This topic contains 31 replies, has 9 voices, and was last updated by jhr 3 months ago.
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Is there a way we can change the filament skip threshold?
www.lee.rcha-uk.com
www.rcha-uk.com
www.rcheliaddict.co.uk@made2fade There is no need to change the slip threshold - if the filament is slipping, your machine is not extruding enough material, changing the slip threshold would just ignore this issue and may cause other damage. You need to find out why the filament is slipping, not just turn off the detection. I would suggest raising a support ticket and one of our tech support guys will work with you to resolve the actual root cause.
Hi Chris,
this particular unit that i am talking about has been back less than a month ago. We have also had a head and extruder back to support twice.
The machine came back and we have done 3 prints before seeing the constant slippage again. We are at the point where it is pointless printing with that machine. To be honest we are about to ditch all 3 of our Cel Robox because of this problem. Another unit which has just came back from support last week is working perfect now but for how long is any ones guess. There is clearly issues with the extruder on these things.
I have narrowed it down to the extruder because when the slippage does happen if you help the filament along by pushing it a little then it works for a small period.
We have seen this same fault on all 3 of our printers now and to be honest we are starting to wish we’d invested in another product.
Let’s see how long the one that has just came back lasts before i start seeing the slippage.
I have not even bothered going back to support about the machine that came back a month ago. All these printers have had less than 25 hours printing on them. They are basically brand new! We should not be seeing these problems. Best part of 3 grand down the drain to be fair. Pretty fed up of this now, i think its time to invest in other machines.
- This reply was modified 3 months, 1 week ago by Lee.
- This reply was modified 3 months, 1 week ago by Lee.
- This reply was modified 3 months, 1 week ago by Lee.
www.lee.rcha-uk.com
www.rcha-uk.com
www.rcheliaddict.co.uk@made2fade What material are you printing with? What software version are you using?
Chris we only ever print with Robox PLA in white/black and red. We are on the latest firmware and software. However i have seen this fault on all firmwares since we purchased the machines over the last year or so.
Pretty fed up with it all now. The newly returned printer has been going for best part of the day and seems absolutely fine… we are hoping this continues however we are greatly held back by the problems on the other 2 units.
www.lee.rcha-uk.com
www.rcha-uk.com
www.rcheliaddict.co.ukJust for grins, why not try printing another filament guide of nylon? Something low friction and wear resistant? Maybe modify the curve to a longer radius. And make it extend out past the current end of the guide (toward the reel) so you can feed flexible filaments without having to use a 5″ piece of Bowden tube.
Kent
Damn Solid DesignHi Kent,
basically because i dont think that the entry to the extruder is the problem. I dont think that it is getting caught up on anything. I think the problem is down to the extruder itself. Like i say… if you give the filament a helping hand by manually feeding it then eventually it catches and the print resumes fine but only for a very short time. In the past few times we have sent gear to support i took the opportunity to run some filament through the bowden tube and it seems as if there is no friction at all. For me that pretty much confirms that the problem is in the extruder. I know if i do the same again now the results will be the same. Personally i think the extruder is not the best design and of all my colleagues (different brand) printers that i have seen, not one of them has an issue with filament slip.
www.lee.rcha-uk.com
www.rcha-uk.com
www.rcheliaddict.co.ukThese things have cost us a small fortune in shipping costs back to support to fix the problems. That money could/should have been invested in another brand or filament.
www.lee.rcha-uk.com
www.rcha-uk.com
www.rcheliaddict.co.uk@made2fade I have one suggestion which will completely change your view of the machines - stop using PLA. Try some nGen/XT/ABS and let us know how you’re getting on. The design of the extruder has little to do with the slip you are seeing - the Robox extruder has more ‘push’ than the majority of extruders on the market due to its worm gearbox and dual-pinch wheel design. I think what we’re looking at here is damp PLA which is getting stuck at the entrance to the heater block. The only reason you have not seen filament slip on other brands of printers is because they are not able to detect it, and will therefore just under-extrude instead.
