Ohm/How to build an OHM

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Contents

Introduction

The Open Hybrid Mendel (OHM) has several advantages over the generic Mendel model. Mainly, it is more flexible. The extruder carriage and printing board are designed to easily pop off the machine without unscrewing any parts.

All STL files mentioned in this article are referring to, and can be downloaded from the OHM Parts section.

Mechanical Construction

Frame

Frame Triangles

Parts

Total # of assemblies: 2

Name Qty/assembly Total Qty Type
Camiel_frame_vertex_6off 3 6 RP
prusa_bar-clamp_4off 1 2 RP
m8-nut 14 28 Fastener
m8-washer 14 28 Fastener
m8-threaded rod D 3 6 Threaded Rod
Reprapped parts

Assembly

(The above list of parts is accurate. The assembly should reflect this) (Assembly guide. Delete this note when section is finished)

Tips

When you assemble the frame triangles, it will be easier if you assemble the two top vertices the last. To insert the rod into the vertices, you can tie two nuts tight together and then use a wrench to screw in the rod.

Connecting the Triangles

Parts

Total # of assemblies: 1

Name Qty/assembly Total Qty Type
y-motor-bracket_1off_mod3-15 1 1 RP
y-idler-bracket_1off 1 1 RP
m4x40-cap 4 4 Fastener
m4-washer 12 12 Fastener
m4-large OD washer (3/16 fender washer) 8 8 Fastener
m4-nylock 4 4 Fastener
m8-nut 44 44 Fastener
m8-washer 44 44 Fastener
m8-threaded rod E 4 4 Threaded Rod
m8-threaded rod F 3 3 Threaded Rod
Reprapped parts

Assembly

(The above list of parts is accurate. The assembly should reflect this) It is a good idea to assemble the pulley bearings before putting the motor mount and idler on (Assembly guide. Delete this note when section is finished)

Tips

It is easier to assemble the triangles, if connected both ends first, and then connect the bottom two rods.(Extra tips to help assemble. Delete this note when section is finished)

Z Drive System

Z-Axis Motor Mounts

Parts

Total # of assemblies: 2

Name Qty/assembly Total Qty Type
z-prusa-motor-mount_2off 1 2 RP
z-bar-top-clamp_2off 1 2 RP
m3x10-cap 4 8 Fastener
m3-washer 4 8 Fastener
m8-nut 2 4 Fastener
m8-washer 4 8 Fastener
Stepper Motor 1 2 Motor
Reprapped parts

Assembly

(The above list of parts is accurate. The assembly should reflect this) Leave the smooth rod clamps loose and save the threaded rod for "connecting the x and z axis" section, since the x assembly needs to slide on before these are attached. (Assembly guide. Delete this note when section is finished)

Tips

(Extra tips to help assemble. Delete this note when section is finished)

Assembly of Z-axis can be started from sticking everything together in one rod. Settling all the parts (including the two top vertices for the frame triangle) on Z axis and connecting them with rod at one side, then insert the rod for the other side.

X-Z Assembly

X-Axis Idler Bracket

Parts

Total # of assemblies: 1

Name Qty/assembly Total Qty Type
x-end-bracket_1off 1 1 RP
x-180-z-bearing-plate_2off 2 2 RP
x-bar-clamp-m3_4off 2 2 RP
m3x20-cap 4 4 Fastener
m3-nylock 4 4 Fastener
m3-washer 8 8 Fastener
m4x20-cap 2 2 Fastener
m4x40-cap 8 8 Fastener
m4-nylock 10 10 Fastener
m4-washer 26 26 Fastener
m4-large OD washer (3/16 fender washer) 4 4 Fastener
bearing-4x13x5 6 6 Bearing
Reprapped parts

Assembly

(The above list of parts is accurate. The assembly should reflect this) (Assembly guide. Delete this note when section is finished)

Tips

(Extra tips to help assemble. Delete this note when section is finished)

X-Axis Motor Mount

Parts

Total # of assemblies: 1

Name Qty/assembly Total Qty Type
xaxis-motor-bracket_1off 1 1 RP
PSU_x_vert_sideplate_360_end_2off 2 2 RP
x-bar-clamp-m3_4off 2 2 RP
x-360-z-bearing-plate_2off 2 2 RP
x-360-z-bearing-plate-mirror_2off 2 2 RP
pulley_w-set_screw_2off 1 1 RP
m3x6 set screw 1 1 Fastener
m3-nut 1 1 Fastener
m3x10-cap 4 4 Fastener
m3x20-cap 4 4 Fastener
m3-nylock 4 4 Fastener
m3-washer 12 12 Fastener
m4x16-cap 4 4 Fastener
m4x20-cap 2 2 Fastener
m4x40-cap 6 6 Fastener
m4-nylock 12 12 Fastener
m4-washer 34 34 Fastener
m4-large OD washer (3/16 fender washer) 4 4 Fastener
bearing-4x13x5 8 8 Bearing
Stepper Motor 1 1 Motor
Reprapped parts

