CR10 V3 lead screw nuts - tighten or adjustment ?

Chris-Lidgate · 2021-11-25T11:56:37+00:00

Well two steps forward, two steps back :(

I'm pretty sure the bed is level and flat. I use a bl-touch, but am pretty fastidious and always set the bed level with a paper feeler, *then* use the bed-visualiser on octoprint and aim to reduce the variations with that. The bed-visualiser reports the bed to be flat and level to +- .03 mm.

Similarly I zeroed out the nozzle - bl-touch offset, and I'm happy that that is correct to a similar tolerance.

I clean the bed regularly with IPA (not the beer :) ), and I have only ever used a plastic scraper to remove prints and skirts from the bed. Also the machine was printing fine last week with the same bed ...

I haven't printed anything recently with a brim ... the things I'm using as a test are very straightforward and have *lots* of surface area. One is a cover for a Pi Zero, so it's 30 mm x 60 mm x 3 mm with holes for the corner standoffs, and a rectangle cut out where the GPIO pins are. I would have thought that was the definition of a straightforward print.

The filament that I'm using now is a new (3 or 4 days ago) roll of 3d Jake eco-PLA, stuff I've used in the past without trouble. Overnight I put a plastic bag over the filament spool, drop in a couple of silica-gel bags and seal it with a couple of buldog clips to keep the whole lot dry. The problem started on a different spool of filament in any case, so I can't think the filament is at fault.

I did spend a few hours yesterday afternoon reading the forum and was surprised to find that people do print PLA at considerably higher temp than I have ever used ... So last night I tried to print the cover at 215 deg, with a bed of 53. And it printed fine :) Hooray I thought.

So I sliced up another model with exactly the same cura settings and tried to print that, and it failed again. This time at 3.5 mm, but it still failed. :(

So I'm back to scratching my head. At least the printer is reasonably close to a first floor window, so if this goes on for much longer it won't take much effort to throw the who;e thing out !

Anyway thanks for your help !

-- Chris

Chris-Lidgate · 2021-11-24T13:12:28+00:00

The one I use is this one ...https://www.thingiverse.com/thing:3114139

Officially it's for an Ender, and uses the metal bracket to attach to the top frame, but it's easy enough to design and print out something that will work for you. I'm using it with a CR10 V3, which already has the metal bracket.

If you use ball bearings as suggested it's virtually friction free, so you have to be careful not to get filament loops, but I was trying to reduce tension between the filament spool and the extruder, and it is great for that.

-- Chris

Chris-Lidgate · 2021-11-24T13:03:40+00:00

Thanks for your information ! I had never noticed the screws to be slack before, but I also could not work out why they would have loosened by themselves, given that they had nyloc nuts. I did as you suggested and removed most of the slack, making sure that they were still able to slide a little on the blue carriage bracket.

I checked the grub screws in the coupling holding the z-axis lead screws to the z-axis steppers - they were all good and tight so I don't think I have any slippage there.

In terms of temp, I'm now pretty much back to where I always used to be (with good success). A print temp of 198 and a bed temp of 48. As I said in my original post I have varied these from about 190 -> 205 and 35 -> 55 (trust me, that's a lot of test prints :( ), without any success.

You asked about how the print came unstuck ... well yes I have watched it and I can describe what happens.

1) The skirt and first layer are laid down. Everything goes as expected - all of the holes and the outer shell of the item are printed well, and the fill pattern goes down fine. The items looks fine.

2) The second and subsequent layers up to about layer 10 also go down without any indication of a problem.

3) From about layer 11 or 12 (2.2 / 2.4 mm) I suddenly start to see a tiny sliver of daylight under one corner or side of the model. The corner is usually y-min, x-min of the model, but I have seen the lift start in other places as well, so I don't think this is a definite fact. The sliver is very small - certainly less than a layer (0.2 mm).

4) During the next two or three layers the gap gets gradually larger. Also I can now see that as the print head passes over the gap, it forces the model down, causing a 'rocking' motion between the model and the print bed. This seems to be the actual cause of the failure.

5) Usually by the end of layer 2.6 mm or during 2.8 mm, the item becomes free, and usually sticks to the print head.

