Mendel90 Build Manual

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Revision as of 16:31, 7 June 2012 by Nophead (talk | contribs) (Z axis)
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Mendel90 Documentation

Bill of Materials

The latest version can be found here: https://raw.github.com/nophead/Mendel90/master/mendel/bom/bom.txt

Vitamins:

                                                Z   
                                                    
                                                l   
D        E                                      i   
         l              X           Y           m   
c        e                                      i   
o        c              c           c           t   
n     B  t     M        a  X  X     a  Y  Y        Z
n     e  r     a     X  r        Y  r        Z  s   
e     d  o  F  c  W     r  i  m     r  i  m     w  m
c        n  r  h  a  a  i  d  o  a  i  d  o  a  i  o
t  B  f  i  a  i  d  x  a  l  t  x  a  l  t  x  t  t
o  e  a  c  m  n  e  i  g  e  o  i  g  e  o  i  c  o
r  d  n  s  e  e  s  s  e  r  r  s  e  r  r  s  h  r
 |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  1 Acrylic sheet 468mm x 432mm x 10mm
 |  |  |  | 2|  |  |  |  |  |  |  |  |  |  |  |  |  |  2 Acrylic sheet 170mm x 324mm x 6mm
 |  |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  1 Acrylic sheet 224mm x 224mm x 6mm
 |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  1 Acrylic sheet 468mm x 324mm x 6mm
 |  |  |  |  |  |  |  |  |  |  |  | 5|  |  |  |  |  |  5 Aluminium foil tape 50mm x 234mm x 0.05mm
 |  |  |  |  |  | 3|  |  |  |  |  |  |  |  |  |  |  |  3 Ball bearing 608 8mm x 22mm x 7mm
 |  |  |  |  |  |  |  |  | 1|  |  |  | 2|  |  |  |  |  3 Ball bearing 624 4mm x 13mm x 5mm
 | 4|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  4 19mm bulldog clip
 | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  1 PCB bed 214mm x 214mm
 |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  1 Belt T5 x 6mm x 674mm
 |  |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  1 Belt T5 x 6mm x 866mm
 |  |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  1 Corrugated cardboard 200mm x 224mm x 6mm
 | 4|  | 4|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  8 M3 cap screw x 10mm
2|  |  | 4|  |  |  |  |  |  | 2| 4|14|  |  | 2|  | 2| 30 M3 cap screw x 16mm
2|  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  |  | 8| 11 M3 cap screw x 20mm
 |  |  |  |  |  |  |  | 2|  |  |  | 2|  |  |  |  |  |  4 M3 cap screw x 25mm
 |  |  |  |  |  | 2|  |  |  |  |  |  |  |  |  |  |  |  2 M3 cap screw x 30mm
2|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  2 M3 cap screw x 45mm
 |  | 4|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  4 M4 cap screw x 20mm
 |  |  |  |  |  |  |  |  | 1|  |  |  | 1|  |  |  |  |  2 M4 cap screw x 40mm
1|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  1 9 way D plug
1|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  1 9 way D socket
 |  | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  1 Fan 80mm x 38mm
 |  |  |  |  |  | 1|  |  |  | 1|  |  |  | 1|  |  |  |  3 M3 grub screw x 6mm
 | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  1 Glass sheet 214mm x 202mm x 2mm
 | 4|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  4 Hex pillar M3 x 20mm
