Parts for McWire Cartesian Bot v1.2

Heya,

I have attached an order form Mcmaster. It contains (i think) all parts (excluding acrylic & bearings) to make a Mcwire Cartesian Bot. Could you please go over it and point out any inconsistencies.

as you might have guessed i am a total noob

Best,

Arun

Arun,

Looks like you have it all covered. You can get the cost down by doing a little shopping around. In the States, I would suggest Lowes or Home Depot. Also, ditch the 1/2 EMT 2 Hole Strap for some 3/8ths Copper Tubing Straps. The OD for 1/2 EMT is 3/4 of an inch and your 1/4-20 Rod Couplings will have an OD of 3/8ths +/-. For what it's worth, I have attached my original shopping list. Prices have been extended and there are notes near the bottom of the sheet. I should also point out that instead of using an actual Pipe Flange, most McWires States-side appear to use a 3/4 floor flange. They *should* be in the Electrical section, but I have seen them in the piping sections as well. Hope this helps and happy building!

(note: If you have a Lowes nearby, they are ususally running a coupon deal this time of year. Meaning: Go in and buy something cheap and with your reciept you may get a 10% coupon off you next purchase of $50 or more. Use the coupon to help fund your McWire. Not gobs of money, but hey...a deal's a deal)

Edited 1 time(s). Last edit at 12/08/2008 02:06PM by Rick.

---

- Rick

A chicken has a head the size of a walnut. Yet, even it has the sense to come in out of the rain.

Do you know, it was just last night I ran into the pipe flange/floor flange problem; the four holes in the pipe flange I bought from the plumbing store don't match up with the four holes in the vertical base I got from the RRRF. Oops. Thanks for just solving that for me--I'll go search out some floor flanges now.

I wouldn't just assume that the Floor Flange is the solution...Check your hole to hole dimensions on the part supplied by RRRF write 'em down and take a tape measure with you to the supply house...or borrow one of theirs to verify that the dimensions for what you are buying is, in fact, what you need.

---

- Rick

A chicken has a head the size of a walnut. Yet, even it has the sense to come in out of the rain.

just an observation on the McWire List - at least in my locale, a lot of the parts in the list turned out not to work in the actual machine:

some examples:

the Flange problem you've mentioned - solved by buying a reducer 1x3/4 and a 1 inch flange - whose holes lined up exactly

A lot of errors of omission in the hardware listings as well...

says you need (12) 5/16 x 3/4 machine screws for the X axis, but doesn't say 8 must be flathead and that the remaining 4 should NOT be flats as the holes for them don't countersink...

Another one to watch for: at least with the 3/4 inch length screws I purchased, for the Y axis - the nuts interfere with the X table on the spring loaded bearings...so slightly shorter screws with thin nuts are required....

all minor problems - but based on a strict interperetation of the plans, a machine cannot be built by following them - you must do considerable interpolation to arrive at a functioning solution.

- James

The "thin nuts" you are referring to are called "jam nuts", just FYI. Another route to fix the Y Stage nuts crashing with the X Stage is to shim your Y Stage rails. One or two 5/16 fender washers should do the trick. I agree that there are a few holes in the McWire build instructions on the RepRap Home site. Once I actually get mine working, I plan on attempting a more comprehensive guide. Keep an eye out, I'm gonna be asking for help in the form of problems you ran into and what you did to fix it!

---

- Rick

A chicken has a head the size of a walnut. Yet, even it has the sense to come in out of the rain.

Just to be clear - no criticism implied to the original RepStrap author on the RepRap site

Hmmm... I wanted to add my 2 cents to this one. I had the same flange problem. The 3/4 inch pipe flange didnt fit, so I did as above about bought the 1" Flange and a reducer. Also, the screw holes on the 3/4" were'nt big enough either. It's almost like the prototype was build with one inch pipe and the plans were never updated to reflect the change.

Also, though, I've been having trouble because the 3/4" machine screws don't seem to be long enough for the acrylic, a washer, and a bearing. They bolt barely make it through and I can't get any kind of secure connection. Then as I was reading the step by step instructions, I noticed that they say to use a 1" bolt. So, that's what I'm going to do.

I am not trying to imply that anyone was wrong or at fault, I'm just supplying this information for those who come after me.

Also, I definitely grok the idea that these plans are just a rough guide and we'll all have to do some improvising to get our machines working.

