Mendel frame

From RepRap
Jump to: navigation, search

Mendel Build Documentation

You may find the Mendel assembly data sheet useful during assembly.

Frame sides


Total # of assemblies: 2

Name Qty/assembly Total Qty Type
Frame-vertex_6off 3 6 RP
Stud-frame-side (370mm "B") 3 6 Studding
M8 washer 14 28 Fastener
M8 nut 14 28 Fastener
z-leadscrew-base 1 2 Assembly

Printed part



The triangle frames should be equilateral (Use the jig J1 to measure all sides).

In addition: each triangle needs a Z-leadscrew bracket and either a Z-motor bracket or Z-tensioner bracket, as shown in the diagram. Tensioner should pair with the leadscrew base which has the opto installed.

Be careful to get the correct orientation on the z-motor and z-tensioner brackets, but don't worry too much at getting the lengths precise because you can adjust them after you thread the poles through the holes. Just remember to put on the washers and nuts on before you thread them all the way through the other part. It's a M8 washer and nut on either side of the plastic parts at this stage.

The length of J1 is 290mm and make sure that the nuts are on finger-tight at this stage. The distance M3 (55mm) applies to both side frames.

NOTE: Make sure the solid sides of the frame-vertex_6off pieces face OUTWARD.

Check the Mendel assembly data sheet for bar/stud lengths and jig/inspection distances.




Total # of assemblies: 1

Name Qty/assembly Total Qty Type
z-bar-top-clamp_4off 4 4 RP
M4x40 bolt 4 4 Fastener
M4 nylock 4 4 Fastener
M4 washer 8 8 Fastener
Stud frame end top (440mm "A") 2 2 Studding
Stud frame end (294mm "C") 4 4 Studding
Stud z base beam short (355mm "D1") 2 2 Studding
Stud z base beam long (418mm "D2") 2 2 Studding
M8 nut 68 68 Fastener
M8 washer 64 64 Fastener
Y motor bracket 1 1 Assembly
Y idler bracket 1 1 Assembly

RP parts



Assemble the z bar-top clamps together in pairs (see diagram below).

Start construction of the base frame with the bottom connecting bars using two of the four 'C' studs - 294mm - as these two have the simplest arrangement of nuts and washers. You will also need the two plastic parts to thread on at this point, as shown in the diagram and photos below. Thread the upper 'C' bars into the plastic parts and add washers (w) and nuts (n) arranged along them as:

n-w-[]-w-n-n--n-w--w-n--n-w-[]-w-n--n-w--w-n--n-n-w-[]-w-n (close up image would be better)

Thread the two bar assemblies (front and rear) roughly in place in the side frames, and loosely secure them with washers and nuts. You might find it helpful to file along the holes in the side frame vertices so that the bars slide through, rather than having to spin them to screw them through (not loosely sliding, but enough).

Now thread and secure the remainder of the frame studs (D1, D2) through the frame and motor mount plastic parts.

Thread the frame head top bars (440mm 'A') through the frame side top vertices and secure loosely with washers and nuts. Thread and secure the z bar-top clamp assemblies.

Check the Mendel assembly data sheet for bar/stud lengths and jig/inspection distances.


Be careful if the upper studs stick within the plastic corner parts. This will make it awkward to adjust the lengths and angles of the frame so that it is even and correctly set.

It's a good idea to put some soft feet on the bottom vertex parts. This lifts the machine off the ground a bit, and also reduces the transmission of the vibrations from the machine when it's working to the surface on which it's standing, hence reducing noise. The simplest way to make such feet is with some pieces of thick (about 1mm) foam double-sided sticky tape. Simply cut squares from the end of the tape reel and stack them to form a soft foot. Leave the tape-cover strip on the bottom-most one. Alternatively, just use small sticky-backed rubber feet.

The best way to line up the vertical (Z) axis that I (Adrian) have found is this:

You will need two plumb lines (cotton with an M8 nut tied on the end is good), a spirit level, some Blu-tack, and a sheet of paper.


