Updated Hotend Effector

The hotend effector has been updated - here's the skinny on why and how to build the new version.  It requires new rail effectors as well, however the only change there is the width of the rods - the build instructions are identical.

Improvements:

1. The new effector is much more compact.
2. Much higher torsional stability
3. Integrated Z-Min endstop (Experimental!)
4. One fan per hotend
5. Simpler hotend clamp
6. Black.

Vitamins

• 3x M5x20 socket cap screws
• 3x M5 washers
• 3x M5x40 socket head cap screw - make sure it's got a smooth part on it
• 3x springs that'll fit around an M5
• 6x M5 nuts
• 1x M3x20mm screw
• 1x M3 nut
• 1x M3 washer
• 1x M3 spring
• 1-3 30mm fans
• 1-3 hotends (pictures are using the e3d hotend.  It comes with 30mm fans, but they're not great.  I used some old ones that blow harder)
• 1 tactile switch (digikey or just ask, I got a bunch of extras)

RepRapped Parts

• Hotend Effector (https://github.com/paenian/bertha/blob/master/hotend_effector.stl)
• Tripleclamp (https://github.com/paenian/bertha/blob/master/tripleclamp.stl)

Assembly

1. Take the Tripleclamp first.
2. Insert the M3 hardware into the center hole - nut into the nut trap, washers and springs above:
3. Insert an M5 nut into all three nut slots, then loosely screw in the shorter M5 screws with washers.
4. Take the longer M5 bolts and springs, and drop in through the top of the tripleclamp (the top is the shiny part).  It should be a semi-loose fit.
5. solder two of the switches leads, on the same side - you'll need to bend them sideways to get it in the hole, and also bust off the other ones.  Make sure to test the switch - if you pick the two wrong contacts, it'll be always shorted.
6. Insert the switch into the hotend effector, wires through the holes.
7. Insert the three long M5 bolts down into the hotend effector itself.  There are three nut traps inside the side holes, hidden away.
8. Tighten lightly.

And there you have it.  Hotends can be inserted now, as well as fans.  If you use the E3d hotend, well, the fans don't fit in their slots - but you can hot glue 'em in just fine.  Wire it up, and let 'er rip!

I am currently stress-testing this setup - running some long prints to shake it down.  Next step is activating the Z-Min endstop, but that'll be another blog post.

Metal Rod Ends

The Igus rod ends are too stiff to use - they were causing all sorts of binding issues.  I tried running the machine in circles for three hours, and even talked to some IGUS engineers.  Their advice was to use 3 in 1 oil to lubricate, but this also failed.

My solution was to order metal rodends from AliExpress.  Along with this I redesigned the rodend mounts, and shortened the arms slightly (400 to 375) because the metal rodends have a bit more travel than the plastic igus ends.

Vitamins:

• 12* Metal Rod Ends - M5 female socket, M5 hole
• 6  * M5 Round cap screws, 20mm long
• 6  * M5 cap screws, 10mm long (leftover from v-rails)
• 6  * M5 washer
• 12* M5 nut
• 6  * 245mm Carbon Fiber Square Tube, 8mm OD, 6mm ID

RepRapped Parts :

• 12 * Rod End  (https://github.com/paenian/bertha/blob/master/rod_end.stl)

Tools :

• 3mm Ball-end hex key
• Knife for part cleaning - exacto or similar

Note that the rods are short enough that you can cut the ends off of your old rods and re-use them.  Also, if you buy the meter-long carbon fiber, you can now get 4 arms per meter instead of 3 - slightly more economical.  Ideally, the rods should be as short as possible - in order to maximize build height.  Using rod ends, this is about as good as it gets - to do better you'd need 12 universal joints.  I've toyed with designing my own u-joints around M5 bearings, but the size is an issue.  I might do more u-joint work in the future sized around M3 bore bearings, but this is as good as it gets for now.

Assembly:

1. Glue the rod ends onto the rods.  Note the cool 45 degree rotation... designed so that they'd print better, no other reason.
1. Once rods are inserted into rodends, arrange hole side up between a clamping surface.
2. Clamp 'em down.  I'm using a cushion to insure that every rod is inserted all the way.
3. Drip one drop of superglue into each rodend.
4. Let dry.

 Next is simply tightening nuts and bolts.

