mcwire build notes (bootstrapping for mendel)

I just finished building my mcwire which I will use to bootstrap the parts for a mendel, here are my notes on the build. I have some pics and video also. How should these notes make it to a more permanent state, should I just edit the wiki or is there some sort of official revision process?

Notes (simple format, will type into narrative or edits if appropriate)

*I ordered my parts from mcmaster. I will update my previously published BOM taking into account lessons learned. Buy extra bearings for extruder and other things... (I bought 2 10-packs).
*The mcwire is not a fancy machine, I would suggest going cheap and cutting every corner possible, it is unlikely to make much of a difference.
*When ordering parts don't bother with the springs (They are the wrong length, use rubber bands, mix pack at walmart for $0.96, the best ones I found where like that used to hold lobster claws closed, you could easily double or triple up weaker bands). Also don't bother with the nails (use small eye hooks, tiniest size they had, 1/16 inch pre-drill hole, I got 8 for $0.98 at the depot, they are just to support the rubber bands/springs that hold the bearing arms against the u-channel). Pre-drill the hole for the eye hook, cracking can be an issue.
*Tolerances on the mcwire are huge, the design is simple enough that you can butcher pretty much everything and still get by. I way over-thought the whole thing.
*I do not see the mcwire as a long term accurate and reliable CNC platform, the design is a hack and I don't think it would really be that good an option. Just noting here a change from my expectations to reality now that I have it built.
*Laser cutting the acrylic parts is grossly necessary if you have table saw, any kind of sander and drill press (you can probably get a table saw and drill press from harbor freight for the cost of laser cutting, estimates I got were $75-$175 and turnaround was slow). Purchase 1/4" (actually 0.22) acrylic or lexan at home depot/lowes (my lowes had a better selection). You need 2 1/8 sheets (1/8 of a 4'x8' sheet) or 1 1/4 sheet. The dxf's and stickers make it seem all fancy, really they consist of big holes to attach bearings and bearing arms, some countersinking, and small holes to screw the PTFE "bearing" sliders on. This is what permits the planes of plastic to slide along the u-channel.
*Regarding countersinking, anything that marginally recesses the bolt heads will do fine, I used 1/2 countersink. The bolt heads stick up a small amount (1/8) but not enough to matter.
*Print the PDF's onto stickers, affix the stickers to the plastic using existing sides corners to reduce cuts. Cut out as squares, ignore rounded corners. On the bearing arms you DO need to round the edge where the bearing goes, the rounded edge allows the bearing to clear and contact the u-channel. I used a dremel with a small drum sanding bit to round it off, again just hack away.
*The stickers for the u-channel and angle bracket are only marginally useful. I suggest drilling or at least marking everything in place. The precise placement of the holes is totally irrelevant except where they mate to the plastic, in those cases your plastic will already have a hole you can use as a drill guide.
*The hardest part of the whole thing for me was drilling the motor mounts, I made myself a little template using the NEMA 17 but getting the screw holes to line up was tricky. Also note that the motors do not always mount in the middle of the piece, they tend to be offset to clear the bearing arms, you just need the shaft to align with where the trapped nut on the acrylic will be, I suggest mounting the trapped nuts and then marking the location of where the motor mounts should go.
*Make sure you order the usb-ttl cable with whatever electronics (I got the pre-assembled from makerbot). You need this cable to update the firmware on the sanguino, this is a serious gap in the docs.
*You also need to buy an ATX power supply, again not well documented in terms of BOM.
*You need a good flat file for the aluminum pieces, you need to debur and align where the uchannel mates with the angle bracket. If that is all messy with shards it is harder to make 4 pieces of each "frame" line up square. You need a half-moon file to clean the threads on the end of the threaded rod cuts.
*Use NEMA 17 motors instead of what is specified (buy 4 motors), you can carry these right into the mendel and also the extruder, see below.
*Extruder parts and electrical parts are NOT part of the mcwire BOM, this is sincerely annoying.
*I suggest you bootstrap a mendel extruder as Job 1. Buy the barrel, tip, PTFE insulator, kapton tape, extruder motor (any gear motor that turns pretty slow will do the job), thermisitor/thermacouple, pulley if they have it. If makerbot is out of the puleys (they always seem to be) any small timing belt pulley with a 1/4" bore (for the makerbot motor) and the grub screws to secure it to the motor shaft will do. I got my pulley at grainger, literally whatever they had in stock (page 142 I think). Mcmaster has plenty, The belt width of the pulley needs to be at least as wide as the width of the bearing. The simplest extruder is just angle bracket with a hole for the motor shaft, a hole to put a bolt through for the bearing and a hole to mount the heater barrel. Operation is idiotically simple, the bearing rides against the pulley at a very small distance (still experimenting but 2-3 mm) . As the motor turns the pulley it pulls the plastic and pushes it into the hole you cut for the heater barrel. That's it, it only needs to work well enough to print one part, the mendel one-part extruder piece. Upgrade to that which is driven by the same bearing (double check that) and a splined shaft on the NEMA (I could not find such a beast) or the tiniest gear (Outside Diameter) you can get from mcmaster for the nema 17 shaft. Again it is simple, just needs teeth, I wouldn't bother splining the motor shaft until you really have a full mendel and have already done a lot of printing and are running into extruder problems.

