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Hangprinter version 3

Posted by tobben 
Re: Hangprinter version 3
June 22, 2019 09:10PM
back again with bag full of questions smiling smiley

as i said, i aim to order most of my parts from aliexpress, mostly from makerbase and trianble labs. Still as Tob's BOM asks for either too a general item or explicitly different item, Id like to confirm a few things before actually placing the order. Here comes...

1) Ramps + arduino mega 1.4/1.6 vs mks gen L
I know BOM asks for RAMPS plus arduino mega. wouldnt Makerspace's mks gen L (aliexpress) do just as well if not better though? I hear there's less hassle with it (plus i may use other hardware from them) but haven't heared of anyone from hangprinter community praising/using it.
if it may not be such a good option after all than should i get ramps 1.4 or 1.6?

2) mechanduino (clones)
makerbase, as you surely know, manufactures mechanduino clones that come hooked to nema17 42 steps stepper already (aliexpress). now, as it is a clone, it should behave the same way (although they told me some pins are weired differently). anyways, does anyone has any experience with them? would you recommend using them or would you not? (id appreciate (expert) guesses toowinking smiley

3) extruder+hotend
im looking at this triangle lab e3d volcano ripp (aliexpress) . i would like to get the whole "set 5" (need to scroll down to see the desription of various sets) which includes extreuder, hotend, motor, and fan. I read its a "good fake" as much of an oxymoron as it sounds. any voices against it?

Id be super happy if someone could get back to me with any opinion or experience. i should be fine with other bits of the puzzle for now, but really can't make up my mind on mentioned topics.

Re: Hangprinter version 3
June 26, 2019 03:16PM
Hello pvsfa!

1) The HP3 should work with any electronics that with 5 stepper drivers or more.
If you plan to use Mechaduinos/Smart Steppers, then you must also have access to i2c pins and step/dir pins. Not all electronics provide that.
Very few have tried anything other than RAMPS, so you might bump into something, but most probably not much.
I've used some RAMBO boards myself, and it was quite smooth. Just configure Marlin right, and it should work out of the box.

2) I haven't tried clones, and I wouldn't recommend them. You will run into some slight differences, and unless you're an electronics engineer, you'll have to ask for help and wait for answers... These boards are quite tricky to make right. I recommend proper Smart Stepper bought from misfittech.net

3) If you don't plan to print much with the HP, then a Volcano clone might be the perfect fit. I do recommend a proper SuperVolcano to anyone who plans to print more than just a few demo objects. The proper hot ends will typically perform much better. They will give you more nice looking prints with less hassle, and last much longer. It might be a super good clone, but it would be the first one that I ever saw. It is very very tricky to make these parts both good and cheap at the same time. If you have to prioritize because you really can't afford originals, then buy a genuine heat break, genuine heater cartridge, and genuine thermistor. You might need a genuine heater block to make everything fit as it should.

I will not be able to support you easily if you have cloned parts, as they could have a very wide range of hard-to-debug faults.

Best regards

Re: Hangprinter version 3
July 01, 2019 12:59AM
Hi pvsfa

Those extruder clones might come as a cheap ootion, but from my experience the extruder/hotend combo is a critical component where you really should invest in quality hardware. For example e3d or Bondtech. I once ordered e3d Titan clones from China and they were so badly manufactured that they were practically not usable. Since then I'm sticking with e3d. It saves you the hassle, trust me.
Re: Hangprinter version 3
July 25, 2019 05:38AM

Do you have had similar issues with print quality than I had with the last project (still going on)?
The skin was partly separated from the printed object and that caused issues during post-processing (sanding, etc.) It affected only the outermost wall, the inner walls were connected as they should have been.
Here's a picture of the crime scene. Any suggestions are warmly welcome, since I'm about to start the next project soon.

Re: Hangprinter version 3
July 29, 2019 09:47AM
Interesting! Haven't seen this issue before, at least not this much.

It would be interesting to know if the effector travelled in different directions on outer versus non-outer walls.
Could it be that the plastic trace will look different when going clock-wise versus counter-clock-wise?

Other than that, I would experiment with trying to make the nozzle mounting more rigid.