 |  |  |  |  |  |  |  |  | 2| 4|  |  |  |  |  | 1|  |  7 M3 hex screw x 16mm
 |  |  |  |  |  | 2|  |  |  |  |  |  |  |  |  |  |  |  2 M4 hex screw x 20mm
 |  |  |  |  |  | 2|  |  |  |  |  |  |  |  |  |  |  |  2 M4 hex screw x 50mm
 |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  1 M8 hex screw x 60mm
 |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  1 PSU e.g. KY240W12L
 |  |  |  |  |  |  |  | 3| 2| 2|  | 3|  |  |  |  |  | 10 LM8UU linear bearing
 |  |  |  |  |  | 1|  |  |  | 1|  |  |  | 1|  |  | 2|  5 NEMA17 x 47.5mm stepper motor
2|  |  |  |  |  | 1|  | 1|  | 1|  |  |  | 1|  |  |  |  6 Nut M3
 |  |  |  |  |  | 2|  |  |  |  |  |  |  |  |  |  |  |  2 Nut M4
 |  |  |  |  |  | 1|  |  | 1| 1|  |  |  |  |  |  |  |  3 Nut M8
2|  |  |  |  |  |  |  | 2| 2| 6| 4|16|  |  | 2| 1|10| 45 Nyloc nut M3
 |  | 4|  |  |  |  |  |  | 1|  |  |  | 1|  |  |  |  |  6 Nyloc nut M4
 |  |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  1 Polypropylene strip 402mm x 17mm x 0.5mm
 |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  1 Polypropylene strip 320mm x 27mm x 0.5mm
 |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  1 Polypropylene strip 275mm x 29mm x 0.5mm
 |  |  |  |  |  | 3|  |  |  | 3|  |  |  | 4|  |  | 8| 18 M3 pan screw x 8mm
 |  |  |  |28|  |  |  |  |  |  |  |  |  |  | 4| 2| 4| 38 M4 pan screw x 12mm
 |  |  |  |11|  |  |  |  |  |  | 8|  | 1| 4|  |  |  | 24 M4 pan screw x 16mm
4|  |  |  |  |  |  |  |  |  | 2| 2|  |  |  | 2| 2|  | 12 No2 pan wood screw x 13mm
 |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  1 Smooth rod 8mm x 22mm
 |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  1 Smooth rod 8mm x 270mm
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2|  |  |  2 Smooth rod 8mm x 275mm
 |  |  |  |  |  |  | 2|  |  |  |  |  |  |  |  |  |  |  2 Smooth rod 8mm x 382mm
 |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  1 Smooth rod 8mm x 428mm
 |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  1 Electronics e.g. Sanguinolou
 |  |  |  |  |  |  |  |  |  | 1| 1|  |  |  | 1| 1|  |  4 Microswitch
 |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  1 Spring 12mm OD x 0.75mm gauge x 10mm length
 |  |  |  |  |  | 2|  |  |  |  |  |  |  |  |  |  |  |  2 Spring 7mm OD x 1mm gauge x 10mm length
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2|  |  |  2 Threaded rod M8 x 211mm
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2|  2 Tubing OD 7mm ID 5mm x 16mm
4|  |  |  |  |  |  |  |  |  | 2| 2|  |  |  | 2| 2|  | 12 Washer M2.5 x 5mm x 0.5mm
8| 2|  | 8|  |  | 3|  | 2| 2| 9| 4|24|  | 4| 2| 1|18| 87 Washer M3 x 7mm x 0.5mm
 |  | 4|  |39|  | 2|  |  | 2|  | 8|  | 5| 4| 4| 2| 4| 74 Washer M4 x 9mm x 0.9mm
 |  |  |  |  |  |  |  |  | 2|  |  |  | 2|  |  |  |  |  4 Washer M5 x 20mm x 1.4mm
 |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  1 Washer M8 x 16mm x 1.5mm
 |  |  |  |  |  |  |  | 2|  |  |  |  |  |  |  |  |  |  2 Wingnut M4
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2|  |  2 Rubber washer M3 x 10mm x 1.5mm
 |  |  | 8|  |  | 3|  |  |  | 3|  |  |  | 4|  |  | 8| 26 Star washer M3 x 7mm x 0.5mm
 |  |  |  |30|  |  |  |  |  |  | 8|  | 1| 4| 4| 2| 4| 53 Star washer M4 x 9mm x 0.9mm
 |  |  |  |  |  |  |  | 3|  |  |  | 3|  |  |  |  |  |  6 Ziptie 87mm min length

