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  #31  
Old Mon 12 October 2009, 19:59
cncb
Just call me: Brian
 
Connecticut
United States of America
Are the photos not showing up for you guys?
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  #32  
Old Mon 12 October 2009, 20:00
cncb
Just call me: Brian
 
Connecticut
United States of America
Thats weird, they show up in IE but not Firefox..
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  #33  
Old Mon 12 October 2009, 20:21
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Brian, try clearing your cache? OR do a reboot?
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  #34  
Old Fri 16 October 2009, 07:49
javeria
Just call me: Irfan #33
 
Bangalore
India
WoW nader, I was away for a while - and looks like you posted soo much man

good for you - and good for the so many people with lesser resources who can still build a cnc by using ideas you have used

RGDS
IRfan
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  #35  
Old Mon 19 October 2009, 12:27
Atifeh
Just call me: Nader
 
Tehran
Iran
Send a message via Yahoo to Atifeh
Progress on the chassis

Thank you all for your support and kind words. I am glad this thread proved to be useful.

Once again back to the first machine. This is still the history of the late works. The machine is undergoing painting and from that point the progress is up to date.


Preparing the legs:
I moved the leg dampers outside of the legs for ease of adjustment.
legs1.jpg

legs2.jpg

The previous method that I devised for welding the transverse frames was complicated and errative due to the fact that the main frames were not guaranteed to be quite parallel and in the same plane. This time I used this method. Measured and welded the frames on a flat surface and then matching the main frames to it. It proved to be better and more precise.
transverseframe1.jpg

transverseframe2.jpg

The end pads of the frames are tack welded in this position:
transverseframe3.jpg

transverseframe4.jpg

Straightening of the beams and rails by welding.
straightening1.jpg

straightening2.jpg

A lesson learned: when straightening a U channel, do NOT weld on the web. It will bend outside, disregarding welding it on the inside or or on the outside. The reason is the low mass of the web relative to the high mass of the wings which holds more internal stress. Even grinding will not return it to the initial state. Instead only work on the wings.

My parameters besides Gerald’s recommendations were:
Use as much amp as you can to concentrate a lot of heat.
Maintain a constant width of weld. This is very important. When I welded wider, more lateral movement was made, the heat concentration was quite high and the bending was more profound.
Start with 600 mm apart. Wait after completely cool. This is also equally important. Then if necessary, make corrections within this distance.
In some cases grinding reversed the action of straightening, in some cases it did not.

Marking and transferring rails holes to the main beam after straightening.
railXtransfer70.jpg

railXtransfer71.jpg

Table beams:
As before a drill mark template was made. I avoided the not so important mistake in the previous make. This time a straight line was drawn along the length of the beams and the template was matched with that line and the center and center pinned. Now, when drilling the table board, whatever longitudinal mis-shape the beam might have, will not interfere with the location of the middle tapped holes, once the first and last holes are matched with the template. Below pictures show this sequence.
tablebeamstages1.jpg

tablebeamstages2.jpg

tablebeamstages3.jpg

tablebeamstages4.jpg

Beams being drilled:
tablebeamstages5.jpg
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  #36  
Old Mon 19 October 2009, 12:40
Atifeh
Just call me: Nader
 
Tehran
Iran
Send a message via Yahoo to Atifeh
Sequences of frame assembly:

01levelling.jpg

02framespotweld.jpg

03framespotweld.jpg

04framespotweld.jpg

05framedeassy1.jpg

06framewelding.jpg

07framereassembly.jpg

08mainbeamassy.jpg

09mainbeamassy.jpg

10mainbeamassy.jpg

11reassembly2.jpg

12railgrinding.jpg

13railgrinding.jpg

14frameassembled.jpg

Please note, the name of the pictures represent the action done.
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  #37  
Old Mon 19 October 2009, 12:51
Atifeh
Just call me: Nader
 
Tehran
Iran
Send a message via Yahoo to Atifeh
Arrangement of the microswitches supports and pylons:

X axis end limit switch and the previously forgotten end stop tab. Now both positioned on the other side.
swX2home_limit.jpg

X axis home switch and end stop.
swXhome.jpg

Y axis limits and home switches.
swYlimit_home.jpg

Supports for the button box.
A hole was drilled to let the cables pass through from the X1 side to the X2 side. Cables will go through a plastic cable duct which will be mounted inside the gantry beam. (details will come later).
switch_buttonbox.jpg

Details of the X and Y echain assembly.
echainsupportY.jpg

echainsupportX1.jpg

echainsupportX2.jpg

echaindetail1.jpg

echainassembly.jpg
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  #38  
Old Mon 19 October 2009, 12:55
Atifeh
Just call me: Nader
 
Tehran
Iran
Send a message via Yahoo to Atifeh
General view as of 2-3 weeks ago

General1.jpg

General2.jpg

Please note: the 4th axis pictures are in the related topic in this forum and will not be discussed here.
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  #39  
Old Sun 25 October 2009, 07:42
wiwatto
Just call me: wiwatto
 
Bangkok
Thailand
Post

Absolutely, Well done "Nader"

Thank you for you best idea, i like the way you worked very much.
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  #40  
Old Sun 25 October 2009, 10:15
boaterri
Just call me: Rick
 
Rhode Island
United States of America
Well done, sir. I also like the adjustable work supports. (the saw horses)

Rick
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  #41  
Old Sun 25 October 2009, 13:58
Atifeh
Just call me: Nader
 
Tehran
Iran
Send a message via Yahoo to Atifeh
Thank you Wiwatto.

