In Mid-Print-goes real slow, then jumps and crashes

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UnLtdSoul
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In Mid-Print-goes real slow, then jumps and crashes

Postby UnLtdSoul » Tue Mar 22, 2016 7:00 am

I have the Rostock Max v1 - been happily using it for over 2 years. Not sure if this is a hardware issue (rambo going out) or an issue with Slic3r/Repetier ?

I am printing a number of parts, about 250mm front end to end 25 layers high (.25mm per layer). Several times on nearly every layer i hear the printer slow down usually for only a second or two, then resumes - What i mean by slow down is 10-20 x slower... crawls.. And usually it is when the head is Not Printing, but moving to a new location. When it gets to the new location it will resume printing at normal speed - most of the time.... But, once in a while, generally about 1/2 way done with the print - it will do this slow down on a longer move, so it will go slow for 5-10 seconds, but, then it violently jumps to another location so fast that the steppers or belt skips and the print is ruined. It is now at the point of messing up on more prints that it completes. Like I said, i don't know if it is a Rambo hardware issue, or something with Repeteir It did it on Repetier vs 1.60, so i updated to 1.61, got 3 prints and thought the issue was resolved, but the last 2 prints crashed. It does do it's slow downs somewhat repeatedly, but, it doesn't jump and crash every time.

Anyone seen this before? Do i look at hardware - chip overheating? Or Repetier? I am using Repetier server, but, i can't say for sure, but i think it happened printing direct without server also, but, can't say for sure. I will try next print direct, without using the server. I have a dual boot with windows 8.1 and windows 10, does it on both versions

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Re: In Mid-Print-goes real slow, then jumps and crashes

Postby CRPerryJr » Tue Mar 22, 2016 9:26 am

If I remember correctly, the Rostock Max V1 had metal universal joints on the effector and carriages that occasionally may seize up. Could you verify that you have them, and that they are operating properly?
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Re: In Mid-Print-goes real slow, then jumps and crashes

Postby mhackney » Tue Mar 22, 2016 10:03 am

The V1 does have metal universal joints but I've not heard any reports of them seizing up - especially not all at the same time in the same amount. The problem you describe sounds like all 3 towers are slowing down in unison and then speeding up and/or violently jumping. That sounds like a buffering/flow control issue in the firmware or communications. Are you using USB to print or printing from a CF card? Which ever you are doing, a test would be to do the other and report your findings.

It is possible that if you are printing from CF that the card is going bad. It from a computer via USB it could be something in the USB path - the cable, any USB hub, and anything else running over USB that might be consuming bandwidth.

It is also possible that overheating is the culprit. I forget how the V1 RAMBo was mounted, I think on the back of the door. Open the door and direct air flow over the stepper driver chips and see if that helps.

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Re: In Mid-Print-goes real slow, then jumps and crashes

Postby UnLtdSoul » Wed Mar 23, 2016 4:06 am

Hey, both CRPerryJr and ULTIMATE 3D JEDDI, thanks for the replies. First, yes, one arm, at the cheap-skate carriage, is seized up. One of the 'bearings', or whatever you call them, is frozen onto the axle-rod, such that the axle rod turns with the bearing. By the looks of it, that has been an issue for a long time. I plan to buy the newer arm/carriage kit soon. So, that may be a contributing factor.

The odd behavior i was observing was that it would slow down only when the head was moving from one location to another, while it was retracted. Here is what I found: Since the day i got it, i have had the slicer settings to print at 30mm/sec. Then i would use the FeedRate in Repetier to adjust the speed. With PLA and ABS I would set FeedRate to 180-188%. At 184% that is equivalent of a print speed of 55.2 mm/sec. That seems to be about as fast as it will go for most of my printing. What I just noticed is the the Travel speed was set to 200mm/sec That is the speed it travels when it is retracted and moving to another location. That is when this would crawl and crash at times. Yet, with my 184% speed factor that was making it travel at 368mm/sec I've never had any issues with it before, and i've printed 'countless' 1 kg reels with this. I was wondering if that be a factor? Maybe with the arm causing a lot of friction it may be overheating a driver? But, why 'crawl', that would have to be a data flow issue? (Maybe the driver overheating would cause a glitch in the power feeds that would cause the USB chip to act 'oddly'??) So, not quit sure i really know the details of what is going on? With my set up I have the door slightly open with a 80mm fan pointed at the Rambo board for cooling. So, it isn't just a over-heating issue... When it slows down, but not crashes, it just crawls when it is traveling to new location - as soon as it reaches the location it resumes printing at normal speeds. Only during Travel it crawls. When it crashes, I notice it does it when it travels a longer distance, like 100 mm just to hit a spot at the end of a fill... if it didn't crash it would just tap a spot - then travel to the next location... but, at the times when it crashes it crawls to the first location - tries to hit the spot and then tries to 'jump' to the second location. It tries to go there so fast that the steppers skip and the head goes way off. It always goes 'up', and off angle, maybe due to the one arm being so tight that it can't 'fly' to the new location, so it skips and throws the head off course.

It never gave this problem before - probably because the arm was slowly getting more and more tight creating more and more friction with age. So, now the problem is showing up.

