Power Resistor Heater Experiment

I have been waiting for my order from the RepRap store to be filled with one of the key items on the order being the Nichrome wire.

So Buzz’s blog entry about using ceramic resistors and one of his replies to the comments resulted in this experiment.
http://builders.reprap.org/search?q=ceramic+resistors+as+a+low-tech+heater+element

His test rig was two 10watt resistors and he had suggested using four five watts resistors instead.

It seems that there is exactly one store left in the Seattle area that is selling components that is run by a number of retired guys; old hams, etc. Anyway after digging though their surplus bins and sorting lots and lots of resistors I managed to come up with two five ohm and two six ohm resistors; which I plan to put the like resistors in parallel and then the two groups in series.

The ideas occurred to me to sand off one corner of each resistor and have it surround the machined heater barrel that I got from reifsnyderb.

http://forums.reprap.org/read.php?94,18969



Which I managed to do and I have the following result.

While I am happy with my end result this was a bit more work then I had anticipated.

1. First up I used a belt sander with a fairly course grit belt and it still took a long time to sand the edges off. This ceramic is really tough stuff! At you can see I did it by hand so things are not too even. I could have made a jig to hold the resistors as I sanded them.
   
2. You have to hold the leads; if you let them vibrate they soon break the cement and start rotating at which point the heat transfer/magic dust inside starts leaking out.
   
3. The cross section on the resistors are not square; so you really have to keep track of which edge is which, especially when you start twisting the leads together!
   

I had an opps where one of the resistors that the magic dust leaked out of. It then fell apart after twisting and un-twisting the wires after making mistakes with the orientation.

As you can see from picture there is a wire wound resistor in the center of the shell, letting the air in might cause it to burn out. We will see as I have one resistor that some of the magic dust has escaped from in my quad pack.

Ok back to putting everything together. Rather then use JB Weld like Buzz did I decide to try heat sink compound so that I could salvage my barrel if it didn't work out.

As you can see from the last picture it almost seems that the heater barrel was designed for this!

To mount the 100K Thermistor on the nozzle I once again visited the sander to file the back side with a flat area and then a notch on the face for the hold down wire that I wrapped around the nozzle. I then used more of the heat sink compound to fill in the gaps.

The power resistors and thermistor are simply secured with twisted copper wire. So it’s easy to take back apart again if necessary.

Getting ready for extrusion tests; after coding up the test routine I discovered my PWM driver board isn’t working correctly so I got to figure that out.

So in the meantime I clamped it to ExMrCleans temporary Z axis arm.





Fixed my PWM driver board this morning, it turns out I got one of the kits with the 100K resistor instead of the 1K’s and didn’t pay attention to the third color band. I must be really getting old as I sure remember resistors being easier to change!

Anyway fired it up and it seemed to climb at a fairly rapid rate, it reached a maximum temperature of 227C with no insulation.

My very first Fiber!

Another item I have been wait from the store is the ABS reel. So in the meantime I decided to live dangerous and experiment with weed wacker cord. They had lots of various white and green cords but I decided to go for Red.

This is what I picked up from the Garden department at the local Fred Meyer, have no idea of what kind of plastic that it is, it measures out to 2.7mm.

After the temperature passed 200C I got a bit impatient and inserted the weed cord and heard some crackling sounds; when I pull it out it sort of looked charred.

So I figure opp’s wrong type of plastic to use and then tried melting it and some white cord (2mm) on the soldering iron shank with the iron turned down to 250C on it’s dial.

The white appeared to melt better so I then inserted that and then started getting red fiber out of the nozzle from my first insertion.

The fiber measured between 0.5mm and 0.6mm out of what I think is a 0.4mm hole that reifsnyderb has in his machined tips.

Further thoughts

• While it did take a bit to do the sanding I am fairly happy with my results.
• My initial thoughts were that the barrel should be a square so that you can simply butt the resistors to the sides. It looks like nophead has come up with a better approch (naturally).

http://hydraraptor.blogspot.com/2009/01/yet-another-quick-heater-hack.html

It does take a bit of fource to hand extrude and it started slipping out of my temporary clamp so going to hard mount it after I come up with a better mount.

Major construction is done!

After discovering that the Sanguino wiring pinout’s is different then my adaptation of the Arduino wiring; it was time to rewire my setup and see if I could true out the alignment of the Z stage more. (Note: The RepRap web site now shows the correct documentation, I was doing my construction during the transition phase.)

