Reprap Forums - Mechanics

Extremely Low Torque to Extruder Stepper Motor (8 replies)

swighton — Fri, 20 Nov 2009 17:22:13 -0800

Hello,

I have just built a mendel and wired it up with the 5d firmware. Everything works perfectly - except for the pinch wheel extruder motor. It turns but has almost zero torque. I can easily stop it with my fingers and there is no way it can drive a filament at all. Is there a reason why the motor would do this? Is there something I can do to fix it?

Its a nema 17 driven by a motherboard version 2.2 and extruder controller 2.2.

settings for differents materials (1 reply)

stasky21 — Wed, 18 Nov 2009 05:52:15 -0800

hello everybody, this is my first post, and I want to aplogise por my bad english.

I need to know all the settings to be able to print my files with the rap-man in different materials like HDPE, PP LDPE and UPVC

what I need are the temperatures, the speed, the extrusion sizes, ....

I look forward to hearing from you. It's quite urgent.

lluis

mendel: one less piece of studding (no replies)

Triffid_Hunter — Wed, 18 Nov 2009 01:20:10 -0800

here's how to arrange your studding pieces (incl. jigs) so you only need 8 instead of 9:

1: A, D2 (142mm left)
2: A, D2 (142mm left)
3: C, D1, E (21mm left)
4: C, D1, E (21mm left)
5: C, C, B (42mm left)
6: B, J1 (340mm left)
7: B, B, J2 (26mm left)
8: B, B, J3 (103mm left)

(letters refer to Mendel Assembly Data Sheet)

I came across a few arrangements with some rods having only 6mm left, but the width of my cutting disc would consume that, leaving zero room for error, plus I still used 8 lengths of studding.

High torque drive belt for z axis? (2 replies)

liav — Tue, 17 Nov 2009 05:24:36 -0800

Before I discovered Stock Drive Products I had a very hard time sourcing reasonably priced mxl pulleys and timing belt. By random luck, though, I found a bunch of plastic 3mm pitch HTD pulleys at a local surplus store. They had 8mm bores *and* just the right diameter to fit between the studding and the smooth rod, along with a nifty optical encoder edge.

Clearly the universe wanted me to use HTD pulleys. Clearly mxl is for chumps.

So, I obtained some HTD belt, and yesterday (finally!) belted up my z axis. The HTD belt seems to works okay-ish mostly, but I immediately noticed that it skipped when the splice point hits at pulley -- it's clearly too stiff, and can't wrap around the radius properly, causing some slippage.

[I also noticed as soon as I took the splicer off that I'd left a left a full turn in the loop, but that didn't seem to effect the drive.]

Q1 - has anyone experimented with HTD belt for z axis?

Q2 - has anyone experimented with using a channel or constraint attached to the M8 rod in order to force the spliced portion to stay in contact with the pulley?

Q3 -- any suggestions?

Cheers,
L.

aluminium barrel? (1 reply)

Triffid_Hunter — Tue, 17 Nov 2009 06:03:16 -0800

anyone considered using an anodised aluminium barrel? anodisation provides a sponge-like layer of aluminium oxide mere microns thick, which is electrically insulating, thermally conducting and should be fairly unaffected by 300 degree heat. At those temperatures, it would effectively be self-repairing against the heater scratching it since it would almost immediately re-oxidise.

Another idea I had was using a large SS washer with 3 holes drilled into it, and 3 SS screws holding the barrel away from the plastic, so it would vaguely resemble this, instead of the ptfe thermal break.

any ideas on how to best implement these?

Understanding Steppers (4 replies)

jhoff — Tue, 17 Nov 2009 22:42:53 -0800

Does a stepper motor have any greater torque potential when microstepping versus full stepping?

Also, should there be any change in potential "top speed" by changing to a half, quarter or eighth step?

The tests that I've done so far seem to suggest no for both of these questions, so I'm wondering if the only difference in microstepping is just greater resolution and higher power consumption.

Thanks,
JHoff

High quality all-around pics of Mendel? (1 reply)

toomanyplugs — Fri, 13 Nov 2009 13:10:37 -0800

Hi folks,

I've got a few questions about the assembly of Mendel that I think could be solved by just looking at the whole thing. Unfortunately, I'm looking for "as built" stuff, so the solid model doesn't quite do it for me.

