An Original Name's Questions about a Mendel build

In the Mendel assembly datasheet, the USA supplier listed for bar (smallparts.com) had no listings for the serial number (CGSX-M08-72) provided for BZP M8 bar. Would this alternate 5/16" dia, 36" length, galvanized steel bar from McMaster work instead? [www.mcmaster.com] . I did the math and found out that 36" ( * 3) in this case was an adequate length for the pieces required by Mendel. I picked galvanized because they had no BZP option and I was concerned with the possibility of rusting on steel. If this ends up a nonviable option, what are some alternate suppliers of bar that would be compatible with the RepRap Mendel design?

Edited 2 time(s). Last edit at 11/09/2010 09:50PM by An Original Name.

You may want to double check this but i think bright zink plating is a form of galvanizing. So the two different suppliers may be refering to the same thing.

I used 5/16 threaded rod from Home Depot for my Mendel.

jkelso Wrote:
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> I used 5/16 threaded rod from Home Depot for my
> Mendel.


Doesn't the pitch on the threaded rod need to be pretty close to the M8 equivalent to get accurate printing (esp. the Z axis), or are the pitches between M8 and 5/16" pretty interchangeable?

At any rate I was talking about round rod, not threaded rod--Mendel calls for both. I think I found a good supplier for this now that you mention home depot! (if 5/16" works, that is). [www.homedepot.com] x5. [www.homedepot.com] x3. A lot less expensive than what I was going with before as far as the threaded rods go ( [www.acehardwareoutlet.com] ).

Now the issue is not so much the material type, but the stone-age measuring system we Americans have.

Have a look at the following link:

Zinc plating vs Zinc galvanising

In essence:

Zinc galvanising will be slightly rougher, but will last a LOT longer than Zinc plating.

As this is for the smooth rods, you may well want to be careful about the roughness.

Note: Post-processing the rods yourself (eg: fine sanding) will damage this layer of zinc, which will reduce the life of the rods.

I was told by Fleming bros. at Fleming CNC where I got my Isaac Mendel parts that 5/16 would be just fine. I've been getting great parts out of it so I can verify that it works just the same.

7.9 mm = 0.3110 inches
7.9375 mm = 0.3125 inches = 5/16
8 mm = 0.3149 inches

of course, it depends on the tolerance they are grinding them to, but 5/16 is pretty close. it's what i'm using (mainly because i couldn't find extruded carbon fiber in metric sizes for a reasonable price.)

If you can, get 48" lengths. you only need two 48" lengths to cut all 6 bearing rods. you'll have to reduce the length by 2 mm for each rod, but they still work fine, and you won't have any leftovers kicking around. also, shipping may be less.

|----z----|-----y-----|------x------|

So the thread/pitch differences between the M8 and 5/16" studding won't be an issue then? I can just change the option for that in the firmware or something? I've done the math and a 5/16" coarse threading is only 0.709 threads per mm of length while the standard M8 threading is 1.25 threads per mm. Will I just have to reduce the steps (on the stepper motor) per Z layer or something?

I know I've been talking about unthreaded rods, but being able to buy 5/16" threaded rods would help my wallet out a lot.

When I first started printing the numbers in my firmware were way off. I think they may be metric values. Here's what I'm using currently and it works perfect with my 5/16" threaded rods: X and Y 7.869 steps per MM and Z at 320 steps per MM.

This might be informative: SAE Mendel

This page needs a lot more info, though. Anybody that's using SAE; please look it over and see if there's anything you'd add/change.

And don't forget to get 5/16 nuts!

Of course. I'm now planning on replacing all M8 components with 5/16" components.

I have another question now though. I'm not very experienced in circuitry (the most I've done is build my own computer and I have a very limited grasp of how volts, wattage, and amperes relate D: ). Keeping that in mind, what is the better option (less experimental, more plug+play) for my Mendel electronics: Gen3, Gen6, or RAMPS? I am currently considering Gen6 the most feasible option for me, but really any of the three seem usable for me (albeit, Gen3 is a bit outdated now, no?). Does Gen6 have support for a heated bed connector?

Also, one more thing: what kind of specs should I look into for my power supply (I don't think I'll be hacking a PC PSU) if I want to run Mendel + this heated bed [reprapsource.com] ?

Oh, and thanks for putting up with my incessant questions.

Edited 4 time(s). Last edit at 11/12/2010 11:47PM by An Original Name.

I'd be looking at a 12V PSU with at least 15 Amps (more is fine). That's 10 Amps for the heated bed and 5 Amps for the rest of the electronics.