My 'solution (until i get the new set of arms) is that I've lowered the Travel Speed to 100mm/sec with the speed factor of 184 that now == 184mm/sec during retracted travel. So far, i've only printed 3 more parts - and not once has it crawled while it is traveling, or crashed. In fact, overall the prints seem a bit better... I think the 200x1.84 or 368mm travel speeds were causing some of the corners to get a little sloppy now and then.
I don't know what the max recommended travel speed is, but, like i said, even the 368mm/sec speed was never was a problem before. But, yes, that one arm is really STIFF. When i disconnect it from the head side, it takes a little effort to move it up - or down... it definitely does NOT free fall on its own. It doesn't swing freely at all. When you move the arm up that is frozen to the axle the other arm moves with it, and that arm is also not freely turning on the axle, it doesn't free fall or swing, but, it isn't as stiff as the other one that is frozen to the rod. So, yes, that along with the higher travel speed 'must' have been causing some sort of issue.

Previously i have had USB communication issues while printing through a 'hub'. My PC is about 15 feet from the printer, and i had a hub half way that i used to plug the printer into. In an earlier version of Repetier I had no issues. But, after I installed an update (this was about 7-8 months ago) I started having USB issues where the printer would Totally Stop as soon as i disconnected or connected another device into the hub. I would use the USB hub to charge my cell phone and/or transfer files. If i plugged in/or out the phone while it was printing, the printer would stop dead in it's tracks. I took up that issue with Repetier forum and they denied it could possibly be a USB hub issue... But, when i reinstalled the older version the problem went away, and installed the update and it would come back. But, even with that proof, Repetier people insisted it could not be an issue with their software or update, although they did admit they did changed the serial communications in that update. They had me use Repetier Server instead, which 'helped', but didn't resolve the issue. My solution was I got a 12 foot USB cable extender, plus the 6 foot cable, for 18 foot total, and plugged the printer directly into the PC, the problem disappeared and never came back. But, that leaves me with 18 foot of usb with a connection midway... So, that 'could' cause data integrity issues?

I don't know if i really know what it is doing - but, it is only slowing down during retracted travel times, and for now slowing that down seems to have fixed it for me for now. The next step is to order a new set of Arms.

BTW - any suggestions on which set of arms? The newer arms from SeeMeCNC means i have to replace the carriage and head plate. That seems like a lot of work, but, if it is better, i am all for that. From day one the 'bearings' - or what ever the things are called, that slip on the axle rods that the arms clip to, a number of them would not even slide onto the rods, and would bind up, where i had to use a large socket as a sleeve and hammer them off the rods to remove them (this was while i was building the unit). Some rods were fatter than the others, so I wound up sanding down the fatter rods. I put them in a power drill and spun them while holding fine sand paper on them to reduce their diameter, then while they were spinning i used rubbing compound and a dremel to buff them to a polish again. I had to do that to about half of them. And, i recall several were still rather 'tight', but, a few i went too far and they where almost too loose, so I left the tighter ones hoping the stiffness would eventually loosen up with wear. I think they began seizing up instead. Thanks

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Re: In Mid-Print-goes real slow, then jumps and crashes

Postby Eaglezsoar » Wed Mar 23, 2016 5:15 pm

The new "ball" arms offered by SeeMeCnc are great but do require you to change out the carriages.
IMHO these are the greatest arms and carriages offered and are well worth the money and time to install them.
The configuration.h file diagonal rod length will need to be changed to 290.8 from 269.
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Re: In Mid-Print-goes real slow, then jumps and crashes

Postby BenTheRighteous » Wed Mar 23, 2016 10:29 pm

I can't speak to any data integrity or USB issues but from what you described it definitely sounds like a travel speed issue.

You mentioned you were printing a large part. Due to delta geometry, travel speed when at the edge of the bed must be lower than when entirely contained near the center.

If you say you've never had this issue before, then I'd guess this is an unusually large part for you. Is that accurate?
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UnLtdSoul
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Re: In Mid-Print-goes real slow, then jumps and crashes

Postby UnLtdSoul » Fri Mar 25, 2016 2:06 am

I will order the new SeeMeCNC arms, after my next paycheck...
As far as printing large objects, I print close to the outer edges frequently enough. I think it is just that the one arm has progressively got worse, and is now frozen on the axle rod.

But, what retracted travel speeds do others use? Like i said, I had it set to 200 mm/sec in Slicer, but, was speeding this up by 1.84x - so the effect speed was 368. What do others use, was that speed over the limit?

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Re: In Mid-Print-goes real slow, then jumps and crashes

Postby Polygonhell » Fri Mar 25, 2016 2:23 am

I run 200mm/s travel normally, if I were printing something big I'd probably run closer to 150.
But acceleration is more the issue anyway, you're never going to actually reach 300mm/s in a reasonable move unless the acceleration is high, and that's what's more likely to cause the lost steps/ slipping belt etc.
If one if the balljoints is seized though, it's likely the issue, I replaced my original metal u joints a couple of months ago and they were all still good, I just put a small ammount of lithium grease on them when I originally assembled the printer.


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