Assembly tips?

Little Monster hardware issues, upgrades and configurations
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Eta power
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Assembly tips?

Post by Eta power » Mon Aug 28, 2017 5:34 am

Hi all,

I recently purchased and have yet to receive my Little Monster kit. However, after some research I discovered that there are a few assembly tricks that get mentioned, but never really get expanded on. It is said that a wise man learns from the mistakes of others, and I would like to do that, lest I break my latest toy.

I have read that a preforming a PID autotune on the hot end is a good idea, and saw that Charles mentioned that the flying extruder should be mounted higher than is specified in the instructions.

Any help is appreciated, thanks!

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Re: Red's Tevo Little Monster Assembly Tips

Post by Redemptioner » Sat Dec 23, 2017 11:20 am

Here are my tips.

1). Make sure you remove every bolt (other than the ones holding the bearings in the carriage as they have a lock nut), add some threadlocker and put back in. Just do one bolt at a time. For the bolts used during assembly use permanant threadlocker (red) on the bottom ones and the ones in the carrage (holding the straps). For everything else use medium strength threadlocker as you may wish to remove this at another stage. I can't tell you how many people have bolts come loose and cause problems on their 3D printers. An I do mean do EVERY BOLT (except the ones in bearings).

2). Check the belts before assembly, just about every one of these comes out with a twist in the belts that requires you to take the zip tie off one end and correct the issue (Great QC on this guys). Buy some decent mini zip ties from your local electrical parts outlet and replace every zip tie holding the belts on as they are rubbish and will break the first time you want to tension the belts (don't be tempted to use the ones that came with the kit). Add 4 zip ties to each belt which will double the number of zip ties ensuring they won't come loose and keep them as close to the carriage as possible, try not to leave any excess belt sticking out after the last zip tie (just one "notch"), cut off any excess if you have to.

3). Take some paper tape and write a small label on it and wrap it around each wire on both sides of connector, it only needs to be like 10pt size text, and only needs to be a letter and number (i.e. F2 for fan 2, T1 for temp sensor 1 etc) and remove the large labels that are on them already.

4). If you have a soldering iron and some small heat shrink, then cut all the plugs off the print head cables one at a time (except for heater element) and solder them together. REMEMBER the BLtouch wires are white to white! This is a lot of "stuff" swinging around and puts additional weight and momentum on one side of the print head. Add a couple of little zip ties to hold the cables against the effector where they are coming up from each side, in other words tie them to the effector. While you are there you can cover them with a little plastic wire mesh if you want it to look nice. and hold them all together, otherwise just add a few more little zip ties.

5). Give the inside of the rails and bearings a small/thin coating of silicon grease, this will make things last a lot longer and everything run a lot smoother.

6). Add the small brass standoffs for the optical end sensors to the top plate before bolting it on, these can be hard to get to once the top place has been added and bolted up. Also make sure all the little M2 grub screws are in the carriages to make these sensors work, these are not put in very far and often fall out in transit. If any are missing you can cut the head off a 10-15mm M2 bolt, just ensure it is black (may require you to paint it).

7). Install the LCD panel and rout the cable up through the top and tape temporarily to the right side. The main board has to go on top of this and have the LCD connect to the right side of it, it is covering the hole the ribbon cable comes up through when you install the main board so better to get the cable in place now save you having to unscrew it once you get to LCD install in the instructions.

8). Before you install the control board, go down to your local electronics parts store and buy a dust cover you can easily pull out and clean (one to mount on the outside of the box). You can put this on the inside as the box opens pretty easily (this will also increase the airflow by about 20%) but it means you are constantly bending the wires to get in and clean it and you are also less likely to clean it as you won't see it. With the dust cover in hand, remove the fan and flip it over so it pushes the air into the box rather than pulling it out of the box. This will substantially increase the cooling of the board and drivers (like 5 times more cooling). It might not be such a big deal in cooler climates but here in Australia it is a must or suffer the board overheating and crashing on a regular basis or having to run the aircon whenever you run the printer longer than 30mins.

9). When adding the idle pulleys, add some Teflon tape to the bolt thread that holds them on, about 10 layers is enough. You want them to go on snug, if you added a little too much (won't push on) just twist the threads in your hand to squash the Teflon tape down into the threads more. They have used a bolt with threads for a bearings which is simply the wrong thing to do, it allows the bearing to move on the bolt which is bad. When you then tension up the locknut to hold the pulley on, do it slowly and once it is near down on the bearing, hold the pulley and spin the aluminium part, it should spin freely and without and vibration. Keep going a 1/16 turn until you feel the small amount of vibration from the bearing bearing squashed (it will be very noticeable), then back the nut off a poofteenth and check to ensure the pulley can't move back and forth on the bolt. Take you time on this as going to far will ruin the bearing, not going far enough will cause additional wear and noise in your prints. Also worth mention here that these pulleys are too large in diameter (so are the ones on the motors), this causes the belts to rub on the bearings up in the carriage, suggest changing them out as soon as you can for smaller ones to bring the belt in closer to the middle of the rails where they will not rub.

