Prusa Mendel

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Prusa Mendel

Release status: working

Assembled-prusa-mendel.jpg
Description
Prusa Mendel is simpler remix of normal Mendel.
License
Author
Contributors
Based-on
Categories
CAD Models
External Link


Also see SAE Prusa Mendel if you are building this machine using SAE (Imperial) Fasterers

The Prusa Mendel is a simpler remix of the original Mendel. I wanted to use bushings instead of regular bearings. The current prototype is using two bearings in total, one for X and one for Y axis. I have the entire machine up and running, with my printed PLA bushings. It's pretty smooth. <videoflash>tyVM3-v84I0</videoflash>

Development

The development of the Prusa Mendel is hosted on github: http://github.com/prusajr/PrusaMendel

You can follow the changes on Changelog

You can sign up for github for free and fork the project to begin working on it.

History

Bill of Materials

The Prusa Mendel BOM is documented here. Please do not use the BOM on github as it is not updated as regularly.

(in works, not complete yet)

Printed Parts

6x frame-vertex       RP

OR

4x frame-vertex with foot RP
2x frame-vertex      RP
2x coupling           RP
3x endstop-holder     RP
1x x-carriage         RP
1x x-end-idler        RP
1x x-end-motor        RP
1x y-motor-bracket    RP
2x z-motor-mount      RP
4x belt-clamp         RP
8x bar-clamp          RP
2x rod-clamp          RP
2x pulley             RP

Printed Bushings

12x pla-bushing        RP-PLA (check your build file, the file makes either 4 or 12.)

Non-Printed Parts ("vitamins")

(verified)

70x M8 nut            Fastener
80x M8 washer         Fastener
3x 608 Bearing        Bearings
 6x M8x370mm Stud side       Threaded rod
 4x M8x294mm Stud end        Threaded rod
 3x M8x440mm Stud top, Z bottom        Threaded rod
 2x M8x210mm Z-Leadscrew     Threaded rod
 2x 8mmx495mm X-bar           Smooth rod
 2x 8mmx406mm Y-bar           Smooth rod
 2x 8mmx330mm Z-bar           Smooth rod
 1x 225mmx225mm Print bed      Thick Sheet
 1x 140mmx225mm Print bot.     Thick Sheet

(unverified)

 3x ??? Optoflags          Thin Sheet
20x M3x?? for motors+pul.  Fastener
16x M3 washer "  "         Fastener
10x M3x10 for X-ends Fastener
 8x M4x15 for X&Y-belts    Fastener
16x M4 washer "  "         Fastener
 8x M4 nylock "  "         Fastener
 3x M4x?? for X&Y-bearings Fastener
 6x M8x30 Mudguard/fender washers Fastener
16x M4 nylock "  "         Fastener
 4x M4x?? for Z-Clamps     Fastener
 8x M4 washer "  "         Fastener
 4x M4 nylock "  "         Fastener
 4x M4x30 for Print bed    Fastener
 ?x M? washer "  "         Fastener
 ?x M? nylock "  "         Fastener
 1x standard Mendel extruder
 5x Nema 17                NEMA Stepper
 1x standard Mendel electronics or Mendel alternative electronics.

(The Prusa Mendel uses the 4 drivers in the standard Mendel electronics package to drive 5 motors by using "two steppers wired in parallel to one driver"[1]).

Printed Parts

A printed set of Prusa Mendel parts

Printing a Prusa on a Mendel

An easier option then individually printing each part if you are printing Prusa on a RepRap Mendel is the pre-assembled build file containing the Prusa parts. With this option you only need to print the Mendel plate and the PLA bushings to get a complete Prusa Mendel:

Printing a Prusa on a CupCake CNC

There are also pre-assembled build files available to fit your CupCake CNC's build area (download using right click => save as)

Note:

  • These plates use the full surface of the build platform, so remove bolts if necessary.

Plates for the MakerBot:

Printing a Prusa on anything else

Last but not least, if you have a machine that doesn't fit into any of the previous options all the .stl files necessary to print a Prusa Mendel are available on the PrusaMendel Github where you can download them and print them individually.

