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Ponoko RepRap - Installing Opto Endstops

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The Opto Endstops tell the RepRap's control system when the axes have moved to their minimum position - or optionally to the maximum position. The Ponoko kit doesn't come with maximum position components, but you can fabricate them once you have completed your RepRap if you wish.

The opto sensors are little "magic eyes" that spot when a flag travels between them. This has two important implications: The flags must not let light through, and if they miss the slot things will go downhill rapidly. Note that opto flags are probably the most likely component to be broken during operation and transit, so check them regularly.


The first step is to make the opto flags opaque to the infra-red light emitted by the opto sensors. A felt pen is unlikely to work. Gaffer (duct) tape does work, but may peel off. A matt-finish auto paint works well and as you can see from the terrible spray job, that is what was used here:


Now fit the Y opto flag into the cavity on the bottom of the X Motor bracket. You should be using the cavity on the side away from the Y axis motor. Do not use a powerful glue - you may well end up replacing the flag and you don't want to break anything else when you extract it. A small amount of multi-purpose clear adhesive is quite sufficient.


To secure the opto sensor board to the Y Opto Bracket, use <part>two M3 25mm screw</part>s. Put an 8mm acrylic M3 spacer between the opto board and the Bracket to keep the solder side of the board off the bracket. This makes it much easier to slide and align the opto components. Fasten with <part>two M3 nut</part>s and <part>two M3 washer</part>s.

If the Opto Bracket is a little loose, pack it by wrapping some tape around the 8mm bar that it is anchored to. The slop is caused by the lasercut sides not being quite square to the surface of the acrylic due to the way the cutting beam is focussed.


The X Axis flag goes in the square hole on the protuberance on the X Carriage. This should be on the side of the carriage closest to the X Motor. Again, very little glue is needed.

The opto sensor board is secured to the X Opto Bracket in the same way, using <part>two M3 25mm screw</part>s, 8mm acrylic M3 spacers, <part p="2 M3">nut</part>s and <part p="2 M3">washer</part>s.


Apologies time. All kits so far have consistently had the slots in the Bed Frame for the <part>two M5 nut</part>s cut too small. File or grind the sides of the nuts until they fit into the recesses as shown. Using the rectangular 4.5mm acrylic part with two M5 holes in it, fasten the long Z Opto Flag into place using <part>two M5 16mm screw</part>s. Do not use washers - there is insufficient room.


Lastly, secure the Z opto sensor board using <part>two M3 25mm screw</part>s, 8mm acrylic M3 spacers, <part p="2">M3 nut</part>s and <part p="2">M3 washer</part>s.

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-- Main.VikOlliver - 03 Jan 2009