Now Cutting! - Auckland NZ

[litemover]

Hey Red, thanks for the advice. I did drill straight through my cross channels for a vacuum plenum later on, so now I know to clamp the board to it and drill through in order to get it drilled. Thanks!

Chris

[litemover]

Help,
Having no luck with bending one of my large beams into place. I heated one of them straight, then the other one over compensated and I haven't been able to get it back.. Can anyone tell me how to weld a beam straight that is bent on the webbing side, not the flange side? Ie opposite to how it is bent in the illustration that Gerald made please?

Thanks
Chris

[KenC]

Applying correct amount of heat with torch is way above me. Hence, welding is my prefered heat source which I can gauge the heat to a very close ball park.
I can't offer much help on the correct way to do your straightening job, also, I really don't understand what you want. a sketch would be really helpful.
For now, all I can tell you is that metal will string towards the side where you apply the heat. i.e. the heated spot will become the inside of a bow. (if the beam started out as a perfectly straight piece; I get confuse with bow-in & bow-out... )

[litemover]

Here is a pic of the bend with explanation. I've tried that but it just became worse. Not sure why.

[xraydude]

Can't quite make out the text on your image. I believe that you are indicating how it is bowed, not how you want to bend it. The method that Gerald described in the thread you mentioned is probably the best. I did not have to do this on my main beams, and have not had to do this with any channel as heavy or large, but it should work. I would start in the center of the bow, make the welds, let them cool and check for any change. If it has improved at all, I would work out towards the ends about every 24 inches as Gerald recommends. How bad is the bow? You may be able to compensate and straighten when welding on the supports.



Ted

[litemover]

Great, thanks for the advice. I'll give it a go. Shall I weld just on the bottom flange or both bottom and top, and do I just weld on the inside?

It's bowed about 8mm, but it was only 4mm till I started heating it.
Thanks,
Chris

[xraydude]

When I have done this on lighter gauge and smaller channel (for trailers), I did both flanges, only on the inside, to try and keep out any twist. You will need a lot of heat. Here is a link that may help explain heat straightening in general. In particular, check out Fig.5.

http://www.metalwebnews.com/howto/co...ntraction.html

Ted

[litemover]

Well, I have nearly finished tack welding the table up. As shown. I gave up on trying to straighten the beam with heat as it simply will not straighten this way. I figured I'd try to install the cross braces then straighten it with an all thread clamp while heating it up, then tighten all the cross members and tack weld them. Anyone else use this technique? As you can see, the dimension is suppose to be 1980 all the way accross, and it is either short in the middle, or long at the ends.

Still a bit of structure to weld on this massive table. Not sure how I will turn it over without 10 guys I used bolts on the cross brace frames so i could take it apart if need be, then turn it over.

[IMG]
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[litemover]

More progress on frame. Need to drill holes on webbing for the all thread clamp to get it to straighten out prior to welding the legs on. I'm also thinking of loosening the cross frames up where the gaps between the main X beams are too long, then welding the legs on where they are supposed to be on the beams, then tightening the cross frames to the legs hopefully pulling the beams straight. Welds are for the most part clean, except for a few that were difficult to get to. The argoshield makes a night and day difference to flux core any day.

[IMG][/IMG]

[Andrew_standen]

Looking good.
That's some heavy looking metal there.
Nice stuff.
Cheers
Andrew

[litemover]

Thanks, it is pretty heavy, that is for sure!

[litemover]

Here is how I managed to correct the beam that was crooked. I use the allthread to pull them together, then I lifted them and hammered in the bottom.



And on the inside to spread them apart:



I'm hoping that this didn't cause any more problems, i.e. twisting, or anything like that. It seems as if my flanges are becoming a bit bent with all the weight on them now.

[smreish]

...love a good trolley jack!

[litemover]

What would I do with the trolly jack Sean? Is that how I should turn it over?

I have 3 mdf boards, each 12mm thick, can I get away well enough with 2x for the support board, and 1 for the spoiler lard, or should I glue all 3 together for the support?

[sailfl]

1 support and 1 spoil board will do it.

[litemover]

It will be quite flexible if I use only 1-12mm board as support, won't it?

[Alan_c]

We usually use a 30mm board as the support and 22mm as sacrificial surface. If you want to use whats on hand, glue two 12mm board together, mount them to the table with the counterbored holes as per usual, fix to the table and glue the last 12mm board on top, you wont get the same working life from you sacrificial board but at least you can start working.

[litemover]

great, I liquid nailed the support boards together. Should be ok. Turned the table over today, all going well. Going to start priming it tomorrow.

[litemover]

Here are some primed bits, going to rust converter the main table prior to priming with a 2k primer..

