Wiring up - Round 1

last night, (as in the date on the photos... I'm re posting this from my back up blog site...) I finally took the time to work on my repstrap again… when I say TOOK the time… look at the time on the photos… all in all I spent 4hours working on the robot.

This is what I did:

1. I placed all the boards on the perspex, and drilled holls for them… making good use of my drill press no photos of that needed.
2. Starting with the arduino and shield, I put :: M3×50 machine screws > washer > PCB > clear tubing > perspex > washer > nut.
   
   
3. Here is the arduino mounted
   
   
4. Here are the 3 stepper driver boards mounted with the arduino showing. This is a view from behind.
   
   
5. Here are all the boards mounted, the two new additions are the PWM driver & the DC motor driver.
   
   
6. And now my wiring nightmares begin… Just take a look at this rats nest! what a mess…
   
   
7. Next I mounted the perspex to the Z axis of the rep strap. The Z axis was taken off to make this a bit easier…
   
   
8. Here is a close up of the clear tubing. Its purpose is to act as a “shock absorber” for bumps and also so that the perspex does not crack if I tighten the screws too tight… which I do… The clear tubing was used to attach all PCB’s
   Because the rats nest is such a mess, I am now going to have to de-solder the IDL headers and hard wire cat 5e cable in its place, this will make it easier to connect to the arduino break away shield and easier to route the wires.

Stepper demo

Here is a short introduction to my RepStrap or CNC machine.


I demo the stepper driver and the stepper motor running the RepStrap test code, stepping the Y axis.

As mentioned... I have no idea how to tell what parts of the wires coming out of the stepper motor are the A,B,C,D wires. All I do know is which two wires make a pair. I couldn't figure out the ABCD cables connection block either. I clamped the wires to small metal parts, then put them inside the plastic female. When I tried to plug the connections block into its male pins the wires poped out. So I have just improvised for now.

The ribbon cable that has ten (10) wires in it... I cant figure out why there was a need for ribbon cable and where the other end of the ribbon cable is supposed to plug into? since only three (3) wires are used and there is no place on the Arduino or the break away board for ribbon cable connection blocks...

Lastly, I may have popped the main or secondard IC on the stepper driver board. I might have not connected the wires properly or something. Nothing was happening & the heat sink was getting really hot. Hope I haven't done too much damage there.

Final Assembly part 1

Last Thursday evening I had a go at assembling the final bits and pieces of the RepStrap. I started trying to mount the opto end stops... I came into a few annoying problems.

As you can see, the RepRap opto end stop does not like my Perspex opto end stop spacer... My holes where not lined up 100% and if I recall correctly either my dad or I said that we wern't building a swiss clock and we could just drill holes where ever so long as its roughly right.... WRONG!!!
Here is a shot of the reverse side once I forced the parts together... as you can see, its far from square.

Then there was a nother battle trying to get that to line up with my holes I drilled into the X & Y end brackes. Ok so I didn't drill my holes properly and rushed them a bit... But does this image not look a bit odd??? Where is the ethernet cable (cat5e) supposed to go? How is it supposed to reach into the connector? & yes if I swapped the opto end stop around that didn't help either because then its up against the drive screw / threaded rod.

I had to cut a bit off the end of the X stages threaded rod. I had a first go at using my Dremel. Its pretty cool...

Unfortunately the cutting disks dont last too long and snap easily... I borke 5 cutting disks that night! I only managed to cut both sides of the Y stage and one side of the X stage.

The next things I need to get done is, cut the other side of the X stage and cut for the Z stage as well. I ordered a piece of Perspex to mount all the PCB's and the hacked power supply on to.

One thing I can't quite understand is why or what is the great need for a OPTICAL end stop and not just a simple limit switch??? surely a simple limit switch is way cheaper???

That goes for the stepper driver board... It looks a lot more complicated than a board that Murray Horn designed.

If I get time - this could be a year from now - I will try contribute my modifications to the RepStrap and show where I deviated and what I think should change to have a successful RepStrap, but just a bit cheaper.

So far I would replace the Z bearing arm holders... The things that hold the Z satage to the vertical base. I used angle brackets for that. I would swap the opto end stops for limit switches. I would use Murray Horn's stepper boards to drive my stepper motors...


One last very annoying thing... I ordered the electronics from the RRRF. They were expensive and took a long time to arrive. The name says Complete Arduino Electronics Kit. In the RepStrap build instructions it say I will need SIX (6) opto end stops... WHY then does the COMPLETE Arduino kit only come with THREE (3) opto end stops???

Very annoying... Now I am going to have to etch another three (3) opto end stops myself - which will take time - and even worse... I will have to covert that opto end stop double sided board to a single sided board - which will take time - because I only have single sided copper and it took me forever (3 months) to master etching PCB's with ferric chloride... stuff I hate! :(

My Dremel

I haven't had the time to blog in a while and a lot has happened so I will have to wade though all the back log. I bought a Dremel 300 to use on the Mc Wire RepStrap. I should mention that I finished building ( and testing) all the electronics this weekend and am just waiting for some Perspex to mount all the PCB's on.

Here is the Dremel in its box.

Here is the Dremel's carry case.

Here is the Dremel.


The idea for the Dremel is that it will let me etch PCB's with it and mill things like aluminium and wood, plastic too. Here is the instructables link: http://www.instructables.com/id/Easy-to-Build-Desk-Top-3-Axis-CNC-Milling-Machine/ and here is the RepStrap link: http://reprap.org/bin/view/Main/McWire_Cartesian_Bot_1_2

Drill Press

This past weekend my Dad found an old drill press hidden away in the hardware. It's from 1613BC & weighs 6 tons. (It took me about 20min to clean it from all the dust) Its a manual drill press! You have to wind a handle to make it work! There are two speeds! slow & very slow! I attempted to drill ~150 holes for the arduino board using this drill press. Take a look at the raw power in the video!