When the new Sanguino motherboard becomes available I will switch over to it, though I think at that point in time I will populate my breakout board and motherboard with components so I have a unit for my nieces and nephews to play with.

Here are the pictures of the main wiring on the Sanguino breakout board/shield.

From ExMrClean

Stepper Motor boards on the other side and bottom.

From ExMrClean

The current plan is to try and mill the Darwin mount base and extruder feeder parts like nophead did for HydraRaptor.

http://hydraraptor.blogspot.com/2007/06/bob-on.html
http://hydraraptor.blogspot.com/2007/10/extruder-dimensions.html

Mounting the Z Stage

I got the metal for mounting my Z stage at a surplus/recycle metals place not too far away.

Wandering around the yard I found a piece of aluminum that was 1/3 inch thick, eight inches wide and about 15ft long which had one end a lot splattered welds and had been drilled for mounting in it’s previous life.

Got them to cut me a few pieces in various lengths of which I used the longer length as a base and split one of the pieces vertically with my small band saw to hold the Z stage vertically.

Needless to say the small band saw wasn’t really up to the task even with a new cutting band on it. The cut wandered all over the place so it you look closely at ExMrClean you will see that the back side edges are uneven for the Z axis mount.

From ExMrClean

The metal was also fairly groady from being out in the elements and sort of had this northwest Seattle climate slime on it. Hmmm, how to clean it up? A couple of passes through the dishwasher on heavy pot scrub cycle did the trick!

In the first mounting it was substantially out of true, it was almost ¼ inch out of true between the top and bottom of it’s travel. Since this spread out over almost 14 inches of travel in the vertical axis I initially left it at that.

With having to rewire I figured time to take it apart again and see if I could get it more accurate. About the only tool that I had that I could use to do this is my bench belt sander and needless to say it was a real adventure to try and sand the Z axis supports true by hand.

After chasing it for quite awhile I finally used a level to make sure the sander surface was level and then clamped the level to the top of the Z stage and watched it while I sanded the supports on the bottom. Still not perfect but a heck of lot closer!

As I mentioned in another post this design that I came up with is not really ridged enough as nophead suggested if you are going to be doing milling you shouldn’t be able to move things by grapping on to them. ExMrClear fails that stiffness test in its current form.

In hindsight the base should have been thicker and like the McWire design the Z movement should have been over the center of the moving table. I have this long arm to reach the center of the XY table from the Z axis so any pivoting permitted by the stage is magnified at the end of the arm.

Given that I can barely pick ExMrClear up now to move him; I will hold off beefing him up more!
Of course part of it might be that the center arm is made of wood. I haven’t been back to the metal place as our area has been fairly much snowed in with a once a decade (or more) snow storm and every time I have been by they have been closed.

More on End Stops

I previously blogged on my X & Y end stop’s being Hall Effect Limit sensors, so I thought I would write more on using the standard RepRap optical sensors on ExMrClean for my Z axis.

In a bit of reading at the CNC zone about the Hall Effect sensors the author mentioned that they are real easy to position to set limits since they in them selves are magnetic.

This got me to thinking as how I would implement a similar functionality on my Z stage since I am planning a lot of dirty activities for ExMrClean.

Since my Z stage is most aluminum I hit on using flexible magnetic strips that I picked up for a buck at the hobby store.

From ExMrClean

Since the strips have magnetic poles you should see how they best join together to not reduce have them fight each other and reduce the attraction power before you peel off the paper over the adhesive. In my case I have two strips on top of each other at maximum travel and two sets of two at minumum travel.

I then took a nylon screw and attached it to a metal strip to dock on to the magnetic strips. I used a nylon screw since it was easy to sand down to a flat surface.

From ExMrClean

Then by moving the status LED to the other side of the board it cleared up the mounting hole on the optical sensor to attach the metal plate too. A little bit of injected hot glue to make the assembly more ridged so it wouldn’t pivot on the screw and I was done.

From ExMrClean

Here’s a picture of the minimum/home sensor magnetically attached. It's simple to slide the sensor up and down to adjust the home position.

The optical interrupter plate/vane is a plastic tool tag from a punch that I brought that I simply mounted on the side of the movement stage.

From ExMrClean

Further thoughts

When I finally getting to extruding I should make a guide to align the metal strip laterally, right now if I do not test after a repositioning the moving stage can knock the sensor loose.

The RJ-45 cables are a bit too stiff to use in this mode, even though they are ok once they aquire a set in the approximate location. I should really use more a flexible cable or wires that will not try to drag the sensor around.