All for now, comments appreciated.

This post is exactly what I was hoping to find here. This gives me the confidence I need to go ahead and take this journey myself. Thank you so much for your hard work and frustration

I would love to see the pictures and video that you mentioned. Also, where can I find your updated BOM?

Nice walk through, thanks. It answered some questions I had like how important counter sinking is (or isn't). One question though, do you think the teeth on a timing pulley will be sharp enough to dig into the filament and provide traction? I am also eagerly awaiting some pictures/video.

PreciousL - The BOM for mcwire can be found here. There is also a link on that page to a Google spread sheet which also has the BOM as well some other useful info.

Below is wait I actually used to order from mcmaster AFTER being edited with my lessons learned. Took off springs, pipe clamps (you get a box of 50 or 100, you need only 3), silicone hose (I have nema 17 motors, it was too big, use vinyl tubing to connect the motor shafts to threaded rod), nails.

Get the list from mcmaster below and at the hardware store get:

*1/2 inch 2 holed pipe "clamps" (you need 3, used to mount pipe to studs securely, they should be tin/raw metal color), these hold down the coupling nuts to the acrylic planes. Get suitable nuts/bolts to affix (I get a tiny 6 pack for .89)
*rubber bands, 3 lobster claw type or 6-8 regular office type (double up)
*tiny eye hooks (mine needed a 1/16 hole) get 10 , one for each bearing arm
*smallest size vinyl tubing

From maker bot:
*USB cable (DON"T FORGET) and extruder parts (tip, barrel, insulation wrap, insulator block/cylinder, nichrome wire (get 10ft, it will come in handy), slow gear motor --if they have it otherwise check forums, etc--, kaptop tape, pulley --if they have it otherwise grainger/mcmaster--, 5lb plastic filament (start with ABS it is easiest), pre-assembled electronics kit (unless you are hardcore and masochistic I think this is well worth $175)

*Misc item:
ATX power supply, I have been on all laptops for about 10 years, I had one in a closet but I tend to hold on to things.

*bearings
get 20 of the skate bearings, mine where from vxd(?) I think which was cheaper than thebigbearingstore when taking into account shipping. The extra's come in handy in the extruder, making 4 vertical bearing retaining arms instead of 2 (directions are ambiguous)

*NOTE: the quantity of plastic parts like bearing arms on the stickers is MORE than you actually need, ergg!

---begin paste---

1 95462A033
1 91083A033
1 90275A714
1 90494A030
1 91083A030
1 90273A581
3 91034A100
1 98273A255
2 8735K111
1 88805K57
1 9001K34
3 4549K606
1 4549K595
2 4549K602
3 44605K115
1 68095K121
1 44605K155
2 44605K105
2 98847A029

---end paste----


Complete detail for informational purposes:

1 95462A033 1 Pack Zinc-plated Grade 5 Steel Hex Nut, 1/2"-13 Thread Size, 3/4" Width, 7/16" Height
2 91083A033 1 Pack Plain Steel Type A Sae Flat Washer, 1/2" Screw Size, 1-1/16" Od, .07"-.13" Thick
3 90275A714 1 Pack Zinc-pltd Stl Flat Head Slotted Machine Screw, 1/2"-13 Thread, 1-1/4" Length
4 90494A030 1 Pack Plain Grade 2 Steel Thin Hex Nut, 5/16"-18 Thread Size, 1/2" Width, 3/16" Height
5 91083A030 1 Pack Plain Steel Type A Sae Flat Washer, 5/16" Screw Size, 11/16" Od, .05"-.08" Thick
6 90273A581 1 Pack Zinc-plated Stl Flat Head Phil Machine Screw, 5/16"-18 Thread, 3/4" Length
7 91034A100 3 Each Black-oxide Steel Coupling Nut, 1/4"-20 Thread Size, 5/8" Length, 1/2" Width
8 98273A255 1 Pack 410 Ss Type 23 Thread-cutting Screw, 10-24 Thread, 1/2" Length
10 8735K111 2 Ft. Bar Made Of Teflon(r) Ptfe, Rectangular Bar, 1/8" Thick, 1/2" Wide, 2' Length
11 88805K57 1 Each Architectural Aluminum (alloy 6063), 90 Deg Angle, 1/8" Thk, 1-1/2" X 1-1/2" Legs, 8' L
13 9001K34 1 Each Architectural Aluminum (alloy 6063), U-channel, 1/8" Thk, 3/4" Base X 3/4" Legs, 8' L
16 4549K606 3 Each Std-wall Galv Welded Steel Thrd Pipe Nipple, 3/4" Pipe, 12"l,thrded Ends,17/32"l Thread, Sch 40
17 4549K595 1 Each Std-wall Galv Welded Steel Thrd Pipe Nipple, 3/4" Sz, 3"l, Thrded Ends,17/32"l Thread, Sch 40
18 4549K602 2 Each Std-wall Galv Welded Steel Thrd Pipe Nipple, 3/4" Pipe, 6"l, Thrded Ends,17/32"l Thread, Sch 40
19 44605K115 3 Each Low-pressure Blk Malleable Iron Thrd Fitting, 3/4" Pipe Size, 90 Degree Elbow, 150 Psi
20 68095K121 1 Each Low-pressure Forged Steel Flange, Threaded, 3/4" Pipe Size X 3-7/8" Od, 150 Psi
21 44605K155 1 Each Low-pressure Blk Malleable Iron Thrd Fitting, 3/4" Pipe Size, Tee, 150 Psi
22 44605K105 2 Each Cast Iron,125 Psi,3/4"pipe,round Head Cap
23 98847A029 2 Each 18-8 Stainless Steel Threaded Rod, 1/4"-20 Thread, 3' Length

Edited 1 time(s). Last edit at 01/28/2010 03:32PM by goinreverse.

Regarding the pulley, you need to be able to print exactly one part (the one-piece mendel extruder mount) so I would say that you can probably use a wad of chewing gum and a paper clip (you get my drift...).

As long as you get the distance between the inner diameter of the pulley and the bearing correct so they are just a tiny bit smaller than the diameter of your filament I think it is fine. Makerbot's cupcake uses a timing belt pulley in their official extruder which is where I got my concept from. Generally the smaller, the higher the force angle and the more teeth the better I would think.

Once you have your mendel extruder mount/base you switch to that. You do need a small gear to put on your nema 17 motor shaft unless it is splined (I could not find where to buy such a beast, maybe a euro thing)

I have started a McWire page on the Wiki. Some excellent points have been made on this thread. Please help me develop the McWire Guide.

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B^2 : [replibot.blogspot.com]

~~ We Are The Factory ~~

Thank you very much for posting all of this. It has been very, very helpful. Which firmware did you use for the Gen 3 Electronics?

I have seen this page.
Generation3Firmware

And I have also seen the SVN Mendel Firmware for Gen 3.

I have even seen pages documenting how to remove components from the Gen 3 boards to make them more Mendel friendly. I'm assuming you didn't do this?

The wiki documentation of this portion of the McWire is either lacking or it is my googling skills that are.

Thanks in advance!

goinreverse Wrote:
-------------------------------------------------------
> *Tolerances on the mcwire are huge, the design is
> simple enough that you can butcher pretty much
> everything and still get by. I way over-thought
> the whole thing.

HAH! You're not kidding! You should see the heap of complete trash that I got to work - and it functions just fine. I did take SOME effort to make sure the X and Y axis were square with eachother. Though I only checked the "referance" rails - the rails that the bearings actually grip, the other rail (on my machine) is simply a support for the other side of the bed, and isn't used AT ALL as a straight line, so it doesn't matter at all if it's straight or not. Also, the it doesn't have to be level - and the two systems (X and Y) don't have to be level to eachother. The reason is that the Z axis only touches (in essence) one spot on the bed - as long as the X and Y move in a straight line it'll be just fine.


> *I do not see the mcwire as a long term accurate
> and reliable CNC platform, the design is a hack
> and I don't think it would really be that good an
> option. Just noting here a change from my
> expectations to reality now that I have it built.

I'm thinking that converting the McWire to belt driven would improve the speed enough to make it viable as a long-term platform. Or longer term, at any rate. Wear on the rails might get to be a problem...