Short of flying across the Atlantic to see the real thing, is there any source for good pics of all around Mendel? The one on the Mendel page on the wiki [objects.reprap.org] is nice, but are there any other views?

Printer mechanism positioning problems (12 replies)

kkannan — Wed, 18 Nov 2009 05:47:17 -0800

Hi All,

I am building an XY table out of two old printer mechanisms and 3.5" in floppy drive as Z axis which is holding a pen right now. The electronics are arduino uploaded with reprap firmware 1.1 and stepper drivers are l297/298 combos.

This crazy contraption is working as a plotter and i could draw some pictures. The problem is, i don't have the specs for one of the printer head driving motor. It has got a 15 mm timing pulley attached to the belt and no word about step angle. I stuck a pen and tried to measure the angle by plotting 1000 step line and divide by inch to obtain the steps/in and came to the conclusion that it is 0.9 deg.

Here i discovered that 1000 steps forward and 1000 steps backward doesn't come to the same position. Each successive 1000 back and forth movement keeps shifting the start and stop positions to one side. I guess it is not missing the steps, because the distance between start and stop is consistent.

Here is the code snippet which moves 1000 steps forward and reverse the same amount once i click on the serial monitor in Arduino (alpha) IDE.

boolean done = false;
void loop(){
  if(!done){
  digitalWrite(7,HIGH);// Enable stepper motor
  digitalWrite(6,LOW); // Direction 

  for(int i = 0;i < 1000;i++){
      digitalWrite(5,HIGH); // step pulse
      delay(5);
      digitalWrite(5,LOW);  // step pulse
      delay(5);
  }

  digitalWrite(6,HIGH);    // reversing the direction
  delay(5);
  
  for(int i = 0;i < 1000;i++){
      digitalWrite(5,HIGH); // step pulse
      delay(5);
      digitalWrite(5,LOW);  // step pulse
      delay(5);
  }
  
  done = true;
  digitalWrite(7,LOW);     // disable motor
  }

I tried changing the board with same results. BTW i am using the unipolar motor as bipolar by using the half coil config. mechanisms are stacked one over the other and the bottom one driving a thick board to hold paper. Both motors are behaving the same way. But i have to mention that the mechanisms are shaky at various places.

Am i missing something obvious ?

Thanks
Kannan

(Running on Vista Home pre/arduino/arduino (Alpha)/ reprap 1.1

Filament sensor (no replies)

Barney — Wed, 04 Nov 2009 15:34:31 -0800

My first contribution to the RepRap project: I've worked out a way to use the rotation sensor to measure the filament feed rate. This means you can sense when the pinch wheel is slipping, as well as using it for motor speed control. Details are in my blog:

Repstrap materials question (1 reply)

Tornadoboy — Wed, 18 Nov 2009 22:59:19 -0800

Hi everybody, here's a dumb question:

What's the thickness of the material for the repstrap stage platforms and bearing arms supposed to be? I can't seem to find it in the instructions anywhere, although I get the impression it's not critical but I thought I had better ask anyway, especially for the bearing arms where bolts might stick out too much.

the cut-out in the thick sheet for Mendel? (3 replies)

pica — Sun, 08 Nov 2009 07:22:48 -0800

[objects.reprap.org] (big picture of Mendel)

There's a notch in the bed table, like it was a clearance cut for a stepper or something, but I can't see why it's there.

Sorry for all the questions, but I'll be attempting a RepStrap and I'll have to translate the design decisions over to wise choices in my material of choice.

I'm probably going to go with a scaled up version of Mendel, using angle iron as the structural supports, and probably a different (SAE) pitch for the Z lead-screws. Extra torque and higher voltage stepper motors with 200 step per revolution. A router for the first toolhead (I plan on some light milling). Oh and relocating the controller boards up top and making a few other design choices so I could retrofit a liquid coolant system later.