SMC mod for single cable end stop sensors

Here's a picture of my modification to use a single RJ-45 cable for the minimum and maximum end stop sensors.

It allows the use of the unused orange wire(pin 2) to carry the opposite signal sense. As you can see from the picture I made use of the signal pad for maximum and soldered it to pin two of the RJ-45 jack.

From ExMrClean

While you are at it might make since to do the same going the other way so if you want to reverse your axis direction you would simply move the plug from the minimum jack to the maximum jack and turn around the motor plug on the other side of the board.

Also a quick picture of the 7404 inverter chip that I inserted/hacked inline to reverse the logic level from my hall effect sensors so that it matched the optical end stop polarity.

From ExMrClean

Hall Effect Sensors

Since my X & Y stages already have endstop sensors that are already mounted and take in account the space needed for the folding shields I most definately want to reuse them. Also since the opto sensors are the wrong physical layout to insert in their place, it makes even more sense to reuse them.

After my shopping trip to get more Allen wrench sizes I start taking off the old end stop sensors and what the heck they are magnetic, not optical!

Hmmm at least they have part numbers on them, time to Google them to figure out what the heck they are. The only hit is for a store for obsolete parts and they want $80.00US apiece for them.

No Matches for technical data so I keep shorting the part number until I finally get some hits as a family of parts.

Turns out they are Honeywell Hall Effect limit sensors, that takes another half a day goggling before I find a circuit to wire them up, which turns out to be simplicity in it self.

From ExMrClean

After a bit of experimenting it is determined that the devices I have are active low. Until the metal vane on the movement stage moves into the sensor zone it is conducting current and illuminating the LED. When it kicks over it stops conducting, which in this case if you monitor signal of the output lead from the sensor it goes from a low to high value.

In examining the standard RJ-45 color code/pin out and how it is mapped into Opto Endstop RJ-45 connector I determined that one of the four pairs of wires is unused.

Since one of my stages has a DB-9 connector for the end stops. I decide to use a single RJ-45 cable for both signals back to the stepper motor board.

In the color code the blue, white-blue is the positive connection. Brown, white-brown is ground. The Green wire is used for the end stop signal and the Orange wire is un-used.

I make a quick mod to the stepper boards to add a jumper from the max optical input pad to pin 2 of the minimum RJ-45 jack. Then at the end of my single Ethernet cable that I have hacked the end off of I wire the minimum output pin of the DB-9 to green and the maximum output pin to the orange wire.

The other stage (Y) used to have a connector but it had obviously failed at some point and to repair it they had fished out the wires and solder new ones directly to it. So for that stage I put the parts onto a small chuck of prototype board and hot glued it in place.

I now had all my end stops working and created a quick exerciser program that cycled all three axis’s between the end stops, counting the steps it took to go from end stop to end stop and let it run for 24 hours.

After looking at the G-code program sketch it has support for active or active low signals from the end stops, but not having mixed values on the same machine!

Since my hall effect sensors are backwards from the normal signal from an end stop, I add an inverter section out of a 7404 chip so it gives the same output as the standard Optical end sensors that we use.

Where to put the need inverter chip? I could have dead bug glued it next to the Sanguino, but elected to install them inline with the cables using plenty of hot glue to encapsulate them and to electrically insulate them.

Rethinking the solution:

I should have simply used the end stop kit from the store and had the LED side of the optical sensor powered via the hall effect sensor.

Initial flurry of activity

DAY 1

Was spend unpacking everything and mounting the first two stepper motors to the X & Y stages. Put aside the electronics control box that came with my stages as I am going to use RepRap electronics.

From ExMrClean

Day 2

Build of the electronics, Sanguino goes very rapidly! Next board is the PWM driver which goes ok. Time to tackle the driver boards, RRRP store link directs me to V1.1 rather then V1.2 drivers, all three driver boards are missing the same components by the V1.1 info.

I follow the v1.1 instructions and am highly unsatisfied with the build progress as it wasn’t like the Sanguino where the installation and soldering was lowest profile component to highest component which make it easy to insert, flip and solder!

Day 3

Was missing components from my driver boards so visited the rat shack for resistors and capacitors to finish my drivers. Researched on how the steppers would be wired up and solder necessary wires together to get down to the four needed to attach to the driver board. Then wired up the remaining stepper for the Z axis to a plug for testing.

Realized that my Antiono breakout board was useless for the Sanguino board! Read that Sanguino was designed to plug into a bread board.

Finish all three boards and then I finally notice the URL reference on the static wrap that lists a link to the instructions for my V1.2 boards!