10).Put the glass plate in last thing you do. I suggest knocking the plate out of it's holder and redoing the glue with some decent black silicon glue. If you don't you will get a couple of prints in and it will come out itself when you go to pull a larger print off, then you will have to pull things apart to fix. If you do this before assembling anything else it will be dry enough to put back in when you finish everything else. Then just heat the bed up to 60 degrees C and leave it for an hour or 2 to fully cure. Alcohol or metholated spirits will clean up any excess silicon.

11). When you add the plate cover material, just peel a small amount of the paper back on the back section (like 10mm) and then cut this off. Then you can align the whole cover from the front and the small exposed sticky part can then hold the "alignment" in place while you remove the rest of the backing (remove the backing from the front, don't try and remove it from the back where you cut it off). Use a credit card or some other small straight plastic edge to slowly work the back on towards the front (from side to side) ensuring there is no air bubbles underneath.

12). Put a paddle pop stick in the centre of the bed before you turn it on for the first time in case of BLTouch failure, this will prevent a hole in your bed and the wood will absorb the impact. Hit calibration and if the print head does not crash into the bed then you can unplug the printer and remove the stick and run through full calibration. Once calibrated then you will need to set the Z height offset.

13). Setting the Z offset can be a pitter if you don't follow these instructions to the letter. The ONLY way to do this is at the firmware level, do not G-code this at the part or the slicer as you will end up with problems later. Go into the large SD card that came with the printer and unzip the file "Pronterface". then follow these steps
- Turn off printer
- insert USD cable in printer
- Turn printer on
- insert usb cable to computer
- open Pronterface
- Connect
- in the box down the bottom right type G28 and hit send(this will send printer home)
- Then Type G0 Z0 hit send(this will send printer to where it things the lowest point is)
- Then take a sheet of paper and put it under the print head
- In Pronterface you will see the controller which kinda looks like a dart board, on the right side there is a Z+ & Z- scale. Hit the 0.1 on this scale, you should see the print head move up a poofteenth. Now there is a grey bar below the "0.1" button then another box, this is the 0.1 down button it just does not have a label. Use this box ONLY, do not click on anything else or you will pay the price. With the paper under the nozzle, click this one click at a time and check to see if it has touched the paper. It will probably need to go down about 15 clicks but take your time. You want it to go down till it barely grips the paper and no more.
- Once the head grips the paper go up one click (button labelled 0.1), then try moving the paper. Go up and down till one click down means the paper is barely being gripped and one click up means no grip at all. You need to be 1 to 2 clicks above it gripping the paper.
- Now you have it where you think is right, go back down to the bottom right box again and type M306 Z0 and hit send (this will save the setting)
- Now type M500 in the same box and hit send (this will force it into the Firmware permanently).
- Now type G28 (sent home )
- Unplug the printer
- Remove USB cable from printer and close Pronterface

You are finished, this now will allow you to run the calibration again anytime you want but it will keep the offset you just worked out. This way you can lay down different print surfaces and just hit calibration and not have to deal with this offset again and you won't have smashed the print head into the bed causing holes and damage.

14). Clean the bed with alcohol (get a spray can of it) and print a 20x20 calibration cube with a 15 line skirt to make sure things are working, pay particular attention to the first layer, you can stop the print after it starts the infill which is about 4-6 layers up. It should not be balling up (first 20-30mm is ok while it starts extruding) and should not be squashing it out (which will have a ruff side and look thin). If it it does not stick well then go back and do the step No.13 and lower another 0.2 (probs will require more if you could see it balling or not sticking but start here), if it is squashing it lift it 0.2, if lifting 0.2 stops it sticking well then go down 0.1 but it is more likely you will have to go up more. Once you adjust it and you do another bottom layer print and it looks good, then go through and run the auto calibration again, go to home then turn off printer. Turn on again an run a full 20x20 cube print and see how you go. I suggest changing the layer height to 0.1618 and the nozzle to 0.4

15). Head over to the upgrade page and print the suggested first prints to add the upgrades needed to keep the printer running well, especially the bracing clips and filament detector/guide. Don't be tempted to print more than the one 20x20mm cube until you do, trust me :D

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Re: Assembly tips?

Post by Xerxes » Sat Jun 23, 2018 6:20 pm

Great post.

I'm about to cut off the connectors to the hotend as well, they aren't worth the trouble.

Another thing I would recommend is remove the thick 10mm wide tube casing over the wiring to the hotend, and replace it with mesh, or something thinner and more flexible. I've had issues with it coiling up in large circles and ending on top of the carriage when returning to home, causing a sort of crash by blocking the carriage from the top of the printer. 99 times out of 100 it was fine like this and pushed the cable out of the way, but if it rotates so the slit in it is facing the carriage it can (will) hook on the set screw that is supposed to enter the z limit sensor and wreak havoc.

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Re: Assembly tips?

Post by Xerxes » Wed Oct 17, 2018 11:25 pm

Update; I did remove all the connectors and it's a massive improvement. I use a bowden setup now 60cm.. I replaced the wiring with my own cable 28awg and 26awg for the heater, and wrapped it on the bowden tube with spiral cable sheath.. Really neat now..

I will write this up in a thread soon..

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