of steam, and how did you measure that?

Thanks
Hein

[ZS6HDV]

I don’t want to hijack or advertise here too much, but I’m keeping a build log at http://reprapramblings.blogspot.com. Currently I’m about at the stage of testing electronics step by step. I’m waiting for srepper drivers but should have them in a few days.

Maybe have a look at the RAMPS rest software rather than the full Marlin as there are checks (e.g. nozzle temperature) that will block the rest of the operation, unless you want to simulate that signal or connect an actual hotend and run it at temperature.

Hein

[ZS6HDV]

Are those profiles printable? Would the bridge and overhangs at the top of the arms not sag during manufacture due to being unsupported?

[ZS6HDV]

My Morgan build is still in progress so I’m working off theory here…

The Morgan Marlin code does not make provision for 32 microstepping selection in software. The 32 ustep board automatically goes to 32 usteps when 16 usteps are selected (as they are).

The BOM shows 2 x 0.9 deg and 2 x 1.8 deg steppers, and 2 x 32 ustep and 2 x 16 ustep drivers. To me this means the z axis and extruder runs at one quarter of the resolution of the arms.

If you run 0.9 degree motors all round, my logic says the z and e drivers must run at 1/8 usteps to be the same step size as 1.8 at 1/16. This option (1/8) is selectable in software.

I’m not sure of your stepper drivers (the circuits for the ones I see online do not have hardware jumper options), but it SOUNDS like you have jumpers on the board?

If I wanted to select 1/16 on one of those (directly connected 32 ustep) driver boards I would de-solder the mode select pins (on the edge connector – just heat the pad and pull out the pin), and physically connect the pad (now not connected to the PC) to power or ground according to the selection table in the data sheet.

But, if you select 1/16 manually as above, you are running a 1/16 and 0.9 combination, whereas the design calls for a 1/16 1.8 degree combination, still double the resolution. I would first try 1/8 0.9.

Hope this makes sense…
Hein

[ZS6HDV]

Quentin

I have already started doing timing tests (separate program simulating the maths), and I’m confident there is potential for gain.

The proof of the pudding, is in running a Morgan as fast as it will go. You’ll have to get me my printed parts ASAP, hee hee. I’m ready to start assembling…

Hein

[ZS6HDV]

I had another look at the DRV8824 Pololu board, and my comments above only apply when using the 8824/5 board as a drop-in replacement for the 4988. 1/16th is available but not when microstepping is selected under software control with software for the 4988.

Hein

[ZS6HDV]

I’m still familiarising myself with the Marlin code (so double check), but I believe that you can also work around the problem in software. In the file Configuration_adv.h, line 192, the microstepping modes are set for each of the five stepper drivers.

The 8825 I believe is configured to automatically go to 1/32 microstepping when the software (written for the 4988) selects 1/16, all the other modes work identical to the 4988. I.e. no 1/16 is available on the 8825 drivers.

[ZS6HDV]

I have found the Alpen drill bit – on my doorstep. Timber City Witbank stocks the long length of the 8mm bit.

Hein

[ZS6HDV]

Answering my own question – I see in the calibration guide that there are slic3r options LQ MQ and HQ for 0.4, 0.2 and 0.1mm respectively.

I figured about as much, as the Alpen drill bit has a twist of around 30 to 40mm, and 400 steps per revolution should give you around 0.1mm (not measured, estimated by eye).

[ZS6HDV]

Hi Robert, thanks for the input. That will be the backup plan, but I’m not ready to give up yet. If I know where Quentin bought his bit, it is no problem for me to drive past the shop and collect one. It is but a small detour for me as I drive that way once a week for work purposes. I live approximately 120km from where Quentin is based.

As a matter of interest, what is the z-axis resolution for the threaded screw and drill bit options? I have not seen any figures, but have not really searched for it either.

Hein

[ZS6HDV]

Quentin

I have spent a significant part of today looking for an 8mm SDS drill bit in 450/400 mm length (four Builders Warehouse branches, three Micas including Mega Mica Eastgate, Cashbuild, Builders Express and various other hardware stores), and nobody seems to stock the long 8mm bit (I can find 8mm in 310/250 length and 10mm in 450/400 length).

Can you tell me where you purchased the drill bit, I drive to Jhb at least once a week and going to a specific store is not TOO much of a problem for me?

Thanks
Hein

[ZS6HDV]

OK, the Witbank (South Africa) Morgan build is under way (or at least, some of the parts are on their way).

I have also decided to create a simple build blog, for anybody interested. More aimed at the novice new to RepRap. Photos will be uploaded and occasionally cross-posted here.

See http://reprapramblings.blogspot.com if you’re interested.

Thanks
Hein

[ZS6HDV]

Hi Quentin

The parts link on the site opens up to show a photo of the parts and price but no place to actually place an order with shipping and payment options?

Can I pay via the donation button? I was thinking a hundred dollars should buy me a set of printed parts and you a roll of filament 🙂

Then I can arrange to collect it once it is printed in the new year (currently we are still on holiday at the coast).

Hein

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