Of note: The RAMPS board has a PTC fuse on it that runs to about 5 Amps. This means you will not be able to drive 15 Amps out of that board with that fuse in place, and I do not know if simply replacing the fuse would be good enough (eg: burning out tracks elsewhere). The MOSFET's will happily push that current.

That said, you could simply drive a relay from the standard MOSFET output and put the heated bed off that.

Sorry for my ignorance... but what's MOSFET?

*edit*

Never mind... Wikipedia rules. [en.wikipedia.org]

But like I said... I'm pretty ignorant about electronic components... would I have to make something like that on my own or would, say, Gen6 support 15 amps?

Edited 2 time(s). Last edit at 11/13/2010 12:38AM by An Original Name.

Your electronics board (or the extruder board if you have gen 3) should have a set of 6 screw terminals that wires can go into, 2 for each MOSFET chip. When you ramp up the nozzle heat you will see the LED by the MOSFET assigned in the firmware start to slowly glow and come to life, it takes a minute. It's possible to run the heated bed from these terminals but I burned out one MOSFET chip on my board so I reassigned the heated bed terminals in my firmware to run the nozzle heat instead. I would recommend not running a heated bed through your electronics board, it's already got too much to handle as it is. Check out danielg he has a new thread detailing his heated bed which runs on a standalone system. I'm going to do something like what he has for mine but I haven't completely decided on which bed yet. I have a 12V 5A power supply running my machine, which I used because that's what most of the complete mendel electronics kits I've seen are supplying.

Alright... I guess I should just focus on getting this build working first, then work on adding a heated bed.

Extruder question: I'm thinking about building a hot end similar to [www.mendel-parts.com] . Is there any reason the mounting block has to be PEEK or could I make it out of wood?

Oh... and one more thing: What is the best nozzle size for a RepRap? I know most RepRappers use 0.5, but does a smaller nozzle mean that I can print parts with smaller feature sizes? What kinds of pluses and minuses are there for using a smaller extruder nozzle?

Edited 2 time(s). Last edit at 11/13/2010 08:18PM by An Original Name.

Smaller nozzle hole requires more force to extrude, and requires a higher quality of plastic.

.5 is a good middle ground, but .35 is better for gears.

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repraplogphase.blogspot.com

.4 also increases print time

If you make it from wood it will burn. It has to be a material that will stand more than 250C, not be thermally conductive and be dimensionally stable under stress.

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[www.hydraraptor.blogspot.com]

The wood would need replacing occasionally. The hotend that was provided with my Techzone Lasercut mendel is an oak block with an M7 threaded hole through it. A teflon tube is screwed most of the way through and the brass nozzle screws in from the other side. Just recently, my hot-end crumbled out of the block for the second time, but it only took a few minutes to cut another block of oak, drill and thread it and have my machine working again.

So I think you can use wood if you want, but you will have to replace it every couple of months.

I got a nice hybrid PTFE/PEEK extruder nozzle from reifsnyderb.
[www.reprapstores.com]

jkelso Wrote:
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> I got a nice hybrid PTFE/PEEK extruder nozzle from
> reifsnyderb.
> [www.reprapstores.com]

Yeah that was actually the set I was going for, except it seems to be missing a mounting block [www.mendel-parts.com] . Right now I'm looking to get [www.reprapstores.com] with the .5mm orifice plus [www.mendel-parts.com] that I can machine myself to fit the other pieces. How machinable is PEEK, by the way? Would I be able to machine it with just a hand-held drill (basically the only boring tool I have at the moment)?

Some nozzles use the mounting block but I don't have one on my extruder. I'm not sure how the PEEK mounting block works/helps. There's also an alternative to using nichrome wire by using a metal heater block too. My nozzle just glues/screws into the mounting hole in the bottom of my Wade's extruder body without a mounting block.

The mounting block is to prevent the typical hot-end failure mode:

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Here's a blog post about what I ordered from McMaster-Carr

[markbova.com]

It references back to a different thread about McMaster, (as a parts source), that you probably haven't seen yet.

I've squared the frame, and all the nuts, bolts, and rods worked out OK, but I've yet to assemble my extruder or mount the control electronics. The O1 Tool Steel Tight-Tolerance Rod worked out great.

I've since found 10 foot lengths of 5/16 threaded rod that were slightly cheaper at Home Despot, but you'll still have to mail order the smooth rod and I don't think it will save you much on shipping to pick up the 5/16 locally. You'll also have to buy different nuts.

I've looked at the SAE Mendel remix, but the truth is that going SAE on Mendel won't save you more that about $2 as I calculate things.

