Are the photos not showing up for you guys?

Thats weird, they show up in IE but not Firefox..

Brian, try clearing your cache? OR do a reboot?

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

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.
Attachment 6720

Attachment 6721

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.
Attachment 6722

Attachment 6723

The end pads of the frames are tack welded in this position:
Attachment 6724

Attachment 6725

Straightening of the beams and rails by welding.
Attachment 6726

Attachment 6727

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.
Attachment 6728

Attachment 6729

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.
Attachment 6730

Attachment 6731

Attachment 6732

Attachment 6733

Beams being drilled:
Attachment 6734

Sequences of frame assembly:
 

Attachment 6735

Attachment 6736

Attachment 6737

Attachment 6738

Attachment 6739

Attachment 6740

Attachment 6741

Attachment 6742

Attachment 6743

Attachment 6744

Attachment 6745

Attachment 6746

Attachment 6747

Attachment 6748

Please note, the name of the pictures represent the action done.

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.
Attachment 6749

X axis home switch and end stop.
Attachment 6750

Y axis limits and home switches.
Attachment 6751

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).
Attachment 6752

Details of the X and Y echain assembly.
Attachment 6753

Attachment 6754

Attachment 6755

Attachment 6756

Attachment 6757

General view as of 2-3 weeks ago
 

Attachment 6758

Attachment 6759

Please note: the 4th axis pictures are in the related topic in this forum and will not be discussed here.

Absolutely, Well done "Nader"

Thank you for you best idea, i like the way you worked very much.

Well done, sir. I also like the adjustable work supports. (the saw horses)

Rick

Thank you Wiwatto.

Thank you Rick. I will post some details of the sawhorse.

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.

Attachment 6786

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

Attachment 6787

This is the detail of the wheel and the damper.

Attachment 6788

Great job, Nader. I really enjoy reading your build and photos!

I waiting your progress

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

Thank you again all done in this forum.

Wiwatto, you have told us enough of your inspiration, now we want to see your progress! :)

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.
Attachment 6806

See here for more sawhorse detail.

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.

No problem, at least my wacky idea was able to help someone :)

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.

Attachment 6826

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.:):):D:D:):)

Yes "ATIFEH" you please post your progressing. :):):)
I like the way your work

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 .

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

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!

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).

Attachment 6907

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.
Attachment 6908

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.

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 . . . . .:D

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?"

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.

Or this:


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