Assembly

This section is work in progress.

Assembling the frame

Assembling the frame vertex triangles (2x)

There is a triangle on each side of the Prusa RepRap, you will need to make 2 of these and then connect them together (see next step) to form the Prusa frame. Each side is an equilateral triangle with a frame vertex on each corner. You can use either footed or non-footed vertices to build this (the footed ones look better, but are not critical.) The instructions assume you are using footed vertices.

Parts Required (per triangle)

  • 2 RP footed frame vertices
  • 1 RP frame vertex (non-footed)
  • 1 RP bar clamp
  • 3 370mm M8 threaded rods
  • 14 M8 nuts
  • 14 M8 washers
  • (optional but recommended)A piece of threaded rod or wood or any other material with precisely 290mm length. This is your frame jig J1.

Instructions

  1. Take one of the 370mm threaded rods, and slip an M8 washer onto the middle of it.
  2. Take the RP bar clamp (the U-shaped bit with the two holes) and slide the threaded rod through the two holes until the clamp sits next to the washer.
  3. Slide another washer onto the rod from the other side.
  4. Thread two M8 nuts onto either side of the clamp, until they are next to the washer, but do not tighten them yet.
  5. Thread another two nuts on each side of the rod, followed by washers. See the picture for what it should look like. <flickr>5188262096|thumb|right|m|The bar clamp on the threaded rod.</flickr>
  6. Slide the rod through the long bottom (footed) side of two vertices. Make sure the feet point in the same direction. Also make sure the bulge on the non-footed side of the vertex points outwards.
  7. Measure the distance. The distance between the two vertices should be 290mm (along the rod). Get it approximately right now, we will check this again later. If you have a frame jig, place it between the two vertices and adjust the nuts until you can just barely fit the jig J1 between them.
  8. Place another washer and nut on the other side of the vertex. Tighten, but not too much. We'll need a bit of flexibility here still.
  9. Take another 370mm M8 threaded rod and place a nut followed by a washer at each end.
  10. Place one end of the threaded rod into the one of the two footed frame vertices. It should be in the same plane as the first threaded rod. fix it in place with a washer and nut. You should now have two sides of the equilateral triangle.
  11. Take the third piece of threaded rod and put a nut and washer on each end. Place it in the other footed vertex and fix it in place with a washer and nut. You should now have a triangle of threaded rods with two footed vertices on two of the corners, nothing in the third corner, and a bar clamp between the two vertices.
  12. Take the third vertex (non-footed) and slide it onto the threaded rods in the final corner of the triangle. Measure the lenghts of the three sides to make sure they are all 290mm long (along the rod from plastic part to plastic part). Adjust the nuts to make sure this is so. Use the frame jig J1 if you have one. Once done, place a washer and nut on the top of the vertex. Tighten all the outer nuts.

<flickr>5188259098|thumb|right|m|The finished frame triangle </flickr>

  1. You should now have a sturdy triangle with equal-length sides, two feet on the bottom, and a bar clamp between the feet. Adjust the nuts around the bar clamp (but do not crush the bar clamp together yet) until it's approximately in the middle of the rod. Leave the nuts there loose. See photo for what you should have at this point.
  2. That's it, that's one of the triangles done. Repeat the entire procedure for the second triangle. It is exactly identical to the first.

Now we need to connect the 2 frame triangles to form the Prusa RepRap frame.

The easiest way to do this is to thread everything onto the front and rear threaded rods and attach those to the triangles first, and then thread the top rods through. That's what the instructions below assume you are doing.

Assembling the front threaded rods

These 2 threaded rods are used to connect the front/bottom vertex of each triangle as well as the y-stage bars and y motor mount to the frame.

Parts Required

  • 2 assembled frame vertex triangles
  • 2 RP rod clamps
  • 1 RP y motor bracket
  • 16 M8 nuts
  • 17 M8 washers
  • 2 M8x30 fender/mudguard washers
  • 1 608 bearing
  • 2 294mm threaded rods.