Printed:

 |  |  |  | 2|  |  |  |  |  |  |  |  |  |  |  |  |  |  2 cable_clip_AB.stl
 |  |  |  | 2|  |  |  |  |  |  |  |  |  |  |  |  |  |  2 cable_clip_AD.stl
 |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  1 cable_clip_CA.stl
1|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  1 d_motor_bracket.stl
1|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  1 d_motor_bracket_lid.stl
1|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  1 d_shell.stl
1|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  1 d_shell_lid.stl
 |  | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  1 fan_guard.stl
 |  |  |  |10|  |  |  |  |  |  |  |  |  |  |  |  |  | 10 fixing_block.stl
 |  |  | 4|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  4 pcb_spacer.stl
 |  |  |  |  |  |  |  |  |  | 1|  |  |  | 1|  |  |  |  2 pulley.stl
1|  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  |  2 ribbon_clamp_12_33.stl
 |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  |  1 ribbon_clamp_20_33.stl
 |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  1 ribbon_clamp_20_44.stl
 |  |  |  |  |  |  |  |  |  |  |  | 2|  |  |  |  |  |  2 ribbon_clamp_22_33.stl
 |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  |  |  1 ribbon_clamp_22_44.stl
 |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  1 wades_big_gear.stl
 |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  1 wades_block.stl
 |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  1 wades_gear_spacer.stl
 |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  1 wades_idler_block.stl
 |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  |  |  1 wades_small_gear.stl
 |  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  1 x_belt_clamp.stl
 |  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  1 x_belt_grip.stl
 |  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  1 x_belt_tensioner.stl
 |  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  |  1 x_carriage.stl
 |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  |  |  1 x_idler_bracket.stl
 |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  |  1 x_motor_bracket.stl
 |  |  |  |  |  |  |  |  |  |  | 3|  |  |  |  |  |  |  3 y_bar_clamp.stl
 |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  |  1 y_bar_clamp_switch.stl
 |  |  |  |  |  |  |  |  |  |  |  | 2|  |  |  |  |  |  2 y_bearing_mount.stl
 |  |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  1 y_bearing_mount_switch.stl
 |  |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  1 y_belt_anchor.stl
 |  |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  1 y_belt_anchor_toothed.stl
 |  |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  1 y_belt_clip.stl
 |  |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  |  1 y_belt_clip_toothed.stl
 |  |  |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  |  1 y_idler_bracket.stl
 |  |  |  |  |  |  |  |  |  |  |  |  |  | 1|  |  |  |  1 y_motor_bracket.stl
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1|  |  |  1 z_bar_clamp.stl
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1|  |  |  1 z_bar_clamp_switch.stl
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4|  4 z_coupling.stl
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1|  |  1 z_limit_switch_bracket.stl
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1|  1 z_motor_bracket_lhs.stl
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1|  1 z_motor_bracket_rhs.stl
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2|  |  |  2 z_screw_pointer.stl

Sub-assemblies:

 1 D_connector_assembly
 1 bed_assembly
 1 bed_fan_assembly
 1 electronics_assembly
 1 frame_assembly
 1 machine_assembly
 1 wades_assembly
 1 x_axis_assembly
 1 x_carriage_assembly
 1 x_idler_assembly
 1 x_motor_assembly
 1 y_axis_assembly
 1 y_carriage_assembly
 1 y_idler_assembly
 1 y_motor_assembly
 1 z_axis_assembly
 1 z_limit_switch_assembly
 2 z_motor_assemblies

Printed Parts

The STLs are links to GitHub, so they are always the latest version. Follow the link and then right click on "RAW" and do "Save As" to download an individual STL. For multiple files the whole project can be downloaded as a Zip from GitHub.