Re: Hangprinter version 3
August 03, 2019 01:47PM
The last project was sliced with cura 3.6 and the gcode wasn't as smooth as the code produced by simplify3d. The printhead jittered quite alot when printing the cura code. Also the print speed might have been a bit too high. But the biggest improvement so far has been the huge 1000 mm dia silicone heater mat, which I got installed a week ago. No more issues with first layer adhesion.

Edited 2 time(s). Last edit at 08/03/2019 01:49PM by atmark.
Re: Hangprinter version 3
August 06, 2019 04:03AM
Could it be that the plastic trace will look different when going clock-wise versus counter-clock-wise?

Yes, this seems to be the case. Could this be an issue with flexing of the line spools since their axle is supported on one side?
Re: Hangprinter version 3
September 03, 2019 02:24PM
Hello Tobben and others! A university on the East Coast U.S. is trying to build some hangprinters. Students at GMU's solar car team are trying to print a fairing for their car with one!

I'm trying to lend them a hand, but the documentation on hangprinter.org seems to be focused on a closed-loop build. They're trying to avoid buying Mechaduinos or the like, and I can't seem to find information on it. Where should I be looking?

Edited 1 time(s). Last edit at 09/03/2019 07:55PM by kenblu24.
Re: Hangprinter version 3
September 04, 2019 01:34PM

This thread and the facebook group contains most of the info. Tom's videos use closed loop. And all the blog posts I wrote before going closed-loop. Good luck with your builds!

Re: Hangprinter version 3
October 12, 2019 04:47AM
I'm currently designing a bracket for the HP4 bldc servo motor and the spool, and I wanted to share my tests so far.
The bracket is meant for the ODrive D5065 motor. My goal is to design a single motion unit, that includes the motor, a belt tensioner and the spool system in one rigid frame, which I probably am going to lasercut out of sheet metal. For now, I'm still thinking about the spool system. If you look few posts back in this thread, there was a discussion about the constant radius of the spool and how to compensate the line build up. An idea I had, was to route the line in a small groove in the middle of the GT2 spool, in the way that the belt is pressing it against the spool as you can see in the last pic.

I just tried to block the spool from rotating and pulled the line as hard as I could and it didn't move at all grinning smiley
It's still too early to say this concept works, but it is a promising start. It might be, that constant line movement is going to bite into the belt and it fails that way. You'll never know. What I'll do next is rerouting the end of the line onto a second spool, which I most likely will attach onto the same spool axle. And that spool will rotate independently from the first one. I was also thinking to spring load it, so that the excess line is always spooled up as the line moves.

Re: Hangprinter version 3
October 12, 2019 06:25AM

Independent spool units are nice.
If you can place them at the anchors (instead of having all several spools at one anchor), you will get less line flex, since there will be less suspended line in the air.

Good idea to pinch the line under the belt.
That might actually work very well =D
You could pinch it for several rounds (along a helix groove), or just increase the spool radius, if one round of pinched line isn't enough.

It might be a challenge assure zero slippage over time, since both line and belt will change properties as they get old/worn down.
Some data on that would be super interesting, like accelerating a 5kg weight quickly up and down 1 m 10000 times or something.
Using high accelerations would be interesting because the belt will flex/contract a bit when tension changes, and I don't know how it will affect the line.
Hopefully very little.

Anyways, that might be a very nice upgrade of the spool system smiling smiley

Re: Hangprinter version 3
October 12, 2019 07:00AM

I just put a heavy weight on the line and looked first if the line holds, and after I couldn't see any slipping, I bounced the whole system until the line snapped Video: testing slipping
No slipping what so ever grinning smiley

I believe the line should be able to handle 40 kg of drag, so friction-wise I can't see any issues. Obviously the long term failure rate is a question mark, but I think it might work quite well because the line isn't cutting radially into the belt. The only force is applied axially and the belt is pressed by the line by only 0,25 mm

Your idea of hooking some weight on the line and do some repetitive acceleration testing sounds very good! I'll try to set up the electronics next week. What values would you suggest for weight, speed and acceleration?
Here are also some close ups of the GT2 spool and the belt directly after the test. For the spool I used Octofiber PETG-CF.