1. For the first end, the sequence is:
1. M5 by 10mm bolt
2. rodend plastic
3. M5 washer
4. metal rodend.
2. Tighten it all down, keeping the rodend planar to the bolt insertion hole.
3. For the second end, the sequence is:
1. M5 by 20mm bolt
2. M5 nut
3. M5 nut
4. Metal Rodend
4. The reason for the two nuts is for fine length adjustment.
1. The second nut locks against the metal rod end, holding it at a certain distance.  This should be adjusted using a gauge to ensure that all rodends end up being 375mm long.
2. Once the length is adjusted and locked in, tighten the first nut against the plastic to keep it from rotating/shaking.
5. Repeat these steps for the other six rods.

Important:

Installing these rods is exactly like installing the other ones, but you should ensure that the bolt insertion holes are facing outwards - that way you can tighten the rodends or adjust their length without dismantling the entire bot.

Calibration!

I've been working away on the printer; figured I should write up the calibration routine, mostly so as I don't forget it.

This is assuming Repetier Host and Repetier Firmware.  The same techniques work with Marlin and Pronterface, but you'll need to modify the variable names a smidge.

Printer Height

1. Set the Z max length.  Mine is 449.65
1. First set the Z Max to higher than your z (in eeprom or firmware).
2. Home the printer, dial M114 - this should spit out your Z_MAX_LENGTH exactly.  If it doesn't, check that the most current firmware is on there, and that the eeprom values match.
3. Lower the hotend - either send G0 Z100 down, or click the Z Down.
1. Repeat until a piece of paper can just slide underneath the hotend.
4. Send M114 - it should be X0 Y0 Z<value>
5. Your Z_MAX_LENGTH is the old Z_MAX_LENGTH minus the current Z<value>.
1. Write this into the firmware.

Ok, so now you've got the max height down, except for now it's just a convenience.  We'll be adjusting it again after we

Level the Build Plate

1. Your plate has leveling screws; the next step is to make sure that the plate is parallel to the plane of the hotends' motion.
2. In Repetier, set up four gcode scripts
1. on the right hand pane, select the 'gcode editor' tab.
2. From the dropdown, select 'script 1'
1. Script 1:
1. g28;   //home the printer
2. g0 f8000 x-133 y0 z10  //move to one of the towers
2. Script 2:
1. g28
2. g0 f8000 x56.5 y97.86 z10
3. Script 3:
1. g28
2. g0 f8000 x56.5 y-97.86 z10
4. Script 4:
1. g28
2. g0 f8000 x0 y0 z10
3. Each script will move the hotend 10mm above the print surface; 1-3 form an equilateral triangle near the bed adjustment screws, and 4 is the center.
3. Run Script 4.
1. Lower the hotend manually 10mm - it should be just touching the bed - if not, adjust your Z_MAX_LENGTH until it is.
4. Run Script 1.
1. Lower the hotend manually until it touches the build plate.
1. If it touches at zero, congrats!  You're level.
2. If it touches above zero, increase PRINTER_RADIUS
3. If it touches below zero, decrease PRINTER_RADIUS
2. I had to add 5.25mm to my printer radius.
1. I did this 1mm at a time, recording the height each time.
2. When it stops improving, go .25mm the other way.
1. I think 1/4mm accuracy is fine, but feel free to go farther.
3. Note that PRINTER_RADIUS isn't in the eeprom - you'll need to set it in firmware and then reload the firmware.
5. The Z_MAX_HEIGHT shouldn't change during this process, but it's always helpful to check and record it every cycle - it ensures nothing odd is happening.

At this point, you should be able to print anything!  Next post will be about checking dimensional accuracy, and I promise to throw some pictures in.

Mark 4 build - step 6: Synchromesh

This step is fairly easy - attaching synchromesh cable to the rail effectors.

Vitamins:

• 3  * Synchromesh pulley
• 3  * 3mm grub screw (comes with pulley) 
• 3  * 2 meter length of Synchromesh cable
• 6  * 20mm long 1/8th inch heat shrink

RepRapped Parts :

• Everything you built so far!
• Idler guide (idler_guide.stl)

Tools : 

• 1.5mm hex key
• lighter  (or a heat gun if you have one)

Assembly:

