Thanks Fox, I can already weld with a mig, just never actually owned one. This one is an inverter mig, not a transformer mig so I need to get familiar with its settings. It has arc and tig on it as well, never tig welded in my life so that is for future learning. Gonna give the arc a go though to see how it compares to the crappy one I had :)

Darren, I am definitely looking forward to that AHA moment, it is so close I can feel it. Just sitting there looking at the work I have to do makes me think it is not far off. Then again they could be famous last words!

TIG for steel is fairly easy, TIG for aluminum has a huge learning curve (very heat and timing sensitive)

I got my gantry welded up on the weekend. While I have no "propeller twist" I found I am about 1mm out of square. That seems to put the gantry out of square with the table on the ends meaning one wheel gets there before the opposite one.

Can I just space each opposite wheel differently or will I need to get the gantry as square as possible to the table. I remember Ross (SurfCNC) doing something similar to his machine by fixing one side to the machine and then pulling the other end until it was square.

I am not going to do anything else until I am 100% happy with the way the gantry rides from end to end so any assistance would be greatly appreciated.

Cheers

Bruce if you are only 1mm out of square, rather than risk making it 2 mm out the other direction, you can adjust your y rails square with the x rails, a lot simpler.

Tom, that's a thought.

I think there must be something else I am doing wrong. I measured the 1mm out of square with a framing square on both ends of the inside of the gantry. When I put the wheels on and run the gantry to end of the machine I can measure just under 10mm offset of the ends. I haven't measured each washer I used but put the same number on each bolt and when measured with a vernier the distance from the wheel rim to the gantry plate is within 0.5mm on all of them.

Very confusing and I am not happy with myself at all as I was striving for close tolerances. I may yet be jumping the gun but my initial thoughts are that I have screwed up somewhere along the line.

Keep going, don't be bolted down with some tiny misalignment, no matter how accurate your fabrication works, you still need to dial in with shims here & there at every stage of alignment.

Go back to check your rails leveling & parallelism.

I may have found some of my problem. My last effort of squaring the table was a while ago and since then I have moved the table a meter more into my garage space. After I did that I didn't think to make sure it was square again. Just checked it and the table is 18mm out of square so I am currently squaring it up again and trying the gantry out again!

Machine is now within 1mm of being square, will chuck everything up top and see what the difference is :)

Bruce, if you go ahead and install your first spoil board, it would help keep it square, plus it gives you a temporary work surface. Just start fastening the ends first, straighten the x rails as you work your way to the middle. Its amazing how much flex there is.

Thanks Tom. When it stops raining I will shoot out and grab a sheet or two.

Up and down week this week. Good thing was welding up the Y car, drilling the final 20mm holes in all the rails and getting the Z plate bearing tracks ground/sanded to shape.

Bad things were the X rails not sitting right, had trouble all week getting the gantry to track properly and the welding on the gantry itself. Even though I had my new mig, I had no gas so I stick welded the gantry. After getting some gas and welding up the Y car I now hate the welds on the gantry so they will be ground back and rewelded with the mig.

Also found the main beams had once again canted inwards at the top, my shims had failed throwing everything out hence my problems getting the rails right. Tonight I stripped the table back to legs and main beams and tomorrow will resquare, remeasure and *weld* the main beams to the legs instead of bolting them. The only down side to this is my wasted time building bolt together sides and the 12mm holes that will be left in the bottom of the main beams. May weld them up for cosmetic purposes. Having the main beams unbolted will also give me a chance to properly weld the ends on (didn't want to weld vertical with the stick when I did them) and derust them at the same time in prep for paint.

Once I have everything back to how I want it I will probably paint the whole base, gantry and Y car as all the welding and drilling will be done on those and then I will finish up the end stops, weld those to the rails after which I will paint those too.

Should be done with all the above by weeks end at which time I will take some more pics.

Oh, and what do you guys pay for 32mm MDF? Priced both 2400x1200 and 2400x1800 sheet at $120 and $150 respectively. Oh, could also get a sheet of 1200x1800 25mm MDF for $100. Would there be anything wrong with 2 sheets of 16mm instead as I can get 2 of those for around $60.00.

I would not see a problem if you are gluing it somehow. Remember you want it to be free of metal so not to contact it with a cutter. So screwing it together would be out of the question. I even went to the extent of using brass flathead screws on the off chance I bored into it. I only used 19mm for the spoilboard.

I just bolted down a 19mm (countersunk) and glued a second on top, certainly sures it up

Excellent thanks guys. Will use 18mm instead and stack.

Welding now finished on the main beams, base squared and straightened and the main beams put back on top, main beam tops set to horizontal plus exactly 1650mm apart and everything squared up ready to tack weld tomorrow before fixing in place permanently.

I have to redo the PFC cross bearers, the holes no longer match up due to the canting over of the beam tops. Will turn them over to redrill and the holes that are in there now will be cut off when I angle the ends.

Also started to de-rust the main beams, need to degrease and clean them before the application of Wattle KillRust-Eeter to settle it all down.

Getting there slowly, eating that elephant once again!

...one bite at a time. Sometimes its hard to swallow though.

Yea, these bits were hard to swallow.

Couldn't resist, just went down and tack welded everything, took the clamps off the spreaders I had and bingo! all square on top and exactly the same distance apart. Am almost back to where I was last weekend, only better this time :)

When it gets hard to swallow, bite an even smaller bite :)

As long as it doesn't get too chewy :)

I love it.
Progress, no matter how small is a good feeling.

Ok, got the table back together after the abrupt welding actions and am again trying to figure out the not square thing. I fixed my rails down and now have around a 5mm difference in the proxies hitting the targets on the X. Diagonal measurements from the rail ends to the holes is spot on.

I clamped some steel to the gantry at the 0,0 end of the table and pushed it up against the front cross beam and one side hits before the other does.

I have been *trying* to get out to grab a sheet of MDF but every time I get about half way to the store it starts pouring with rain. Tomorrow after work looks hopeful weather wise to finally get one, hopefully then I will be able to see what is actually off, the table or the gantry. Its getting bloody annoying I can tell ya!

The rain is a sign.... :D
People upstairs are jealous of your progress. :D

Don't worry about the absolute squareness now, you had done very well in deed.
The real squareness tuning will come after installing the spoil-board AND conduct your door skin ply test.

Your opening lines made me laugh Ken! :)

Just reread Gerald's thread on squaring the gantry and in tandem with Kens post I will now wait until I can get that elusive sheet of MDF to lock the base square.

Just bought a pack of 0.10mm shims so I can space the V wheels on the gantry if need be, I reckon 100 should be more than enough for the job :D

Sometimes we work so hard for a solution that the answer will present itself if we just get out of the way. Food for thought.

Too true Pete, sometimes I am my own worst enemy. ...

Don't forget to get 2 pieces of 1/8" door skin plywood while you get your MDF spoil board.

I would grab 2 6mm mdf sheets but in my garage they would be like 2 bananas by the time I used them. They will come when I buy the next 2 sheets of thicker mdf for the actual cutting surface.

Ken what's a door skin ply test? Is this something I should know about? Or is it known by another name?

Tom, its this .
I call it door skin ply test because I used door skin ply for the test :)
Sorry for the confusion.

Ok, shimming the gantry to square. I thought maybe I missed something.