Start by levelling the machine. Put the spirit level across the threaded rods as shown. Put folded pieces of paper under the sticky feet to level it up. Rotate the level by 90o to level the machine across the other diagonal. You will find that a spirit level is surprisingly sensitive, given that it's just a bubble in a tube. It will respond to just one or two thicknesses of paper.


Drop the plumb-lines down through the holes that will accommodate the tops of the z-bars and through the corresponding holes at the bottom. Use the Blu-tack to hold them in place so that they are at the middle of the holes on the edges towards the centre of the machine.

Use the nuts to move the parts in the base that the spirit level is resting on in the picture to centre-up the plumb roughly. Then use the nuts at the top to move the point of suspension so that the plumb-line is hanging a millimeter or two away from the edge of the bottom hole.

Go back to the nuts on the bottom and centre the bottom up precisely on both sides. If you look down the holes you are lining up, you will find it quite easy to judge this by eye.

Check the measurements from the ends. They should be equal, but give the plumb-lines priority over measurement.

Tighten the nuts symmetrically to keep the plumb lines true.

Finally, move the top z-bar clamps inwards to take up the couple-of-millimeter gaps that you left so that the threads just touch the inside of the bottom holes.

Check that they are square - the gaps between each of their two sides and the vertex parts should be equal - then tighten them too.

Finally tighten the nuts on the cross-bars (the ones the level was resting on), taking care not to bend the side bars at right angles to them.

Installation of X-axis and Z-axis


Total # of assemblies: 1

Name Qty/assembly Total Qty Type
z-bar (330mm "Z") 2 2 Bar
x-axis 1 1 Assembly
z-leadscrew 2 2 Assembly
M4x16 bolt 6 6 Fastener
M4 nylock 6 6 Fastener
M4 washer 12 12 Fastener
z-belt 1 1 Belt


Screw both z-leadscrew assemblies (with the ball bearings at the bottom ends) from below the x-axis, about half-way through the M8 nuts that they drive on the X axis vertical bearings.

Roll the frame onto its back, and position the x-axis into the top end (the Z M8 screws are not shown on the next picture, but you should have them in place).


Thread the z-bars through the leadscrew base, x-axis and top-clamp. Fasten the z-bars.

Unscrew the z M8 screws until the bearings on them are flush with their mountings in the base. Fasten with six caps.


Complete the leadscrew assembly with the parts which were temporarily removed in the initial assembly. Repeat for other side. Check that the z-axis studding hasn't jammed and can rotate freely. If the 608 seals aren't recessed into the bearing and if the washers extend past the inner ring and make contact with the seal then it's possible for the bearing to lock up once the M8 nuts on either side have been tightened. If this happens then try using a different assembly order to the one below which doesn't press the washers against the bearings i.e. NUT-BEARING-NUT-4 WASHERS-PULLEY RIM-PULLEY-WASHER-NUT.


Keep frame on its back.

Whilst still keeping the x-axis at the top end of the leadscrews, rotate the leadscrews until the x-axis is approximately square.

A jig is handy for this; set a spare piece of bar or rod (or maybe even a screwdriver) on the z base plate, next to the leadscrew, and then lower the x-axis until it touches the jig. Repeat for the other leadscrew.

Better calibration will be achieved later, however, both leadscrews should turn fairly freely. The ultimate goal is having the Z-screws vertical and parallel to each other. This will be accomplished by adjustments to the x-axis mounts and the top mounts. Use the distance between the z-screws at the base as a starting point.

Attach the z-belt. How taut should it be? The answer is: as loose as possible without backlash. Tighten it too tight, and turn the Z stepping motor by hand. You should see both Z screws rotate, even when you turn the motor by a single stepper step (you can feel the detent).

Now, gradually slacken the belt so that you are at the limit where it still behaves like this: as you turn it one detent, then back again, both Z screws turn forwards and backwards.

Tighten the sliding components of the X axis in position. Run the Z axis up and down by hand a few times. As long as you keep the two ends at the same hight (you can feel when one is going further that the other as the movement gets tight) it should move easily up and down. If it doesn't, slacken off the X clamps that set the X-axis length slightly and adjust them.

When you've got everything right, tighten the X belt. Again, get it as loose as it can be without backlash: when you turn the X motor forwards and backwards by a single step by hand, you should see the X carriage move in both directions.