Seriously - just ditch the PLA, and your world will change.
@chrisyt Is it generally PLA or some specific brands? Of all filaments I tried including nGen (I didn’t try nylon and like) ColorFabb’s PLA seemed to be one of the most forgiving and the easiest to print - no warping, perfect adhesion of the first layer, nice finish, etc…
@click there are certainly some PLAs that are better than others - you will see many being sold as ‘clog-free’ or ‘jam-free’ or PLA+ or ‘Advanced PLA’. These are all attempts at raising the glass transition point (Tg) of the material to make it easier to print with. They do this with a variety of additives to the raw PLA, and in fact the resin manufacturer NatureWorks have just released a new stock PLA+ grade which is compounded at their factory specifically for 3D printing. The main problem with PLA lies in getting it into the heater block with enough force to get it through the nozzle.
Because this force is quite large, you need a rigid piston in the form of the solid filament to force the melt into the block. If the filament starts to heat above its Tg before it gets beyond the heat bridge, it will soften and buckle in the tube, causing all force to be diverted outwards towards the sides of the tube and is what often causes filament slip.
The original version of the head had a piece of PTFE lining inside the heatbridge to reduce the frictional coefficient on the walls to try and prevent material clogging by sticking to the sides. This is the reason the original design of the head is limited at 260deg due to the operating temperature of PTFE. However this piece of tubing is also an insulator, and therefore reduces the ability of the heatsink to draw heat out of the cold side of the bridge and therefore keep the filament rigid or ‘glassy’. You need to make the transition from solid to melt as short as possible, to give you the maximum pushing force into the head.
The latest design of the Robox printhead, which is used in DualMaterial (DM) and the soon to be released V2 of the Single Material Dual Nozzle Head (S2) utilises Titanium for the heat bridges. This allows us a huge performance increase and allows much larger flowrates, particularly with the DM head due to the much smaller melt volume.
Titanium has an extremely low thermal conductivity coefficient combined with very high tensile strength. These two properties allow us to have a thinner wall section in the bridge section, higher internal surface finish for low surface energy and friction due to the higher rigidity when machining. These two factors mean considerably less heat is transferred from the heater block to the heatsink and therefore we can keep filament rigid for longer and the transition zone is much shorter. This also means we have a faster heat up time and more accurate thermal control, combined with a new silicone jacket to insulate the heater block and keep it clean and new high temperature thermal cement for potting the thermistors.
All of these changes have been made during the development of the DM head in response to new information and testing, and we think we have built a great new head design for the future. We are therefore taking these things we have learnt and implementing them on v2 of the single material head, which will be available to buy soon, as well as being fitted as standard to all new machines.
The current SM head, while being able to print PLA, is just not as efficient as the newer design, and can therefore cope much better with lower flowrates such as when printing on fine, as the volume of material extruded per unit distance is much lower. This is why printing on Draft (the highest flowrate) and purging can sometimes display filament slip with PLA. All of the other materials I mention have a higher glass transition temperature and are therefore better for bridging, extruding, low warp in many cases, and general ‘ease of printing’. They exhibit excellent surface finish, and many useful mechanical properties.
My current favourites are nGen/XT (very similar but XT is slightly stronger), PolyMax (a PLA blended with (we think PC)) to create a high strength, easy to print PLA and a premium ABS often called MG94 - it exhibits lower warp than other ABS and produces excellent prints.
@chrisyt really nice explanation. Only thing I am not 100% sure is that why I had more ‘filament slip’ with nGen in comparison to this ColorFabb’s PLA(*). Roll of nGen I’ve got exhibited more warp than PLA, too.
(*) I deliberately use brand as I have no idea what specific kind of PLA is that - and it seems to be quite different to some cheap original CEL’s PLA and some cheap third party I tried in the past. ColorFabb’s seems to be less ‘runny’, ‘shiny’ and didn’t see any warping issues almost at all.
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