Required

Quantity Description File Picture
1 Bar Clamps stl Mendel90-Bar clamps.png
1 Cable Clips stl Mendel90-cable clips.png
10 Fixing Blocks stl Mendel90-Fixing block.png
2 Pulleys stl Mendel90-Pulley.png
1 Ribbon Clamps stl Mendel90-ribbon clamps.png
1 X Carriage stl Mendel90-x carriage parts.png
1 X Idler stl Mendel90-x idler bracket.png
1 X Motor Bracket stl Mendel90-x motor bracket.png
1 Y Bearing Mounts stl Mendel90-y bearing mounts.png
1 Y Belt Anchors stl Mendel90-y belt anchors.png
1 Y Idler Bracket stl Mendel90-y idler bracket.png
1 Y Motor Bracket stl Mendel90-y motor bracket.png
4 Z Coupling stl Mendel90-z coupling.png
1 Z Motor Bracket stl Mendel90-z motor brackets.png

Modified Wade's Geared Extruder

Quantity Description File Picture
1 Extruder Body stl Mendel90-wades extruder.png
1 Small Gear stl Mendel90-wades small gear.png
1 Large Gear stl Mendel90-wades big gear.png
1 Cable Mount stl Mendel90-d motor brackets.png

Optional

Quantity Description File Picture
1 Fan Guard-If you have a fan stl Mendel90-fan guard.png
4 PCB spacers stl Mendel90-pcb spacer.png
2 Z Pointers stl Mendel90-z screw pointer.png

So far the parts have only been tested in ABS.

The latest STL files are on GitHub at github.com/nophead/Mendel90/tree/master/mendel/stls/printed. These are for the default "mendel" configuration. The STLs for the "sturdy" version are also there: github.com/nophead/Mendel90/tree/master/sturdy/stls/printed. For other configurations build the STL files from source using the scripts provided.

NopHead prints the gears, pulleys and cable clips with a 0.35mm nozzle using 0.3mm layers. The pulleys don't fit the belt well when printed with a bigger nozzle, even at the same layer height, because the teeth become too rounded. The gears can be printed with a 0.4mm nozzle but the M8 nut will be tight to press in because the corners of the hexagon get too rounded.

All the other parts are printed with a 0.4mm nozzle and 0.4mm layers. The W/T ratio is 1.5 in both cases. These parameters are defined in the config.scad file and affect the minimum horizontal and vertical feature sizes. Changing them will affect all the printed parts and sheet drawings slightly.

The relationship between nozzle size and maximum layer height depends on die swell, which in turn depends on the plastic and the length of the nozzle hole, so your mileage may vary.

The recommended infill density settings are as follows: -

Fixing blocks, Wades block, Wades idler block, Wades small gear 95%
Y bearing mounts, Z couplings 75%
Z motor brackets 75% hex
Bar clamps, Y belt anchors, Y idler bracket 50%
X carriage, Y motor bracket 50% hex
X idler bracket, X motor bracket 25% hex
Everything else 25%

Printed with these setting the parts weigh about 400g, a little less than a Prusa. There are a lot more parts, but most are a lot smaller.

Most of the holes are Polyholes, so they should come out the right size on a well calibrated printer. The pulley and small gear holes are deliberately undersized to allow them to be reamed to exactly 5mm. cal.stl is a calibration object for testing hole sizes.

Parts which have holes in surfaces where there is nothing underneath have a support membrane that needs removing. The 8mm holes in the X ends and Wades block plus the rectangular hole in the top of the X motor bracket are best removed with a small knife. The smaller holes in the Y belt anchors, Z couplers and the X carriage are best cleared with a 3mm drill.

General tips

  • All screws have a plain washer where they meet the plastic to spread the load and prevent the plastic being chewed up by the rotation of the screw head. Most fixings have a captive Nyloc nut to prevent them vibrating loose. You can use plain nuts but in that case you should add a star washer between the screw head and the plain washer. The screws into the panels have star washers for the same reason.
  • If you are worried about the plastic nut traps being strong enough for Nylocs you can thread the Nyloc onto a spare screw first to loosen it. Nophead hasn't found this necessary.
  • Washers tend to have a smooth side and a side with a burr from being stamped out. Make sure the smooth side faces bearings and belts.
  • Chamfer the ends of the rods with a file to remove any burr, otherwise they can knock the balls out of the linear bearings.

