Retraction Issues

[msimpson]

I have given up on the Extruder and bowden tube that came with the Rostock Max. I started working on mounting one of my QUBD extruders. It will have to be mounted under the platform as thier is not enough room on top.

[msimpson]

I got the modified QUBD extruder mounted on the rostock max. I had to mount it under the delta platform as there is not enough room on the top. I was able to print a calibration cylinder in PLA but need to order a MK7 frive gear as the brass gear that comes with the qubd extruder jams too easy.

I have a couple on order. Once I get them I will resume my testing and let you folks know.

[msimpson]

OK, while waiting for my new drive gear for my QUBD, I went through the YouTube vid on loading the Repetier firmware into the Rostock.

I loaded it and made the changes indicated in the video. First off I have to say that you need to also give the settings for the eeprom as the settings there took me a while to trouble shoot.

As for the results, the Rostock Max still has horrible retraction. Im using the slicer settings given in the 1.17 manual. If there are others please advise.

It seems to be like pulling teeth to this thing setup correctly. I have four other 3D printers and all of them give me better prints. I really need to get this machine working properly as I will be writing the third article in the magazine series and this one is where the rubber hits the road. Print tests. I have been holding off saying anything about the print cabablities of this printer in the hopes that the issues could be worked out. But it will all come out in this next article good or bad.

[Flateric]

This is my very first printer ever. I can't really say I have been having such a hard time. Perhaps it's time for a step back and a refreshing head shake to help get a fresh veiw on it.

I'll help ya out if I can.

Ok, after the step back lets start from the top here.

Can you give me a list of the top say three issues your currently having and we'll hit them first. I myself had some retraction issues at first but I have not really put a whole lot of thought into them in a long time. They are just perfect.

But I ramble, ok, list em and let's fix em!

[cambo3d]

OK, while waiting for my new drive gear for my QUBD, I went through the YouTube vid on loading the Repetier firmware into the Rostock.

I loaded it and made the changes indicated in the video. First off I have to say that you need to also give the settings for the eeprom as the settings there took me a while to trouble shoot.

As for the results, the Rostock Max still has horrible retraction. Im using the slicer settings given in the 1.17 manual. If there are others please advise.

It seems to be like pulling teeth to this thing setup correctly. I have four other 3D printers and all of them give me better prints. I really need to get this machine working properly as I will be writing the third article in the magazine series and this one is where the rubber hits the road. Print tests. I have been holding off saying anything about the print cabablities of this printer in the hopes that the issues could be worked out. But it will all come out in this next article good or bad.

have you contacted seemecnc with your troubles?

[msimpson]

I built my unit as a kit. It is assembled rock solid and can print without retraction perfectly. I can do calibration cylinders and print the strechlet bracelet perfectly. Its when retraction comes into play that its a big fail.

On all the other printers in my article series I have been able to tune the retraction to almost perfect.

On the Rostock Max extruder their just seems to be too much latency between the extruder and the hotend to get it tuned out.

Now keep in mind what I call a good print may be different than others. I can only judge based on what I can print on my other machines.

As for in contact with SeeMeCNC, they know I am having troubles as we have exchanged emails. They have a vested interest in my success as the readers are about to see the results.

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In any case I am about to rip the Rostock Max extruder off and add my modified direct drive QUBD extruder to the delta platform. I have too much time and money invested in this printer to give up.

FYI I just ordered a Solidoodle 2 Extruder assembly. Its a direct drive as well. I will also mount it on the Rostock as I am thinking of doing a blog on the various extruders.

[cambo3d]

ive heard bad reviews of the qubd extruder so i dont know if that would be any better.

[msimpson]

The QUBD extruder is a horrible extruder (as it ships) all the extruders based on that design (MK7) are. However, with a true hobbed drive gear, and spring/bearing tensioner it's a great extruder.

The Solidoodle 2/3 extruder is a takeoff of this design as well. Hobbed drive gear and a dual spring/bearing tensioner. There are some differences though, they moved the fan to the back to cool the motor.

The thing is you have to use the smallest extruder possible because of the weight. The plastic delta platform and plastic arms on the Rostock Max get wobbly with any amount of weight.

I have other extruders to try as well. MakerGear Extruder, PritrBot Extruder. They weight more and are larger, but can be fitted.

[cambo3d]

what do you think about the pg35L steppers with the mk7 filament roller.
i was tinkering with this idea http://forum.seemecnc.com/viewtopic.php ... o+extruder

[Flateric]

Funny that you mentioned the spring tensioning. I replaced the rubber washer and flat washer design of the max extruder with some small but powerful short little springs. I had noticed that when the extruder was functioning that the gears would ride ever so slightly out of round. I doubted that the little rubber washers would be up to the job of constant flex and have enough range of flex to compensate very well.

