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A notice about these instructions!

Since 1st April 2013, the RepRapPro Mendel has been superseded by the RepRapPro Tricolour and Mono Mendel.
If you are building the new machine, use the official, and most up to date, instructions on the RepRapPro wiki here

Goal

By the end of this stage, your machine should look like this:

Tools

You will need the following tools

M8 (13mm) spanner
Adjustable spanner
300mm Rule
(optional) Spirit level, cotton and Blu-tack

Step 1: Frame triangles


Item	Quantity
370mm M8 rods	6
Printed frame vertex with foot	4
Printed frame vertex	2
Printed U clips	2
M8 nuts	28
M8 lock washers	28

Split the above components into two equal sets, then loosely screw them together into each frame triangle. Make sure you slide a belt clamp along the bottom M6 threaded bars between the frame vertices with feet, with a serrated washer and nut either side. The other nuts should also all have serrated washers under them.

Make the gap between the frame vertices measured face to face next to where the nuts and washers tighten about 290 mm.

Don't tighten anything at this stage.

Step 2: Cross bars


Item	Quantity
330mm M8 rods	4
470mm M8 rods	2
Printed U clips	4
M8 mudguard washers	2
8mm bearings	2
M8 lock washers	8
M8 washers	29
M8 nuts	46

Assemble the bars as shown in this picture:

From top to bottom and left to right the sequences are:

Nut, nut.
Nut, nut, lock washer, lock washer, nut, nut.
Nut, nut, lock washer, U, lock washer, nut, nut, mudguard, washer, bearing, washer, mudguard, nut, nut, lock washer, U, lock washer, nut, nut.
Nut, nut, lock washer, U, lock washer, nut, nut, washer, washer, bearing, washer, washer, washer, washer, washer, nut, nut, lock washer, U, lock washer, nut, nut.
Nut, 5x(nut, washer, washer, nut), nut
Nut, 5x(nut, washer, washer, nut), nut

Take care not to confuse lock washers and ordinary washers.

Step 3: Put them all together


Item	Quantity
M8 nuts	12
M8 lock washers	24
Printed XLR panel-plug holder	1

Firstly screw the cross bars into one of the triangles as shown:

This is the moment of what embryologists would call gastrulation: the point at which your RepRap acquires a front, back, top, bottom, left and right - as shown. The x, y, and z coordinate directions of the finished machine are also shown. If you like, use sticky tape to attach small labels to the rods while you are building so you can remember which side and which direction is which.

On the bottom, and using the numbers of the rods from Step 2:

Back top: Rod 4, with the 5 washers together to the left.
Back bottom: Rod 2.
Front top: Rod 3.
Front bottom (yes - we know this is funny...): Rod 1.

And at the top attach the two long Rods: 5 and 6.

Use two locking washers and a nut on each rod.

The XLR bracket attaches back left. The indentations on it go towards the inside of the machine - they accommodate the washers on the frame.

Next screw the second triangle to the other end of the cross bars:

Now go round the frame tightening everything up using two spanners. Tighten the triangles first, then the six bars in the x direction.

Make the gap between the faces of the vertices on the triangles 290mm, as mentioned above. Make the gap in the x direction between the faces of the vertices 273mm.

Get the two top rods even, with an equal amount projecting each side, then move the back one 5mm to the right and the front one 5mm to the left.

Try to get the measurements accurate. But it is more important to get the lengths equal than to get them precise.

You will find that you can make very fine adjustments when things are almost tight by slightly slackening a nut on one side of a join then tightening the nut on the other side.

Step 4: Z-motor mounts and power connector


Item	Quantity
470mm M8 rods	2
Printed Z motor holders	2
Printed U clips	2
M8 nuts	12
M8 lock washers	10
M8 washers	6
XLR panel plug	1
12mm M3 caps	2
M3 washers	2
M3 nuts	2

Put the two U clips already on the frame roughly in the middle of their bars, then push one of the 470mm rods through. You may have to twist it, using its thread to move it - it can be quite a snug fit. Use nuts and lock washers to put two more U clips on its ends, as shown. Leave all these lose:

Next thread the base diagonal rod through two of the four feet. Put nuts and lock washers on it, but leave them lose.

Put four smooth washers on the top bars, then put the Z motor mounts on as shown. Secure them with two nuts each, with one smooth washer and one lock washer. The smooth washer goes on the clamp that will hold the Z rods. Tighten the other nuts against their lock washers, but leave the Z-rod-clamp nuts lose:

Fit the XLR plug using the M3 screws, nuts and washers. The washers go under the nuts. Fit the plug so that the triangle formed by its three pins points upwards.