Instructions

  1. Thread the bottom rod first. Thread an M8 nut onto the middle of the rod. Slide an M8 washer next to it.
  2. Thread the rod through the bottom hole of the RP y-motor-bracket. The bottom hole is the one with the odd-shaped (not circular) hole next to it.
  3. Slide another washer onto the other side of the rod and add another M8 nut to hold it in place.
  4. Add a nut and washer to each end of the rod.
  5. Now thread the top rod. This is a complicated one, so make sure you get it all done in the right order. From left to right, the rod should have: 1 washer, 2 nuts, 1 washer, 1 rod clamp (threaded through the holes), 1 washer, 2 nuts, the y-motor-bracket (with the circular hole pointing towards you), 1 fender/mudguard washer, 1 washer, 1 608 bearing, 1 washer,1 fender/mudguard washer, 2 nuts, 1 washer, 1 rod clamp (threaded through the holes), 1 washer, 2 nuts, 1 washer.
  6. When you hold it with the bigger part (with the circular hole) of the motor bracket towards you, it should look like the picture below. Verify this now.
    Front-rods-bare.png
  1. You can now attach this setup to the triangle sides. Make sure the bigger part of the motor bracket points OUT of the triangle. Thread the ends of the rods through two of the footed vertices. Put a washer and nut on the end of each threaded rod.
It should now look like this:
Front-rods.png

Assembling the rear threaded rods

These 2 threaded rods are used to connect the back/bottom vertex of the 2 triangles together as well as the y-stage bars and belt pulley.

Parts Required

  • 2 assembled frame vertex triangles
  • 2 RP rod clamps
  • 14 M8 nuts
  • 14 M8 washers
  • 2 M8x30 fender/mudguard washers
  • 1 608 bearing
  • 2 294mm threaded rods

Instructions

  1. Thread the bottom rod first. Add a nut and washer to each end of the rod.
  2. Now thread the top rod. This is again a complicated one, so make sure you get it all done in the right order. From left to right, the rod should have: 1 washer, 2 nuts, 1 washer, 1 rod clamp (threaded through the holes), 1 washer, 2 nuts, 1 fender/mudguard washer, 1 washer, 1 608 bearing, 1 washer,1 fender/mudguard washer, 2 nuts, 1 washer, 1 rod clamp (threaded through the holes), 1 washer, 2 nuts, 1 washer.
  3. It should look like the picture below. Verify this now.
    Rear-rods-bare.png
  4. Attach the two rods to the two remaining footed vertices. Thread each end of the rod through the vertex, and add a washer and nut. It should now look like this:
    Rear-rods.png

Your frame should now be standing on its own feet without support, but the tops sides of the triangles will still be wobbly. We'll fix that next.

Assembling the top threaded rods

These connect the 2 frame triangles at their tops as well as providing mounts for the z-axis motors.

Parts Required

  • 2 assembled and connected frame vertex triangles
  • 2 RP z motor mounts
  • 12 M8 nuts
  • 16 M8 washers
  • 2 440mm threaded rods

Instructions

  1. Slide one of the threaded rods through one side of one of the top vertices. Put a washer, two nuts, and another washer on the part of the rod between the top vertices. This is what it should look like when seen from above:
    Top-step1.png
  2. Repeat for the other rod. It should now look like this:
    Top-step2.png
  3. Slide the rods through the opposite side vertex. Thread the nuts up to the vertices on each side.
  4. To each of the four ends of the threaded rod, add a washer, a nut and another washer. Your setup should now look like this:
    Top-step3.png
  5. Take one of the RP z motor mounts and attach it to the ends of the threaded rod. The side with the two holes and the indentation should point towards the outside. Add a washer and nut to the end of each rod.
  6. Repeat this on the other side. The top of the machine should now look like this:
    Top.png


Tightening the frame

Now that the frame is fully assembled we can adjust and tighten each of its threaded rods. You will need your frame jigs if you have them, or a reasonably precise length measurement tool.


