Thursday, July 31, 2014

No cigar ...

After all the effort of creating a separate speed control for the wire feeder ...
Now the TinyG motion control board is not activating a command to start the motor.
The strategy was to use the coolant on / off pin to run this circuit.
Commands M7 / M9 should be switching on / off  3 volts at the pin. 
G code commands M 3 / M5 are used to switch the welder on / off  with the spindle pin on the board.
The welder turns on / off as expected.
When the wire feeder is connected to the spindle pin all is fine.
Hooking two circuits to one pin out didn't seem like a good idea ... but ... I tried it anyways.
Both circuits switch on but won't switch off.
Operating both circuits from one pin isn't going to work.

A solution ? My first guess ... a firmware change or upgrade will need to happen.

Happy to say the feeder drive board has evolved away from bread board testing to a soldered connection prototype board. Also changed the potentiometer to a 10 turn precision version for finer  speed tuning. 

Wednesday, July 30, 2014

Bench Test Power Supply

As the control electronics evolve so do the voltage requirements supplying each board.
TinyG is 24V, Arduino is 12V and the H-bridge chip is wanting 5V.
The work bench is getting messy with all the various hook up wires and alligator clips that keep slipping off while doing a test.
so ...
I've seen PC power supplies being being converted to a bench test power supply. I hacked this one with a little guidance from wikiHow.

Wednesday, July 23, 2014

The gears are turning ...

The current design task is to adjust wire deposition rate with the turn of a knob.
After getting stuck trying to figure out Arduino stuff I was able to bounce questions off  Jonathan Ward at OtherMill an Zach Radding at zachraddingdesigns to good results. The motor runs and is speed adjustable.
Yesterday the motor was bench tested with no load for several hours and no issues. Microchips and motor temperatures were on target.
Today I'm trying to test the full load of the wire feeder and push some wire. Unfortunately something in the system is not happy and lays down for a nap after running just a few minutes. It appears the H-bridge chip taking a temperature spike causing a shut down. Allowed to cool a few minutes and away we go again. First impression for the cause of the problem is the input power to the H-bridge chip is not regulated.
More testing needed ...
The motor RPM has been slowed to the expected inch per minute wire speed which has lowered the chip temperature.
With this change the system has run for 3 hours with no problems.
This chip is a little too close to heat failure so when doing the final soldering a second chip will be stacked parallel to add a measure of reliability. On future builds a larger chip would be better ...

The Arduino code that works :

#include <Stepper.h>

// change this to the number of steps on your motor
#define STEPS 200

// create an instance of the stepper class, specifying
// the number of steps of the motor and the pins it's
// attached to
Stepper stepper(STEPS, 8, 9, 10, 11);

//Create starting position for motor / pot
int previous = 0;

void setup()
 //How fast will we try to move the motor
 //If your motor stutters, its too fast so just lower the value

void loop()
 //Read analog 0 (pot) and map it to the range of the motor
 int val = map(analogRead(0), 0, 1023, 30, 0);
 Serial.print(val, DEC);


Sunday, July 20, 2014

Solidoodle calibration

This early model Solidoodle V2 was purchased from a Kickstarter campaign a couple years ago. It has been attached to several different computers but has never produced exceptional quality prints.
I decided that with this latest computer set-up to spend the time to sort the parameters all the way thru to achieve the best possible results. 
When purchased the Solidoodle came with PLA filament so that set the template of use. The general defaults were used to produce OK prints.
The last time we tried to use the printer it was switched to ABS filament with very little success. Mostly because we couldn't run the temperature the material wanted. Scouring the internet I learned this early drive board has overheating protection written into the firmware that prevents it from running the temps ABS filament needs.
SO, then, to run ABS the drive board will need a cooling fan and an firmware change.
OK, then
How about refining the PLA settings ?
Easy enough ... oh sure ...
With PLA the machine prints the perimeters well but the infill and support just didn't work no matter what speed or heat setting is tried. The infill is a mess and this effects the top layer quality.
After about 20 tries of printing calibration cubes I finally hit the internet to understand what's going wrong. Turns out PLA needs a cooling fan which is absent from this machine.
So a small fan was attached to the print head by using some hardware wire. Power to the fan comes from an open 12V port on the board. Not the best fix as the fan runs continuously. This band-aid approach help print quality tremendously.
Done properly the slicing software can output different cooling speeds depending on what pat of the model the machine is printing. A different speed is used for perimeters, infill, support, bridges etc.
This Solidoodle drive board doesn't have the capability to turn the fan ON, OFF or change speed.
The board can be modified with some soldering and firmware changes.
Gosh ... what a couple days of lessons that was ...
Now I know all the major shortcomings of the early Solidoodle printers.

Saturday, July 19, 2014

Projects with wood

Lately  I’ve been feeling compelled to expand my artistic horizons with a few wood projects.
This is one of them.

The cutting board backstory.

Start of the idea ...
On the drive home from visiting mom I stopped at an intriguing wood fantasy castle in Kirby Oregon called the Burl gallery. Actually a gathering of wood artisans who have made an awesome roadside attraction.
One artist is doing fine cabinet work featuring dovetail joints as the cornerstone of his artist expression. Mostly a build to order craftsman he also had a collection of cutting boards made from the scraps generated from the cabinet work. The tourist trinkets for the walk-ins like me.
The artist sales pitch for his superior cutting board was how the dovetail piece keeps the board flat and solid making a longer lasting product. Something the engineer side of me can cherish.
His dovetails were done as “legs” that protruded off the bottom so the boards are “single sided”.
Second part of the idea ...
At home, my spouse, Chaney has a bamboo cutting board that she wrote “meat” on one side and “vegi” on the other with a black permanent marker. This made hers “double sided”.
Third part of the idea, materials …
While out on a morning walk with the dogs we came upon an old dining room table busted down to fit into a dumpster. Being in decent condition and solid oak construction it looked too nice to discard. This re-purposed wood comprises the main board. The materials used for dovetail come from the front lobby of the 140 year old Chronicle building in San Francisco. I only saved a dozen boards from a large pile. The grain is very tight, strong and straight.
My part of the idea …
A drip rail that morphs into a deeper well to capture the spilled liquids. 
And some engraving. One side is engraved "carnivore" the other side is "herbivore"

The finish coating is olive oil which should be reapplied every now and then.

 The CAD software I like for a project like this also has a powerful CAM package. By taking the time to do this project I discovered a way to reconfigure subtractive machining software to output additive control. A new lesson to be put to use soon.

Friday, July 18, 2014

Wire feeder control

The current task for the welder project is to separate the control of the extruder (wire feeder) from the software so that the speed can be controlled from an analog potentiometer.
The idea is to have the slicer software output on or off commands to the wire feeder and then I can adjust the speed of the wire by eye and feel. A little bit of an "old school" hands on fix. The long view advantage to this strategy will be the ability to pulse the wire.
I'm trying to use an Arduino for the task. The programming language is not intuitive to me yet so there's a bunch of head scratching going on. 

Image courtesy of Arduino Knowledge Base

Tuesday, July 1, 2014

Remote Amperage Control

My schedule has opened enough to make some progress on the robot welder. Yeah !
This remote amperage control will allow subtle power adjustments during the welding.
It plugs into the port normally used for the foot pedal remote.
Hopefully it will be one of those "small details" that makes a difference in weld quality.
Finding a suitable large enough potentiometer to match the needs of this old welding machine turned into a bit a treasure hunt. A modern welding machine won't need one so large.