Mendel questions on 0.1 mm positioning accuracy (4 replies)

pica — Tue, 03 Nov 2009 11:24:55 -0800

The x axis seems to be a gear mounted on a stepper with several idlers and directly driving the extruder. Assuming 200 steps per revolution of the stepper, you would get a tenth of a millimeter per step by sizing the gear on the stepper to have a circumference of .1 x 200 mm or a diameter of 20/3.14 = 63.7 mm (which seems reasonable from what I can see)

Am I on target here or are you doing half-steps to get that resolution?

Is the y axis substantially the same?

The Z axis is interesting, and I really like the way you use gravity to overcome blacklash. I know that you are using 8 mm threaded rod, but is the pitch 1.0 or 1.2? Do we have the same resolution on this axis too?

Stepper Motors out of old printers (9 replies)

Benni — Fri, 06 Nov 2009 04:17:51 -0800

Hello,

First of all sorry for my bad english, i'll try my best!

I would really like to build a reprap. So i looked around which materials i already got and i found three working HP 895 Printer.
I opened them up an found - beside the two smaller steppers which are needed for the paper-feeding - a bigger one (40x40x40mm). They are labeled with 1,3V / 0,3A.
I searched the web for more information about the motors like torque etc. but i didn't find anything.

Can anyone of you please tell me if these steppers are suitable for building a reprap. Or should i use gears to boost their torque a little bit?

greetings
benni

How to wire a stepper motor? (2 replies)

drummerboyx — Wed, 28 Oct 2009 17:47:55 -0700

I have a five wire stepper motors along with a four wire bipolar stepper motor. I'm not sure if my five wire stepper is bipolar or unipolar but it seems unipolar. I also have the stepper driver from makerbot.com: [store.makerbot.com]

How can I wire my 5 wire stepper with the bipolar 4 wire stepper driver?

Thanks,
Drummerboyx

PA instead of ABS? (6 replies)

Sebastian — Thu, 29 Oct 2009 14:59:59 -0700

Hi,
right now I'm trying to get my parts for Mendel from a RP-Company. They asked me if PA could also be used for the parts instead of ABs, because this would be cheaper. Do you know anything, which would be against making it out of PA?

Thank you,
Sebastian

Mendel total build (no replies)

Sebastian — Tue, 27 Oct 2009 00:26:53 -0700

Hi,
could you please give me the total build ( image from wiki ) in .stl-Format. I'm on the way getting Solid Edge Academic, but I need this file urgently.

Thank you for reading and (hopefully) helping me,
Sebastian

Why Not Kapton? (1 reply)

ziplock — Mon, 26 Oct 2009 06:33:14 -0700

To build an extruder for a Reprap, you have to use a piece of copper pipe and fire cement to keep the heating element and temp sensor on. On the Cupcake CNC, Kapton tape replaces those two parts.

Why isn't it standard procedure to use Kapton to hold an extruder together? Kapton works just as well (if not better) than fire cement, and is easier to use. Also, if you need to take the heating element out, you just undo the tape.

I'm pretty sure that Kapton makes for an easier to build, and (probably) cheaper extruder. Please, leave your opinions below.

-Adam

Mendel Ball Chain (2 replies)

ziplock — Sat, 24 Oct 2009 02:15:30 -0700

Is it possible to use a ball chain to drive Mendel's axes, instead of a belt?

Just wondering.

-Adam

-EDIT-
Thanks to MotorAssist for the tip about the plural form of axis!

How many bearings does Mendelssohn use? (3 replies)

Triffid_Hunter — Thu, 22 Oct 2009 15:50:46 -0700

have been scouring the site for this tidbit of information, but can't find it anywhere.
Quite a number of the assemblies in the mendel mechanical construction guide in the wiki don't mention the bearings used in the BOM.
The bearing video suggests that there are 10 per axis for a total of 30, but I'd like something a bit more definite, as much as that's possible with a beta design.

I'd expect it to be in the assembly datasheet somewhere too, but no such luck.

Aluminium bars (8 replies)

Lionel — Thu, 29 Oct 2009 20:18:09 -0700

Hi,

Now that the Mendel's design is very good at avoiding jammings, could it be possible to replace the stainless steel bars by cheaper aluminium bars? It would be cheaper and easier to cut.
Plus, aluminium has a relatively low melting point (~660 C) so the parts could be prepared in ceramic molds from recycled cans or foil and distributed cheaply by anyone who does a bit of pottery...