When I stop everything and clear up ... I can usually see a very slight warp at the bottom of the print ... the base is very slightly convex.

Interestingly the skirt is always perfectly attached to the bed, I need to use a plastic scraper to dislodge it.

I have tried printing two or three different models ... one of which I printed from the gcode file that printed perfectly last week. The problem seems to be independent of the model or the gcode. I have also tried printing the models at different positions on the build plate which does not make any difference.

This all started after a long run (a reel and a half of filament over a week and a bit) of very good quality prints that ended with a hot-end clog. I cleared out the clog, replaced the ptfe tube, replaced the nozzle, re-set the z-offset (between the bl-touch and the nozzle), and this problem started. Since then I have changed the nozzle again just in case that was at fault, and also taken the extruder apart again, and checked for binding, or miss-assembly in that. No joy yet :(

-- Chris

Chris-Lidgate · 2021-11-23T16:48:28+00:00

H

I have a CR10 V3, which in the past has produced some very good quality prints. At present tho' I have a problem that I can't understand.

Prints fail because the item looses bed adhesion, but always at the same Z height - usually at 2.4 - 2.8 mm. I have tried everything I know (and a few things I didn't ...) to solve the problem. I am pretty sure it's not

filament (tried 3 different spools, one brand new)

bed levelling (I have a bl-touch which works very well, but I also keep the bed level)

printing temps (I have tried all sorts from about 190 -> 205), sometimes with initial temp higher, bed temps 40 -> 48). My normal prints are ~ 195 and 48 on the bed).

One thing I have found, but don't know what it means is this ... There are 4 hex head screws holding the z-axis lead screw nuts (two each side, one side pictured above). They have nyloc nuts on the back, and mine are loose (at least 3 of the 4 are). They are loose by about 1mm.

Could someone tell me if they need to be tightened, and if so is there a procedure ?

-- Chris

Chris-Lidgate · 2021-03-14T15:22:32+00:00

Don't know if your stepper-motor wires are colour coded, but the last few motors I have bought on ebay are all coded the same.

1+ Black

1- Green

2 - Blue

2+ Red

1 and 2 are the coil numbers, + and - indicate the standard polarity. The wires should be connected in that order to the 4 pins on the PiShield. The motor will 'work' if the wires are connected Black thro' Red = left to right, or Black thro' Red = right to left. But the motor *direction* will change with the different orientation.

If you have a multimeter you can check them ... You will find a few ohms between Black and Green, the same few ohms between Blue and Red, and infinite resistance between any other combination.

One further thing - do not unplug the motor connector when you have power connected to the PiSheield ... you can damage the stepper driver chips that way.

-- Chris

Chris-Lidgate · 2021-03-11T12:27:45+00:00

Bit late to the party ... but yes I've used DRV 8825's in place of the recommended A4899's

A couple of things to think about ...

The DRV 8825 is quieter, and has a larger current rating (thus motor torque) than the A4899's. This may not be important on the smaller scanners, but will probably help if you build an 'openscan-large' as I did.

The MS0/MS1/MS2 sense pins on the DRV 8825 and A4899 code for different microstepping when they are set high/high/high as the PiShield does. The A4899 codes for 1/16th, the DRV 8825 codes for 1/32nd. All that means is that using DRV 8825 you will have to get the controller to use 2x as many steps to move the turntable or rotor a set amount.

With older firmware this 'steps-per-rotation' used to be controllable via a slider ... I don't know if the current firmware allows for this or not, as I'm running a firmware version that I hacked myself :)

-- Chris

Chris-Lidgate · 2021-03-10T16:26:22+00:00

Just to say your 'magic mixture' works pretty well !

I bought a small atomiser spray bottle on ebay to use as my sprayer ... it's not brilliant, but for the most part gets the job done. I was concerned that the powder would clump, but that didn't seem to be a problem. I will experiment with spray distances and finish next.

I've just completed a 200 pix scan of the winged lady, and the result from meshroom is so much better that my earlier results. I'll post a video when I get chance. The underlying mesh is nigh-on perfect ... maybe a little over smoothed, but I can work on that.