Leave assemblies in their current position for the next phase.

Fitting the bottom circuits


Total # of assemblies: 1

Name Qty/assembly Total Qty Type
circuit-board-spacer-m4_2off 2 2 RP
y-bar-clamp_10off 2 2 RP
m4-nylock 4 4 Fastener
m4-washer 8 8 Fastener
m4x40-cap 4 4 Fastener
Bottom-circuit-board 1 1 Assembly

RP parts



Position the board over the larger gap of the base, nearest the y-motor, with the XLR and USB sockets facing out (1). Use the spacer and clamp assembly attach to the frame (2).

(The first picture incorrectly shows an additional 4 y-bar-clamps and two y-bars installed, which are actually installed in the next step.) Installing-circuit-board-bottom.PNG

Put the frame back in its upright position. Leave the x-axis at the top, out of the way for the next phase.

Installation of Y-axis


Total # of assemblies:1

Name Qty/assembly Total Qty Type
y-bar-clamp_10off 8 8 RP
m4x40-cap 8 8 Fastener
m4-washer 16 16 Fastener
m4-nylock 8 8 Fastener
y-bar (406mm "Y") 2 2 Bar
y-belt 1 1 Belt

RP parts



Loosely install the y-bar clamps and y-bars. Set J3 (157 mm) so the bar clamps are in approximately the right place. (Bottom circuit boards hidden for clarity)


Now retract the y-bars. Position the y-chassis and thread bars back through the y-chassis. Re-confirm J3 and fasten the y-bar clamps fully.


You should now adjust the bearings on the chassis. The 180 bearing assemblies can be adjusted side-to-side to allow the bearings to run along the centre of the y-bars: check that they are centred at each end of the chassis' travel before tightening them down to the chassis. Now adjust the upper bearings so that they lightly grip the bars: again, check this across the travel of the chassis before tightening them and ensure that they rotate freely without any slop between the bar and the upper and lower bearings.

Note that if you build the chassis from 4mm ply or MDF, the rectangle that forms the tray for catching exudate at the beginning of a build is held on with 15 mm M4 cap screws. But if you make the chassis from 6mm (which will give a better sturdier machine, and so is recommended) you will need 20 mm M4 cap screws.

Fit the y-belt. How taut should it be? As with Z, the answer is: as loose as possible without backlash. Tighten it too tight, and turn the Y stepping motor by hand. You should see the Y carriage move, even when you turn the motor by a single stepper step (you can feel the detent). Now gradually slacken the belt so that you are at the limit where it still behaves like this: as you turn it one detent, then back again, and the Y carriage moves both forwards and backwards.


Installing the bed


Total # of assemblies:1

Name Qty/assembly Total Qty Type
bed 1 1 Sheet Image
m4x40-cap 4 4 Fastener
m4-nylock 4 4 Fastener
m4-washer 8 8 Fastener
bed-spring 4 4 RP

RP parts

RP spring design may vary



Fit bed to chassis trapping the springs between the bed and the bearing brackets.

If you have the W-shaped (\/\/) springs and find that the M4x40 bolts are not long enough, clip off one of the ends to form an S-shaped (\/\) spring. This will shorten the spring by ~10 mm and hopefully give you enough extra length to screw on the nut and washer.


Fitting the top circuits


Name Qty/assembly Total Qty Type
circuit-board-bracket-m3_4off 4 4 RP
m3-capx20 16 16 Fastener
m3-nylock 16 16 Fastener
m3-washer 32 32 Fastener
Top-circuit-board 1 1 Assembly

RP parts



Wind x-axis down to the bed, as this will get in the way. Wind by lifting the frame up to pull the z-belt. Do not let nozzle closer than 1 cm to bed – if the bed slides around before calibration it may damage the nozzle by scraping against it. Position circuit board at the top of the front side, as high as possible (1). Use four bolts per clamp and fasten securely as this element improves chassis rigidity (2).



Congratulations! You have completed the assembly process! We hope you enjoy your new 3D printer! NOTE: Before printing anything, don't forget to square the axes.

Back to Mendel mechanical construction root.