The Chimera Project - Laser + 3D Printing

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RepRap In Control!

Postby bdring » Mon Aug 30, 2010 10:45 pm

It works! Stupid "parallel port" cable didn't have a pin 25. Some 25 pin cables are actually serial port cables. Video coming soon!
Bart
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Re: The Chimera Project - Laser + 3D Printing

Postby rEd86 » Mon Aug 30, 2010 10:48 pm

Wow, that must have been fun to debug. Glad to hear you figured it out. We look forward to seeing things in action!

--Ed
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Re: The Chimera Project - Laser + 3D Printing

Postby bdring » Tue Aug 31, 2010 2:10 am

So I debugged the cable problem pretty easily. I was then able to control the motion via the ReplicatorG control panel. +/- was right on all axes. I know you can easily change it, but how lucky is that.

I am new to RepRap, so I played around with it a little to get familiar with it. The speeds and resolution were all wrong so I needed to create a new driver for my machine. You do this by modifying machines.xml. It took me a while to figure out the one in the program directory is not the one you change on Rev 0018. It is in C:\Documents and Settings\bdring\.replicatorg. I copied the basic CupCake machine and only adjusted the axis parameters. See my settings below.

Code: Select all
<machine>
      <name>Buildlog.Net G540 Laser</name>
      <geometry type="cartesian">
         <!-- different pulleys on X and Y axii -->
         <axis id="x" length="300" maxfeedrate="1800" scale="49.2126"/>
         <axis id="y" length="300" maxfeedrate="1800" scale="49.2126"/>
         <axis id="z" length="300" maxfeedrate="500" scale="5669.2913"/>
      </geometry>
      <tools>
         <tool name="Pinch Wheel Extruder v1.1" type="extruder" material="abs" motor="true" floodcoolant="false" mistcoolant="false" fan="true" valve="false" collet="false" heater="true"/>
      </tools>
      <clamps></clamps>
      <driver name="sanguino3g">
         <!-- optional, defaults to first serial port found.    <portname>COM1</portname> -->
         <!-- required: we need 8 bit and 38400 baud. -->
         <rate>38400</rate>
         <parity>8</parity>
         <!-- optional, defaults to 1.                          <databits>1</databits> -->
         <!-- optional, defaults to N.                          <stopbits>N</stopbits> -->
         <debuglevel>0</debuglevel>
      </driver>
      <warmup>
      </warmup>
      <cooldown>
(Turn off steppers after a build.)
M18
      </cooldown>
<machine>


rep_driver.jpg


Since my extruder is not setup, I did not try to run a real STL file. I did create G-Code for one so I could study it. I made a simple "draw a box" program and it worked. There is no acceleration parameter, so you need to keep the speeds pretty low to avoid jerking.

I then wanted to have some fun so I wrote a very basic post processor for Vectric Aspire. I drew a quick Hello World and generated a g-code file from it.
.
hw_aspire.jpg

rr_post.jpg
rr_post.jpg (10.25 KiB) Viewed 14871 times


I imported it into ReplicatorG and gave it a whirl. It is drawing HELLO WORLD. It would actually do it with the laser, but the speed is a little low and it would not turn of the laser between strokes because the laser enable is not hooked up to a RepRap.
.


Next step is setup up the extruder and mounting the printer head on the track.
Bart
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Re: The Chimera Project - Laser + 3D Printing

Postby bdring » Wed Sep 01, 2010 1:04 pm

I got the whole thing assembled and installed last night. The extruded heater and thermistor behaved perfectly getting up to temp rather quickly and holding there with a nice flat line. I fed some ABS into my motor and it started pushing it through the long 30" PTFE tube. It took about 5 minutes.

The head started squirting plastic, but the motor was slipping a lot and I did not feel I was getting much material out. I made a quick set of set screws to add a micro adjust method of pushing the idler wheel. That helped a lot and while I was not real happy with the plastic volume coming out, I decided to give a print a try. The sequence of everything looked good, but the head was moving way faster than the plastic was coming out. I ran out of time and stopped there. I need to figure out how to adjust for all that.

