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Prusa i3 3D printer


tekkydave

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Its all looking very clever Dave.

Keep up the good work as it's an interesting thread. I'm sure that in the future there will be quite a few questions for you to answer as more people take on these projects.

Damian

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Its all looking very clever Dave.

Keep up the good work as it's an interesting thread. I'm sure that in the future there will be quite a few questions for you to answer as more people take on these projects.

Damian

Thanks Damian.

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Hope our summer student gets our high temp i3 working quicker than this thread.... ;-) looks like you got it working nicely. For pla you probably don't need a fine hood, some taulman nylons are the same.. Abs and hips stink and need fume handling.

All the best

Peter

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Hope our summer student gets our high temp i3 working quicker than this thread.... ;-) looks like you got it working nicely. For pla you probably don't need a fine hood, some taulman nylons are the same.. Abs and hips stink and need fume handling.

All the best

Peter

Thanks Peter. You are quite right - I have only used PLA so far but will need the hood if I try ABS which I want to do at some point.
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I've found ABS much easier to print with than PLA - it needs higher temperatures but it's much more forgiving.  I haven't tried printing PLA on glass yet though.

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I have been printing more things today. First I printed an updated front panel for the control box. The previous version had the Mega holes 4mm too far to the left. This one has come out a lot better since I recalibrated the bed level and height.

post-28249-0-42222700-1440868858.jpgpost-28249-0-01735100-1440868874.jpg

I also printed some adapters for the anti-vibration feet so they fit the prusa feet and also the frame.

post-28249-0-80012100-1440868884.jpgpost-28249-0-24433000-1440868898.jpg

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Looking good Dave - particularly the panel :)

Thanks. Third time lucky. The first 2 attempts had quite a lot of delamination on the first couple of layers as well as having the Mega holes in the wrong place. I have got better prints and less delamination by setting the z home height quite low to the bed. I have set the z endstop so that when I put a piece of doubled printer paper on the bed the extruder nozzle grips the paper. Not so tight you cant pull it out but you can feel there is some friction when you move the paper. I suppose it ensures enough pressure to make each layer stick to the previous especially the bed. I am also using a bed temperature of 75° with PLA.

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Busy again today. The control box front panel I printed yesterday was a good fit. After some judicious finishing (i.e. filing and drilling) I fitted it to the box and set all the connectors in. The separate connectors for the extruder and bed heaters have been replaced by a single Speakon connector to save space.

The ribbon cables to the LCD will be replaced by a 25 pin d-sub in due course.

There are 2 connectors in the RPi's USB sockets - one loops into the Arduino Mega to control the printer, the other connects to the webcam above the printer. The RPi network connector is connected via a cable to my network switch giving access to the Octopi web application from any device with a browser. I could use a WiFi dongle but the box is only a few feet from the switch so not much point.

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  • 2 weeks later...

I was getting constantly frustrated by the idler of my Gregs Wade Accessible extruder. More specifically the screws, springs and washers used to provide pressure to keep the idler pushed against the filament. Whenever I released the idler to change the filament it was very fiddly to get the washers and springs back in position to put the screws in place. So I bought some longer M4 bolts 70mm long and also a selection of springs. I printed a spacer to sit between the springs and the idler to make it easier to get them into position once the idler is replaced. I replaced the single spring on each bolt with two slightly weaker springs making it easier to compress them and push back into position.

The spacer and springs fitted. The idler is in the open position.

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With the idler closed the spacer is pushed back and dropped into position.

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I also printed up some nut traps to fit the prusa's sub-frame to hold the m3 nuts on the bed levelling screws. This saves struggling with a spanner and an allen driver to level the bed.

post-28249-0-72936100-1442002639.jpg

post-28249-0-34136100-1442002650.jpg

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The 25-way IDC D-Sub connectors I was waiting for arrived in the post today so I can finally complete the control box. The connectors are for the LCD connection. I made up the following with the help of my trusty mini bench vice:

25w female D-sub 2x 10w headers. This was fitted in the control box.

25w male D-sub 2x 10w headers. This connects to the LCD and will eventually be inside an LCD enclosure.