> *Laser cutting the acrylic parts is grossly
> necessary if you have table saw, any kind of
> sander and drill press (you can probably get a
> table saw and drill press from harbor freight for
> the cost of laser cutting, estimates I got were
> $75-$175 and turnaround was slow). Purchase 1/4"
> (actually 0.22) acrylic or lexan at home
> depot/lowes (my lowes had a better selection). You
> need 2 1/8 sheets (1/8 of a 4'x8' sheet) or 1 1/4
> sheet. The dxf's and stickers make it seem all
> fancy, really they consist of big holes to attach
> bearings and bearing arms, some countersinking,
> and small holes to screw the PTFE "bearing"
> sliders on. This is what permits the planes of
> plastic to slide along the u-channel.

I am forced to admit that I built mine without any sort of guides at all. Eyeballed it after reading through Mr. McWire's design over on whatever website that was. Used scrap MDF I had laying around. Only things I bought where the skate bearings, the pipe & flange, and aluminum. Even scavenged to stepper controllers, and a friend gave me an arduino.

> *Regarding countersinking, anything that
> marginally recesses the bolt heads will do fine, I
> used 1/2 countersink. The bolt heads stick up a
> small amount (1/8) but not enough to matter.

Countersinking? Huh... I didn't do that at all... Maybe that's why I had to put a few extra washers under the Y stage rails... But my design was slapped together so haphazardly that this may not be applicable to anyone else.

I'm serious. I only used two actual pieces of bailing wire, but this design lends itself very well to sloppy workmanship a.k.a impromptu replacements a.k.a. Jury rigging.

Luckily for me.

---

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I'm building it with Baling Wire

I't very comforting to know that the McWire is so forgiving, I've been studying the design almost ad nauseum and have come to the same conclusions, but having them confirmed is great, although the mounting of the Z axis carriage look a bit flimsy to me.

I haven't assembled it yet, still waiting for the electronics to make it worthwhile to do the assembly.

I'm working on a BRL-CAD model, using metric measurements, with only a few slight changes to the design:

1) I aluminum angles only, replacing the U profiles with angles
2) The dimensions on the X,Y and Z beds are based on pythagorean triples, meaning that measuring if the diagonals between the two rails on any bed will yield an integer number, making measurements simpler. (What can I say, my ability to do precision craftsmanship isn't that great, so changing the design to accommodate for that makes sense to me)

Wow! Thanks for this! I'm just getting into the meat of my McWire build and am running into pretty much everything mentioned so far.

Also helpful was actually looking at the flickr stream that includes the photos on the current web page, there's a lots of pics that weren't included that cleared up confusion for me. I'm still unclear on the drilling templates for the other ends of the U rails. I assume the intent is that you would use the acrylic stages as guides, rather than try to pre-drill the rails and stages separately and hope they line up.

Any tips for working on the acrylic other than with a table saw? I experimented with Dremeling using a variety of bits and speeds, but that ended up poorly, with the bit melting it's way through the piece and being very difficult to control (evidence here: [www.flickr.com]). I did a little digging and supposedly you can use a saber saw with a 10 tooth blade, which I do have and will try out later today.

You could easily use a circular saw instead of a table saw. Probably a jig saw too. Not sure if you live in a place where there is a harbor freight but for cheap chinese tools it can't be beat:

harborfreight.com , decent table saw for $150.00 or less on sale. I wouldn't use it in a cabinet shop but around they house it will probably last you years.

Acrylic likes to chip/crack a lot (especially extruded) you really need something with 60+ carbide teeth to get any kind of good straight cut (though for mcwire you can probably even just use the score and break method of cutting plastic no saw needed)

I have a bad stepper motor driver board (2 working fine, 1 is fritzing) so I am stuck until I get that working again (erghh!).

Anything regarding the reprap software is a complete waste of time in my opinion. It is one of the worst pieces of software I have ever seen and the documentation takes you in 500 different directions. Use replicatorG, it auto-updates firmware for both the sanguino and extruder controller built in, no arduino setup needed (also note the annoying sanguino hold/release restart button at exact right time or firmware updates fails issue) . Particularly use the preferences screen in replicator with the nudge controls and the extruder motor control to test all you motors and boards before you plug/wire everything in (lesson learned).

My vinyl tube linkages are not working very well so I need to think up a better way to link the motor shafts with the threaded rod. When the motors reverse direction the threaded rod end is unscrewing out of the tubing. Possibly I can just epoxy the tubing to the threaded rod and leave the shaft end separable. Need to test more.

goinreverse Wrote:
-------------------------------------------------------
> You could easily use a circular saw instead of a
> table saw. Probably a jig saw too. Not sure if you
> live in a place where there is a harbor freight
> but for cheap chinese tools it can't be beat:
>
> harborfreight.com , decent table saw for $150.00
> or less on sale. I wouldn't use it in a cabinet
> shop but around they house it will probably last
> you years.
>
> Acrylic likes to chip/crack a lot (especially
> extruded) you really need something with 60+
> carbide teeth to get any kind of good straight cut
> (though for mcwire you can probably even just use
> the score and break method of cutting plastic no
> saw needed)


FWIW - I used a 10 tooth blade in an saber/reciprocating saw today with very good results. It's not nimble enough to carve the arcs on the bearing arms, but the major stuff went very well (table saw's in storage due to lack of workspace).

goinreverse- try splining the end of your threaded rod ala stepper extruder, then clamp hose on with cable ties or hose clamps or something

Regard my notes on the bearing arms. I cut them square and rounded them using a dremel drum sand bit.

