Spool failure

Well, today when i was printing the filament spool holder broke off at the arms that hold the rod up. This caused the entire spool assembly to come crashing down on top of me. Luckily no injuries to myself but it looks like the spool will need to be redone with some new support structure, the spool itself is fine likely to the face that it was printed in parts that lock together so when it crashed it came apart rather than breaking the arms off. My supports that i designed to hold up the 1x1 posts held just fine likely due to my over design of them. Ah well, back to the drawing board i guess.

printing well for a few days now

Things have been printing well for about 4 days now, I'm starting to get a small pile of mendel parts. I've solved the phantom print layers by unchecking an option about adding a raft when i've turned them off. Also I found that my printer wasn't moving high enough or the material was swelling and I had to adjust height the print moved each level. Last problem to get solved were that some files seemed to print in the wrong direction causing them to squish, or simply become blobs of uselessness. After receiving some advice that I can reorient things in the control program itself, that issue should no longer be a problem. Hurray!

printing mishaps

Thursday I began attempting to print the first of my RepRap parts for the Mendel I've been working on for some time now. I would get part of the way through the print and the whole print would shift in each new row after that point. Thinking it was a bad file I redid the file to generate new code for the machine and this time it got further before the same problem began again. Thinking maybe the base file was flawed I tried another part. This part also was screwed up. That's when I found the problem. One of the drive belts/pulleys had gotten loose causing slack that would make the whole access fall out of alignment as it printed and hit that slack point. Having found this I cooled down the machine and attempted to tighten the tensioning part associated with that pulley/belt.
Today I updated the firmware, and the controlling software. Things were printing out wonderfully but again it became messed up at a certain point past the others. So first thing I checked was the tensioning part, and low and behold it appears to have slipped again. Looks like I'm going to have to try again or perhaps look for some other locking mechanism to hold it if it keeps slipping. So now I have to wait for it to cool down, then its back to fixing it up so I can try again.

Well, the new extruder came last week, and I've scanned all the acrylic parts in case I need to replace any of them I can make exact replicas. After hooking it up and doing a heater test, and a filament test, I was set to go. This new extruder is majorly more reliable than the old one, and the power resistors don’t explode as I had a problem with my homebrew attempt. Also found out that my block was much larger which could have explained that problem as well.

Now that I have a reliable extruder I’ve been able to start calibrating the skeinforge settings again. I got a very rough but workable version going, but thanks to makerbot forum user Sideburn, I was able to use his setting profile for the heated bed, and I’ve been able to get some pretty decent results, it may just require a tiny bit more tuning to get it to run a little faster.

On a separate note I’ve completed assembling all the electronics for the Reprap I had started before purchasing the makerbot. I now hope to use the makerbot to print out the support parts so that I can complete the reprap. Hopefully once I have two bots able to run I can get more output perhaps work on an automated print system for at least one of them while I do normal printing on the other machine. Then it’s back to trying to make a CNC mill.

Didn't want to, but I had to do it

Well, I finally broke down and ordered the newest version of the makerbot plastruder. I was really hoping that my DIY efforts could make me a suitable plastruder clone, but I guess the software/firmware for the makerbot is made to a very tight tolerance and my parts are over that tolerance. But this time i'm going to make patterns and take measurements of all pieces I get so that I can keep within tolerance. So until it arrives, I guess I'll work on my filament spool/holder.