I've been a lurker here for ages, and throwing in my 2 cents (ok, 1.76 cents US, 2 cents canadian) The plans are definitely not perfect, but the original source instructable wasn't either I've got a rough (really rough) CNC setup built according to the instrucable and I'm working on a repstrap-ish McWire version.

Some hiccups, sure, but a heck of a lot better than either of the systems I tried building from scratch. I'm a mechanic, not an engineer

One last thing, "stove bolts" in canada don't come in a thick enough gauge to be able to fit the skate bearings unless you happen to get very lucky. Most hardware stores around here stock a much thinner gauge

I'm working on a McWire as well following the instructions here: [dev.www.reprap.org]

Though the instructions are the best I've seen around (Thanks Zach), I'm finding it hard to follow also. A couple examples:
What thickness acrylic do I use?
What kind of skate bearings do I use? The parts list says 'Skate Bearings'. I assume all bearings aren't created equal. (maybe they are)
The Aluminum Channel detail page is missing (http://parts.reprap.org/part/misc/3%2F4%22+x+3%2F4%22+Aluminum+Channel)


I guess what I'm asking is: Since there are a number (well, a few!) of us working on building this device, can we get access to edit that page to update it with more accurate information?

Also - it would be great if we could also update the 'suppliers' pages as well. I know I've found some parts at Home Depot, some at Canadian Tire and I had to get my 6" and 12" galvanized parts made at Mr. Plumber. These details would be a great addition to the suppliers list (with prices too, perhaps).

I'd be happy to add any details I have to the appropriate pages.

Thanks,
Rick

Rick: Can't help you much, but skate bearings are all (or at least mostly standard). 8mm internal diameter, 17 external diameter, 7mm depth if I recall. I agree it would be great to get write access, you could try pestering whoever over irc at #reprap on freenode, its a pretty active channel.

I'll give that a try. Thanks, James.

Maybe it's just me... but I'm having a heck of a time finding out exactly what thickness acrylic I should use. The parts list (http://parts.reprap.org/part/module/McWire+Cartesian+Bot+v1.2) doesn't mention it at all. I realize that it DOES mention 'lasercut' parts. But, it doesn't give any specifics. Neither does the McWire page (http://dev.www.reprap.org/bin/view/Main/McWire_Cartesian_Bot_1_2)

I think I've heard mention around of using 1/4 " acrylic.

Any anyone confirm?

Thanks.

Well, I seem to have been able to answer my question. According Zach on

[forums.reprap.org]

"most of the pieces should be 1/4" thick. there is one piece that should be 1/2" thick which is the 'vertical base' part."

I'm just wondering if these are still correct. That post is 1+ years old now.

Hi Rick,
I can source 5mm thick acrylic easily, but do you know why the vertical panel was originally made of thicker acrylic?
Does it matter - or can suitable adjustments be made?

If you have any info, it could be very useful to know before I buy the wrong stuff....
Hazel

Arun,

I don't know if it's too late but I looked over your parts list and noticed that you bought 1/2"-20 hex nuts but 1/2"-13 machine screws. That will give you problems.

Peter

Hi all,

First of all, great tips in this thread and things to look out for!

I am getting ready to put together my McWire Cartesian Bot v1.2 and had a few logistical questions.

Right now, my question is about the silicon tubing. I am wondering if using a 1/4" inner diameter tubing is too big since the 1/4"-20 thread is 1/4" diameter. Would using 3/16" inner diameter tubing be a tighter and better fit?

Also, at my local Home Depot, they don't stock silicon tubing but the closest (to the photos) are vinyl tubing. Is this a good alternative?

Thanks,
Peter

I agree with Peter on this one - 3/16"(5mm) inner diameter is a better fit. I found some tubing at a plumbing shop, but had much better luck at Roger's Aquatic and Pet Supplies (http://www.perkyspets.com/)

Just a few more modifications I've made that I hope others can verify before I start building:

- It looks like the Y rail mountings (on the X stage) are too wide apart. If you overlay the printout of the Y stage over the X stage, it looks like the edge of the teflon mounting holes (on the Y stage) are close to the Y rail mounting holes (on the X stage). I changed the X stage so that the Y rails mounting holes are closer together. I brought the bearing mount holes closer in to the center of the Y stage since the fixed bearing holes (on the Y stage) seemed too close to the edge and the bearing would protude so I brought them in to be more like the fixed bearings are placed on the X stage.