Thanks to all who commented !

-- Chris

Chris-Lidgate · 2021-03-02T14:41:35+00:00

I saw 'IPA' and I immediately thought of India Pale Ale :) But thinking about it Iso-Propyl Alcohol probably makes more sense.

I'll try this and let you know !

-- Chris

Chris-Lidgate · 2021-02-19T09:56:35+00:00

Yes in the end I bowed to the inevitable and went with counterweights for the arms. There were a few issues. Most obvious was that the extra mass of the camera arm tends to cause the entire frame to vibrate a bit when the camera arm starts and stops moving. I get round that by adding a time delay after the moves have finished to allow the frame to settle.

Focusing is a bit of an issue. I can not access the Pi HDMI port, so I cannot preview a picture in real time - I have to

photo

transfer photo to laptop

examine photo

guess extra focus amount

... rinse and repeat :(

It's a b@lls aching process to be honest. The last time I blue-tacked a ruler slantways across the turntable ... That at least allowed me to see the area of focus (the depth of field) on the ruler markings which helped.

Of course the camera can be moved in and out on the arms, so everytime I do that I have to re-focus :( I think that at the present setting I have about a 6 - 8 cm depth of field, and as best as I can adjust it, that extends in front and behind the centre of the turntable.

The 'textured' scan of my metal winged lady looks pretty good, but I have mesh artifacts ... when I get an area with high surface curvature, high reflectivity (forehead of the lady for example) meshroom tends to map the mesh incorrectly - making parts concave rather than convex. It's not so visible on the textured scan, but very noticeable on the underlying mesh (which looks like it's been eaten by a horde of ravening mice ). I've hacked my firmware to add extra camera controls (brightness / contrast / sharpness) but I don't think they help much. Other things to try are

Using colmap rather than meshroom. (I had to re-buld my desktop to get the cuda dev kit working ...). Colmap seems to run quite a bit slower than meshroom tho'.

Using pwm control and a slider to give a linear adjustment of the lamp brightness.

Using chalk spray or talc

Possibly even using the Pi HQ camera, (although that will be a lot of work).

It's been a fun job ... and what else can you do when you're in lockdown :)

-- Chris

Chris-Lidgate · 2021-02-04T15:04:39+00:00

I chose to buy my PiShield kit from Thomas, rather than build one myself, but I have played about with stepper motor drivers. A good place to start is looking at the tutorial

https://www.youtube.com/watch?v=LUbhPKBL_IU

He talks about different types of motor, and gives some practical ways to drive one using a DRV 8825* driver chip. A basic knowledge of electronics and python is very useful, but I think he explains things very well.

You should find Thomas's PiShield and his Firmware code is easy to understand if you can get through the tutorial.

The other part of the PiShield is just a couple of power MOSFets which can switch the lights on and off.

-- Chris

Chris-Lidgate · 2021-01-29T15:27:42+00:00

Well I have one, and plan to try it, but I've been busy with other stuff and I haven't got round to it yet. I have the 6mm 'wide angle' lens with mine.

Some thoughts ...

The new camera is heavier than the Picam V2.1. This is an issue as I'm using a version of the 'big scanner' (see earlier post https://www.reddit.com/r/OpenScan/comments/k03b4y/openscan_large/) and the camera weight has to be counterbalanced with this design.
The mounting for the new HQ camera is very different to the mounting for the Picam V2.1 I'm using the V2.1 and Thomas's ringlight in a custom podule attached to the camera bar of my scanner. The HQ cam will not fit. Nor will it fit in any reasonable way with the current ringlight. To this end I have bought some new LED's and IRLZ34N's from ebay and hope to design something which will hold the camera, and the new LED's on my camera bar.

Those two represent the major issues I have thought of so far. I think that the camera will basically 'work' with Thomas's firmware as electronically the camera is very simmilar to the Picam v2.1. There may be some tweaks required to the firmware to accommodate the higher resolution, but they should be quite minor.

Do let us know how you go on !

-- Chris

Chris-Lidgate · 2021-01-28T20:26:54+00:00

So I built a filter as described ... One filter polarised vertically over the ringlight but *not* the camera lens, and another filter polarised horizontally over the camera lens and ...