Parts Required (per triangle)

  • 2 RP bar clamps
  • 4 M8 nuts
  • 4 M8 washers
  • 1 440mm threaded rod
  • (optional but recommended)A piece of threaded rod or wood or any other material with precisely 290mm length. This is your frame jig J1.
  • (optional but recommended)A piece of threaded rod or wood or any other material with precisely 234mm length. This is your frame jig J2.


Instructions

  1. Verify that the triangle vertices have distance J1 (290mm) from plastic to plastic along each of the three sides. Once you are sure of this, tighten the outer vertex nuts until they are firmly attached and unable to move, but do not crush the plastic parts.
  2. Adjust each of the bottom rods until it has distance J2 (234mm) between the inside ends of the vertices. Use frame jig J2 to check this if you have it. Once you are sure this is true, tighten the outer vertex nuts until they are firm, but do not crush the plastic.
  3. Adjust the top of the frame so that the distance between the inside ends of the vertices is precisely J2 (234mm) and the length of rod outside the vertex on one side is the same as the length outside the vertex on the other side. Double-check the distances before tightening the nut on the outside of the vertex.
  4. The frame should now be fairly stable. Using a plumb line or similar (for example a nut hanging on a length of yarn), adjust the bar clamps on the bottom side of each triangle until they are directly below the middle of the top vertices. Do not tighten the nuts either side of the bar clamps yet.
  5. Insert the 440mm threaded rod through the two rod clamps on the bottom of the frame. make sure the new rod is on top of the triangle bottom rod. Adjust it so that the same length sticks out on each side.
  6. On each side, place a nut, washer, rod clamp (threaded through the holes), washer, and another nut. The setup should look like this when seen from below:

Bottom-rod.png

Assembling the y stage

Parts Required

  • 4 PLA bushings
  • 2 belt clamps
  • 1 225x140mm print bottom plate
  • 1 225x225mm print top plate
  • 2 406mm smooth rods
  • 1 y timing belt
  • 1 stepper motor
  • 1 pulley
  • 4 M3x20 bolts
  • 4 M3 washers
  • 4 M4x20 bolts
  • 4 M4 washers
  • 4 M4 nuts

Instructions

  1. Mark each of the four corners of the print bottom plate 8mm from each side with the marker.
  2. Carefully drill a 3mm hole in each of the four corners.
  3. Clamp the print bottom plate and the print top plate together, so that the bottom plate is equally far from each edge of the top plate. Drill 3mm holes into the top plate through the corner holes in the bottom plate so that they match on both plates.
  4. Slide the two 406mm smooth rods through the rod clamps on the front and rear threaded rods. They should fit

snugly and be approximately parallel.