In the meantime I had fired off a QA report to Zack suggesting better build procedure of lowest to highest that was fairly much reflected in the actual build instructions once I found them, missing components are actually optional opps! Sorry Zack!

Day 4

Purchased breadboard for Sanguino on way home, scavenged a couple of AT style power supplies from the IS department at work along with old Ethernet cables. During the day printed out diagrams for recommended Arduino wiring and Sanguino pin outs on works color printer.

Assembled the breadboard and find that Sanguino doesn’t fit the rat shack version! Sanguino design assumes standard IC width between the rows, not rows that are butted together.

Figuring out what wires of the ribbon cable are for what for getting the Z axis stepper motor to spin, ten wires are present but only five of them are in use counting the ground wire.

Wiring on the ribbon cable from left to right with red strip on the left is:

1. No Connection
2. Ground
3. Step
4. Direction
5. Enable (tied high to VCC via a resistor so not used, so effectively no connection)
6. Minimum sensor line
7. Maximum sensor line
8. No Connection
9. No Connection
10. No Connection

Solder wires to some header pins to plug into breadboard, decide to reinforce with hot glue to turn into mini plug.

Discover hot glue gun must have been left on for months at low heat, filled with dry brown gunk; after poking various gauges of wire up nozzle finally get it to flow. It takes quite a while to flow and most of a long white glue stick as it flushes out the old stuff before it turns white again.

Make handle with painters tape and hot glue and burned fingers; I guess I will have to predict a lot of this with this project?

Test power supplies; second power supply I grabbed just in case is the one that works.

Hook up stepper boards one by one and observe that the LED’s work. Followed by hooking up the Z axis stepper which gives a little scratchy noise on power up as it jumps into phase/step.

Use screw driver to momentarily ground step line and watch the motor step and the step LEDS change colors as it moves from phase to phase.

Day 5

Figured out how to compile a sketch and upload it to the Sanguino, did the blinking led test.

Then I ran my first stepper test with the motor waving the tape flag! Opp’s half of one of the drivers board is not working, must be a bad L298N. Though interesting enough it will step at some speeds but not others!

Experimented if we could drive the motor faster than the lower 600 value in the stepper motor test, no luck.

Day 6

Started wiring up the steppers for the X & Y axis’s and laying out the wiring on the breadboard for my repstrap!

Assembled the X&Y stages by stacking the Y stage on top of the X; quite a chore to get them to snug up together over the registration / alignment pins.

Given how tight the tolerances are I have a very high confidence that it is square.

Started figuring out how the desk is going to look and how I want to route the wires.

From ExMrClean

Day 7

Need to figure out what the wiring is for the limit switches that are on the stages, do not have a Allen wrench that will fit to take off the old sensors so off to the tool store (Harbor Freight ) to buy more tools, end up spending most of the morning wandering around shopping!

Finished wiring up the breadboard and the stepper motor to driver cables. Time for some movement!

I am kind of worried that since these stages are fairly massive that it will just sit there and groan.

X stage starts right up, takes a while for me to realize that it is actually working right off the bat, no complaints!

It goes though the speed tests and doesn’t like 750 or 600 values of the stepper motor tests.

Now since the X stage is carrying the Y stage around with it I assume that the Y stage will move better, wrong guess. Y stage for some reason 900 and below it moves one direction but not the other; might a resonance thing?

Manually centering the stages before running the tests and it is getting closer to a limit with each failed movement and I have no limit switches wired up or software that is testing for them since I am using the stepper motor test program.


Day 10

Time to tackle the Z stage which has a Pittman motor on it which is not a NEAM mount. Pulled up the engineering diagrams for our stepper motors and make multiple attempts to figure drilling dimensions for the center of the Pittman motor which has an offset center for the shaft; to the NEAM 23 mount.

Doesn’t work out until I actually measure my stepper motors! Lots of tiny drill marks that are thankfully hidden by the stepper motor once I get it mounted.

Work kicks into high gear with massive overtime so I have been stalled for a while!

Things learned:

1. Sanguino is still the new kid on the block so not to order the Arduino bundle. (Store now has a Sanguino Breakout Shield Kit, so will place another order.)
   
2. The stepper motors selected for our projects actually have some fairly good strength.
   
3. Electronics are fairly advanced; almost turn key, great work everyone!
   

Work still to do:

1. Get Hall Effect end stops wired up and tested.
   
2. Test Z axis now that the stepper motor is mounted.
   
3. Mount the Z axis.
   
4. Figure out how to calibrate everything!
   
5. Start thinking about the extruder!

EBay Purchase

After waiting a bit for my xy table/slides to be motor freighted to me, it finally arrived on a Monday.