Oversights

So with the printer shelved until either I find a fix for the relay problem, or makerbot releases a fixed firmware update, I'm back to working on my Mantis 7 DIY mill. I originally started this project in hopes of making the pcbs for the reprap that I couldn't order from makerbot, wasn't practical to send out for fabrication, and my own prototyping. The mechanical building had some small issues but I eventually got those solved out. Then came the electrical/computer parts, I chose the brute force stepper driver from the Mantis 7 Wiki but when I hooked up the design nothing happened. I tried running through it to find shorts and whatnot but couldn't find much. I then ordered a probotixs breakout broad to avoid the hassle and possible shorts of wiring my own port to individual wires. I then made boards that were controlling a single motor per board and hooked those up through the terminals on the probotix board. Again things didn't work and I didn't know why. Next I ordered a unipolar stepper driver board from probotix, and hooked that up to the controller board and the motor, still nothing. According to the original plans from mantis I was using a 12V DC external power supply to run the system. Well after picking up the project again and trying to find if all the connections worked, I noticed something that I had overlooked. What I had overlooked was that the stepper motors were only needing 4V and 1.2A, the spindle motor was the only thing that needed 12V dc, and one reason things weren't working is that my motor coils were completely saturated so there was never a change in coils regardless of what signals were sent from the controller board. So now I have to wait for the coils to de-energize completely before I can try anew without the external power supply to see if that works. I guess it would have really been helpful if the mantis site had a BOM including steppers so that everything was on the same page or if needed to be tweaked had some sort of base to calculate from. Ah well, just another day to learn things.

More problems, but maybe not my fault?

So I had to make a new heater core to accommodate a second heating resistor because of some problems with stabilizing the temperature, and that I think I had uneven heat distribution causing a clog that eventually burned a little making the old barrel very dirty. I then worked with my father to generate a new barrel/tip combination similar to that done by makerbot on their new MK5 extruder. I now have a steel barrel going to the heater block, and a brass tip made from a MIG welding tip that we retrofitted to fit our needs. The block is now more of an I-beam with the barrel running through the middle of the I and one resistor located within each of the side openings.

This then lead me to my test the new heater, which I discovered quickly could not be run through the extruder board but had to be run through the relay board, which I had been trying to use due to its own little problem. So I looked into that problem to see what was behind it. I found that it had to deal with the firmware update and how they were dealing with slowing the heater as it reached the set temperature by cycling the power on and off for shorter periods of time so that it wasn’t being constantly driven and overshooting the set temperature by a good deal. Either the waveform they decided to generate didn’t have high enough bounds or the signal was picking up a lot of static or interference, and this caused the signal to cross the working thresholds of the relay. This made the relay switch at very high speeds causing a loud and annoying screeching noise as well as never allowing the system to reach the set point before it gave up and allowed to go into the cooling cycle before kicking the heater on. This would be similar to using cheap push button and it seeming to have multiple presses when only pushed once by a phenomena known as “bouncing”. This can be solved in software or hardware and its much cheaper to solve this with software. To debounce the system allow the software to only send an output and/or receive and input within a set period of time before being allowed to react, this allows the signal to settle before the next test cycle occurs removing many of the erroneous signals that may become present.

Due to the fact that I know nothing of the software environment of the system I can’t readily solve this problem without learning a lot of about the system, but I could create a hardware solution to hopefully solve the problem. I’m hoping the folks over at makerbot will be able to send out a firmware update soon so I don’t need to buy components to make a solution with hardware to solve this minor shortcoming.

working, well almost

So I know that my new heater core works, I did notice that I was still having problems with the idler wheel. I took it off and found some epoxy had spilled onto the outside edge, and was a little bubbled near the bearing. So I cleaned these up and went to put it back on and realized that one problem was the epoxy, the other was the idler was rubbing against the bottom of the geared tooth pulley. So I added another washer to fix the height and now it moves properly. When I reconnected everything I figured this time I would run the heater core through the relay board. Everything was going well until I neared the set point at which there was this strange screeching noise coming from what I thought was the board. Upon looking at it closer I found that the extruder board must be sending something like a square wave to the other board as it nears the set point so that it doesn't overshoot too much. Well as it would get close my homemade heater core must work very differently than their so it would send the relay board into a fit switching the relay so fast it would sound like screech. Guess I'll just have to run it through the extruder board again, so much for trying to be nice to the board.

Working thermal core design

After playing around with the thermal core using non-aluminum resistors, and doing a little milling, and finding a little ceramic insulation I now have a working thermal core that can hold a temp near 234C.

