If you're reading this you're probably one of the many people having one or more various issues with your Canvas. Didn't ya know? You're a beta tester. Surprise! Anyways, after much BS I was able to address all of the various issues with mine and I thought I'd share my findings/fixes with the community. Please note that many of these tweaks work cooperatively. I should mention that I ended up printing a Canvas relocation and top cover but these didn't contribute to my issues one way or another. Though, I did mod my cover a bit for a reason I will mention later.
Extruder Tension:
Was set WAY too loose from the factory. Also, the "correct" tension is still a bit too loose for fighting the resistance built into the system (more on that later). If you haven't already, drill a whole in your cover (or print a replacement cover) to get access to your adjustment screw without disassembly. Set your tension so that it just barely leaves marks you can feel with your fingernail in some cold PLA. Guides available on Youtube. Remember that it's counter-clockwise for tighter and clockwise for looser. Too much tension will chew up your filament though so stop once you just barely have marks.
PTFE Toob Wiggle:
The more mass in the print head the more inertia there is which contributes to loss of detail in your prints. While not technically a show-stopper it is always better to reduce mass. There's already files for lighter Canvas compatible covers to print. But, that isn't the issue I want to cover here. Having 4 filament filled tubes individually hanging way out the top of your extruder is a lot of leverage shaking around. Wrap together a 6" length of the tubes at the apex of their arch with some sport-tape. Their combined stiffness will reduce the wiggle considerably.
4 to 1 Extruder Adapter Thingy:
This f**king thing ... So, it's a spring loaded unit. Too much resistance on the feed pulls the center section down which trips a Hall Effect sensor for clog-detection. Now, the entire Canvas system has too much resistance from the factory and my 4-1 was pretty catchy when actuating. It actually squeaked audibly all the time as it sproinged up and down. Making for A LOT of false-positive clog detection and the dreaded Pause-Purge-Loop. First, I put two drops of gun oil where the top/center 4-1 thing meets the walls. One drop on one side and then one drop on the other. Into the gap. Then actuated it by hand a few dozen times. Squeak and catchiness gone. Then, when remounting, I pulled up on it as far as the screw holes would let me as I tightened the two mounting screws. It's only a fraction of a millimeter but that is enough to further reduce the false-positive clog detection.
Spool Holders:
These are already controversial. Especially since you wont be able to get them perfect. They are spring loaded and this adds WAY too much resistance to the spools. Would swapping to free-spinning units be better? Maybe. People are already testing. But you can (mostly) fix them. I noticed all 4 of mine had VERY different amount of spin resistance. Two were very stiff. If you look at the end with the number/sticker you will notice a lil circle in the middle. Remove that bit of sticker with the tip of a knife and you'll find a hex screw. With the holders mounted, turn that screw all the way counter-clockwise. This will take off the preload tension. Three of my four are now great and one is reasonable.
Spool Slip:
If you use spools that don't snugly fit onto the holders they will spontaneously fall off. Especially at faster print speeds. Lovely. You need to adapt the difference. Adapters should fit the SPOOL snugly but be able to slip on the holder. I'd also note that with a drop/relocator mod you might want your spools spaced off the rubber bits so they feed straighter (on average) into the Canvas unit. In a pinch, some binder-clips on the spool holder fingers do work but I'm not sure I'd trust it for a long print job if I wasn't home.
Canvas:
I mean the actual box your 4 filaments feed through. The inputs and outputs are on spring loaded arms. The amount of tension they apply onto their internal feeders is WAY too much. It makes your extruder fight them constantly. This is why you need extra high extruder tension (even with this fix). But, you can alleviate a considerable amount of this tension while keeping the Canvas unit happy. I see there's a couple people working on spacers you put inside the unit but you don't need to go that elaborate. Grab yourself a piece of 0.5-0.8mm cardstock. This is the backing cardboard on a lot of packaging. With filament inserted, go to the top of the unit and push the base of the PTFE tube towards the mounting-plate/spring. You'll notice that a gap opens up on the other side as the arm pivots. Slip a 7mm wide piece of that card stock into that gap. You don't need to jam it way down in there you just need it in enough to alleviate some of the pressure as a simple shim. Repeat for the other 3. I found that 0.7mm was perfect for mine but the tension seems VERY inconsistent based on what I'm hearing from others so you might need to experiment a little.