It did seem to improve my extruders consistency is the best way to describe it. The forward motion even without retract was not always perfectly uniformed and even. Only slightly but it was not.

Might be something to try on your current extruder.

I also as I mentioned previously keep my tube as short as possible without introducing straining corners, also cover it with a 4mm OD tube and then secure both ends of both tube with not only the PTF connectors but also a couple wraps of caption tape just to kill any lag from flex or tube shifting. And of course the obvious, of making all the connections tight and free from the slightest play.

This extruder can and does retract well. I do believe that it is slightly over geared however in my opinion. It could rip the filament out of a pair of vice grips, but this is also it's down fall in a slight way because as you try to feed faster and faster the stepper loses torque as it tries to spin up all that low gearing. Causing the stepper to stall. Which sounds like a grinding rock sorta noise.

So I dial my retract speed way back, WAY back at time if I think I will be playing with the speed % during the print. Since I don't want that stepper to stall even if I crank the speed in repetier to 300% sometimes. So my retract speed will often be as low as 10 or 15. But after cranking up speed that value is obviously much higher. Often so high it give the grindy rocks stalling noise and you get zero retract, but sometimes the feed will function and then you are all out of sync with what repetier believes is happening.

I always sit and watch a few retracts to be sure I hear nothing but a smooth and un-stuttering stepper motor run for retract and feed for a few cycles. Then while cranking the speed I always pay attention to the retract and feed sound. As soon as I hear the grinding I stop and go back, knowing that I have pushed the stepping so fast it's not useless and stalling on the extruder.

If it's not silky sounding smooth it is not doing anything useful for your print.

Thats how I get my extruder to retract well and for the entire print. Just a little verifying at the begining of the print job.

Hope that may help you or someone out.

[msimpson]

Got the QUBD extruder fully modified and mounted. Its using a hobbed driver gear (MK7) I got off ebay. Got it in 2 days. Using the upper larger spring/bearing tensioner. I did have to put a small .06 thick piece of acrylic over the stepper to rais the extruder and tensioner so the holes lined up with the drive gear. Im running a .4 nozzle and a 12v heater cartridge on the hot end.

It is mounted under the delta platform. First I calibrated the filament and adjusted the nozzel bed height. I got Perfect calibration cylinders.

Next, I printed my retraction calibration objects. It consists of four single walled cylnders spaced about 15mm apart. This shows up many retractions issues and I found it a good place to start.

Well with stock MK7 settings the retraction was as good as on most of my other printers. Very happy with the extraction. The down side is that the added weight on the bottom of the platform cause too much vibration when the delta changes direction. These vibrations show up in the layers.

What I have to do is experiment with some acceleration settings, not sure where to go as the ones in Slic3r do not work. I am going to look at the ones in the eeprom. See if I cant smooth things out a bit.

I will post some vids and pics once I get some testing done.

[msimpson]

Well, unless there are some kind of delta accel settings its a lost cause. The acceleration settings are for the motors them selves not the delta x,y movements. This translates into inconsistant acceleration control as the Rostock changes directions. Its a shame as I can see the benifits during some of the delta movements when only one axis is operating.

[msimpson]

Ok, been playing with the new extruder and the settings. If I run things at 30mm/s and use a acceleration setting of 1200 on all axis I can get a very nice print.

Here is a video showing various angles of the extruder making a potato chip bag clip. Quality was not important here so I was doing perimeters at 45mm/s and infil at 60mm/s

[youtube]http://www.youtube.com/watch?v=9ALKoD72zjE[/youtube]

The extruder is performing well. I have printed several objects at several speeds without a single missed step. Retraction is perfect, no strings or blobs. You got to love direct drive extruders.

The only downside is that the stepper motor gets very hot. I may have to mount a fan on the back of the motor.

[cambo3d]

looks like you lost some z height on that one, there is a mount on thingiverse made for the qubd extruder for the rostock,.. that doesnt look like it would take up as much z height

as far as the stepper getting hot, maybe try adjusting settings for the extruder that my help also.

[msimpson]

No thats my mount. It was cut out on my laser. It was ment to be temparary as this was only a proof of concept. Im not too worried about the height as I still have over 9" of height.

I had to extend the extruder with long machine screws because the tensioner is in the way. I need to reposition the mount so that the tensioner is dead center. It will probably fit through the hole then. That will gain me back about an inch, and stiffen the mount. Im sure the long screws add to the vibration effect.


There is only a QUBD hotend mount on thingiverse, not the whole extruder. The extruder is too large to mount on top. It has to be mounted under the base.

[cambo3d]

i see, I thought the qubd extruder and hotend was an all in one type thing.

[msimpson]

It is all in one. However some people only use the hotend. The hotend is nothing more than a block of aluminum, a nozzle and a stainless steel hollow screw. The other end of the stainless steel screw normally attaches to a larger aluminum block that allows for cooling. The front fan cools this block.