Thank you Rick. I will post some details of the sawhorse.
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  #42  
Old Sun 25 October 2009, 14:02
Atifeh
Just call me: Nader
 
Tehran
Iran
Send a message via Yahoo to Atifeh
Parts all painted and re-assembly begins

All fasteners were put in place loose. The wheels and dampers were installed and the set was levelled. I squared the assembly diagonally and tightened the first and last table beams. There was about 8 mm variation in the width of the machine on the rail rest beam. With flat belt tightener I narrowed the distance and tightened all the table beams while measuring the diagonals on the frame. There remains about +/- 2 mm variation which will be adjusted during the rail adjustment. Then I tightened the transverse frame bolts.

assy01.jpg

Placed the rails and X axis echain support in place and scraped the paints on the contacting face of the rails.

assy02.jpg

This is the detail of the wheel and the damper.

wheeland damper.jpg
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  #43  
Old Mon 26 October 2009, 00:06
buibui
Just call me: John #34
 
Seattle
United States of America
Great job, Nader. I really enjoy reading your build and photos!
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  #44  
Old Mon 26 October 2009, 10:10
wiwatto
Just call me: wiwatto
 
Bangkok
Thailand
I waiting your progress

For me, Absolute confirm " Your are my inspiration " MechMate

Thank you again all done in this forum.
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  #45  
Old Mon 26 October 2009, 10:30
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Wiwatto, you have told us enough of your inspiration, now we want to see your progress!
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  #46  
Old Mon 26 October 2009, 15:25
Atifeh
Just call me: Nader
 
Tehran
Iran
Send a message via Yahoo to Atifeh
Thanks john.

Rick, here is the details for the sawhorse. The original credit goes to Fabrica. His posted pictures inspires lots of ideas for sawhorses.
sawhorsedetail.jpg
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  #47  
Old Tue 27 October 2009, 00:04
Alan_c
Just call me: Alan (#11)
 
Grabouw (Western Cape)
South Africa
Send a message via Skype™ to Alan_c
See here for more sawhorse detail.
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  #48  
Old Tue 27 October 2009, 02:26
Atifeh
Just call me: Nader
 
Tehran
Iran
Send a message via Yahoo to Atifeh
Alan,

Sorry for the mix up. I stand corrected. The idea was yours but it was in Fabrica's thread. My MechMate picture files are sorted by the name of the initiator, e.g. Yuri, Irfan, AlanC... therefore I only referenced from the folder. I should be more careful when referencing.
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  #49  
Old Tue 27 October 2009, 09:45
Alan_c
Just call me: Alan (#11)
 
Grabouw (Western Cape)
South Africa
Send a message via Skype™ to Alan_c
No problem, at least my wacky idea was able to help someone
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  #50  
Old Tue 27 October 2009, 10:02
Alan_c
Just call me: Alan (#11)
 
Grabouw (Western Cape)
South Africa
Send a message via Skype™ to Alan_c
I am not an engineer, but I am a bit worried about your placement of your damper/foot, is there not a danger of that plate bending once the gantry, support board and spoil board are in position (I also tend to climb up on my machine quite a bit, but then again I am on the wrong side of 100kg's)

Maybe you could think about adding a brace as shown below, that should not hinder your adjustment of the dampers/feet.

wheeland%20damper added brace.jpg
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  #51  
Old Tue 27 October 2009, 11:25
wiwatto
Just call me: wiwatto
 
Bangkok
Thailand
Quote:
Originally Posted by Gerald D View Post
Wiwatto, you have told us enough of your inspiration, now we want to see your progress!
Hi Gerald

After "ATIFEH ( Nader )" finish his job i will post some picture in 2 years ago, that started building 1st MM. Nowday i have plans to rebuilding it again. Also i have something i never told your are "YOU ARE MY "HERO" since i start to interesting CNC Machine.

Yes "ATIFEH" you please post your progressing.
I like the way your work
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  #52  
Old Tue 27 October 2009, 15:44
Atifeh
Just call me: Nader
 
Tehran
Iran
Send a message via Yahoo to Atifeh
Alan,

Thanks for the idea. I should have done that before but I have to figure out a way to add this brace without dismantling it, since I am not good at welding vertical joints. The plate is 10 mm thick and only 32 mm projected.

If Gerald and everybody else agree and feel suitable, lets allocate a thread for different jigs, fixtures, clamping and work holding systems, intermediate storage systems and likewise that the members have made .
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  #53  
Old Fri 30 October 2009, 10:44
KenC
Just call me: Ken
 
Klang
Malaysia
Nader,
Alan is right to point the need of reinforcing the legs. If you are not confident with your vertical weld, I would suggest you "joint-up" many spot welds to form a strong weld. That what I'll do

Cheers

Ken
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  #54  
Old Mon 02 November 2009, 11:26
Atifeh
Just call me: Nader
 
Tehran
Iran
Send a message via Yahoo to Atifeh
Bending stress = Bending Moment (N.mm) / Section modulus (mm3)

For cantilever beams:
Bending Moment (N.mm) = concentrated load (N) x distance (mm)

Assuming that the total weight of the machine+mdf boards+workpiece+myself =12kN, each leg will take more or less around 4000N of load.

