New SeeMeCNC Extruder

General discussion of 3D printers

Re: New SeeMeCNC Extruder

Postby cvoinescu » Fri Jul 19, 2013 10:15 pm

I like 3 mm for all the reasons Orcinus listed. Judging by the ease with which my geared (5.22:1) extruder breezes through PLA at less than half the rated current of a 4000 g cm NEMA17, I assume I won't have any trouble direct-driving the filament with a 4800 g cm NEMA17 at the rated current, provided I keep the effective diameter of the drive gear the same or smaller. Currently it's 7.5 mm (a shallowly hobbed M8 bolt), and I plan on about 6.5 mm (with serious bite). The main problem with 3 mm direct drive attempts that I see out there is that they use large drive gears. The otherwise excellent MK7 drive gear is 10.56 mm: switching to 6.5 mm is virtually the same as adding 1.62:1 gearing, or getting a 62% more powerful motor -- nothing to sneeze at, at the cost of using less metal!
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Re: New SeeMeCNC Extruder

Postby fma » Sat Jul 20, 2013 6:05 am

The problem with 3mm filament is about the pressure in the hot-end, which is much higher, and leads mor often to problems (leaks or so)...
Frédéric
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Re: New SeeMeCNC Extruder

Postby orcinus » Sat Jul 20, 2013 3:21 pm

Actually, no, the pressure in the hot end (as in - nozzle) is the same at worst, maybe slightly smaller (according to some) at best.
The force required to drive the filament is greater. Nozzle pressure != extrusion force.

The cross section of the melting zone for 1.75 mm is much smaller than for 3 mm.

P = F/A

Ceteris paribus, smaller A results in greater P.
Since the F is greater for 3mm, it (almost) evens out.
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Re: New SeeMeCNC Extruder

Postby Turbo442 » Sun Jul 21, 2013 8:31 pm

Here are some thought for you guys having issues extruding.

I have found that to make an extruder work reliably you need to have the following conditions met.

1. The extruder steps need to be calibrated properly. Too much plastic and the pressure will build up causing all kinds of problems. Too little and you will have an ugly print but not a plugged extruder. If you dont know how to calibrate your extruder steps...STOP that is your first problem.

2, Your z height steps need to be calibrated properly. Too little steps and once again the pressure will build up. Yes problems. Layers mushed onto layers. Too large of a step and you will have an ugly print but not a plugged extruder. If you dont know how to calibrate your z height steps...STOP that is your second problem. Mount a dial indicator on your carriage if you need to confirm.

3. Your stepper driver current needs to be set adjusted properly for both z height and the extruder so you don't miss steps. The current can be too high or to low and cause issues.

4. Your hot end temp needs to be calibrated and stable. Temp too low and the pressure goes up. Problems. Temp too high and the filament can get soft, shear, bend, heat soak the motor, etc.

5. Your hot end needs to be insulated to protect it from fan air flow and movement. This will keep the temperature more stable and at the correct temperature to extrude.

6. Using a modified Makerbot style hotend (QUBD style) I have found that bolting the heat sink block directly to the back of the ORDBOT aluminum carriage sucks the heat out of the block better and prevents heat creep. I was thinking if we re-thought the design a bit we could completely get rid of the fan and heat sink and turn the carriage into a moving heat sink with some fins. The carriage is a big chunk of aluminum with large surface area.

7. Once you assemble your hot end bring it up to temp and prepare to tighten everything while its hot. This will keep it from loosening up the first time you run it. Loose hot end parts creates a big mess.

8. I machine and polish my own barrel from a bolt. I make sure the barrel diameter is exaclty that of the inlet hole on the nozzle. My nozzle outlet is .35mm. I hone the barrel and nozzel together on a lathe after they are mounted on the heater block. Try not to have any steps, gaps, size changes between the barrel and the nozzel until it gets to the .35mm outlet hole. I am not using any PFTE tubing.

9. Make sure you have your thermisister mounted in a hole inside your heater block securely with a dab of heat sink compound in the hole. DO NOT EVER LET YOUR THERMISITER FALL OUT...IT COULD CAUSE YOUR HOT END TO BURN YOUR HOUSE DOWN.

10. I am currently printing most PLA at 200C and ABS at 230C. Not having any plugging issues. The blue vase was PLA and took 6 hours. The wall thickness is one layer thick though, pretty easy to make look good on any printer. The yellow quadcopter leg was abs at 230C which was printing while I made this post.
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Re: New SeeMeCNC Extruder

Postby albill » Tue Aug 13, 2013 12:02 am

Turbo442, how did you attach yours?
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Re: New SeeMeCNC Extruder

Postby JakeS » Tue Aug 13, 2013 4:35 am

I have a SeeMeCNC EZstruder with a J-head printing with 1.75 mm PLA and I am very happy with it. I am curious about everyone's experiences with print speeds- what are your max print speeds with a similar setup?

Thanks
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Re: New SeeMeCNC Extruder

Postby goopyplastic » Mon Sep 02, 2013 3:39 am

did the source file for the 6mm blue acrylic carriage ever get posted somewhere?
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Re: New SeeMeCNC Extruder

Postby flickerfly » Mon Sep 02, 2013 1:58 pm

Yeah, the STL is around somewhere, but I don't recall where. I'd assume in the forums here. A new version of the off-center spacers (or whatever they are called) that are appropriate for that material also was put up for sale on Instructables IIRC.
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Re: New SeeMeCNC Extruder

Postby flickerfly » Wed Nov 27, 2013 3:36 pm

I just ran across this in thingiverse - a Dual EZStruder mount that looked interesting:
http://www.thingiverse.com/thing:138425

Image
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