The Bowden cable appears to add some extra resistance to the motor. The bowden cable stores a lot of compression in the filament, so it continues to squirt a lot after stopping. I might see if I can add some extra reverse time to the stop sequence to relieve this. I have no real feel for what is right and what is not. I need to do some research and watch some videos.
Bart
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Re: The Chimera Project - Laser + 3D Printing

Postby rEd86 » Wed Sep 01, 2010 2:06 pm

Can you back off your idler wheel enough so that you can feed the 30" of ABS into the cable quickly? That will be a must for when you're changing plastics - both for loading it and backing it out. (with several colors available for printing, your creative side will want to express itself)

Even though there is compression in the filament, I would think that backing it out would act the same way - you've just got more pressure in the cable as well as at the nozzle. Keep in mind there is some squirting on a Makerbot as well when you stop the motor. I can record/post some video for you so you get a baseline if you want. The three factors that effect how much ooze are the temperature of the nozzle, the size of the nozzle hole used, and the speed of the extruding motor. (how much pressure has built in the nozzle)

This is going to require a lot of trial and error since there isn't any good documentation (to my knowledge) about bowden cable use with extruding. A lot of tweaking on the extrusion speeds and the motor speeds and various times. (straight lines verses tight curves, etc) There are a lot of settings in Skeinforge that the community has tweaked for the Makerbot over time. I don't know if you've found this reference yet but it may be helpful:

http://wiki.makerbot.com/configuring-skeinforge

Good luck!

--Ed
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Re: The Chimera Project - Laser + 3D Printing

Postby bdring » Wed Sep 01, 2010 2:47 pm

Back off the idler for quick feed...yes probably. That is a good idea.

I am not sure I meant the "compression" is totally in the filament. If the filament were incompressible the PTFE jacket might start to stretch to store some "pressure". There might also be some energy stored in the geometry of the loop. A classic Bowden cable is the hand brake on a bike. When you pull hard the jacket moves and and returns. That move back is a release of some energy. There is no visible effect like this, but it would happen slowly on my setup.

Videos: I would like to see just a free feed of material into the air so I get a feel for that. Then a print speed with that setting. I am working with a totally new machines.xml that is probably screwed up too.

I wish I had taken some pictures and videos. I just ran out of time last night. I'll post something soon.
Bart
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Re: The Chimera Project - Laser + 3D Printing

Postby bdring » Fri Sep 03, 2010 2:37 am

I can't get the Bowden cable system to push enough to get decent flow. Here is my setup. The cable is a smooth fit with just enough clearance, but it still adds a couple pounds of force. Note my little tensioner screws the push on the pinch wheel. That allowed me to fine tune the pressure, but still not enough. I was all a temporary setup of course.
.
bowden_setup.JPG


So I decided I need to crawl before I try to run, so I made a smallish mount for the motor right on the carriage. I will give it a try tomorrow.
.
local_motor.JPG
Bart
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Re: The Chimera Project - Laser + 3D Printing

Postby bdring » Tue Sep 07, 2010 12:28 pm

I finally got my extruder working enough to print a few test prints. I need to make a decent bed to print on. I am just printing on a piece of Acrylic now. I am going to laser a cross hatch pattern into it to give it something to bite into. A heated bed would help too.

I had some trouble with the Z axis misbehaving. It would not move consistently. It appeared to be missing steps. I currently have very high steps/mm. I lowered the max speed and it does a lot better.
Bart
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Re: The Chimera Project - Laser + 3D Printing

Postby rEd86 » Tue Sep 07, 2010 12:44 pm

So did you get it working with the motor mount on the carriage or with the bowden cable system?

What type of motor are you using for the extruder? If it's the one that comes with the Makerbot, I wonder if it has enough torque to work with bowden cable system.

--Ed
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Re: The Chimera Project - Laser + 3D Printing

Postby bdring » Tue Sep 07, 2010 1:08 pm

Extruder is mounted on the carriage. I just duct taped the 3D printer carriage and laser carriage together for the X motion. It worked fine.

The motor has never stalled or even slowed down with either method. It just slips on the ABS. I am using the MK5 drive wheel. I tweaked the design of the idler wheel and the split Acrylic pieces right around the wheel and that seamed to help. I also ran the temp up to about 240C. It is not a very robust design. It would be nice if it just worked...no adjustments needed.

I might upgrade to the whole MK5 system soon. I hate to pay for a whole system, because I have a lot of the parts already. I asked on Thingiverse about the material thickness, but no responses yet. I would like to hold out for the stepper motor too. The Bowden cable needs a high speed feed method.
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