Tools Required

  • Long posidrive screw driver.
  • 2.5mm and 3mm Allen keys.
  • 7mm spanner.

Sheet parts

Mendel90 have been made successfully from MDF, Acrylic, Polycarbonate and DiBond.

If you cut the frame parts out of a sheet of MDF with just simple tools: the original sheet very likely has pretty square corners. Cut the parts in such a way that the original square corners of the sheet are in the most important spots. A sheet of MDF of 2 by 4 feet (61x122cm) is enough for a Mendel sized Mendel90.

Drill and cutting guides

The PDF files of the sheets contain marked positions for all holes to be drilled. These PDFs can be printed on normal sized paper (A4 or Letter). To print the files: open the PDF in Adobe Reader, select: File -> Print. Choose "Poster" and select "Cut marks". This will print the drilling guide on a number of sheets of paper which can easily be glued or taper together. Cut out the corners of the sheets that are on top exactly along the cut marks so that the cut marks of the sheet below can be lined up exactly.

Frame assembly

Refer to frame_assembly.txt for the parts list. If there are are two screw lengths the longer ones go in the base. Each screw should have a star washer on top of a plain washer.

  1. Attach three fixing blocks to the left and right stays with two screws each, noting that they go on the side that faces inwards. Stand the sheet on its edge on a flat surface and slide the block down to be flush with the edge before tightening the screws.
  2. Fit the remaining four fixing blocks to the back of the gantry in the same way.
  3. Fix the stays to the gantry using one screw in each fixing block from behind. Use the stays to align the sheet vertically.
  4. Screw the gantry to the base with six screws. Align the stays with the back edge before tightening.
  5. Loosely attach the five cable clips. The biggest one goes at the back of the base for the bed wires, the middle size ones go on the gantry for Z motors, fan and limit switch. The two small ones go on the base for the Y motor and limit switch. Orient them to match the wires holes.
  6. Loosely attach the two ribbon clamps. The longer one goes at the back of the base for the bed wires. The shorter one goes at the top of the gantry for the X axis cable.

Bed fan assembly

The fan is optional. It is used to cool the bed rapidly at the end of a build so that the parts can be removed quickly. Refer to bed_fan_assembly.txt for the parts list.

Make sure the fan is blowing inwards. This is usually indicated by an arrow on the frame and is ofetn the side with the label.

The four screws pass through a plain washer, the fan guard, the left stay, the fan and finally a nyloc nut. There isn't a washer behind the fan because fan frames tend not to have room for one.

Z axis

X idler end

Using the parts in x_idler_assembly.txt assemble the X idler end.

Remove the support material in the nut traps with a drill or a small penknife. Also remove any loose filament created by the overhanging dividers in the bearing channel.

To insert the linear bearings it is easiest to push the end which is towards the middle in first. Then slide it up against the divider in the middle before pushing in the other end. Insert a rod to check they are aligned well.

It can be easier to pull the M3 nuts into their traps using one of the long screws.

Leave the long bolt that forms the idler axle loose to allow the X bars to be inserted later.

X motor end

Using the parts in x_motor_assembly.txt assemble the X motor end. Don't fit the limit switch, leave it to the wiring stage.

Z motor assemblies

Using the parts in z_motor_assemblies.txt assemble the two motor assemblies.

  • Drill out any support material in the Z couplings.
  • Degrease the motor shafts before fitting the plastic tubing but be careful not to degrease the bearings. Fit the coupling loosely over the tubing.
  • Twist the motor wires in pairs and feed them through the hole in the gantry before attaching the motor assemblies.

Z axis assembly

Use a large set square to ensure the left hand Z bar is vertical. The clamps at the top and bottom of the bar are identical so they can be aligned rather than the bar itself.

Leave the right hand top clamp loose until the X axis is fitted.