Picked up the XYZ stuff from the shipper at lunchtime so I could draft an employee to carry it into my place once we had broke it down on the shipping pallet it had arrived on.

Gloated over my massive hardware! (Ok someone with a CNC mill would not think it massive.)

Electronics and stepper motors also arrive from the store; box is almost totaled on one corner but everything appears to be ok.

That evening I started unwrapping everything to figure out what I had, found out the XY stage had servo’s rather then steppers motors.

My question about how many wires coming out of the motor was answered by the number of the pins on the connector; which was four and turned out to be two for the motor, ground and an unused pin!

Dumb luck aside the old servos were NEMA 23 mounts, the same as the stepper motors from the store! Good thing I decided to order the steppers motors from the reprap store!

But hey the old servo's are NEAM 23 mounts, so I rapidly mount two of the steppers!

Needed to slightly drill the coupling plastic in the center to make the motors fit as the shaft is a bit longer on the stepper motors. Fifteen minutes of work and my X&Y stepper motors are mounted!

In looking over the electronics portion that I had brought from Ebay it was very interesting and told me a bit about its history.

From ExMrClean

Look at that locking emergency stop button!

First off it wasn't recent hardware as the PC portion of the main control unit did not have a PS/2 style keyboard connector and most of the boards plugged into it are ISA style. (Still haven't fired it up to see what was on it, suspect DOS).

From ExMrClean

Another big clue is as clean as the electronics are it had to have spent it's working life in a clean room, (not a speck of dust on any of the four fans) so the dust shields on the mechanics where more and likely to protect what was being handled verses the mechanics them selves.

So I suspect given that the control box also had pneumatic valves and that only the X&Y connectors are wired and the Z electronics were unused that this was a part of a semiconductor manufacturing line.

From ExMrClean

Ah the easy clean life of your first career is over, your new name is ExMrClean!

Given what I know now, should have told the vendor to keep the electronics and just shipped me the mechanical components. That way they could have been shipped UPS, rather then on a crate via motor freight.

From ExMrClean

From ExMrClean

From ExMrClean

EBay Lessions Learned:

1. Pure dumb luck that my stages arrived in NEAM 23 format, should have queried as to the actual model number of the motor. My Z axis had a Pittman GM9000 series motor so was enough real estate on its mount to overlay a drill pattern for the NEAM 23 format.
   
2. E-Bay XY stuff is more in likely for fine positioning rather then motion control (CNC) for handling semiconductor masks in IC manufacturing. Very precise stuff; but analog which doesn’t fit our model. I could have avoided truck shipment of the package as the electronics module is what put it over UPS standards.
   
3. Might have been able to re-use the servo motors by buying Gecko G320 drivers for them, but then would have also needed a higher voltage power supply. Motor’s are brush driven, might have needed new brushes, etc.

E-Bay Adventure

Hi Everyone

First off I would like to thank everyone who has gone before and contributed to this project!

I now have my repstrap moving in all three axis’s and figured it was time to start blogging about. Sort of the job is not done until the paperwork is!

I bit the bullet and ordered the electronic kits and stepper motors from the online store. My initial order was for the “Complete Arduino Electronics kit” and the Sanguino processor.

The original plan was to build the electronics first and then work on the mechanical. However the store was back logged on deliveries; so after reading a lot of blogs and forum entries I decided to follow NopHead’s example and start with a XY table.

So off to Evil-Bay I went!

Given the cost of a gold reprap kit I knew I could spend a fair amount of money and still have something that would give me a good quick start.

Since I am thinking of subtraction processes like milling a bit more robustness would be a great plus. (Great to see NopHead now has a mini mill, how long before he drives our solutions to be more universal? I personally can not wait.)

E-Bay search terms that I evolved to look for something usable are: xy stage, xy table, linear stage, linear slide and linear actuator.

Anyway after loosing a number of bids in the ball park of a Gold kit I managed to get an XY table and another slide to use for the Z axis for about $400.00 plus shipping.

Here’s the picture that enticed me as it already had the dust shields for milling.

From ExMrClean

After questions to the vendor the question that I posed was how many pins on the motor cable? The answer was four which I assumed was a stepper motor (opps more on this later)!

So I placed my order, contingent on the vendor throwing in the Z axis stage, which he accepted.