My testing was the same block as the aluminum clad resistors but with a hold drilled and the resistor inserted (it was a square resistor) so that didn't work too well as there was lots of air around the resistor that stole the heat instead of heating the block. Even when adding aluminum foil 66C was the best that did.

The second test was an aluminum block made thinner in width but with a channel cut from the side for the resistor to sit in, and taped with kapton. This got me to 207C which is close but not hot enough.

My final test was using the same block from test 2 covered in ceramic insulation that is 1/2 inch thick that I acquired from a nearby fireplace store. This got up to the 234C that I listed at the beginning. This means I can finally get back to printing!

Background

I have decided to write this blog in order to write about my trials and tribulations of creating DIY machinery to help me create things in a somewhat automated way. This all began when I stumbled upon the RepRap project through an instructable about CNC laser cutters and mills. It took nearly a year before i decided to build a reprap and by the time I had returned to the reprap page version 2 "mendel" was now up and running, so this is where I decided to start.

I made up a bill of materials, bought boards, components, rod, and belts. I was able to assemble almost all the electronics within a week after learning how to do surface mount soldering with a hotplate. I figured with that kinda speed i should be able to knock out this project in a month. Little did i know the hard part had just begun...

I was short 3 driver boards, and found that makerbot didn't sell the bare pcbs for them anymore. No matter i didn't need them till all the mechanical stuff was done anyway. This is where all the trouble started. Almost all the structural parts were made on a reprap and i did not have access to one already so i had to find other options to get those structural pieces. I found a set of 2d parts that could be printed and used as guides to handcraft the 3d parts necessary. This seemed all well and good, but due to heat issues i was limited to the amount of time i could spend outside in our garage shop. This made making the parts very difficult as i lack the skill needed to make the parts within a tight enough tolerance needed. So i enlisted the help of my father. Being that our time available in the shop was limited the parts moved slowly. I then decided it was a better use of our time if i bought a prefab machine to make the rest of my parts and then i'd have two working models so i could experiment on the other. So i purchased a makerbot cupcake cnc.

This proved to be a pretty straightforward build except that i found the acrylic parts in the extruder broke very easily and i had to make new parts to fix the broken ones. This set me back perhaps a day to get it all sorted out and then i was printing. Then i found that my barrel was pushing out of the thermal barrier because in replacing the block i neglected to put something to attach the retainer ring which seemed unnecessary at the time. I fixed this problem only to have to make a new barrel and tip as i ruined them when the barrel pushed out and crashed into the bed. This proved to be a time consuming and annoying problem. I started out by trying to make a piece of brass rod lathed down to the proper size to thread and then drill out the proper hole. While attempting this i had problems with the rod bending, or the drill not being centered and coming out the side. Most of these problems may have been due to an uncentered part in the lathe. I finally decided to cut down my problems by purchasing brass bolts of proper thread and length, cutting the head off, and drilling down the middle. This worked well except some bolts have hard spots that cause the drill to deflect, so its a matter of finding a good bolt. To rebuild the tip i used a tip on the reprap site and i got brass acorn nuts and just drilled out the little hole needed after i rethreaded the inside to work on the new barrel. This started to work but then failure of my nichrome wire. Again i had to wait for new materials to arrive.

While i was waiting i also started to read other blogs about reprap and found nopheads blog which led me to try a heater core instead of the finicky nichrome. This lead me to my current predicament. I started using some 12ohm power resistors but was unable to make the working temperature i needed so i looked back at makerbot which had just released their new extruder. It also uses a heatercore but uses 5 ohm 10watt resistors, so i went and got the exact specified resistors. When i attached them and fired them up they exploded, after a little fiddling i could get them to near 200C before they exploded but still failure. So i got some 15watt rated resistors and those exploded faster, which doesn't make that much sense. So going back to nopheads blog i decided to try his other heatercore version of inserting a vitreous resistor into the block instead of attaching the aluminum clad resistors to the outside. So this is where i sit.