- The pipe flange from Home Depot is not nearly as big as the flange in the v1.2 Vertical Base's template. I changed the flange mounting holes to fit the 3/4" floor flange from Home Depot and to use 1/4"-20 countersunk screws instead of the 1/2" in the v1.2.

- Also on the vertical base, I changed the mounting of the vertical bearing arm supports to use the 5/16" countersunk screws instead of the self-tapping screws. I figure it will be more secure.

Peter

Question about using a countersink bit:

I've been having trouble with the countersinking and was wondering what's the best method of drilling the countersink holes? I am just using a handheld corded drill but the countersinks seem to take forever to do in the acrylic. I drill the 5/16" hole first and then do the countersink bit but I am getting uneven countersinks and the drill seems to spin forever and not cut anything... any ideas?

Also, on that note, what's the best way to drill the holes in the acrylic with normal drill bits? What I've been doing is stepping up drill bit sizes starting from 1/8". It drills fine up until the 1/4" drill bit and I start to hear cracking as I'm drilling the hole. After drilling with the 1/4" bit, I move on to the 5/16" bit and again, I hear cracks as I drill and I back up the drill and keep going at it until I get it through. My method has been to clamp the acrylic to a piece of wood to give it a backing and then (on the bigger bits), start off the drill before pressing into the hole as it seems to crack less when I start the drill first. Don't know if that makes sense. Anyone have any suggestions as to how I can reduce cracking and chipping of the drilled holes at bigger hole sizes?

Thanks,
Peter

For the countersinking, you could try a (slow) pecking motion to give the swarf chance to clear before it melts.

For the large diameter holes you may find it better to drill the hole full size rather than building up to it. Possibly piloting it with a small centre drill if you're concerned about it wandering. The diameter of the centre drill should be slightly bigger than the flat point on the finish drill. Again a pecking motion might help.

Definitely start the drill before approaching the workpiece.

HTH
Mark

Thanks for the suggestions, Mark! I will give them a try and let you know how it goes.

Peter

Hi Mark,

Thanks for the tips. It seems to be working better but occasionally, the workpiece catches on the drill bit and gets stuck in the drill bit. Maybe because the drill isn't perfectly perpendicular... I may get access to a drill press soon so I will try it on the drill press and hope for better results...

Peter

Hi Peter,

A drill press will definitely help. If you move the drill from the perpendicular (even slightly) the edge of the drill will bite into the edge of the hole and try and pull it into the workpiece. I'm impressed that you are only getting occasional problems!

You could also try a lubricant - I've seen both water and candle wax mentioned but avoid hydrocarbon (paraffin etc) ones unless you can clean the workpiece thoroughly afterward.

Cheers,
Mark

Just got to try out the drill press tonight and what a difference it makes! The drilling went so much easier and they were actually straight! Go figure I didn't realize how un-perpendicular my drilling was until I used the drill press.

Still had trouble with the countersinking, even in the drill press, though. The countersink bit wasn't taking out too much material when I pressed down and it took a while and I wasn't able to cut it to the proper depth. Definitely the woodpecking motion helped, though, but I would get frustrated and hold it down and get nasty melty clumps.

Sounds like your countersink bit is blunt.

---

[www.hydraraptor.blogspot.com]

Except that I just bought these new. I bought another one at Lowe's and I had the same problem. They were cheap, though, so I guess they come blunt. Is there any way to sharpen them?

Did you try changing your drill press rpm? I had to lower mine to drill acrylic/lexan or it melted every time, even for quick pecks.

---

----
[www.binaryconstruct.com]

I put it at the second to slowest speed. I thought about setting it to the slowest rpm next time I use it. Thanks for the suggestion.

It might be possible to sharpen the bit using a grinding wheel or angle grinder, if it will fit that is. I have sharpened bits like this:
[www.lowes.com]
in a vice using a thin cutting wheel on an angle grinder. I have also destroyed bits trying to do that too, but going slow and a steady hand helps. Be sure to wear goggles, those bits of metal really hurt.

Once you sharpen a bit like that, it tends to dull out again really quick, probably from shaving off the coating, so you get a lot of practice sharpening.

Edited 1 time(s). Last edit at 05/07/2009 02:14PM by Jeff.

---

----
[www.binaryconstruct.com]