1. Install the idler guide if you haven't already.
1. Pop out the bearing
2. Press the bearing all the way into the idler guide
3. reassemble
2. Loosen the idler slider - it should be as loose as it goes without falling out.
3. Attach the pulleys to the motor shaft with the grub screws.
1. Be sure to use the flat on the shaft, if your motor has flats.
2. You might want to grind a flat if you don't have one.  Slipping pulleys sucks.
4. Loop!
1. Slide the heat shrink onto one end of the synchromesh.
2. Form a loop, and then slide the loop end into the heat shrink as well.
3. You want about a small loop, but big enough to easily slide onto a 5mm bolt.
4. Make sure the synchromesh is doubled up for the entire length of the heat shrink.
5. Shrink!
1. The loop should be rigid, with the synchromesh locking against itself.
5. Slide the loop onto the lower bolt of one of your rail effectors.
6. Route the synchromesh onto the pulley, keeping it taught.
7. Route the syncromesh up and around the idler, keeping it taught and not twisting anything.
8. Finally, form another loop around the top peg
1. It doesn't need to be too tight.
9. Tighten the idler slider until the synchromesh is tight.
1. When plucked, it should vibrate to a low note.
2. Do not overtighten, you'll irritate your motor.
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   

Mark 4 build - step 5: Connecting the Rods

The fifth step is to take the assemblies you have already created and attach them together.

Vitamins:

• 12  * M5 flat-head screws, 25mm long.  The angled head is needed for the IGUS ends.
• 12  * M5 nuts

RepRapped Parts :

• Hotend Effector (hotendeffector_fixed.stl)
• 3 * Rod assemblies from step 4
• 3 * Rail effector assemblies from step 3

Tools : 

• 3mm ball-end hex key

Assembly:

1. Find a nice big, flat table to work on.  I think it's easiest to place the hotend effector triangle-side down and work from there.
2. Grab the hotend effector
1. Insert nuts into each nut trap on the ball ends of the hotend effector - the nut traps in the triangle are for later.
   
   
   
   
   
   
2. Screw a flathead screw through one end of a rod end assembly and into the hotend effector.
3. Tighten it down, rotate, and repeat for each rod.
3. Grab a Rail Effector Assembly.
4. With the triangle side of the hotend effector on the table, the wheel side of the rail effector should be facing up for attachment.

1. Make sure they all face the same way!
5. Insert two nuts into the long nut slot on the top of the rail effector.
6. Thread an M5 flathead screw through the rod end assembly attached to the hotend effector.
1. Repeat this step for the other arm.  Parallel arms only, please!
7. Repeat 3-7 for the other two rail effectors.

1. Insertion.

1. Remove the v-wheel sliders from the rail effectors.
2. Place the hotend assembly ball-down in the center of the prism
3. Attach each rail effector in turn.

Mark 4 build - step 4: Arm construction

Step 4 is to assemble the carbon fiber arms, six of which will connect the hotend effector to the rail effector.

Vitamins:

• 1  * 325mm Carbon Fiber Square Tube, 8mm OD, 6mm ID
• 4  * M5 nuts
• 2  * IGUS KARM-05 rod ends

RepRapped Parts :

• Rod End (rod_end.stl)

Tools :

• Saw, if your rods aren't cut to length.
• Knife for part cleaning - exacto or similar
• Long tweezers - getting those nuts in is a pain.
• Super Glue - thin cyanoacrylate adhesive 

Assembly:

1. Cut your rods to length.  The best way to do this is a chop saw, table saw or similar with a repeatable stop - making all the rods the same length is pretty critical.
1. Use a fine-tooth blade.  They're expensive, but worth it.  Mine was 80 tooth, on a 10 inch radial arm saw.
2.  WEAR PROTECTION!  Eyes, lungs, ears and hands.
1. Carbon fiber fibers flit about, and will take up residence in your lungs or eyeballs.
2. Do I need to tell you why that's bad?
3. Vacuum up all the bits BEFORE you take off your protections.
4. Alternately, you can hand-cut with a hack saw; the rod ends are adjustable enough that you should be able to shore up the lengths.
2. Clean the parts.  Where the rods insert should be OK, but the nut insertion hole is finicky.
3. Assemble the rod ends.

1. Take a KARM and thread a nut all the way down.
2. Take a rod end and slip a nut into the long slot.  The slot is wider at the base.
3. Screw the KARM into the nut in the rod end - tighten it down lightly.
4. Do this twice - each rod has two ends :-)
4. Place the rod end assemblies onto the ends of the rods.
5. Tap the rod ends into place.  The square rod hole becomes hexagonal halfway up - you want the square rods to be touching this hexagonal transition.
6. When the rod is all the way in, place a few drops of cyanoacrylate in to hold them in place.
7. Repeat for the other 6 rods.
8. Align the rods - I did this by inserting threaded rod through each rod end eyelet.  Adjust the rod ends 1/2 turn at a time, then tighten them down.