Assembly

(The above list of parts is accurate. The assembly should reflect this) (Assembly guide. Delete this note when section is finished)

Tips

(Extra tips to help assemble. Delete this note when section is finished)

X-Axis Vertical Bearing

See Mendel X-Axis for further information.

Parts

Total # of assemblies: 2

Name Qty/assembly Total Qty Type
x-axis-side-plate-nut-jig_2off 1 2 RP
x-bar-clamp-m4_4off 2 4 RP
x-vert-drive-nut-trap_4off 2 4 RP
x-vert-drive-side-plate_4off 2 4 RP
m4-nut 4 8 Fastener
m4-nylock 4 8 Fastener
m4-washer 12 24 Fastener
m4x40-cap 8 16 Fastener
m8-nut 1 2 Fastener
Reprapped parts

Assembly

First, assemble the x-vert-drive-nut-trap_4off. To do this, you need a lighter, four m4 nuts and a m4x40-cap. Place an m4 Nut on the end of the m4x40-cap and heat with the lighter. Caution: Do not heat for too long or the m4x40-cap will become very hot.

Push the heated nut into one of the hexagonal holes in the x-vert-drive-nut-trap_4off. Repeat for all four nuts.

Screw x-vert-drive-side-plate-180-end_2off and x-bar-clamp-m4_4offtogether using m4x40-cap and washers. Do not screw them all the way in.

Screw x-vert-drive-nut-trap_4off into x-vert-drive-side-plate-180-end_2off using a diagonal pattern. Remember to use washers. Do not screw them all the way in.

Repeat previous steps to create other half. Make sure that you place the screws diagonally in a way that they do not interact with the other screws.

Place the x-vert-drive-nut-trap_4off in between the bottom half of the two sides and line up screws. Screw in the M4 screws until they sit in the nuts and are firmly in place. This could take some adjustment.

Place an M8 nut in between the two trap sides. Then screw the upper screw together. Tighten all screws in steps.

Tips

  • In some cases, though it is not necessary, it may help if you drill out the holes before assembling.
  • To help align the screw holes, place on screw in, clamp the parts, and drill the rest of the holes.

Assembling the X-Axis

Parts

Total # of assemblies: 1

Name Qty/assembly Total Qty Type
m8-smooth rod A 2 2 Smooth Rod

Assembly

(Assembly guide. Delete this note when section is finished)

Tips

(Extra tips to help assemble. Delete this note when section is finished)

Connecting the X-Axis to the Z-Axis

Parts

Total # of assemblies: 2

Name Qty/assembly Total Qty Type
pla_coupling_nophead-1piece_4off 2 4 RP
prusa_bar-clamp_4off 1 2 RP
m3x20-cap 4 8 Fastener
m3-nylock 4 8 Fastener
m3-washer 8 16 Fastener
m8-nut 2 4 Fastener
m8-washer 2 4 Fastener
m8-threaded rod G 1 2 Threaded Rod
m8-smooth rod B 1 2 Smooth Rod
Reprapped parts

Assembly

(The above list of parts is accurate. The assembly should reflect this) (Assembly guide. Delete this note when section is finished)

Tips

(Extra tips to help assemble. Delete this note when section is finished)

Z and X axes Endstops

Parts

Total # of assemblies: 2

Name Qty/assembly Total Qty Type
endstop-holder_microsw-1_small enstops_3off 1 2 RP
m3x20-cap 1 2 Fastener
m3-nylock 1 2 Fastener
m3-washer 2 4 Fastener
Reprapped parts

Assembly

(The above list of parts is accurate. The assembly should reflect this) (Assembly guide. Delete this note when section is finished)

Tips

(Extra tips to help assemble. Delete this note when section is finished)

OpenY Axis

Y-axis Guide Bars

Parts

Total # of assemblies: 2

Name Qty/assembly Total Qty Type
y-bar-clamp_8off 4 8 RP
m4x40-cap 4 8 Fastener
m4-nylock 4 8 Fastener
m4-washer 8 16 Fastener
m8-smooth rod C 1 2 Smooth Rod
Reprapped parts

