Overview

The PIKA XY Flexure Table is a 3D printable stage that can move freely by up to 8mm in the X and Y axes without moving significantly - even on the micron scale - in the Z axis. The X axis flexures and frame are printed as a single piece. The Y axis is fitted to the top with three adjustable screws that level the integrated Stage. It requires three Axis Drivers (one fitted with Z Axis parts) and the Microscope Pole. Note that the Stage and Central Pillar may have different dimensions on different PIKA variants, but that the assembly method is identical. The mechanism is designed so that screw lengths that are +/- 1mm can be used, and in many cases significantly more.

Part Preparation

The Stage holds a 390μm-400μm UV LED in its central Light Well. A diffuse UV source is preferred to a point focused one, and USB UV LED lighting strips are an inexpensive source of UV LED modules (though if you have an SMT UV LED and know what to do, feel free to improvise) . Choose an LED strip that can have the LEDs cut off individually - some have a minimum cut size of more than one LED and are not suitable. Look for ones that have pairs of solder pads between every LED.

The LED used by this particular prototype runs off 5V, and the CNC Controller supplies 12V. Therefore a 680 Ohm resistor was needed in series, not shown in these instructions. Otherwise, choose an appropriate combination for your CNC Controller.

A UV LED needs to be wired on flexible multi-strand leads and mounted. A grounding probe for the CNC Z Touch function needs to be fabricated from a length of multi-strand insulated copper wire and a washer. Various holes and slots need to be checked for printing debris.

UV LED Safety

While a single small UV LED of wavelengths 390nm or larger is not instant death to your retina, it is still unhealthy to look at for an extended period. Try not to. If doing something that requires a lot of looking at the LED, wear sunglasses or use a camera. The more severe problems are generally caused by people using large UV lamps for "indoor gardens" or mistakenly purchasing UV-C (180–280 nm) light sources online.

Wire Up The UV LED

Take a length of 8mm LED UV strip light and cut off one segment, including solder pads on the segment.

Take each of the wires that will connect the UV LED to the CNC Controller and wind them closely 10 times around a small screwdriver shaft, leaving about 50mm of unwound excess at one end. Apply heat with flame or heat gun, and allow to cool for 30 second before slipping the wire off the shaft. They should maintain a coil. Using this coiled wire will place minimal force on the Stage when it moves.

Heating the coiled UV LED attachment wire

Finished coiled wire

Strip the short ends of the wires and solder them to the UV LED strip's positive and negative contact pads to complete the UV LED Wiring.

Ground Lead For Touch Probe

Z Touch Grounding probe made from an M8 plain steel washer

This provides the connection to the Touch Plate on the CNC controller, so select a suitable lead. The return path for the Touch Plate is attached to the Probe on the Z axis, for which you should have already selected a lead. If not, please read the Z Axis construction instructions re Z Touch Wire.

Onto the end of the lead solder an M8 steel (plain steel or zinc plated) washer such that the lead passes over the centre of the washer. Stick the lead to the opposite edge of the washer to the soldering using a generous quantity of hot melt adhesive. The intention is to provide the lead with strain relief. Ideally, the lead should be coiled in the same way as the UV LED wires.

Clearing Holes

Sweeping printed debris from a nut slot

With a small screwdriver sweep the insides of all nut slot cavities and ensure that the screw holes are clear.

Removing hole supports from Stage underside

Pick the hole supports from the underside of the three holes in the Stage. Ensure they are completely removed. Note: the width of the Stage may vary across PIKA versions.

Inserting magnets into Stage

Insert two 30mm x 10mm x 3mm magnets into the cavities in the upper surface of the Stage. These must sit below the Stage's surface. If they fit poorly, use a weak adhesive or very small spots of cyanoacrylate to secure them in place.

Fitting the UV LED Strip to the Stage Window

With a piece of thin adhesive tape, fix the UV LED to the underside of the Stage such that the LED shines into the window. The wire for the LED should fit into a groove

Set the Axis Drivers To Centre Position

Axis Driver set to central position

Ensure all the axis driver are at their central position as shown above. If large manual movement of an Axis Driver is required, this can be rapidly effected by pushing the Flexible Coupling with the side of a glue stick rod.

Nuts in Axis Drivers

The X and Y Axis Drivers each need a pair of nuts to be added. These will anchor the Axis Driver to the main body.

Nuts inserted in X and Y Axis Drivers

For each Axis Driver, insert two M3 nuts into the lower nut slots on the Axis Driver's Motor Pillars, as indicated above.

Assembly

Inserting nuts into Central Pillar

Insert three M3 nuts into the nut slots in the central Stage Pillar ensuring that the sides of the nuts are parallel to the sides of the nut slots. Note that the two slots on the left side are angled.