I tried to drill a hole... Broke the first bit on the first try! The chuck comes down with too much force & when the pit hits the fiber glass it snaps! This was with a 1mm bit! I put a new bit in & tried to control the decent a bit better. I then realised that if I let go the handle, the momentum from the top piece of spinning metal at the top, is enough to make the handle swing round with enough force to knock teeth out! I got fed up very quickly with this... It just wasn't going to work!
This how ever was! :) Its a Ryobi drill press, with 5 speeds & a 13mm chuck! Cost me R450! It was a demo model at some other hardware & they wanted to get rid of it... & I wanted it!

Here you can see it in action! I didn't set the bit in the chuck 100% so it wobbled a bit... I just wanted to test it out & drill some holes! Works like a dream! (& yes, when I drill proper boards I will have 1 hand holding the PCB & 1 on the acent/decent leaver so the PCB wont spin!)

SUCCESS: Toner trasfer 3rd try

FINALLY!

I finally have the toner transfer method for single sided boards down! The important thing is to use PHOTO PAPER... I was trying to get away with standard printer/copier paper...
I used HP Everyday Photo Paper, on an HP LaserJet 1012 printer. 25 sheets cost me R75, so R3 a shot. Let me explain why you need to use photo paper instead of normal paper... Toner is plastic particles... that get burned on to the paper by the laser in the laser printer. On the normal paper the plastic toner particles get infused with the paper fiber & then they dont seperate properly in water... maybe if I left a board in water over night normal paper could work...? (I'm not really patient enough to find out...) With photo paper... & if you look click the packaging phtoto to enlarge it, you will see it is SEMI-GLOSSY... I think this means that there is only 1 glossy side... which is perfect for me... the glossy side is glossy enough... so the toner gets burned onto the thin plastic layer of gloss on the phtoto paper... which allows for this... :)
The paper layer magically seperates from the thin plastic layer! I just pulled one corner of the paper & it all came off at once together!
I rubbed the rest of the paper residue off with my thumb, took the board out & dried it... it looked like this! What you see is a thin layer of burned gloss! so I...
Re submerged the board in the water, got an old tooth brush & scrubbed that all off... scrubed pretty heard... the toner was firmly attached to the copper.
& the finished result :) pretty much perfect... there were two tracks that had a small gap in them...
It was a hot day, not a cloud in the sky, probably 35 degrees Celsius! I heard the ferric chloride reaction works better the warmer it is & in direct sun light... which it did. I used another tooth brush to rub the copper. It was a much faster reaction! Probably under 10 minutes... & yes! I am fed up with the smell of ferric chloride & the fumes that it releases. I decided to use the protective equipment I have! Because I was using a tooth brush in the ferric chloride, some ferric chloride sprinkled its self onto my cloths :(
This is the result after rinsing in water. I'm told another way to speed up the reaction is to put a second paint tray with boiling water under the paint tray with ferric chloride! This also work, I made a stepper driver this weekend using the hot water in the bottom paint tray, it was a cloudy day that day... the reaction was very quick, also around 10minutes or less!
Left: the new PCB etched, Right: an older PCP.
I left the toner on, so I could identify where to drill the holes a bit easier... I think all the holes, pads & via's should be 1mm! getting hold of 0.7mm, 0.8mm was difficult... I couldn't find any 0.9mm bits! My drill press is still on its way! I used a drill press for the first stepper board! A drill press makes a 1hr40min job complete in 20 minutes! I am seriously considering trying a board with an SMD component! since I have my toner transfer method working well... I dont want to WASTE time drilling holes!
I placed all the components on the board just to make sure all the holes were drilled & that everything could fit where it was supposed to. I have 5mm LED's, but now see that i need 3mm LED's instead.
View from the side.
View from under.
I decided to put the top ink on!
I didn't align it 100% but it was good enough, also I didnt let the paper soak in water long enough so some markings stayed on the paper...
I then cleaned the toner off with thinners & soldered the most exciting componet first... I now realize that the smallest components should be first... resistors...
capacitors & the choke
I started tinning as I went along. I now know a better technique! Tin the whole board first, then put in the components!
resistors & diodes...
tin
tin for more components. my soldering iron's thermostat was still broken at this time so the tracks started lifting off the fiber glass :(
Finished top view
Finished bottom view.

I read somewhere that opaque transparencies can be used... when you iron the PCB layout onto the coper, just the toner moves off the transparency then you submurge in cold water & the plactic transparency just seperates from the copper, leaving the toner on the copper & then you can reuse the transparency :) I might trie this...

so im waiting for my soldering iron to come back from repair before make another arduino, & then make some stepper motor dirver boards!

Weekend Build 2

This Weekend (Saturday to be precise) I finished the McWire RepStrap mechanical side... The Z stages was all I needed to get done...
My captive nut was secures by a copper U shaped clamp. It had 6mm holes already. I counter sunk the top side of all the stages so that the mounting screws can be flush. Its an M8 nut.
X stage with captive nut & M8 thread rod. Some 20mm tubing is used to connect the stepper motor to the thread rod.
Same thing for the Y stage.
Vertical base with Flange attached, Z rails & the Z bearing arms to hold the Z stage to it.
Close up of the Z bearing arms on the vertical base. I used some angle bracket to attach the bearing arms. The holes that mount the bracket to the perspex are 3mm, I had to widen the other end to 6mm so that the bearing arms could be held properly with a M6 bolt. There is a self tapping screw with a spring to pull the arms together.
There we are... all done! The flange is mounted with (not enough) thread lock. Everything has just enough clearance to pass. Click on the pic for a high res view! You'll see that the Z stage is leavel!