With 18mm distance from the cantilever fixed point, the bending moment will be:
4000N x 18 mm = 72000 N.mm

The section modulus on X-X axis for a 40x10 mm hot rolled strip will be:
(40x10^2)/6 = 667 mm3

Therefore:
Bending stress = 72000/667 = 108 N/mm2

For mild steel (st37) the median bending stress limit is 290 N/mm2 > 108N/mm2

Alan, Ken,

These calculations were meant for only one purpose. To ease my conscious, refraining from a vertical welding with unsuitable electrodes, 100 mm above the ground, a lot of paint scraping and paintworks to be mended later!
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  #55  
Old Mon 02 November 2009, 11:28
Atifeh
Just call me: Nader
 
Tehran
Iran
Send a message via Yahoo to Atifeh
I had a cold this week, so I stayed at home and worked on the electric wiring. Here is a zip file containing: the wiring diagram (dxf) and the simulation (ekts).

electrical.rar

Earlier this week I bought a Q2HB68MG bipolar driver (www.bsjd.com) for testing. These drivers are microstep, 24-80V and 0.5-6A. I have never before used bipolar motors, so this was an exciting experience.

I had 2 types of motors available:
4 wired 4.2 N.m, 6A/phase, 2.4V, 0.4Ohm/phase, 3.4 mH/phase
8 wired 2.2 N.m, 4.5A/phase, 2V, 0.45Ohm/phase, 1.7 mH/phase

You can see the pulse generator I built with a NE555 with jumper selectable capacitor rows and a pot. It gives 0.8Hz up to 10.9kHz pulses.

Also note the power supply unit I use for bench testing. Tied to a 24VAC, 250VA transformer which gives approximately 36VDC.
motortest.jpg

The driver was set to 1/5 step. The 6A motor which has higher inductance, topped up the frequency and the rotor could not be stopped by hand. The lower inductance motor (4.5A) would not turn beyond 7.76kHz in serial wiring but did the full 10.9kHz in parallel mode.
Since maximum 3 motor will be working simultaneously, I think Mach could manage turning these three.
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  #56  
Old Mon 02 November 2009, 22:25
wiwatto
Just call me: wiwatto
 
Bangkok
Thailand
You have done some amazing things.
A picture is worth a thousand words
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  #57  
Old Mon 02 November 2009, 22:32
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by Atifeh View Post
. . . . For mild steel (st37) the median bending stress limit is 290 N/mm2. . . . .
Just a casual note: Mild steel and ST37 are not quite the same thing. I agree with about 290 N/mm2 for mild steel, but you may be interested to know that ST37 was a German abbreviation for "Steel 370 N/mm2"

We could have a long discussion on stress calculations, but just some quick observations:
- Most times, in the frame of the CNC machine, we are concerned for stiffness, and not so concerned for risk of failure.
- But, at the support feet, often a spring element (low stiffness) is used for damping/isolation - you can claim that you have an isolator
- But, if it were a true isolator, then you need to design for fatigue. The fatigue limit of mild steel is about 50% of the upper stress limit. (Plus you have a weld at the highest stress area)
- But, the loading for the fatigue condition will not be 12kN - subtract your body mass
- etc.

Engineers sometimes calculate, sometimes use instinct . . . . .
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  #58  
Old Tue 03 November 2009, 12:46
Atifeh
Just call me: Nader
 
Tehran
Iran
Send a message via Yahoo to Atifeh
Gerald,

Unfortunately the term mild steel has found a very wide definition by people who are paid to complicate things! Long ago, it was only meant for the cheapest structural steel. Now there is a whole range of disputes around its chemical composition and/or its strenght. To make it even more fun, mild steel is now even graded! like Grade 250, Grade 350, etc.
These standards and there desparate attempt to adapt to each other make me crazy. To tap a M6 thread, DIN says drill 5.0mm, ANSI says drill 5.15 mm (or at least this the the preference for my MDT6). Low quality drill bits have some wobble, so I drill 4.9 mm!

You and Alan were right. It is the stiffness concern. I agree and believe that this little brace would give the construct a lot more rigourous look. And about the failure, actually I was thinking "how would a 36mm tab be bent when it is supported on some sort of polymer?"
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  #59  
Old Tue 03 November 2009, 21:29
Leko
Just call me: Leko
 
Kaukapakapa
New Zealand
Just a thought. If you have difficulties with vertical welds, a brace like this could alleviate them. Drill for the two bolt holes and then you only have to horizontal weld it.
Attached Images
File Type: jpg LEKO brace.jpg (196.5 KB, 1398 views)
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  #60  
Old Tue 03 November 2009, 22:51
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Or this:


. . . . but in real life I would leave it as it is now!
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