Machining Aluminum #122 - Sydney, Australia

[racedirector]

Got the beast standing right side up yesterday, my 13 year old assisted with lifting the beams into position. Need to shim the beams slightly to get the tops perfectly flat and then I will continue with the gantry.

Going that way so I can then move to the main rails and get them spaced correctly. I would rather use the machine parts to do that than to rely solely on drawing measurements. I will say that my drawings have been spot on to this point but there is nothing like real world stuff for checking on things

[racedirector]

Diagonal main beam measurements.... will do me nicely thanks. Or can someone see the point of chasing 3mm?

[Tom Ayres]

uhh, nope.

[Fox]

yes, our amusuement

[racedirector]

Hehehe, point taken. I am going into bad parent mode..... going to buy some cans of coke to make shims out of, don't drink alot of it myself but my kids definitely will

[Tom Ayres]

Yes they will!

[racedirector]

Well, I have disappointed my kids without them even knowing Didn't need to go buy cans of coke, I found my roll of aluminium tape and made up a bunch of shims from that. I now have 2 beams perfectly flat (with one another) tops. It has changed the overall outside measurement but I can allow for that when I drill and mount the X rails.

I am a happy camper now and can now start gantry construction, first up will be cutting down the angle iron legs to 28mm which will give me the nut strips inside the gantry tubes.

[racedirector]

Just wanted to add..... thank you to all that have gone before me, all the little tips contained in build threads help us newbie builders immensely. I would particularly like to thank Ross (SurfCNC) who highlighted the beams tilt problem in detail, allowing me to follow suit.

[racedirector]

Think I stuffed up my first rail, I eyeballed 28mm on the ruler and proceeded to cut it in many, many passes. Just finished and it (somehow) varies in height from 27.78 to 27.65, from one end to the other. I have a couple of "spare" bits of angle from my foray into building a 4x4 so I think I redo this one at 30mm and sand down the remaining 2mm rather than trying to cut it to 28mm in one go....

[Tom Ayres]

I cut mine at 29 then sanded with 50 then 80 grit when close, probably sanded too lightly. Measured every pass marking the measurements in front of the location on the rail (looked like a pyramid of numbers on the board as it got closer to finished height) Ended up within 0.05 mm total, took a long long time to get that accuracy.

[KenC]

The trick is to have smooth "wave" rather then saw tooth like cut. Mine +/-3mm over every ~3 meters. That is why we shim

[racedirector]

Thanks guys, you have both instilled some confidence.

Ken, was wondering why everyone was shimming,now I know

Tom, sounds exactly like what I should be doing. Have adjusted my grinder to around 29.5mm and will give it another go tomorrow.

My only other possible issue may be the cheapo grinder I bought for the job. Didn't sound too good while grinding, we shall see how long it lasts

[dbinokc]

The numbers look pretty good to me. A variation of .13 mm and off at most .35mm from the 28mm target. Looking at my build, I think the worst that may happen if you are a little low is that the stop bumper on the gantry could drag. In which case you could trim it up.
I think the main cause of the variation I had in my rails(.25mm, .01") was due to not blowing the grit away after each pass of the grinder.

[Tom Ayres]

Oh yeah, that's a big factor.

[racedirector]

Just finished cutting the second rail, varies in height from 30.24 to 29.88. Multiple slow passes in one direction only, cleaning the runway between passes. I think the variations are coming from disk changes, cutting a little tall covers that as sanding will finish them off.

After I sand this one (the mate to the Y rail cut yesterday) I will see what the total variation between the 2 is and decide if I still use my first one.

Off to cut down the X rails while I have the jig set up, they are a bit trickier being 65x65 instead of 65x50....

[racedirector]

Got all the rails cut and started on sanding one of them down to ~28mm. Cheapo grinder died, the blue smoke escaped and the brushes disintegrated. I have another 125mm grinder but my grinder plate doesn't fit and I am having problems modifying it to fit.

I am looking at a new grinder and have my eye on either a 1100W AEG 125mm grinder or a 720W Bosch 125mm grinder. Will go up to the shop with grinder plate in hand to see what fits best....

[racedirector]

Went with the AEG, brilliant piece of kit! Slight mods to the grinding plate and I will be in business again.

[darren salyer]

Good its only a temporary setback.....onward!!

[Bazza]

Hi Bruce
Mate You have definitely moved along nicely since I last checked out your progress
I'm pulling out my plans tonight and putting pen to paper
Hope to get my metal cutting list sorted (might borrow some of your design work if you don't mind, bloody sturdy stuff)
Then set out a budget and wish list for the mechanics and electrics
I'll post them up hopefully next week on my thread, any advice as always is gratefully accepted
Cheers
Bazza

[racedirector]

Hi Bazza

Thanks matey, getting there slowly. If I may suggest something, scour the plans for the right way to do things, I missed a bit on the base and ended up following others in what they had done. I bolted my base as we rent and I know we will have to move at some stage, if you have the opportunity to fully weld I would go with that.

Cheers

[racedirector]

Question for those that have been there, done that. How anal were you on your rails?

I am regretting cutting mine to between 29 & 30mm now and it is taking forever to get them down to 28mm. One Y rail is close, from 28.18mm to 28.34mm and I am still sanding more to get it better (36 grit sanding pads). Definitely NOT looking forward to another week or so of grinding and sanding to get the other down in the 28mm region, not to mention annoying the neighbors with all the grinding noise

[dbinokc]

While I am not cutting yet, you are way closer than me in precision. I decided to run with what I have and if I find that the rails are causing me problems with getting accurate cuts I will pull the rails and work on them more.

[Tom Ayres]

I was pretty anal because I wasn't sure how "accurate" they had to be, yes it was a pain in the butt and yes it was annoying. Mine are not exactly 28, they are in the 28.49-.52 range, was taking too long to get there, ha ha. I felt 0.5 mm wouldn't matter, heck I'm sure I'm off more than that elsewhere.

[racedirector]

Thanks guys. I stopped on the Y rail I was doing, 28.18 to 28.34 (used disc). The 2nd Y rail is slowly coming down, currently at about 28.55 average (new disc), will keep swapping out the old for new discs until I get close to rail 1....

[dbinokc]

If I do need to work the rails more on my machine, the plan is to get a good machinist straightedge and some bluing compound(dykem). I can use that to find the high spots on the rail and file them down. Then come back with the grinder to rebevel the edges.

[racedirector]

DB, I had a bad experience with my previous machine I am trying to get this one as perfect as possible. Sometmes I spend way too much time getting things right but I am hoping this one trait will give me a machine I can be proud of instead of making excuses for....

With that said, and I know I am documenting way too much in my own thread, I now have both rails within .10mm of each other, end to end. Gonna give rail sanding a break for now and start work on the gantry just for something different.....

[F.A.B]

I don't know I might be bad but I didn't even measure mine off the grinder, well only with a steel rule to know I was in the park. I did take some time with the straight edge, wire line, lazer and anything esle I could find when it came to shiming in final position on the beams. seems to have worked for me..

[racedirector]

Thanks Mich, as usual I over think things. Grinding down the X rails today instead of moving to the gantry - going to get them "close" to 28mm and be happy. I have acquired lots of cans for shims so I *should* be good to go when the time comes.

[racedirector]

OK, I am setting myself a target, if I make it I will be running the gantry up and down by the end of Feb 2014. There, I've said it now, off to make it happen

[darren salyer]

You can do it.