Mendel90-Z axis alignment.JPG

Y axis

Fit the long Y bar first and use a large set square to make it perpendicular to the base sheet before tightening the base screws.

Mendel90-Y axis alignment.JPG


Y Heat Shield

The heatshield prevents heat radiating downwards from the bed heating the Y carriage, which can make it warp due to the top surface expanding more than the bottom. 6mm corrugated cardboard is used as a cheap and effective insulator and aluminium foil tape on top reflects heat back towards the bed.

Mendel90-Heatshield.png

Start by printing a paper template from the pdf drawing https://github.com/nophead/Mendel90/raw/master/mendel/sheets/y_heatshield.pdf. Cut out the outline with scissors or a craft knife. Place the template over the cardboard and cut round with a straight edge and craft knife. Cut through the holes.

Mendel90-Heat sheild cut.JPG

Apply the tape strips with some overlap. Turn it foil side down and trim round with a knife.

Mendel90-Head sheild tape.JPG

X axis

Wiring

Y & Z axis wiring

The motor wires should be tightly twisted in pairs to reduce RFI. The normal coil pairings for the recommended SY42STH47-1684A motors are red / blue and black / green. The easiest way to twist them is to tie a knot at the far end of the wire pair and spin it in the chuck of a drill with some tension on the wire.

The motors come with 2.5m of wire so it is best the cut them roughly to length before twisting them, but leave at least 0.5m spare to account for it getting shorter when twisted.

The spare wire can be used for the limit switches, fan and thermistor. Use different colour pairs to make them easily distinguishable from the motor wires and each other, e.g. red / black for the fan and green / blue for the limit switches. They should also be twisted to reduce induced noise.

The wires should be soldered to the limit switches before the switches are fitted. Use the outer two pins for normally closed.

There are three sizes of cable clip, each with two slots. The largest is for the bed and thermistor wires. The smallest is for the Y axis motor and limit switch. The middle size clips are for the Z axis motor + fan wires and the Z - limit switch.

The clips keep the sensitive input wires away from the power wires and there are separate holes in the frame which line up with the clips.

Bed wiring

The bed is connected via a 22 way ribbon cable.

The pads on the bed are too small for the size of wire that is appropriate for the current, so remove some of the solder resist by scraping with a sharp blade. Scrape towards the edge to avoid the risk of damaging the finer heating tracks.

Mendel90-Scraped bed connections.JPG

Block the holes on the back with some tape to prevent solder flowing through. Strip about 12mm of the outer ten wires on each side and twist them tightly together and solder to the pads.

The middle two wires should be soldered to the thermistor leads. Keep the thermistor leads full length (because the are less thermally conductive than copper wires) and insulate them with PTFE sleeving. Use heatshrink sleeving over the solder joints.

Glue the thermistor to the underside of the bed using a thermally conductive high temperature glue such as JB-Weld, or tape it on with a high temperature tape such as Kapton, or the aluminium foil tape used for the heatshield.

Mendel90-Bed thermistor.JPG

Note that the ribbon cable leads off towards the centre of the bed initially and then curls back towards the edge. Put the cable through the top ribbon clamp on Y carriage and screw the bed to the pillars. Loop the cable back underneath the carriage through the bottom ribbon clamp and put the cable strip underneath it in the same clamp.

Mendel90-Bed underside.JPG

Slide in the heatshield from the front and fix it front and back with high temperature tape.

Terminate the ribbon cable just past the end of the cable strip as shown below. The thermistor connection can be made with left over motor wire. The bed wires should be 40 strands of 0.2mm, e.g. 13A mains cable.

Mendel90-Bed soldered.JPG

Fasten the free end of the ribbon cable and the cable strip to the base using the ribbon clamp. The strip should press against the cable to force it into a smooth loop. Use the cable clip to take the wires through a 90° bend and feed them through the holes in the right hand stay.

