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After I preinted a number of boxes to calibrate my extruder I decided to try my hand at this bracelet.

This is the slow (or calibration speed) test:
[youtube]http://www.youtube.com/watch?v=-X48mogzGtg[/youtube]

It took 48 Minutes to complete.


This is the same thing but with the feedrate set to 181%
[youtube]http://www.youtube.com/watch?v=vyaD1qulnCY[/youtube]

It took 28 Minutes to complete.


This one I set the feedrate to 300%
[youtube]http://www.youtube.com/watch?v=_-PT1LsaTik[/youtube]

It took 15 Minutes to complete.

For a first run, it worked pretty good. All three prints came out exactly the same. I am sure I can do it faster, but I need to rework my homing switches.

Very nice, that's awesome you can get good prints that fast! Couple of questions, so far when I try to push my feedrate faster my prints aren't coming out nearly as good as when slow...

1. What size nozzle are you using?
2. ABS or PLA, 1.75 or 3mm?
3. What layer height are you printing at?
4. Are you printing at the same temp for all speeds?

I am running stock. .5mm Nozzle.
1.75 ABS
.2mm layer height
250C Etemp 70C Bed Temp

All the speeds are set to 20mm/s. I just increased the feedrate once the first layer or two has printed.


You have to realize I did the following:
I spent hours calibrating the bed. I stopped when all were with-in .1mm as the switches dont have much repeatability beyond that.

I then calibrated the filiment here are calibration prints I created to get the temp and flow correct fo both my white and silver ABS.
[img]http://www.kronosrobotics.com/3dprinter ... G_4021.jpg[/img]


Also these are very simple prints. Single perimeter. No retraction. I still have to come up with a retraction calibration system.

Do you have a detailed picture of the best hollow cylinder? It seem, that you have very little blops, and I'm wondering why you get it so good, with this high temp and no retraction
Do you use Z-Lift? Which nozzle-type do you have? (old or new?)

Thanks!

those are probably some of the better photos i've seen of the rostock calibration done by customers..

i'm still on the fence whether to purchase one because of this.

If you look at the rats nest object next to the cube, that was my very first print. That one was easy and the manual gives you a clue. All I had to do was tighten the extruder clamps. Then I was able to print the cube.

It was not perfect but it printed. You have to get the filliment flow perfect. First I was using the box method, but found that printing the cylinder to be easyer and it would give me more consistant results so that I could measure the fliiment width. Once I did that I could set my flow perfect and procede to temperature settings.

Problem 1 is that when printing small objects the heat can build up and eventualy lead to small strands that look out of place, or in extream cases total melt down. Its easy to identiify this problem as the print will look good for the first 10 or so layers then start to slowly degrade.

With ABS you only have a few choices when this happens:
1. print slower
2. Use a fan
3. print larger object

There are also some cooling options in slice3r but, they can create more problems than they solve.

If you look at the large cylinder. It came out perfect in every way. The small melted cylinder to its right was with the exact same settings and speed. The problem is that heat built up as it wrapped around each time. On the large object there was enough time between layers to allow the ABS to cool.

My number one recomendation is to start with ABS as it is much easier to work with. PLA has its own set of issues that I am trying to over come now.

My next set of calibrations are going to be on retraction settings. You have to keep in mind that the above prints as well as the bracelet do not stop the extrusion process once it starts. So retraction is turned off. This is important for calibrations.

I will be covering all these calibrations in more detail in the 3D printer series I am doing in Servo Magazin starting in MAY.

Another option:

4. print 2 or more parts

This is a trick to deal with heat build up.

But keep in mind. Here I am doing calibration. Extraction is turned off so you will get a bridge between the two objects.

OK, I started my retraction calibration testing, and their is a major problem with the extruder. Its slipping but not the filament. The faster I go the worse it is. I have to take the extruder off the machine and dissasemble it to find the problem.

I do hear a kind of grinding sound from time to time. If I hold my fingers on the filliment I can feel ot retract but some times it does nor move forward. I suspect those of you who are haveing problems with your first print may be having the same problem. Turn of retraction and print a simple hollow box and see if it does not come out perfect.

i've heard the retraction speed is where the problem lies with the bowden design.

I'm curious as to what you find out.

I've seen other posts about the gears coming into contact with the fitting on the inside?

I found the problem. The Stepper was loosing steps on retracts. It has plenty power for normal flow. Coming from a CNC background I lowered the acceleration of the retract. That seems to have stopped the skipping. I am going to do some experiments and find its sweet spot. I will do a video of the problem and fix as well.

This problem has nothing to do with the Bowden design. I dont even have filement attached and its skipping. I suspect with the latest changes they set the default too high for the microstepping upgrade.

FYI, while the Bowden design does have its cons, however, the UitlMaker 3D printer is one of the best print producing designs available and they use a Bowden feed. It was also one of the top rated machines in the Make 3D printer guide.

Dont discount the Bowden design just yet:)

well that's just what i hear people say about it. its not my opinion.

glad it wasn't the bowden actually, considering i just placed an order for a kit..

I was never able to get the retraction to work properly. I started another post over in the Rostock Max section.

Hey msimpson, John here. Also, you can try bumping up the motor current in the FW. The newer 1.1 and up boards had a change that required just a tad more PWM to drive the same current. I left it alone in the stock FW, feeling that it's better to ask someone to turn it up rather than down

I changed it to 222 as recomended by another owner. I will give the settings a try.

msimpson wrote:I changed it to 222 as recomended by another owner. I will give the settings a try.

How did you make out?

No luck. I would really like to hear from some individuals who have their printer working properly. It ether works or it does not. The fact that the folks at seemecnc have not chimed in to solve the retraction problem makes me think its a major issue with this printer.

Personally I feel the problem is in the extruder and Bowden cable set up.

Here: http://www.geneb.org/images/bearing-and-rod-ends-1.jpg - the tall parts are about 5" high.

This Spitfire grip: http://www.simpits.org/geneb/wp-content ... grip-1.jpg took a little over 11 hours to print.
No retract issues.

(The second link is not working for me.)

I just checked and it's working fine - you may have tried it while I was chasing down an issue with the web server.

g.