XYZ Dark Vader Test

Last weekend, I found some time to work on my RepStrap once again! There was a problem with the Z plain. I thought it was the stepper driver board, because there was smoke coming out of it, the last time I tried running it, but it turn out it was something wrong with the stepper motor. It appeared to be seized!

I found a replacement stepper motor in an old dot matrix printer, and swapped it out. It was at that moment that my dad walked in and asked what was wrong with the previous stepper motor. I showed him it would not move, not even if you took a pliers, gripped the axle and tried turning it. My dad asked if he could open it up and take it apart, and since it was not working, I said sure, since I was curious to see what the insides of a stepper motor looked like... Once it was open, we could see the two coils. Everything looked fine. There where 2 bearings on the top and bottom of the axis. My dad thought that the problem could be a seized bearing, but they where fine... So I tried again with the pliers... and after applying some force, it began so spin like the others when you finger-turn them...

So I hooked it back up and tested it... and it worked... I found the test code for the steppers on the reprap site and burned it to the arduino... I had to comment out some code... like PSU stuff, and the stuff for the enable pins... I will post my code, but here is the link to the original for now: http://reprap.svn.sourceforge.net/viewvc/reprap/trunk/reprap/firmware/Sanguino/Sanguino3G/testers/imperial_stepper/imperial_stepper.pde

Here is the result!

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! :(

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!

Weekend Build 1

Here are the photos & the story for last weekend's build!
Bolt -> perspex -> washer -> bearing -> washer -> nut
I bought the wrong size bolts so I had to cut them down to size.
I had to clamp a #13 spanner to the table then use a screw driver to fasten it.
The first bearing arm done.
There were fine particles of metal powder form the hack saw that stuck to the bearing. :( they were all nice & oily, moved nicely when I bought them. Not any more.

BREAKAGES

The hack saw blade that came with the hack saw snapped in 4 places!
Bearing arm shattered! I think I had the clam on too tight whilst trying to cut the bolt shorter...
X stage perfectly parallel with 1 Y rail support mounted
Y sage on top of X stage, all working nicely after a 2nd attempt at the y stage rails... the first attempt was badly miss aliened. Take a look at everything working here: http://iouzo.blogspot.com/2009/01/x-y-done.html

This weekend I will try get the Z stage done & then start making PCB's again.

X & Y done

Over the weekend I build the RepStrap... taking lots of photos of all the steps... somehow my camera's memory card became corrupt & I can't access the pics... for now... I'll find a way to get them off the camera.

In the mean time... check out my X & Y stages! Not bad hey :)

McWire - metal done: Part 4

Today I did all the metal work.
In my lunch hour I went to the skate shop & bought 16 ABEC3 bearings for R160 so R10 a bearing...
Cut the aluminum angle iron [35mm X 35mm] with a hack saw. It was a new hack saw so i just used the blade that it came with, which seamed pretty decent since it was a ~R150 hack saw... I clamped it at 1 end & left the other (larger) end to hang free, that way the weight of the bigger piece would make a gap & it worked out easier to cut this way than having both sides clamped.
The cutting left burs that need deburing, so I...
Used a file so file down all the burs, using my thumb to gage weather it was acceptable.
Drilled all the angle aluminum. Looking that the line of the door & the line of the drill bit, you can see I'm not quite parallel... not quite square :(
& again there was "walking" of the drill bit... really annoying because once your at this point you have to continue.
I had to convert the 21" & 13" to millimeters for the U aluminum.
I tried to use as much down force as possible & to cut as fast as possible. Both the U and angle aluminum pieces can be cut in under 30 seconds. Aluminum is a softish metal I'm told.
There you see all the metal cut to size. I will only drill the U aluminum once i have the fasteners for the perspex... which I will have to sort out on Saturday.

McWire - plastics done: Part 3

Today i finished off the plastics...
I counter sunk all the bearing arms.
Used prit to glue all the stage stickers on then used the clear tape on the edges so that the drilling & jigsaw cutting wouldn't lift the sticker. I made this observations a bit too late... when drilling, just use the weight of the drill as the downward force, if you apply pressure to the drill while drilling perspex... it snaps/shears!
Here you can see the jigsaw fastened under the chip wood, & the chip wood clamped to the ironing board. I trimmed of the exes perspex from the vertical base & Z stage, there was s strip on the Y satge... i can't remember about the X stage. However... this method of cutting long pieces of perspex worked really well. My Dad poped in & suggested a guide rails srewed into the chip wood because i was drifting a bit... but i don't thing I drifted a significat amount...
Good advice thou...
Stuck all the PTFE bearing stickers on & used a heavy duty scissors to cut them to size. Then drilled them & pealed off the stickers.
There we go... all the plastic done...

I'm still waiting for the springs, skate bearings & nails - we might use screws that have a 90 degree bend in them already... the ones used to hang keys on... instead of the nail method...

I recieved the aluminium today. I will cut it to size... as soon as i convert all the sized to the METRIC system... I still need to suggest to the reprap team to put all measurments in imperial & metric... some of the drill & screw sizes sound rediculous... like this... 6 and 3/3 inches... & 5/16" compaired to say 220mm & 45mm... the metric system just sounds more human... water freezes at 0 (ZERO) degrees & boils at 100 degrees... not 32 & 212 or what ever its is in the imperial system... In anycase... I thought the international standard for measurements was the metric system. SI = Metric!

McWire - Perspex parts: Part 2

My Dad came home today with all the plastic bits... the perspex & PTFE bearings...
4 A4 size perspex sheets for the X, Y, Z & Backing stages. 2 Strips of perspex for the bearing arms. A meter of PTFE bronze plastic for the bearings. All the perspex is 5mm in thickness.
I decided to cut a PTFE bearing first. My dad & I had an argument about printing out the templates & using them... so we drilled the holes with out sticking templates on top... then put the drilled baring against the template... & it was slightly off... so we used the templated from here onward.
Easy descision really... (His argument was that it would take too long to cut them out & stick them on...)
We didn't have any prit so we used clear tape. A little tricky to align on the perspex.
Drilled the holes.
Cut the end stop off. I clamped the strip to a piece of chip wood & cut through the perspex & the wood so that when I got near to the end of the perspex it wouldn't flap around with the vibration of the blade.
There's the first end stop... not to bad I think! Its a bit big on the sides but I will file it down later if it is an issue.
After idividually sticking on each sticker, drilling the holes, then cutting it off, we decided to get clever... I stuck the remaining 5 end stop stickers on, leaving enough space for the jigsaw to cut inbetween, then drilled all the holes at once.
My Dad drew some alignment markings & screwed the jigsaw in place & flipped it over so that just the blade was exposed to us. Our jigsaw had a trigger with a switch to have the jigsaw permanently on...
This slowed us to cut much faster & do the curves of the bearing arms. I'm not sure how actuate these semi circles need to be... some of our bearing arms have triangular corners. I'm quite happy with this jigsaw cutting method. No more vibrations going through my arms!
It took about 3hrs to get the 10 end stops done & 7 bearing arms done (the 8th sticker became unusable) I have stuck the rest of the bearing arms on the perspex & will do them tomorrow. Then the PTFE bearings, Then the 4 stages... :) Hopefully that will all get done tomorrow..

The aluminum is on order & should also hopefully arrive tomorrow as well as the springs & the skateboard ABEC3 bearings.

I really hope to have the mechanics of this McWire cartesian robot done by the weekend so i can work on the electronics side... more etching...