  1. Place the narrow side of the "print bottom" plate between the rods. This ensures they are exactly 140mm apart from each other. Adjust the nuts on the front side rod clamps until the print bottom plate just barely fits between the rods. Try to get them at an approximately equal distance from the middle of the rod.
  2. Tighten the front nuts just enough that they do not move on their own, but no further.
  3. Measure the distance from the left front vertex to the left smooth rod. Adjust the distance from the left rear vertex to the left smooth rod to match it. This ensures the left rod is parallel to the frame. Tighten the nuts on the left clamp just enough that they do not move around.
  4. Place the print bottom plate next to the left smooth rod on the rear side. Adjust the right rear rod clamp's nuts until the narrow side of the bottom plate barely fits between the rods.
  5. Recheck the distances from the left vertex to the left rod are the same at the front and rear and that the short side of the print bottom plate fits snugly between the smooth rods both at the front and at the rear. This should ensure that the rods are parallel to each other and to the frame. Use the diagram below to see what it should look like from above.
    Y-rods.png
  6. Tighten the nuts on all of the four rod clamps now.
  7. Snap 2 PLA bushings onto each of the two smooth rods. Place them about 120cm apart on each rod. Make sure they slide freely on the rods. Put a dab of glue on the top side of the bushings (the side opposite the open side). Carefully place the print bottom plate on top of the bushings, so that it's equally far apart from each of the two triangles (see diagram below). Wait for the glue to dry.
    Y-plate.png
  8. While the glue is drying, adjust the bearing on the rear threaded rod until it is exactly across from the front threaded rod. Tighten the nuts on the y motor bracket and the bearings at this point. All nuts on the front and rear rods should now be tight.
  9. Also while the glue is drying, ensure that the hole in the center of the pulley matches your motor shaft (it should slide on and fit very snugly). If it is too tight to fit, drill it out.
  10. Insert an M3 nut into the rectangular slot on the pulley bottom. You may need to widen the slot slightly to do this. Make sure that the center of the nut is aligned with the channel in the pulley that goes to the center hole.
  11. Once you are satisfied with the position of the nut, insert an M3 grub screw into the channel on the rim of the hub. Tighten it until you see the end of the screw inside the center hole. Then unscrew it enough to slide the pulley onto the motor shaft.
  12. Slide the motor shaft with the pulley on it through the circular hole in the y motor bracket. Slide it in from the left, so that the pulley ends up on the side of the bearing.
  13. Adjust the pulley position on the shaft so that when the motor is flush with the bracket, the teeth on the pulley are approximately at the position of the bearing.
  14. Carefully slide the motor back out, without changing the position of the pulley on the shaft, and tighten the grub screw so that the pulley cannot move along the shaft.
  15. Slide the motor back in, and fasten it with 4 M3x20 bolts. Put a washer between each bolt and the y motor bracket.
  16. Position the y belt on top of the print bottom plate and through both of the bearings. Pull lightly on both ends so that it is straight. If the belt is not straight, adjust the position of the rear bearing until it is. Use a marker to mark out the position of the belt on the print bottom plate. Also mark which side of the plate is on the left.
  17. After the glue has dried, carefully pop the print bottom plate with the PLA bushings off the rails. Place the two belt clamps perpendicular to the marked position of the belt, several centimeters apart. Make sure the belt position is between the two holes on each clamp. Use a marker to mark where the holes of the belt clamps would be on the plate.
  18. Carefully drill a 4mm hole through each of the four marked belt clamp holes.
  19. Place the print bottom plate back on the smooth rods, paying attention to the marking to make sure the correct side is on the left.
  20. Place one end of the belt, toothed side down, where the holes for the front belt clamp are. Put a washer onto each of two M4x20 bolts, and thread them through the holes in one of the belt clamps. Then attach the clamp to the top of the plate, clamping down the belt. Leave several centimeters of the belt behind the clamp.
  21. Put two M4 nuts underneath the plate and thread them onto the bolts. Tighten both nuts so that the end of the belt is firmly attached to the plate, toothed side down.
  22. Pass the belt over the front bearing, around the motor pulley, and then up underneath the plate to the other bearing. Pull it tight, then lay it on top of the plate, toothed side down.
  23. Put a washer onto each of two M4x20 bolts, and thread them through the holes in the second belt clamp. Then attach the clamp to the top of the plate, clamping down the belt.
  24. Attach an M4 nut to each of the two bolts, and pull the belt tight before tightening the two nuts.
  25. Turn the motor by hand. It should turn with little effort, and each slight rotation should be matched by a slight movement of the plate. Make sure it slides smoothly along the entire length of the rods. Pushing the plate should immediately make the motor turn. Make sure the belt is not too loose (plate and motor should not be able to move independently) or too tight (taking a lot of effort to move the plate). Once you are confident your belt tension is correct, tighten the clamps very firmly. You may now trim the belt, but leave several centimeters behind each clamp for future adjustment.



Assembling the z stage

Parts Required

  • 2 shaft couplers
  • 2 PLA bushings
  • 2 stepper motors
  • 2 threaded rods (TODO: size)
  • 2 smooth rods (TODO: size)
  • 1 prusa frame (see previous step)

Instructions

Assembling the x stage

Parts Required

  • 4 PLA bushings
  • 2 smooth rods (TODO: size)
  • 1 x timing belt


Media

See Also

External Links