Step 5: Smooth rods


Item	Quantity
400mm smooth rods (Y)	2
350mm smooth rods (Z)	2 -} Adjust the U clips for the Y rods at the front and back of the frame so that the gaps between their outer nuts and the nuts on the frame vertices are about 20mm. Slide the Y rods through. Don't tighten them: Now we need to slide the two top bars through the top frame vertices. Slide each bar through one vertex, then fit one serrated washer, two M6 nuts and another serrated washer before sliding the bar through the opposite vertex. Next, slide a Z motor mount onto each ends of the top bars. This may need a little force as the holes through the z motor mounts tend to be quite a tight fit on the M6 threaded bars (it's usually a good idea to make sure you can push a spare length of M6 threaded bar into each of the z motor mount holes before trying to fit them to your frame). Add the lasercut filament drive bracket so it is inside the left Z motor mount and frame-vertex, and is held against it by the inner nuts and washers. The front slot next to the rounded end goes upwards, the middle slot goes at the back and downwards. Imagine hanging a weight on the projecting end - the slots need to go in the way that makes the weight tend to pull things into place, not to release them. Before tightening the M6 nuts on the top bars, slide the bottom cross bar through the two bottom bar clamps. You do not need M6 nuts or washers either side of these bar clamps. At each end of this bottom cross bar, fit an M6 nut, a serrated washer, a bar clamp, a serrated washer, and another M6 nut. At this stage, the frame should be quite loose, so just jiggle everything around until it all the angles look about right. Once you are happy with this step, you can tighten the nuts on the cross bars. The distance between the frame vertices along the cross bars should be 146mm. When tightening the M6 nuts on the top cross bars, please note that you do not need to tighten the nuts which clamp against the Z smooth rods too much, only enough to stop the smooth rod from sliding down. If you slip two washers into the groove on the Z-motor mount (with the threaded rod run through their holes) you will be able to clamp your frame solidly and grip the Z-rods without over-stressing the plastic. Your kit doesn't come with these washers. 1/4" washers work well for this. Before tightening the bar clamps on the bottom cross bar, slide the Y axis smooth rods (270mm) into place. (These are easily confused with the X axis rods, which are 265mm - get the right ones.) Aligning the Z Rods You can now slide the two Z smooth rods (length 235mm) into place. Use a set-square to get the angle of the Z smooth rods correct. Make sure you get the right smooth rod for the Y-axis; if you swap them you will have to go back and take things apart again. You can now tighten the M6 nuts along the bottom cross bar. Alternative alignment method Some people swear by this method, others hate it... For this you will need the spirit level, two pieces of cotton, and a small blob of Blu-tack. Build the frame as above, as far as "Aligning the Z Rods". Place the frame on a flat surface (40mm-thick Formica-covered kitchen worktops are remarkably flat). You will almost certainly find that the feet aren't quite level and that the frame rocks a little about a diagonal. Tightening the frame has distorted it slightly. Put an object about 10mm high under a foot on that diagonal, and very gently push the other two diagonal corners down. Try the feet on the flat surface again. Repeat this until the frame does not rock, but instead sits four-square on the surface. You can carry out this process at any future stage in the build to re-square the frame. Put the spirit level across the Y smooth bars, and place folded paper shims under the left or right feet until the frame is level left-right. You will discover that a spirit level is an exquisitely sensitive instrument, and that it can easily detect a couple thicknesses of paper. Rotate the spirit level through a right angle so it rests between the front and back cross bars, and get the frame level front-back too. Check the frame is level in both directions. Now thread two lengths of cotton down through the top bracket and the U clamp on the bottom where the Z axis smooth rods will be. Attach it to the Z-axis-smooth-rod holes at the top with Blu-tack such that it is half-way round the inside of the clamp arc. Put a small blob of Blu-tack on the bottom of each piece of cotton to act as a plumb weight. Now adjust the positions of the threaded rod at the bottom and the Z-axis-smooth-rod U clamps so that the cotton falls freely in the middle of the U-clamp holes. Tighten the nuts on the main frame holding the threaded rod, making sure that the cotton stays in the middle of the holes where it was. Now tighten the inner nuts to move the U clamps outwards so that the cotton just kisses the edge of the U holes in exactly the same relative position as it is falling through the clamps at the top of the frame. Slide the Z-axis rods in, tighten the clamps from the outside, and check with a square as in the section above. If you've done everything carefully there should be little or no discrepancy, but it is more important to have a right angle than to have the Z-rods plumb. Frame finished You will now have an assembled RepRapPro Huxley frame: Next stage assemble the Y axis.