In the event you have not purchased the makerbot DC extruder drive motor, DON'T. I am finalizing a setup to use my "hacktruder" to start with the NEMA 17. It should also be re-usable in the mendel extruder.

If you are in an experimental mood try assembling with regular hex-head bolts (whatever you can get that is close and available at the lowes/depot), that is on my todo list.

stepper shaft is the end that is sticking fine. The threaded rod side is what is failing (reversing off). Hose clamps are a good idea on that, will give it a try.

Thanks for this posting, it's very helpful and burden relieving

As a note to add to anyone reading, I found some insulated cable clamps at my local hardware store for about $1 a piece. They come in packs of 2 and are perfect for the captive nut on each stage. They have rubber insulation on them which provides and excellent fitting: Cable Clamps I found mine in the electrical section.

I have added some additional information to the McWire Development Page. I hope everyone will take some time and contribute to it to help those who are just getting started on the RepRap Journey.

I take back what I said about the makerbot gearmotor, right now I am in extruder hell. To find a good combination of motor (gear or stepper), gear (splined shaft, timing belt pulley or gear), idler (bearing or acriylic) and compatible firmware is a complete disaster.

I was able to spline the shaft of a 4th stepper motor I have, I did not use the crazy hinge jig nonsense I saw. Instead I mounted the dremel vertically with the bit pointing up (like a router table) by tapping a hole in some extra 1/4 inch acrylic. Then I clamped some layers to adjust to the correct height and clamped on a stop to control depth. Just push the motor slowly into the bit and the stops make sure you stay straight and don't cut too much into the shaft, actually much easier than I though it was going to be.

Problem now is that the stepper feed doesn't seem that strong (though I am using the vexta stepper not the makerbot stepper), the splines slice the heck out of the filament, the stepper gets damn near hot enough to catch fire and I can't find an extruder firmware that supports steppers compatible with ReplicatorG. AHHH!!!

Makerbot seems to have excellent service, they are shipping a replacement stepper driver board asap.

goinreverse Wrote:
-------------------------------------------------------
> Anything regarding the reprap software is a
> complete waste of time in my opinion. It is one of
> the worst pieces of software I have ever seen and
> the documentation takes you in 500 different
> directions. Use replicatorG, it auto-updates
> firmware for both the sanguino and extruder
> controller built in, no arduino setup needed.

I agree that the reprap host software isn't work the time to download it, much less the headache to get your java environment set up so that it runs. Nevermind getting it to actually work.

Haven't looked at replicatorG though. I've just been using skienforge from the command line. It's also important to note that you can compile the firmware without using the arduino environment. You still need to download it to get the library source files, but you can compile using a makefile instead of running some awful java app. The arduino environment comes with a makefile intended to do just that, except that it doesn't work right out of the box.

I would show y'all what wonderful print quality I'm getting with it, but my McWire is also stuck at the "plotter" stage - no working extruder. I've got the parts (finally) and should have the time to assemble it sometime this month. Sometimes having a day job really stinks. But at least in means that I have the money to spend on the parts.

---

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I'm building it with Baling Wire

I don't mind compiling in the Arduino environment, that tool runs fine on my mac and windows systems. It is a little more picky on linux.

If anyone needs an extruder pulley compatible with the kysan dc motor from makerbot this one from mcmaster works: 1375K15 . Makerbot has been out of stock for a while now and probably won't have more in for individual purchase anytime soon. The bore has to be widened out to the shaft size of the kysan motor but otherwise it provides plenty of torque and grip. Be very careful drilling out the larger shaft bore, the pulley is mushy aluminium, I would strongly suggest buying 2 or 3 in case you break the first one. Use cutting oil (3 in 1 would probably work too) and use a series of progressively larger bits. It is very hard to suitably clamp the pulley without mangling it, I used a small set of vice grips on the base (non-toothed part) and also be sure to leave the set screw in there and pushed in as far as possible without interfering with the drill bit. The pulley is 2 parts pressed together, without the set screw the drill with cause the inner part to unstick from the outer collar.

While not perfect replicatorG is a very good strong start.