1. Accurately measuring this length is crucial!
2. Making sure it's the same length for each rod is also crucial!
3. Write down your length, the firmware will need to know about it later.
4. 400mm even is the design length with the given parts.
5. 
   
   
   
   
   

Mark 4 build - step 3: rail effector assembly

By now, you have the rough outline of your printer, and even some motors mounted - the next step in the build is to put the rail effectors together, get some linear motion going.

Vitamins:

• 3  * Delrin V-wheel kit (openbuilds)
• 4  * M5 Round cap screws, 25mm long
• 4  * M5 nuts

RepRapped Parts :

• Wheel slider  (https://github.com/paenian/bertha/blob/master/wheel_slider.stl)
• Rail effector (https://github.com/paenian/bertha/blob/master/rail_effector.stl)

Tools :

• 3mm Ball-end hex key
• Knife for part cleaning - exacto or similar

Assembly:

1. Clean out the nut trap and cut away the onion skin from the Wheel Slider.
2. Assemble the Delrin V-wheel kits - note, the metal shim goes between the bearings - it's not a washer.  Don't put the nuts on yet.
                                                
3. Insert the lock nut from one wheel kit into the Wheel Slider, then bolt on one of the wheels.
4. Clean out the nut traps and cut away onions skins from the Rail Effector.
5. Insert the other two lock nuts into the outermost nut traps
6. Insert 4 nuts into the inner nut traps, two on the base and two for the wheel slider.
   
   
   
   
7. Screw two round-head screws through the inner nut traps, all the way in.  These are for attaching the syncromesh later.
8. Insert and screw in the Wheel Slider.  Screw down all the way.
9. Insert and tighten the other two V-wheels.
10. Test it on the rail!  You'll likely need to adjust tension on the wheel slider. 

It should look like an android head.  Note that you shouldn't install the IGUS ends yet.

Repeat for the other two assemblies.

Mark 4 build - step 2: Prism: assembly 1

Once the triangles are complete, you can construct the uprights for the bot.  It uses 2060 extrusion with OpenRail attached.  In the future, this may change to using v-groove rail directly.

Vitamins:

• 3   * 1000mm 2060 aluminum exrtusion (misumi)
• 3   * 1500mm openrail v-rails
• 24 * T-nuts (included with openrail)
• 24 * M5 by 10mm button cap screws (included with openrail.  Be sure to specify 10mm screws!)

RepRapped Parts:

• No new parts, Just the brackets from the triangle assembly.

Tools:

• 3mm ball-end hex key
• Rubber or wooden mallet
• Knife to clean parts
• M5 tap

1. Tap your extrusions.  This isn't necessary for this step, but it'll make adding feet much easier in the future.  I tapped the center hole of each end of the long exstrusions for good measure.
2. Cut the openrail in half.  You should have 2 750mm sections.
3. Pre-thread the T-nuts through the rails.  I used every other hole.
1. Notice the v-sections interlocking.

4.  Slide the v-rails into the 2060 aluminum.  Lightly tighten a few bolts such that there's about 125mm gap at either end.

5.  Clean up the brackets - make sure that both top and bottom of each bracket is free of lips/ridges that could catch on the extrusion.

6.  Slide the rails into the idler triangle.  Carefully align the t-nuts in the brackets, and tap home with the mallet.  This step is tedious!  Go slow and make sure all the t-nuts slide in.

7.  When all three vertical beams are installed, repeat for the motor triangle.  Be sure that your colors line up!  Hint: You can flip the motor triangle to make the colors align.  You can't flip the idlers, which is why we started up there :-)

8.  Finally, loosen the rails and slide them tight against the idler brackets.  There will be a gap above the motors.

9.  Align the v-rails on the extrusion and tighten every screw.

That's me!

Bertha Mark 4 next to Mark 3.  3 looks bigger, but the print area will be about the same.

Mark 4 build - step 1: Triangles: assembly 3

The next step is to pop in the idler sliders.

• Assemble the bearing first - it goes on the raised impression, with a m5 nut on the back.  Tighten down.
• Next insert the other nut into the rectangular slot.  It should be a reasonably tight fit.
• Insert the idler slider into the idler bracket, with the bearing on the inside.
• Drop the final screw into the hole on top of the idler bracket, then through the idler slider and screw it into the captive nut.
• Done!