Building a Mendel: A Noob's Tale

Hi everyone,

I'm absolutely new to this but I have been interested in building a rep rap for a long time. I just recently graduated college as a mechanical engineer and decided now is a great time to take on a project like this.

I wish to construct the Mendel with the lowest cost possible.

The first step of my plan is to purchase all of the electrical components at once to make sure they interface well with my computer. I have found the RepRap parts lister to be extremely helpful and based on that I intend to purchase all my parts from Digikey and Mouser.

On to the questions:

Various components call for a 15pF Ceramic Capacitor but the model specified by the parts lister seems to be discontinued at Mouser. the part number is 77-VJ12A100V150J. Is it possible to substitute this guy in its place: 77-VJ12A50V150F?

The A3982 and A3949 Allegro chips seem to be out of stock and I cannot order them. I've checked the Allegro site for these chips and they list the parts with an addition of TR at the end of the part numbers. For example the part provided in the part lister is A3982SLB-T while the part available is A3982SLBTR-T. Is it okay to purchase the part that is available?

The only supplier of bare PCBs seems to be MakerBot.com. They do not seem to carry The Stepper Motor Driver 2.3 or the Motherboard 1.2 for the Mendel. How can I get my hands on these? Will I have to create these circuits on breadboards?

For now that is all the questions I have but as I wade through this project I'm sure more will arise and I will update this thread as necessary. I am completely new at this and if I am doing something glaringly wrong please tell me.

Thanks for your help.

Wai Jun Ho

> Hi everyone,
Hi, and welcome!

I'll try to answer some of your questions.

> The A3982 and A3949 Allegro chips seem to be out
> of stock and I cannot order them.
If you're going to use a separate stepper controller for the extruder motor, which is a good idea, you won't need the A3949 chips on the extruder controller.

> The only supplier of bare PCBs seems to be
> MakerBot.com. They do not seem to carry The
> Stepper Motor Driver 2.3 or the Motherboard 1.2
> for the Mendel. How can I get my hands on these?
> Will I have to create these circuits on
> breadboards?
There are quite a few people selling PCBs in the For Sale forum.


If the components to the Gen3 electronics are difficult to source, may I perhaps suggest a consideration of Pololu Electronics?

Good luck with your RepRap, and keep us posted on your progress

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-Nudel
Blog with RepRap Comic

Hey Nudel,

can you elaborate on how I would use a separate stepper controller in place of the A3949? Just directing me to the relevant documentation is fine. Understanding exactly what every electrical component is a daunting task and I'm still feeling my way through it.

Hi

You send the step and direction signal from to the motherboard to a fourth stepper board, which then drives the motor instead of the extruder board.
Of course this would have you need another stepper board, and that would make the cost go up.

There is a lot of threads in the forum about this, just have a look around.

I'm sure you're aware of the complete electronic sets from tech zone, and (soon) mendel-parts.org ?

-Nudel

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-Nudel
Blog with RepRap Comic

After some convincing from the people in the IRC channel I have decided to wait for the gen6 electronics, so I will change my efforts to building the physical parts.

In the AOI solid model files provided by the website is it possible to extract dimension data for each part from it? and What measurement is the grid in? units or millimeters? If its in units how would i covert 1 unit into mm?

Waiasaur, are you making yours from metal or wood?

Mendel is a cult object, it makes wonderful good sense to print one.
But if you're fabricating using metal or wood, build one of these:
http://reprap.org/wiki/WolfStrap-English
http://reprap.org/wiki/Eiffel

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

I would love to print my own Mendel but I dont have one to print a duplicate. Printed parts go for 260 USD + shipping and that is not something I can afford at this moment.

I intend to build my reprap out of wood. I have been reviewing various wooden mendels on this website and was interested in doing something similar. I can definitely see the reduction in difficulty in building a wolfstrap instead.

Is the easiest way to duplicate Mendel parts to print 1:1 scale 2D models and using it as a tracing template? I am able to load stl files in proEngineer but I cannot find a reliable way to dimensionally locate the holes.

If I were to build a Wolfstrap I would probably get it working and then build a mendel out of it because it looks so much prettier. (No offense to the original creator, but the wolfstrap is a good definition of function over form). If I were able to duplicate the Mendel with wood however, I think I wouldnt mind having something like that sitting on my desk.