Hexagonal grid in printed parts (5 replies)

gerard94 — Tue, 20 Oct 2009 15:07:41 -0700

Hello all,

I use Skeinforge with a BitsFromBytes Rapman. By default the printing uses an hexagonal grid to fill the printed shapes. Does this option give a sufficient strength to Mendel printed parts?

Thanks.

gcode for milling mendel parts (3 replies)

KaiBackman — Sun, 08 Nov 2009 00:39:46 -0800

Has anyone produced gcode for milling the mendel parts? I have a 4 axis mill and a quick glance at all the parts seems to indicate they could be milled out of HDPE.

New salvage steppers (13 replies)

JohnW — Thu, 22 Oct 2009 11:08:31 -0700

Been struggling to get started really - did find some new stepper motors today in the car park on some salvage copiers. Should be good for the CNC milling machine I am planning on to produce the parts for a reprap. Plan is a Sieg X1 home CNC'd to make the parts for the reprap.

These motors are pretty beefy - havent had a chance to lookup any data on it but did notice they have encoders built on the back end which may or may not be of any use?

8mm shafts dont know the voltage or current yet but should be ok for a small CNC mill surely? Mounting holes look like 47.5mm apart

I need STL files for the Darwin Z Pulleys (4 replies)

Curlrup — Tue, 20 Oct 2009 05:15:28 -0700

Hello,

I really need an STL or CAD file of the z stage pulleys for a Darwin. The current STL package only has the molds and I was hoping someone took the time to model one up so you can print it instead of molding it. Thanks a bunch

Curly

simplest comercial machine (7 replies)

VDX — Tue, 20 Oct 2009 02:21:56 -0700

Hi all,

look into the documentation of a comercial paste-dispensing 3D-roboter: [www.globaco.de]

It's an extreme simple setup but has a price of 5000 Euros ::o

Anyway ... it's much lower parts count, than any other actual system (:P)

Viktor

Various mechanical questions about Mendel (2 replies)

ziplock — Sun, 18 Oct 2009 22:17:29 -0700

I have a few questions about Mendel:

Mendel Bearings question (10 replies)

SOI Sentinel — Mon, 09 Nov 2009 20:25:42 -0800

I was thining about all the bearings required for the Mendel, and I was wondering why we're using roller bearings on a fairly low mass/low force machine instead of plastic linear bushings (Igus parts for instance). I've had the prices come out pretty competitive, and one bushing would replace three bearings plus much of the associated steel hardware. Some variants run on steel without issue (most prefer aluminum).

Any thoughts? I'm curious to hear from those who were more involved in the design.

Printed drive belts? (6 replies)

elf — Thu, 15 Oct 2009 09:40:21 -0700

Could Reprap print drive belts? as these seem to be hard to find and expensive.

Wedge: Y-axis conveyor belt? (1 reply)

Triffid_Hunter — Wed, 14 Oct 2009 22:34:47 -0700

Has anyone tried fitting a conveyor belt to the wedge's Y-axis instead of the moving table? Looks to me from the videos that it wouldn't be too difficult, and would allow it to drop printed parts into a bucket for very long runs, and/or print very long parts if the conveyor was extended out the front.

Are there any flexible materials that the extruded plastic will stick to enough for a solid print, but not so much that it causes problems when the belt goes around a roller?

Discuss!

alternatives to nozzil - hyperdermic needles (9 replies)

stephen george — Tue, 03 Nov 2009 00:27:41 -0800

Hi

Has anyone considered hyperdermic needles for the nozzle of the extruder?

I assume they are cheap. Can be easily cutdown to size with snippers and if
made from steel would take having hot plastic shoved down them by a stepper motor.

Looking at [wapedia.mobi]

Guage 23 has an outer size of 0.64mm and an inner of 0.337mm
Guage 34 has an inner size of 0.08mm for super high resolution plastic delivery.

Probably get them free at the needle exchange ..... Yep I am a reprap addict and I need my fix.

Just a thought.

But if it worked creating a nozzle with 8 high precision outputs would not be far away. (I am thinking of the 8 pin dot matrix printer style here)

Stephen