Assembly

(The above list of parts is accurate. The assembly should reflect this) (Assembly guide. Delete this note when section is finished)

Tips

(Extra tips to help assemble. Delete this note when section is finished)

OpenY Assembly

Parts

Total # of assemblies: 1

Name Qty/assembly Total Qty Type
OpenY_Arm 90 - 180_2off 2 2 RP
OpenY_arm45 1 1 RP
OpenY_8mm Crossbar Mount_2off 2 2 RP
OpenY_8mm Belt Harness_1off 1 1 RP
OpenXY_bracket 2 2 RP
m4x20-cap 8 8 Fastener
m4x25-cap 4 4 Fastener
m4x40-cap 4 4 Fastener
m4-nylock 16 16 Fastener
m4-washer 36 36 Fastener
m8-nut 4 4 Fastener
m8-washer 4 4 Fastener
m8-threaded rod H 1 1 Threaded Rod
bearing-4x13x5 12 12 Bearing
Reprapped parts

Assembly

First, the bearing should be placed on the OpenXY_brackets, OpenY_Arm 90 - 180_2offs, and the OpenY_arm45. A total of 4 bearings will be put onto each of the OpenY_Arm 90 - 180_2offs (as can be seen in 3rd picture in the pictures above). One bearing each should be put each of the 4 OpenXY_brackets and 2 bearings onto the single OpenY_arm45.

After the bearings are mounted a OpenY_8mm Crossbar Mount_2off can be fastened to one side of one ofthe OpenY_Arm 90 - 180_2off (like in the 3rd picture. The other OpenY_Arm 90 - 180_2off will have the the OpenY_arm45 in between these two parts with the bearings on the same side as the bearings on the large piece.

A piece of threaded rod needs to have the OpenY_8mm Belt Harness_1off in the middle of it. It should have a washer and nut on each side of it. A additional nut followed by a washer needs to be on both sides. The rod must then be threaded to into the large hole in the OpenY_8mm Crossbar Mount_2off. It then must be threaded onto the other OpenY_8mm Crossbar Mount_2off and then the nuts can be tightened against them.


(The above list of parts is accurate. The assembly should reflect this) (Assembly guide. Delete this note when section is finished)

Tips

Using two temporary nuts against each other on the opposite side of the threaded rod you are trying to screw in, can allow you to thread it using a wrench on the nut. You can them remove those nuts before screwing on the other side.

(Extra tips to help assemble. Delete this note when section is finished)

Print Bed

Parts

Total # of assemblies: 1

Name Qty/assembly Total Qty Type
bed-spring_4off 4 4 RP
m4x50-cap 4 4 Fastener
m4-nylock 4 4 Fastener
m4-washer 8 8 Fastener
Reprapped parts

Assembly

(The above list of parts is accurate. The assembly should reflect this) (Assembly guide. Delete this note when section is finished)

Tips

(Extra tips to help assemble. Delete this note when section is finished)

Motors, Belts and Endstops

Parts

Total # of assemblies: 1

Name Qty/assembly Total Qty Type
pulley_w-set_screw_2off 1 1 RP
endstop-holder_microsw-1_small enstops_3off 1 1 RP
m3x6 set screw 1 1 Fastener
m3-nut 1 1 Fastener
m3x20-cap 1 1 Fastener
m3x25-cap 4 4 Fastener
m3-nylock 1 1 Fastener
m3-washer 6 6 Fastener
Stepper Motor 1 1 Motor
Reprapped parts

Assembly

(The above list of parts is accurate. The assembly should reflect this) (Assembly guide. Delete this note when section is finished)

Tips

(Extra tips to help assemble. Delete this note when section is finished)

Extruder

Carriage

Parts

Total # of assemblies: 1

Name Qty/assembly Total Qty Type
OpenX_Carriage_1off 1 1 RP
OpenX_arm_PSU_1off 1 1 RP
OpenXY_bracket 2 2 RP
m4x20-cap 14 14 Fastener
m4-nylock 14 14 Fastener
m4-washer 34 34 Fastener
bearing-4x13x5 10 10 Bearing
Reprapped parts

Assembly

(The above list of parts is accurate. The assembly should reflect this) (Assembly guide. Delete this note when section is finished)

Tips

Make sure you have a good hot tip before you attempt to install it. Ask around to see if the hot tip you are using is a good one. Quite often the extruder body or parts are not perfect. You must do a judgement call to determine if the parts are still usable. The extruder must still be accurate where it counts. You can also fix imperfections with a soldering iron to melt extra plastic that's in the way.