Temporarily retaining nuts in Central Pillar

Secure the nuts loosely in place with three convenient M3 screws to stop them falling out during the assembly process.

Inserting nuts in underside of Base

Take the square Base and insert eight M3 nuts into the cavities in its underside. Ensure the nuts are fully seated into the bottom of their cavity (see General Notes On Assembly).

Cutting away unwanted filament on X Axis Arm

Find the point on the main body where the X Axis Arm protrudes. You may find a pair of very thin filaments holding the arm in place. These only serve to prevent 3D printers from filling the structure if a brim is used during printing. Cut these off short.

Screwing the Base to the main body

Flip the Base over and place the main body on it. Use eight M3 x 15mm screws to secure the main body to the Base.

Inserting captive nuts into Axis Driver Mounts

The framework has two Axis Driver Mounts, one on the left (Y) and one on the right (X). Take four M3 nuts and insert one into each of the four nut slots on the Mounts. Ensure that a screw can be inserted and removed from the captive nuts.

Motor Mount nut slot locations on later versions

Note: The Motor Mount nut slots have been moved slightly on later versions to make them easier to access. The other XY Table nut slots are no longer captive, so that the user puts less stress on the frame during assembly.

Inserting captive nuts into Z tower sides

Insert two M3 nuts into the horizontal nut slots below the tall pillars on the Z Axis Mount.

Inserting captive nuts into the rear of the Z Axis Driver Mount

Insert two captive nuts into the vertical nut slots at the rear of the Z Driver Mount

Insert three M3 x 25mm screws into the three holes in the Stage, from the magnet side. Ensure that the screw heads are all below the level of the Stage surface. Take three springs and put them on the ends of the screws. Critical dimensions are that the spring should have a maximum compressed length of 2.5mm, a minimum uncompressed length of 6mm, and be wide enough to give complete generous clearance on an M3 screw. This particular build was done with 6.5mm dia x 10mm, 0.5mm wire section springs.

Fitting Stage to Centre Pillar

Remove the temporary screws from the Centre Pillar and screw the Stage on top. Leave 3mm clearance between the Stage and Centre Pillar.

Checking spacing between Stage and Centre Pillar

This can be easily achieved by checking spacing with an M3 screw (or even easier with two screws held together with a bit of tape). If it is difficult to keep the centre spring in place during assembly, temporarily hold it with a piece of adhesive paper tape.

Aligning the Axis Driver to the central position

Take all three Axis Drivers and ensure that the Drive Nut is in the centre position of the Drive Screw as shown in the picture above. If you cannot conveniently rotate the motor electronically, a glue stick pressed against the Flexure Coupling will rotate it quite easily.

Correct positioning of Axis Driver driven end behind the X Linkage Plate

Try fit the X Axis Driver to the main body, ensuring that the driven end is behind the X Linkage Plate as shown in the image above.

Securing X Axis Driver Frame

Secure the frame of the X Axis Driver to the X Motor Mount using two M3 x 25mm screws.

Securing the bottom of the X Axis Driver

Secure the underside of the X Axis Driver to the main body using two M3 x 25mm screws. Insertion of the lower screw may require a utensil.

Attaching X Axis Driver to X Linkage Plate

Attach the driving end of the X Axis Driver to the X Linkage Plate using two M3 x 12mm screws. Try to tighten these screws evenly so as not to cause lateral strain on the X flexures.

Attaching Y Axis Driver to main body. Note alignment of Y Linkage Plate

As with the X Axis Driver, attach the Y Axis Driver's frame to the main body with two M3 x 25mm screws. Again, ensure the Driver's driving end is behind the Y Linkage Plate. Then secure the bottom of the Y Axis Driver's Motor Pillar to the main body with two M3 x 25mm screws (not shown) in the same manner as you did with the X Axis Driver.

Attaching Y Axis Driver driven end to Y Linkage Plate

Attach the driving end of the Y Axis Driver to the Y Linkage Plate with two M3 x 12mm screws. Again, try to avoid any lateral tension. Note that the Y Linkage Plate's holes are elongated. If the height of the Stage is substantially adjusted during calibration, these two screws will need to be slackened and re-tightened to avoid stresses on the Y axis flexures.

Attaching Z Axis Driver to the Z Tower

Using two M3 x 25mm screws horizontally and two M3 x 50mm screws vertically, secure the Z Axis Driver to the Z Tower as shown in the image above.

Inserting the Microscope Pole

Insert the 16mm x 230mm Microscope Pole into the brackets at the front of the main body. No fasteners are required.

The completed PIKA μRepRap

Connect the stepper motors, limit switches (note that the Z Axis has the limit switch at maximum extent), Z Touch probe, and UV LED to the CNC controller. The PIKA μRepRap assembly is now complete and you can proceed with alignment. Congratulations.