Third part of frame: Finishing the X and Y-axes

Hopefully this stage is again following the prusa mendel instructions, although the order has been slightly modified because of the order that we have printed/received delivery of the parts in.

Making smooth rods orthogonal

Just realised that we haven't dealt with making the smooth rods for the y and z axes orthogonal, in phase 2 so we had better do that first.

Make sure that the y axes smooth rods are horizontal in all directions using a spirit level. This can be achieved via a levelling table (build instructions available from Hugo (darkling) or Malcolm (alianmac)) or by using thin bits of card under the footed vertices.

Be patient and be as precise in the levelling as you can. Try to get the bubble exactly central in the sprit level in all directions.

Once the x axes smooth rods are horizontal, adjust each of the z-axis smooth rods in turn to be vertical, using the nuts on either side of the bar clamps on the bottom threaded rod of the triangle and the bottom 440mm threaded rod (that runs underneath the two triangle frames).

Check the vertical setting of the z-axis smooth rods by aligning the spririt level in the x and y directions and ensuring that the "vertical" bubble is as central as possible.

Once the z-axis smooth rods are vertical, tighten the 8mm nuts on th bar clamps to ensure that the rods are locked in the vertical position.

Double check horizontal and vertical alignments of smooth bars.

N.b. It is the alignment of the smooth rods that matters. As long as they are orthogonal and the threaded rods are tight and don't move, the alignment of the threaded rods is academic.

Fitting pulleys and motors

Insert 3mm nuts into the square holes in the bottom of the two pulleys (x and y axis).

Insert a 3mm grub screw into the round hole in the side of each pulley and screw it into the 3mm nut using a 1.5mm Allen key. Do not screw the grub screw in too far. It should not protrude into the central hole in the pulley as this will prevent the pulley fitting onto the shaft of the motor.

Place each assembled pulley onto the shaft of a stepper motor so that the grub screw aligns with the flat on the motor shaft. Fit one pulley as shown below - with the base next to the body of the motor (for the y-axis) - and one with the base away from the body of the motor (for the x-axis).

Mount the y-axis motor on the y-axis motor bracket (the y shaped bracket attached to the two threaded rods joining the two triangular frames at the rear of the frame) using 3 off 10mm x 3mm set screws, each fitted with a 3mm washer.

Mount the x-axis motor on the x-axis motor end bracket (the bracket on the x-axis without the bearing guide fitted) using 3 off 10mm x 3mm set screws. Fit a 3mm washer with each set screw if the holes in the plastic bracket permit but do not force the washers in.

Fitting y-axis belt

Identify the y-axis belt clamp tensioner. This is printed in white plastic and is the deepest one of the four clamps. It also has a third hole through the body with a cut out for a 3mm nut and a slot in the bottom.

Fit a 3mm nut into the cut out and use a 20mm x 3mm set screw to hold it in place. This is to tension the belt once fitted.

Place one end of the 850mm long T5 toothed belt on top of the tensioner. Hold it in place with one of the other y-axis belt clamps (making sure that the slotted section of the clamp mates with the teeth on the belt) and then pass the belt back through the slot underneath the tensioner.

Mount the clamp on the front of the bottom plate, aligning the holes in the clamp with the holes in the bottom plate. Fix the clamp and belt in place with 2 x 30mm x 3mm set screws, washers top and bottom and nylock nuts on each set screw.

Make sure that the tension set screw is withdrawn (i.e. nothing protrudes from the nylock nut).

Then pass the belt over the bearing guide at the front of the machine and back between the bottom plate and the bottom 440mm threaded rod. Pass the belt over the y-axis pulley and the rear bearing guide and back to the rear oof the bottom plate.

Fix the rear end of the belt using the remaining two y-axis belt clamps, together with 2 x 25mm x 3mm set screws, washers top and bottom and nylock nuts. The clamps are identical, but it is important that the slots on the bottom clamp faces upwards and engage with the teeth on the belt.

Assemble and fit the x-carriage

Make sure the 2 x x-axis belt clamps have been removed from the x-carriage. During the print process these might have become connected to the body of the x-carriage.

Fit 3 x LM8UU linear bearings into the x-carriage. Secure with tie wraps. It is suggested that the "single" bearing is secured with 2 x tie wraps.

(Photo to follow)

Remove the bolts holding the the x-axis smooth rods in place. (These are in the idler end of the axis.)

Partially withdraw both rods to allow you to place the x-carriage on the smooth rods.

When fitting the carriage, the side with the two LM8UU bearings shoudl face the front.

Refit the smooth rods into the x-axis motor end and then replace the bolts holding the the x-axis smooth rods in place. Secure these bolts with a washer and a nylock nut on each bolt.

Check that the x-carriage moves freely.

Fitting the x-axis belt

This is similar to the assembly of the y-axis belt in that there is an adjustable tensioner for one end and a clamp for the other. The main difference is that both clamps use the body of the carriage more than the y-axis uses the bottom plate. The nylock nut for the tensioner is mounted in the body of the x-carriage

with clamps fitted above and below, with a 30mm bolt, two washers, and a nyloc nut:

And, as you can see from the picture above, at the other end of the carriage and the belt is clamped between the carriage and one printed piece above the carriage body, with a 20mm bolt, two washers, and a nyloc nut.

Check that the y-belt run looks square and solid.

Fitting the bed

Use 4 x 40mm set screws with washers and nylock nuts to fix the 4 bed springs betwen the bottom plate and the plywood bed.

You can then fit the PCB heated bed if you wish, but you may well have to remove it to solder it up, so this step is optional at this stage. Use at least 6 x 3mm washers to raise the PCB above the plywood bed. (20mm x 3mm bolts)

The finished article should look something like this:

when viewed from the rear and like this:

from the front