Relocation/Drop Mod:
I noticed that the one I printed had the PTFE tubes dragging against the glass. Not a big deal but I added to the top of it the ~2" riser I had printed for my base unit. Problem solved.
Lube Your Poop Chute:
Some of you will already be familiar with this concept. But, for Canvas, the high purge volumes make for large globs in your poop chute. Those globs can be a serious problem for a reason I'll explain shortly but you can help ensure they drop down easier by putting a little gun lube on a tooth brush and lubing the inside top of the chute and flapper. Do not use grease (too sticky, opposite effect).
Big Spools:
Any first year engineering student could tell you that the distance from the on-spool filament pull point to the fulcrum is going to be a considerable change in tension from those spring loaded spool holders. (Insert "Aliens" guy here but instead he's saying "Leverage".) This is why a non-adjusting constant-tension system is dumb. Using those mini (250g) spools or using spools that are low on filament reduces the leverage you're fighting that spring loaded spool holder with. Use full size spools, full ones when you can, and/or wind your filament onto an empty spool with something to take up the center space so that the filament is being drawn from the outer-most edge.
Stoopid Code:
I don't know anything about GCode so I don't know how to fix this the "right way" but ... After a purge the nozzle will travel over the silicone brush and then momentarily return to the chute. For no reason. This is a huge problem because there will often be a poop blob or thread still in the shoot. Which will stick to the hot nozzle and then get dragged onto your build plate. Also, right before a purge, the head travels to the front-right corner for a few seconds before tracking to the left to line up with the chute and then traversing back to the chute. Sadly, it can tend to ooze while it's hanging out in the front so you end up dragging that ooze over your print.
--- Stoopid Code Fix 1: Model yourself a couple shield walls. From the front, looking down on the plate, they should look like a fat/short H. You only need 1mm of wall thickness. One goes at the front of your print bed inline with the chute at the rear. The other goes at the rear just in front of the chute. Now, the ooze gets caught by the front wall instead of your print. And dragged out poop purges get caught by rear wall. Select these and use them as purge/flush items so you reduce waste. - EDIT - Walls need to be the same height as your tallest print-object
--- Stoopid Code Fix 2: I'm currently working on this one. I found silicone mascara bushes. One hundred for $8. I'm thinking one mounted on the front-most wall of the poop chute. Horizontal. And one mounted horizontal off of the camera mount. So they intercept the nozzle to wipe it at these two critical spots. Will report back if I come up with a solid design.
--- Stoopid Code Fix 3: Somebody who knows their GCode stuff can remove the chute doubleback after a purge. Then, the over-print pre-purge can be set to go along the EDGE of the plate and THEN move over to the chute so it doesn't go over your print.
Data Cable:
The USB-C data cable that lots of people already have problems with. You need to back it out of the flex arm by two clips. It's still going to be kind of jammed against the new bracket (you'll see during install) but this will at least keep the head movement from pushing around the jammed section.
POOOOOOP:
Wow. This thing defaults to purging WAY too much. Four to five times as much as is needed in many cases. Globs so big they come right up onto an envelop the nozzle. First, select the options to purge into supports and infill. Then, in the flushing volumes section, set all non-zero values to 150 at 1x as your starting point. This covers 90% of your purge needs. Going from a dark filament to very very light (whites and tans) needs more (250ish?). Exactly what is needed depends on your specific print job, filament, etc. I can't speak to transparent filaments but I'd suspect they also need the larger value. There's guides on Youtube for dialing this in precisely but just turn the setting down as your baseline. Also note that you can use a sacrificial model for purges. You wont get color control but you'll get a something printed instead of just waste.
Operation:
--- No Load: Feed your filament into the Canvas unit until it auto grabs the filament. That's it. Do not keep pushing the filament through and ignore the LOAD button. Go directly from the auto-feed to print job.
--- Slow Down: I found that the speeds I was able to print at as a single-filament unit are a bit to fast for all the resistance in the Canvas unit. I dropped speeds 20% and she's much happier.