So long story short, I would like to duplicate the Mendel out of wood.

On a side note, can somebody explain to me the purpose of the springs under the print bed?

Oh another question: why does the Mendel use belt drive instead of screw drive? Like the Z axis, it uses belt to drive a screw, why not just have the motor drive the screw?

The springs under the bed allow it to be adjusted so it is exactly level.

X & Y use belt drives because screw drives are not fast enough. Z uses a belt because it has two lead screws and one motor.

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[www.hydraraptor.blogspot.com]

ahh i see! thanks for clearing that up!

after inspiration from Sebastien's post, I've decided to try my hand at designing my own wooden mendel rep strap so I no longer need Mendel dimensions. Thanks dude!

Edited 1 time(s). Last edit at 09/03/2010 03:58AM by Waiasaur.

after inspiration from Sebastien's post, I've decided to try my hand at designing my own wooden mendel rep strap so I no longer need Mendel dimensions. Thanks dude!

Yay!!! Are you doing "Rods-and-Knobs" (Mendel-esqe) or more "Lots-of-Wood" (WolfStrap-esqe)?

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

I plan to duplicate the driving mechanisms from the Mendel as closely as possible, but at the same time making it easy for wood construction. Things that do not have 90 degree angles are more difficult to construct accurately on wood.

I am in the design stage now and as far as my foresight can tell I will have the x and y axis motion achieved through a cart with ball bearing wheels ontop of wood rails. If the wood rails turns out to be too soft or bumpy I will add a hard sheet on top. I may also try laying a sheet of rubber on top of the rails to contact with bare bearings: this may simulate the dampening effects of a car tire, perhaps lending to smoother tray motion.

Currently I cannot think of a better way to move the Z axis than the method employed by the Mendel, so I may just duplicate that system on my repstrap. My x axis is going to be rather heavy due to the wood and for something like that, screw drive would be fantastic.

Here is a an update on my progress. I modeled it in Pro E and had easy wood construction in mind, so everything is a rectangle derivative.

I still need to figure out how to make the moving cart/motor assembly for the X axis. The Y and Z axis will use the same system as the Mendel.

putting it as a picture doesn't seem to work so here is a link.

[i54.tinypic.com]

Edited 1 time(s). Last edit at 09/16/2010 06:08PM by Waiasaur.

Hi!

So I'm pretty much done building. All the axis seem to move around quite smoothly. The print head part is still a solid block of wood because I haven't received my wades extruder yet and I don't know what kind of mounting it requires. When I get the extruder I will use a router and hollow out the center. Or if I'm really lucky i could just use a drill press. I havent mounted my circuit board yet or installed my optos. So far this project has run me about $400. Not bad compared to maker bots $1500? price tag. Half of my expense was buying the Gen 6 electronics for $200. Almost all of my building materials are from home depot.

I hope it all works out when I test print!

Picture!



Wai

Pretty enough for my desk. Have more pictures? I'd like to see how you did the z axis. The xy rollers on soft wood? Hmmmm....might have to put a metal plate on top to keep it from making indentations.

I'm trying to use some electical conduit for the x and y axis that seems to be working. But really interested in what you're doing on the z.
Arvin

That looks great!

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-Nudel
Blog with RepRap Comic

The X is on hardwood and the Y is on softwood (based on the materials I had handy). The bearings don't seem to make any marks on the rails even with moderate force applied but I wouldn't know for sure until I get my extruder and start printing.

My Z axis is driven by 4 threaded rods that are held in place by a bearing and 2 nuts squishing the bearing. The inner sleeve of the bearing turns freely with the rod and the outer sleeve is press fitted into a wood block. At the bottom of the rod I have timing pulleys so that a belt can drive all 4 at the same time. At the top, the rods are secured using the same method of a bearing and 2 nuts.

I have one picture of my Z axis and will try to get you more as the opportunity presents itself.

Picture!

Four bearings and GEARS! Sorry for shouting

Which gears. The couple I bought were like $7 each. X4 ouch.

More pictures please.

Took a while to get back to you. Been getting the Christmas lights up and running. Look good.
Arvin

Edited 1 time(s). Last edit at 12/03/2010 10:34AM by Arvin.

I got these for my timing pulleys Pulleys

I havent had a chance to get to it this past week so I still dont have an opportunity to take pictures, I will post up more when I get a chance.