Mendel90-Bed cable clip.JPG

The suggested wiring sequence for least thermistor noise is : -

Wire number Signal
1-10 Heater -
11 Thermistor GND
12 Thermistor signal
13-22 Heater +12V

X axis wiring

The X axis motor and the extruder are connected by a single 20 way ribbon cable. The following pin connections are used to minimise cross talk.

Wire number Signal D type connector pin
1 Extruder motor black Pin 5
2 Extruder motor green Pin 9
3 Extruder motor blue Pin 4
4 Extruder motor red Pin 8
5,6 Heater - Pin 3
7 Fan - Pin 7
8,9 +12V Pin 2
10 Spare
11 Thermistor GND Pin 6
12 Thermistor signal Pin 1
13 X limit GND
14 X limit signal
15 Guard loop GND
16 Guard loop GND
17 X motor red
18 X motor blue
19 X motor green
20 X motor black

Start with about 1.5m of 20 way ribbon cable and put it through the ribbon clamps of the X motor bracket. Split off 12 ways and solder them to the D type connector. Pull the other ways back to the X end. Leave two long enough to go through the hole to the X limit switch and cut the rest just long enough to connect to the motor.

Attach the ribbon clamp at the extruder connector to trap both the wire and the polypropylene cable strip. Form it into a loop to reach the extruder before tightening the ribbon clamp at the X motor end.

Make the connections to the motor and limit switch and then fit the switch.

Mendel90-X end wiring.JPG

Note the two guard wires linked together and insulated.

Tuck the connected wires into the hole in the the bracket.

Mendel90-X end wired.JPG

Fit the remaining cable strip and tighten the two 20 way ribbon clamps. The ribbon cable goes over the top and down into the electronics bay where all the other wires terminate.

Connecting the electronics

Fit your preferred electronics and connect all the wires. The example below shows a Sanguinololu connected as shown here:

Sanguinololu12.svg

Mendel90-Ratsnest.JPG

Note:

  • It could be a lot neater if the ribbon cable had not been cut too short and the other wires too long.
  • The standard connectors have been replaced by screw connectors and ferrules as Nophead finds these more reliable.
  • The X, Y and Z motors are wired in reverse compared to the diagram above because the motors are all reversed compared to a Prusa.
  • The bed is connected directly to the PSU and the tab of the MOSFET with a ring terminal to avoid the underrated connector on the PCB.
  • There is nowhere for the fan to connect on a Sanguinololu.
  • The mains connections to the PSU should be completely covered and the cable should have strain relief, TBD.

Extruder wiring

The thermistor and heater wires should be kept at full length to minimise the temperature at the solder joints. PTFE sleeving and PTFE insulated wires are used close to the extruder to handle the temperature. Preferably the heat shrink sleeving should be silicone. The black heat shrink will degrade at hot end temperatures and can't be relied upon as insulation, so the heater joints are made inside the PTFE sleeving.

Mendel90-Extruder wiring.JPG

Testing

A simple way of testing is to talk directly to the board with a terminal emulator. This is assuming it comes preloaded with firmware. Sanguinololus tend to come with Sprinter installed. The PC also needs a USB FTDI driver for the serial port to appear.

Suitable terminal emulators are Hyperterm, Tera Term or the one built into the Arduino IDE.

Configure the terminal emulator for the correct port and baud rate, usually 115200 for Sprinter. The serial port will be the highest numbered comm port on Windows if it was the last thing plugged in.

When the connection is made, or the reset button is pressed, the motors energise for a few seconds and then "start" is printed. If instead you get gibberish with more characters then most likely your terminal baud rate is higher than your firmware board rate. If you get less then characters then your terminal baud rate is too low.

Type M115 to show the firmware installed:

start                 
FIRMWARE_NAME:Sprinter FIRMWARE_URL:http%%3A/github.com/kliment/Sprinter/ PROTOC
OL_VERSION:1.0 MACHINE_TYPE:Mendel EXTRUDER_COUNT:1 UUID:00000000-0000-0000-0000
-000000000000
ok

Check that the endstops are working with M119. When no endstops are triggered they should all read low:

x_min:L y_min:L z_min:L
ok

Check that manually triggering each switch causes the corresponding input to change from L to H. Also check that the axis is able to hit its endstop. For X the extruder wingnut can get in the way. If this is the case simply rotate the hex head bolt in its socket. For Z make sure the limit switch is high enough to activate before the extruder hits the bed.