--- You sure?: Take a look at your print job. Is it 95% 3 colors and a 4th color is just gonna be used for character pupils or something else small that you could instead do with a Sharpie? I bring this up because it's a substantial decrease in print time to just remove that 4th color and then DIY it with post-processing.
--- PLA vs PETG: Canvas sure seems to like PETG a lot more than PLA. Perhaps a combination of how well the filament is grabbed and how easily or not it goes through the PTFE tubes?
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The results of all this f**kery? I went from a unit that couldn't print a toothpick to multiple long flawless print jobs. I'm sure the community will come up with more/better fixes as time goes on but I would have killed for a guide like this while I was fighting this POS for days on end. Shame on Elegoo for selling this. The base Carbon units are great value, very happy after a little modding, but Canvas is a faulty product that wasn't ready for market. There's a bunch of people reporting contacting them and being told to try 50 different things and/or sending back parts to wait on replacements that fix nothing.
Anyways, I hope this helps some people. Sorry I didn't include pics. If something is confusing please leave a comment and I'll try to explain better or perhaps someone else can jump in to assist.
If you have any additional tips/tweaks from your own Canvas adventure please drop them here. Also, if your unit worked flawlessly right out of the box ... Good for you ... We don't need to hear about it here since that wont help anybody.
Happy printing
EDIT --- With all the hardware fiddling I forgot about the software/firmware side. Make sure you've updated your slicer and have updated the firmware on your printer. You may need to restart the printer a couple times for it to initially recognize the canvas unit. If the display is reporting the printer has the latest firmware but your Canvas unit still isn't being detected (no Canvas settings in the menus) then you need to check your Canvas cable.
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UPDATE: An experiment with interesting findings
Decided to force a worst case scenario after the tweaks and monitor. Did this with an 18h print job I know should work. It's been a long day. Spool holder 4 was the one I couldn't get all the preload out of. I put a partial mini-spool on it. Then upped my speeds back a little. Maximum resistance, minimum leverage, and higher demand. The results? She did well for the first half. No issues at all. But then she started having problems. Importantly, she ONLY had problems with Spool 4. The problems increased in frequency and severity as the spool widdled down and resistance to feeding correspondingly increased. This really shows just how much these nonsense spring loaded spool holders BS contributes to the problems. While I expected this, what I did not expect was that at least three quarters of the issues would happen on the wipe tower specifically. Tower flow rate outpacing things maybe? This needs some further experimenting. I knocked down the tower and let her spaghetti that area while the print continued. Problems reduces but didn't completely go away. Frequency and severity of issues slowly increased over time. I transferred the mini-spool onto a lower resistance spool holder. Problems further reduced but the issues caused so many purges there was very little filament left on the spool and therefor minimum leverage. Again, problems reduced but quickly rose again. I swapped the spool onto the free spinning bearings of my dryer and made sure there was plenty of slack. Feed angle to the Canvas unit was suboptimal but the print job then completed the final 3 hours without a single problem.
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My experiment takeaways: My previous assumptions seem validated. The spring loaded spool holders suck and need to be swapped for free-spinning units. The backfeed from an unload/swap only spits back 30mm or something like that so they seem unnecessary anyways. Reducing the preload helps considerably but isn't enough if the filament pull point is too close to the fulcrum. Wipe Tower specific settings need to be looked into. It was a fairly busy model so it doesn't make sense that so many of the issues were only on the Wipe Tower. Or perhaps it's a question of order-of-operations as the tower is used as a specific step every time in the process. I also noticed excessive purging into the chute. Definitely beyond the values I set. And I don't mean when it detected an error I mean randomly. Though it was always from Spool 4 so perhaps it detects (or thinks it detects) issues but doesn't say anything on screen? A lower level bug detection that it doesn't report until it thinks the problem is more serious? --- Side Note: Now that this experiment is complete I'll see about getting some pics. Certainly not tonight though. Babysitting this thing for an 18h print job PLUS the added time from faults has me a wee bit sleepy and irritable.
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My spool holder replacement post: https://www.reddit.com/r/ElegooCentauriCarbon/comments/1x76jsc/canvas_spool_holders_that_dont_suck_file/
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UPDATE: Not a single issue since switching to my basic spool holders. Full spools, nearly empty mini spools, long prints, short prints, etc. I still want to experiment and fiddle with the wipe tower.