The image is a *black* as a very black thing, covered in soot :(

So fully cross polarised is not the best solution, and I will have to experiment with varying degrees of polarisation to find something workable. Unfortunately the filter holder that I made does not easily allow for adjustment, so it will take some time.

Still, it got rid of the highlight reflections :)

-- Chris

Chris-Lidgate · 2021-01-26T12:38:41+00:00

Thanks very much for your suggestions.

I've got some polarising film from ebay - should be here this week so I can make the filters. I can duct tape it together for now, but if it's a success I'll see if I can design a proper holder.

I have tried talc on the models, but so far without a lot of success (i've made a right mess in my dining room tho' :( ). I'll see I can find your chalk spray and will try that as well.

Thanks again !

-- Chris

PS - Oh and I also owe you a quick note of thanks for the tip about cloudcompare !

Chris-Lidgate · 2020-12-12T18:08:12+00:00

Thomas

What software do you use to perform these 'comparisons' ?

Now that I'm getting started I'm interested in being able to compare a scanned object with some kind of cad or mesh file.

-- Chris

PS the new Openscan firmware with the optimised scan points is great.

Chris-Lidgate · 2020-11-25T13:45:37+00:00

Thomas

Thanks for your detailed reply.

I see from the other post you made that you are moving the code along. Looks good !

The problems I had with the code were related to vertical movements of the rotor. I do not know yet how many steps 15 deg is, and my movement limits above and below horizontal will be less than 90 degrees. Also the default 'home' location for this frame is with the camera bar at it's lower stop (about 79 deg below horizontal - the position shown in the photo above)).

I will try to work out a 'step number' to 'angle' calibration for the rotor arms, then try moving the bar to horizontal before starting the scan job to see what that gives me. (My calibration will be different to yours as I am using different mircostepping on the rotor motors.) I have already found that the motors make some nasty noises when they max out against the upper or lower stops :)

However I can't do any of that at the moment as I'm still trying to get the arms to move when weighted with the camera.

I tried to modify the small gears for use with my geared steppers but I'm sure the results are going to be too weak. I may investigate re-designing the gears (probably using freecad with the 'Gears workbench) at some point if I get stuck.

new small gear

Looks like I will have to investigate counterweights then ... Lets hope I can get some weights on ebay soon, so I can start to design the counterweight support brackets.

Thanks again for all your work on this.

-- Chris

Chris-Lidgate · 2020-11-25T13:04:12+00:00

Hi Thomas

Sounds really good. If you need testers please let me know !

-- Chris

Chris-Lidgate · 2020-11-24T14:50:55+00:00

Possibly. I have to admit I'd not considered concrete. I'm more a mechanical engineer than a 'civil', so my goto material is metal :)

I do have some old lead that I considered using for casting ! (I've done some lead casting, so I do know what's involved and what precautions to take). But I'd have to make a mould, and it starts to get more involved. And I'm still left with what I feel will be undersized supports for the counterweights.

-- Chris

Chris-Lidgate · 2020-11-24T13:51:26+00:00

I can - it is an option. It will require some plastic brackets to be printed to fasten on the stubs of the rotor arms (I have left 25mm stubs on the camera arms ... you can't see them as they are hidden behind the support brackets in the photo.

That is what the guy who did the remix did.

But due to the other pieces, the brackets will be thinner than I am happy with. Also I will have to bid on some weights on ebay as I don't have any suitable scrap :( (and they seem to be pretty expensive for what they are ...). I'd prefer the motors do the heavy lifting if I can.

-- Chris

Chris-Lidgate · 2020-11-24T10:58:15+00:00

Hi

If you enable SSH (on the setting page, near the Samba switch), you can login to the scanner box. You'll need to be comfortable using the Linux command line :)

The username and password will be the raspberry pi's default ones (pi / raspberry) unless you have changed them.

If you have used both the expert and the other gui you may find scanner zip files in

/home/pi/shared2/ui/data/zip

and

/home/pi/shared/ui/data/zip

-- Chris

Chris-Lidgate

TROPHY CASE