The for each axis check it moves away from the endstop with a positive movement and back towards the endstop with negative movements by issuing G1 commands. E.g. G1 X10 should move the X axis to the left, away from the endstop. Then G1 X0 should move it back towards the endstop. Note that both the X and Y axes are backwards by normal conventions when viewed from the front of the machine.

Once the endstops are verified to be working and the motors running in the right direction it is safe to home each axis with G28 XYZ. One can then centre the axes with G1X100Y100Z100.

Check the the extruder feeds forwards with a positive E value, e.g. G1E10 and rewinds with G1E-10.

To check the thermistors are working type M105. That should report the extruder and bed temperatures which should be close to room temperature: -

ok T:23 B:24

If the thermistor is not connected the temperature will read very low and if it is shorted it will read very high. If it shows an incorrect temperature than is not at the extremes then most likely the table in the firmware does not match the thermistor being used.

Verify the hot end can heat by issuing M109 S50. That should result in increasing temperatures being printed.

T:24
T:25
T:25
T:25
T:25
T:26
T:28
T:30
T:30
T:32
T:35
T:36
T:38
T:40
T:43
T:45
T:47
T:49
ok

M105 should show the temperature hovering around 50 but expect some overshoot at such a low temperature.

To test the heated bed issue M140 S50. Unlike M105 this command does not wait for the bed to reach the target temperature but returns immediately. Use M105 to show the bed climbs to and then hovers around 50C.

This completes the electrical testing. The next step is to configure and load your chosen firmware and then calibrate the machine.

Calibration

Bed levelling

The best way to level the bed relative to the nozzle is to use a dial gauge mounted in place of the extruder using this clamp. If you don't have a dial gauge you can roll a rod or slide some film under the nozzle and feel when it is just touching.

Mendel90 Carriage dial gauge.JPG

The two pillars at the back of the bed have a washer under them to ensure the front can be made both higher or lower than the back. Those pillars are tightened and not adjusted. Front - back adjustment is achieved by adjusting the two pillars at the front. Left - right adjustment is done by turning the Z lead screws. Ideally there would be only one mounting point at the front as only three points are needed to mount a stiff sheet like glass. Having four makes the adjustment more tedious as they tend to bend the sheet and interact with each other.

Start by sliding a washer under the front pillars to set them to the same height as the back. Move the gauge or nozzle to the middle of the back of the bed. Note that level on the gauge, or nudge the Z axis to just touch your feeler. This is the level that we want the whole bed to be at.

Move to the back left corner and adjust the left lead screw to get the same level as the middle. Move to back right and adjust the back right lead screw. Moving the gauge all the way across the back should now read the same height.

Now move to each of the front corners in turn and turn the pillar until the height is correct. Lock them in place by tightening the top screws through the bed.

The whole bed should now be level but usually you need to repeat the procedure a few times due to the interaction of the four points.

Z home point

TBD

When the Z home point has been set rotate the two Z screw pointers so that they point directly at the Z bars. One can now see if the lead screws get out of sync.

Thermistor Calibration

For best results thermistors should be individually calibrated for two reasons. Firstly they are usually only 5% or 10% tolerance components. 10% at 240C has a significant effect on the plastic. The datasheet value of beta is for a subset of the temperature range because it isn't actually a constant (the two parameter equation is only an approximation).

The second reason is that the bed thermistor is underneath the bed but we are interested in the temperature of the top surface. The extruder thermistor is in the heater block but we are interested in the temperature inside the barrel because that is where the plastic spends most of its time. Plastic has a high specific heat capacity and low thermal conductivity so it is likely to leave the nozzle at a similar temperature.

TBC

Extruder Calibration