150 prints then crunch

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Robin
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150 prints then crunch

Post by Robin » Tue Jun 25, 2013 6:28 pm

I have the Afinia version of the UP and I have it printing the same thing, day in day out.
I use the perf board covered with Kaptan tape and a wash of ABS/Acetone between prints.
It does about 150 prints then the nozzle ploughs in to the board tearing the tape.
I have to replace the tape and adjust the flying height before I can start the next 150 prints.
If I do not adjust the flying height it ploughs within the next 3 prints.
It is not a problem, I just can't help but wonder what is moving.
It cannot be the table adjusters because the table stays square.
Is the nozzle moving slowly downwards?
What else could it be?

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JuliaDee
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Re: 150 prints then crunch

Post by JuliaDee » Tue Jun 25, 2013 11:58 pm

Robin wrote:It cannot be the table adjusters because the table stays square.
Are you sure that's a valid statement? When the adjustment screws loosen, the platform moves up...

An experiment that might shed more light would be to "initialize" the printer (via the menu or the front-panel rocker switch) right after a "crunch" and then try to print again without adjusting anything else. This will reset the platform's initial positions via the limit switches and the printer's expectations of where the platform will be after a given number of steps to the stepper motors. If it still crashes right after that then I think your platform has moved (adjusting screws). If that solves the problem for another 150 prints then it seems like it could be some sort of cumulative error in the motors, belts, etc.

Have you contacted Afinia?

julia

Robin
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Re: 150 prints then crunch

Post by Robin » Wed Jun 26, 2013 9:58 am

It isn't really a problem, after 150 prints the Kaptan is in need of changing so no great loss.

But something is moving. Originally the print height was over 130mm, it is now nearly 128mm.

The table height adjustment is 3 screws, surely they cannot self adjust and keep the table square to the slides.

The printer gets to reset itself to its' limit switches every morning so it isn't a cumulative error, something really is moving.

It's a bit like that statue of Osiris in Manchester museum, it refuses to stay still :mrgreen:

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JuliaDee
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Re: 150 prints then crunch

Post by JuliaDee » Wed Jun 26, 2013 12:58 pm

Robin wrote: The printer gets to reset itself to its' limit switches every morning so it isn't a cumulative error, something really is moving.

It's a bit like that statue of Osiris in Manchester museum, it refuses to stay still :mrgreen:
Well, it is cumulative in that it keeps growing until you re-init. Whether it's mechanical or software is unknown.

Yeah, that statue is cool :)

julia

Robin
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Re: 150 prints then crunch

Post by Robin » Wed Jun 26, 2013 2:58 pm

I was talking about Osiris with my buddy the physicist. We think it is rocking on his base and has become Focault's pendulum inverted. It is not Osiris who is turning, it's the Museum :mrgreen:

With the UP! I think the nozzle/heater module is slowly moving downwards in the heatsink :mrgreen:

DytHlt
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Re: 150 prints then crunch

Post by DytHlt » Wed Jun 26, 2013 6:22 pm

It's probably the belts stretching over time. The vertical belt holds the weight of the entire platform. To assume it doesn't stretch would be asinine.

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JuliaDee
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Re: 150 prints then crunch

Post by JuliaDee » Thu Jun 27, 2013 12:30 am

DytHlt wrote:It's probably the belts stretching over time. The vertical belt holds the weight of the entire platform. To assume it doesn't stretch would be asinine.
The OP hasn't stated the period of time involved ("150 prints") but 4mm would seem to me to be a lot of stretch for these types of belts.

Robin
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Re: 150 prints then crunch

Post by Robin » Thu Jun 27, 2013 8:23 am

The belts have a trick. Between the teeth and the cloth backing they include a non-stretch cord layer. The best use steel, cheaper ones use glass fibre, Kevlar, that sort of stuff. When you spec these belts you usually only worry about having enough teeth engaged on the driving pulleys so you don't rip them off under load.

roller
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Re: 150 prints then crunch

Post by roller » Thu Jun 27, 2013 10:27 am

It's probably the belts stretching over time. The vertical belt holds the weight of the entire platform. To assume it doesn't stretch would be asinine.
The loads on these printers will stretch belts negligibly and if they did stretch the platform would sag down ie nozzle to high not sag up ie nozzle crash.

original
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Re: 150 prints then crunch

Post by original » Fri Jun 28, 2013 3:05 am

My 5 cents, I have had it on a few occasions when the screws used to level the platform come loose over time. That is the first thing that I would check

nickw
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Re: 150 prints then crunch

Post by nickw » Sun Jun 30, 2013 12:30 am

original wrote:My 5 cents, I have had it on a few occasions when the screws used to level the platform come loose over time. That is the first thing that I would check
I would have to agree with this. Those bed screws aren't torqued down and the machine is pretty much a vibration monster.
Those screws have a natural tendency to loosen when subjected to those vibrations.
I have had a bed leveling spring vibrate completely out of its place. Ever since then I re-tighten and level my bed screws
after about every 15-20 prints. This is probably a little (lot) excessive, but i feel bad for the nozzle when it crashes.

Sourcery
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Re: 150 prints then crunch

Post by Sourcery » Wed Jul 03, 2013 11:17 am

If it is the screws that come loose, print a plastic ring that fits the screw head, that way you can tighten the screw harder with the plastic ring working as a tightener :)

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