25w female D-sub 25w male D-sub. Connection from Control box to LCD enclosure.

I haven't decided where the LCD enclosure will finally be located - on the printer chassis, base or somewhere else.

post-28249-0-78206700-1442075718.jpg

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I have also calibrated the stepper drivers to maximise the output for the motors I am using. I put my DVM in series with one of the motor coils on the 10A DC Current range. Trying to measure the current whilst the motor is moving isn't possible and I would probably need a scope to do that accurately. But when the motor is stationary with a holding current measured I adjusted the trimpot on the driver to set the current to 1.65A which is the maximum current per phase for the NEMA14 motors I am using. Repeated this for all 4 drivers. I probably already had them in about the right place. If you want to set them roughly then point the flat on the rotating part of the trimpot towards the main chip, which probably has a heatsink on it.

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I have also calibrated the stepper drivers to maximise the output for the motors I am using. I put my DVM in series with one of the motor coils on the 10A DC Current range. Trying to measure the current whilst the motor is moving isn't possible and I would probably need a scope to do that accurately. But when the motor is stationary with a holding current measured I adjusted the trimpot on the driver to set the current to 1.65A which is the maximum current per phase for the NEMA14 motors I am using. Repeated this for all 4 drivers. I probably already had them in about the right place. If you want to set them roughly then point the flat on the rotating part of the trimpot towards the main chip, which probably has a heatsink on it.

Correction: They are NEMA17 motors.

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Anyone thinking of buying or building a 3D Printer especially a Reprap type could do worse than get this book

http://www.amazon.co.uk/Maintaining-Troubleshooting-Your-3D-Printer/dp/1430268093

It can also be downloaded in PDF format from http://www.it-ebooks.info

I'm sure I don't know everything about 3D printers though probably more than some so I guess it could be useful.

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Anyone thinking of buying or building a 3D Printer especially a Reprap type could do worse than get this book

http://www.amazon.co.uk/Maintaining-Troubleshooting-Your-3D-Printer/dp/1430268093

It can also be downloaded in PDF format from http://www.it-ebooks.info

A very interesting book and a very interesting web site. Bookmarked for future reference.

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A very interesting book and a very interesting web site. Bookmarked for future reference.

I've downloaded dozens of good books from there. It appears to be legal. Many of the books are older versions of current books but still good nevertheless. The one I mentioned is very up to date. There is a whole chapter on Reprap & Marlin config and calibration.

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I have also calibrated the stepper drivers to maximise the output for the motors I am using. I put my DVM in series with one of the motor coils on the 10A DC Current range. Trying to measure the current whilst the motor is moving isn't possible and I would probably need a scope to do that accurately. But when the motor is stationary with a holding current measured I adjusted the trimpot on the driver to set the current to 1.65A which is the maximum current per phase for the NEMA14 motors I am using. Repeated this for all 4 drivers. I probably already had them in about the right place. If you want to set them roughly then point the flat on the rotating part of the trimpot towards the main chip, which probably has a heatsink on it.

After reviewing the notes on setting these drivers up on the Reprap Wiki http://reprap.org/wiki/Pololu_stepper_driver_board#A4988_and_similarI decided to follow their advice.

I measured the Vref on the pot wiper at only 0.35V so I had set them a bit low using my method for the motors I am using. Plus I think the method I used trying to measure the coil current doesn't give you a true reading.

My NENA17 motors have a stated current per winding as 1.68A

Using the same method as on the wiki and setting the  I_TripMax to 1.68/sqrt(2) = 1.188, gives:

Vref = 1.188A * 8 * 0.05 = 0.4752V

So I set the Vref to as close to 0.475V as I could get it on all four driver boards. The pots are very tiny and its a bit precarious trying to hold one probe of the DVM on the GND pin and the other on the pot. But I managed it in the end.

Doing a test print I can feel the X,Y and E motors are slightly warm to the touch so probably a good method to follow. The Z motors are not warm at all. They are only doing work when the layer changes, and even then they get powered off after a while when they are not active.

The drivers themselves are hot but not so hot you cant hold your finger on them. I could probably use a smaller fan in the control box or slow the 120mm one down to reduce noise.

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