My variant is mostly using standard instead of nylock nuts, and adding a $6 bottle of green loctite threadlocker, (the type that seeps into a joint after everything is adjusted). I saw the threadlock at Advanced Auto (parts) store.

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My blog's Reprap feed: [blog.markbova.com]
I'm currently working on a stock Mendel build with a Seeeduino Mega and four Pololu A4983 stepper controllers.

A quote from the SAE wikipage:

Quote

An attempt to build a Mendel from 100% SAE components. In Canada (and USA I hear) SAE parts are not only MUCH easier to find, but are much less expensive as well... This should help reduce the price, and make sourcing parts a lot less painful for those of us on this side of the pond.

I've found the above statement completely untrue, unless of course you are trying to source everything from the hardware store, where the odd metric part might be double the price if it's available at all.

Once you commit to ordering some parts from McMaster-Carr, you find that the price difference is but a few cents, and it is far more worth your time to keep with the proven design instead of forging ahead and making you own mistakes on your own time. Metric is common and plentiful via mail order (But I should note that McMaster does not ship to Canada so if an in-country supplier isn't available it still might make some sense to the original wiki page creator)

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--
My blog's Reprap feed: [blog.markbova.com]
I'm currently working on a stock Mendel build with a Seeeduino Mega and four Pololu A4983 stepper controllers.

pica Wrote:
-------------------------------------------------------
> A quote from the SAE wikipage:
>
> An attempt to build a Mendel from 100% SAE
> components. In Canada (and USA I hear) SAE parts
> are not only MUCH easier to find, but are much
> less expensive as well... This should help reduce
> the price, and make sourcing parts a lot less
> painful for those of us on this side of the pond.
>
>
> I've found the above statement completely untrue,
> unless of course you are trying to source
> everything from the hardware store, where the odd
> metric part might be double the price if it's
> available at all.
>
> Once you commit to ordering some parts from
> McMaster-Carr, you find that the price difference
> is but a few cents, and it is far more worth your
> time to keep with the proven design instead of
> forging ahead and making you own mistakes on your
> own time. Metric is common and plentiful via mail
> order (But I should note that McMaster does not
> ship to Canada so if an in-country supplier isn't
> available it still might make some sense to the
> original wiki page creator)

I looked at McMaster already. They're much more expensive than the 5/16" rod I could buy from Lowes or The Home Depot. Compare:
[www.mcmaster.com] $7.07 per meter. [www.lowes.com] $0.84 per yard, $0.91 per meter.
[www.mcmaster.com] $5.34 per meter. [www.homedepot.com] $4.28 per meter.
Also note that the smooth rod I found from McMaster is not BZP; it's just plain steel, meaning that it will rust.
I can't seem to support your results; perhaps I am not looking in the right categories but the materials I found at neighborhood hardware shops in 5/16" are much cheaper than the M8 from McMaster.

And, while we're on the topic, how are McMaster shipping charges?

On to stepper motors... Now that I have sent my electronics order in with mendel-parts.com, I can begin testing the electronics once they arrive, but I hope to have the stepper motors ready by that time as well.
I have several models in mind (all NEMA 17), some with less torque but cheaper, some with quite a bit of power but a bit more expensive. Which ones would be adequate for the three axis steppers + Wade's Geared Extruder and compatible with Gen6 electronics?
[www.alltronics.com] Only 8 dollars but it probably doesn't have a lot of torque. *edit* Wow they've been raising the prices... it's 10 dollars now!
[www.alltronics.com] A bit pricier (12 dollars), but more torque.
[www.alltronics.com] Again, 12 dollars, but it has dual shafts from each side. Those would probably just get in the way on a RepRap?

Edited 4 time(s). Last edit at 11/16/2010 06:15PM by An Original Name.

The dual shaft ones work fine without getting in the way. All mine are dual-shaft,

Greg Frost Wrote:
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> The dual shaft ones work fine without getting in
> the way. All mine are dual-shaft,

Hmm... In that case [www.alltronics.com] look the most appetizing to me at the moment. They were only $10 a couple of days ago but they raised the price. I guess I'll have to buy them before they raise the price again

Edited 3 time(s). Last edit at 11/16/2010 06:26PM by An Original Name.

Does anyone have the dimensions for the thick sheet items? All I could find are the .dxf files, but I don't have a laser cutter and the files don't import with proper dimensions in OpenOffice.

Import them into a drawing program and the dimensions will become obvious.

Something like Solid Edge is free.

[www.plm.automation.siemens.com]

Edited 2 time(s). Last edit at 11/29/2010 07:43PM by m100.