[litemover]

Ok, back on the rails now that I have a flat surface to work on. Built the jig for the rail grinding, per Ross' rig. Used 300mm x300mm Melamine about 16mm thick x2. Did a test and it worked out so much better. On the test rail, I was only off by .2mm across apprx 1.2m stick from 28.25mm to 28.45ish mm. Hoping that is going to be acceptable on the big pieces.

A note: I upgraded to 125mm Pferd Discs as they were only .30c more ea for 10mm extra material. Seems to be worthwhile and they smell just as good as the smaller ones (love the smell of pferd discs burning in the morning ). They fit my Bosch 115mm grinder post so I figured what the hey. I also purchased some F clamps, which seem to do a heck of a better job than the old plastic clamps I had around.

Also, made heaps of progress on the rest of the table, and now switching into electronics mode, and working on the Zslide. I'm going to get everything rolling on rails before I paint over the primer incase I need to rip into something to straighten it out as the x beams still are on perfectly level or straight, though they are much closer now. What a headache it was fixing messed up 180pfc beams. No matter what the guy says, next time I won't take delivery on the beams if they are mucked up as it will cost triple in gas and time just to straighten them out.

Here are some pics.

[smreish]

...I think you figured it out, but the slower (lighter) the passes you get better results.
As you push to hard, the blade deflects up and gives you those minor errors.
As a finish - put that sanding disk on the grinder with 36/80 grit on that grinder and surface grind that rail section dead flat. Then you have a really flat top referenced surface to grind your profile on.

I have now made 3 sets of rails from scratch!

Sean

[litemover]

Cool, thanks Sean. I was doing the lighter passes, but when I got to about 2 mm left on the rail, I went for one heavy pass as the wheel gets stuck when it gets too deep. Is that what I'm supposed to do? I'm going to sand them out today flat on top.

[Surfcnc]

Chris

The jamming is from the cut closing up a little, probably from the heat.
So stop and relieve the cut by bending the remaining top back slightly to open it back up again.
Use some vise grips and run along the top of the cut bending it back every 200mm or so.

Ross

[smreish]

...Ditto what Ross said.

[litemover]

Thanks guys, yes I figured out the vice grip trick. It seems that the best time to cut through all the way is when the other side of the rail is smoking a bit. After you see smoke, then the next pass should cut right through fairly easily. It takes a lot less disc too if you just keep cutting until it slices off. I did one 2.5m rail yesterday with half a disc so that worked out well. It seems the sanding though gave the top a bit of a slight convex shape. Not sure why that happened, perhaps the backing disc was not as hard as I had hoped for. Will try with a different backing disc today.

Thanks for all the help, it's really working well now. .1mm variance last night across 2.5m so looking quite nice.
Chris

[smreish]

Use a regular grinding disk (new) as the backer. This is a very rigid precise backing plate.
Or, one of your thin cut of disks. Light pressure until you see even sparks.

[litemover]

Well I finished all my cutting and sanding, they turned out good but I have a slight problem. One X rail is 28.9 mm and the other is 28.1mm give or take .2mm tolerance. Should I grind down the 28.9 mm one to match? I recall doing something like this before but ended up messing up the evenness of the rail by trying to take off too much material. I learned that one should do all the cutting with the jig at same settings, then all the sanding, then all the profiling. Don't cut, then sand the same rail, and move on to a new one to cut or you'll end up with uneven rails from one to the other.

Anyhoo, a whole manual could be written about grinding rails! Tomorrow I will profile them.

I ended up welding two pieces of smaller rail together for one of the Y rails so I wouldn't have to order yet another one. Here is how I did it. (Excuse the welds))

1. First I put the two manufactured ends together, which made them relatively fit easily together, straight.
2. Clamped the two halts flush to the edge of the main X beam with a melamine board underneath.
3. Then clamped a piece of 50mm x 6mm flatbar on the backside of the rail.
4. Took a piece of yellow nylon line and stretched from end to end to make sure everything was straight (it was)
5. Tack Welded, then welded them together, rechecked the line.
6. Grinded out the welds and flap disced them flat.

Thanks for the help Ross and Sean, and everyone. They are very precise now over the length of rail.

Cheers
Chris

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[Gerald D]

1mm difference in rail height from one side to the other is no problem. At the end of the day you trim/face the table surface so that everything comes to "zero".

[litemover]

Thanks Gerald, That's good news that I don't have to grind the tall rail down further. Do I shim up the opposite rail to match in the end when shimming them?

[Gerald D]

Why bother to raise the rail if you don't even know your main beams are the same height, taper or whatever? Believe me, when you start shimming, you will be grateful for having one less factor to measure.