Re: Hangprinter version 3
October 12, 2019 11:14AM
Woah, that's even more friction than I imagined. Impressive!

CF enforced plastics have a quite rough surface.
Where did the line snap?
Was it the CF that wore down the line?

Since I would be aiming for HP usage, I'd test numbers relevant to the application first.
I'd use ca 50% more weight, speed and acceleration than my HP4 prototype is experiencing.
So ca 5 kg of weight, accelerate 15 m/s² , up to 1 m/s. Use a distance of 1 m up and down, say 10k times.
That's a 3h test. You could go crazy and just let it run all night if you're feeling confident winking smiley

It would also be interesting to know if the mechanism works with pure PLA.
A spool out of PLA printed hot (say 240 C) would give much less friction than the PLA-CF in your prototype, I guess.
It would be interesting to know if it would still be enough, or if the CF is required.

Images like the one you showed would be a very interesting part of the result.
In particular, if the line does slip, I'm interested in how damaged the belt gets.
Also interesting to know if a slipping line cuts into the spool.

The mechanism is interesting in it's own right, so if the HP4 application proves to be well within limits of the mechanism, I would have done additional tests.
Like, measuring a slowly applied force up until the line breaks or starts slipping, or until the plastic spool breaks.
(Film a weight that is hooked onto a one end of a line, and pulled. Could capture both force and amount of slip/flex in one shot.)
Abruptly applied force is also interesting (requires a high-speed camera, or a weight that can store a max value).

Re: Hangprinter version 3
October 12, 2019 12:37PM
Yeah, I was quite amazed too to be honest.

The line snapped 5 mm before the knot I made to hold the weight. So the CF spool didn't have any effect on the snapping. I'm aware of the abrasive nature of CF, so it's not said that it could not happen, but in this case it didn't. I can print a new spool out of PLA, no problem. It will be interesting to test it.

Let's see how I can setup a test rig. The motion repetition won't be a big issue once I get to setup the ODrive board and Duet. Is the firmware easy to install? Then, I assume a simple gcode does the magic?

Btw, I wrote you yesterday a mail, but it's still in my to be sent folder (I forgot that the schools network is down for maintanance for couple of days) anyway, I wrote that I ordered braided PE fishing line that is two-colored (yellow/black), so it has a repetitive weave pattern, which could be used for line length readout with a IR sensor, as black plastic does not reflect IR light very well. That's why the material of black plastic can't be identified in automated recycling. Different plastics reflect IR light differently.

So, additionally to the mechanics I was thinking about position feedback via sensor readout. Whats your opinion on that? There was also some discussion about measuring the line tension. Could that be useful to integrate in the motion system? At school we have a quite big range of sensors and other electronic equipment for prototyping. You can check technIcal details at Seeedstudio Grove
You can hook these sensors very easy to arduino, rasbi, etc.
Re: Hangprinter version 3
October 13, 2019 05:28AM
Yes, the firmware should be straight forward to install. Just use the Duet2CombinedFirmware.bin you find in the repo (https://gitlab.com/tobben/hangprinter/tree/version_4_dev/firmware/RepRapFirmware), and follow standard Duet installation procedure. Gcode should to the magic, yes smiling smiley Be aware that your ODrive configuration will affect the movements. Max acceleration, max speed, step size etc needs to be configured correctly in the ODrive firmware. There's an example that matches my specific motors here: [gitlab.com] Follow the official ODrive documentation to find numbers that match your motors.

If the fishing line has any flex at all, this will affect the readings. So if the line (and hence the pattern) is stretched out, you might wind in 10.1 mm when you thought you did only 10.0.
On the other hand, since you're detecting the pattern, you'll know when you have unwound the same segment of fishing line, regardless of how stretched it was when wound and unwound.
This makes the system immune to a family of errors where flex is "stored" on the spool when wound in under heavy load.

The line will always be twisted though. How would the system cope with that?
And how would it behave if the line got very slack? Could we route the line through a very thin transparent tube, to keep it from kinking under the sensor?
For such a sensor to be useful, it would need to be very fool proof since so many weird things can happen during a print.

Re: Hangprinter version 3
October 13, 2019 05:35AM
Let me do a dedicated thread to this topic, and we continue the discussion there grinning smiley
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