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Gina

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Blog Comments posted by Gina


  1. Starting the year with a widefield narrow band rig with 135mm f2.5 Asahi Super Takumar Lens as used on vintage SLR film cameras such as the Pentax Spotmatic.  These are superb quality lenses even at full aperture and all my imaging has been with full aperture.  Camera - ZWO ASI 1600MM-Cool with ZWO EFW and Astrodon 3nm filters.  Rig mounted on EQ8 and without guiding at first.  Capture with RPi 3 running INDI firmware and saved in Linux Mint desktop indoors running KStars/Ekos.

    • Like 1

  2. Finished clock.  Apart from changing to gear drive from the motor I've cut out the ball bearing on the moving hours gear - it's sufficient to run PLA on a stainless steel bolt with washers either side of gear.  With such a low speed, wear will be insignificant.  (Bolts and washers are not shown in this model.)
    563510821_Screenshotfrom2019-12-2713-43-02.png.05d75a10cabcc52b1151c82ca87f7a1e.png

    Fixed hour and minute gears are attached to base plate with three countersunk bolts.  Then washer, moving hour gear, another washer and all retained by a 6mm SS bolt into the base plate.

    171683594_Screenshotfrom2019-12-2713-17-53.png.34fe18ce8850a279860e9f0dde9775d3.png

    1542160599_Screenshotfrom2019-12-2713-17-05.png.e6bc53ce8062abb8431ca1d54a7c3d55.png


  3. Now for some calculation for a pair of spur gears for the seconds drive.

    1. Seconds wheel wants to turn once a minute = 60s.
    2. Stepper motor driven by TMC2100 in it's quietest mode takes 3200 microsteps per revolution.
    3. With a 6:1 reduction ratio (16t motor pinion and 96t seconds wheel) motor takes 10s per revolution.
    4. This means 320 microsteps per second.
    5. In the Arduino sketch above the 1600 pulses in a half-second becomes 160 (which agrees with the 1/10th speed of the motor).

  4. I'm no longer sure about using the C-Beam and Gantry Plate system in view of the cost mainly though if I decide to change the Z axis on the Concorde I would have most of the parts to transfer from Concorde to Giant.  The Concorde printer Z drive system does not appear to be performing as well as I had expected though I'm not sure the rail system is the cause, I have some investigations to do.

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  5. The hotend heatsink cooling on this printer uses a radial fan without any ducting to concentrate the airflow through the fins.  To test that this would be adequate I made a small modification to the same part on my Concorde printer then checked the heatsink temperature when printing PETG at 240°C - it ran quite cool even with only half the heatsink being cooled.

    694768399_Screenshotfrom2019-12-0421-42-34.png.bdf5590864626122e467319ddc0f981f.png

    273408848_ExtruderHeatsinkCooling01.JPG.665cb9b4c38e3c2611121e71e7f77b79.JPG


  6. Now to work out what depth the printer needs to accommodate the extra Y dimension.  The full Y range can be produced with a 362mm Y bar and 2x 13mm thickness of mini linear rail.  This gives a total of 362 + 26 = 388mm.  To allow for tolerances I think I'll make this 390mm.

    Next to work out how this can be cut from the 900mm x 900mm x 18mm sheet of plywood.  The inside width has already been determined as 410mm.  Since the back, front and base fit inside the sides, this will be the cut width.  Overall height of the box (outside) will be half the height of the ply less cutting, so a little less than 450mm.  Width of the side panels will be 390mm (from above) plus twice the plywood thickness ie. 390 + 2x18 = 390 + 36 = 426mm.  Base will be 410mm x 390mm.  This gives a total width of plywood of 410 + 426 + 5(ish) = 841mm Add another 5mm for the cutting gives 846mm and therefore just 54mm wide strip left.

    Adding up the back and base from the height of the board, we get 457.5mm + 5mm + 390mm + 5mm = 857.5mm leaving a strip of about 42.5mm.  I was hoping it would be 100mm to use as the top front piece.  However, I have some 18mm plywood left over from making my Concorde printer that I can use in necessary.


  7. Went on to design the XY Carriage - what on a standard 3D printer would be the X Carriage but in this case runs on two round bars at right-angles.  This carries extruder & motor, hotend with heater block and nozzle plus Z probe and cooling fans for the hotend heatsink and parts-cooler.  Four linear bearings run on the two cross-bars.  As a result of the design model and comparison with the print bed size, the depth has had to be increased a bit to give full bed cover.

    Here are some screenshots.

    431040185_Screenshotfrom2019-12-0120-20-59.png.70ce113d0ffaea3e7631a5ae6c9867da.png

    1964981422_Screenshotfrom2019-12-0413-08-20.png.340481cce7ed89db5bf340aed4f7a70a.png

    1442263144_Screenshotfrom2019-12-0413-08-55.png.ed3e5c0ef3f0f46b0342c633dbfae79f.png

    953711086_Screenshotfrom2019-12-0413-10-32.png.40a9db0fe35730b6f3603875523a68de.png

    1660204573_Screenshotfrom2019-12-0413-11-40.png.64015996b2fae4f72c68d7aa78e35ac7.png

    115419076_Screenshotfrom2019-12-0413-15-38.png.3156fba0eab8262903b9c95081b05f46.png

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