Motor Mount

Parts

Total # of assemblies: 1

Name Qty/assembly Total Qty Type
Gregs_accessible_wades_v6 1 1 RP
Gregs_accessible_wades_idler 1 1 RP
HerringboneDrivenGear 1 1 RP
HerringboneDriveGear 1 1 RP
m3x6 set screw 1 1 Fastener
m3-nut 1 1 Fastener
m3x10-cap 4 4 Fastener
m3-washer 4 4 Fastener
m4x25-cap 3 3 Fastener
m4x40-cap 2 2 Fastener
m4-nut 3 3 Fastener
m4-nylock 2 2 Fastener
m4-washer 8 8 Fastener
m8-hobbed bolt 1 1 Fastener
m8-nylock 1 1 Fastener
m8-washer 2 2 Fastener
m8-smooth rod (stub) 1 1 Smooth Rod
bearing-8x22x7 3 3 Bearing
stepper motor 1 1 Stepper Motor
Reprapped parts

Assembly

(The above list of parts is accurate. The assembly should reflect this) (Assembly guide. Delete this note when section is finished) This unfinished part includes the main driven gear, idler and lastly the main section.

Tips

(Extra tips to help assemble. Delete this note when section is finished)

Hot Tip

Parts

Total # of assemblies: 1

Name Qty/assembly Total Qty Type
metal base plate 1 1 Misc. Hardware
metal exruder shaft 1 1 Misc. Hardware
brass tip 1 1 Misc. Hardware
heat sink 1 1 Misc. Hardware
fireplace cement? 1 1 Misc. Hardware
m3x25-countersink 2 2 Fastener
nichrome wire 1 1 Wire
thermocouple 1 1 Wire

(These parts need to be more specific with details) (Parts needed for assembly. Delete this note when section is finished)

Assembly

(Assembly guide. Delete this note when section is finished)

Tips

When you feel like the tip is stuck, heat it up, and then use another piece of filament to quickly suck out the part that were stuck in the tip. (Extra tips to help assemble. Delete this note when section is finished)

Spool

Spool Assembly

Parts

(Parts needed for assembly. Delete this note when section is finished)

Assembly

(Assembly guide. Delete this note when section is finished)

Tips

(Extra tips to help assemble. Delete this note when section is finished)

Spool Mount

Parts

(Parts needed for assembly. Delete this note when section is finished)

Assembly

(Assembly guide. Delete this note when section is finished)

Tips

(Extra tips to help assemble. Delete this note when section is finished)

Electrical Construction

RAMPS

Motherboard

Total # of assemblies: 1

Name Qty/assembly Total Qty Type
Ramps_Mount 1 1 RP
RAMPS 1.4 1 1 PCB
zip-tie 8 8 Fastener
Reprapped parts & motherboard

Connecting Power

Parts

Total # of assemblies: 1

Name Qty/assembly Total Qty Type
AC Computer Power Adapter (12V, 6A) 1 1 Power Supply

Assembly

Connecting the Motors

After assembling the RAMPs shield following these instructions, place your Pololu boards into the driver sockets marked 'X', 'Y', 'Z', 'E0', and if you have 2 extruders 'E1'. The Pololu drivers should be placed with the metal potentiometer facing away from the power connector of the RAMPs. After the drivers are placed, the motor 4 socket connector should be plugged into the 4 pin on the RAMPs that corresponds to the axis the motor controls. The direction of the sockets will determine which directions are positive and negative. Reversing the socket connector will reverse the directions. The z motor sockets must face the same direction, or the motors will rotate opposite directions.

Connecting the End Stops

After assembling the end stops, two of the pins must be connected to a 2 socket connector. This connector will fit into the 2x4 (or 3x4) set of pins in the opposite corner from the power connector. The row to use is marked with an 'X', 'Y', or 'Z'. The direction of the socket connector does not matter, but it must be on the 'S' and '-' rails, not the '+' rail closest to the middle of the shield.

Connecting the Hot Tip

The hot tip's 2 leads fit into the connector labeled 'D10' and can be secured using the screw at the top of the MOSFET. The polarity does not matter, meaning either lead can go into either socket.

Connecting the Thermocouple

The thermocouple is placed on the hot tip and the leads should go into the MOSFET on the thermocouple board. This board has a integrated circuit as well as a 3 pin connector. The 3 pin connector should have cables connecting to the 3 pin connector on the RAMPs shield along the same side as the power connector.

RAMBO

Motherboard

Motor drivers

End Stops

Hot tip