A advise,
I have a completely bolted frame, but i didn't use oversize holes in my frame
I made a small simple devise to drill my holes for my cross beams
I cut the tread holes In my c beams, that's M8 if i remember well. then i mount my cross beam with one bold and at the other side i use a clamp. than I have a small devise. that's a m8 bold with a 1.2 mm hole in the center. In this hole a 1.2 mm hardened nail is placed. ( the one you use to nail in a stone wall to hang a painting) I place this bold with the nail in the middle of the all ready made tread hole in the c beam, take a nice hammer, and make a center hole in the cross beam.
Remove c clamp and mounting bold at the other side, and use the center hole to drill the 8 mm second hole.
You have to mark your beams and holes, so you can re-assemble. my marks are engraved in the parts, so I can recognize them after the paint job.
I only use over sized holes for mounting my guiding rail.
For mounting the bolds on the c frame i used standard tapered wigs, the flanges from the c frame are not flat. place a tapered wig in between the bold head and the c flange. otherwise your bold will bend, or break.
12.9 bolds will break when not mounted flat.

Thanks mate, much appreciated for the advice.

Has anyone had any experience with this Belden 4 core cable? I think it might work well, but ran a search and hadn't seen it. Perhaps it is a new type?

http://newzealand.rs-online.com/web/p/cy-cable/6282264/

I use those. On 2 built. ;)
Its considered a reputable brand where I'm from.

Here are some pics of my progress. Finished welding the Y car, squared the verticals on it using m10 allthread, which worked well. Worth the $6.50.

Having a problem with my grinder head, bought a Bosch GWS 150, which has the appropriate screw profile as the laser cut grinder plate, but the head used to position the guard plate is too big to get the rail grinder laser cut piece over. Any recommendations? I didn't use this grinder yet, just bought it, so I suppose I could return it, however, there weren't any other grinders with the correct head profile. It looks like it may screw off somehow, but before I try, wanted to get input.

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Getting the Gantry ready and square. So glad I purchased an accurate level, makes a huge difference.
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For the grinding skate.
I also had to remove the protection cover from the disc grinder. I did not feel comfortabel with the uncovered disc. I saw to many accidents with disc grinders. I placed a wooden block around the disc. Just make it quickly from some waste material with a jacksaw. The wooden block is fixed with 2 screws to the scate. i do not remember if i had to drill aditional holes in the scate. It did not catch fire from the sparks. You can see some pictures on my build history

This is common challenge.

How much is too big? 1mm or 5mm? I was about 1mm shy of being correct on build #28 so I used a die stone on a drill motor/drill press to open up the profile.
I also was able to purchase 4 new screws that matched the grinder head that were 35mm long and added 7mm spacers to get the grinder to sit in plane and level with the skate.

Both solutions worked.

Personally, cutting up the skate to make your grinder fit is easy and quick. It is a one-time use tool thus doesn't have to be pretty!

Hey Sean,

Thanks, I'll have to cut the skate up as I don't think the collar will twist off the grinder. I think it's about 3-4 mill off.

Regards,
Chris

Should I be using a digital spirit level for the gantry? The level I have is accurate, but I can still shim up things quite a bit before the bubble moves significantly. I'm concerned that it won't be level. Where should I be checking levels on the gantry?

Hi guys,

I've finally accomplished getting the gantry level, and squared while upseide down, but I when I tacked it, then turned it over, I measured how far down the holes were for the rollers with my square from the beams, and one side was off by about 3 mil. When I squared and levled the piece upside down, I used my square to the top of the near and far carrier plates, making sure they were equal and level. But when I turn it over, I am pulling the dimension off the holes for the rollers, and they are not even. Should I be squaring this based on the rollers from the beams dimension, as well as the beams level, or did I do it right when upside down? How would I correct the rollers if they are off? Any tips would be helpful.

Thanks,
Chris
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Chris

The gantry can be pulled into position with a system of clamps.
Find your high side and then secure the other three ends on some blocks.
On the high side then progressively wind down a clamp to flex the gantry into the correct position.
You will need to wind the clamp past the "exact position' as it it springs back up when released.
This method makes it very easy to correct any distortion from welding.

Regards
Ross

Thanks Ross, I read that process, was just trying to get it within 1mm before I tried it. I think I managed to get it real close now. It should be simple to true now with the blocks. Onto the table now.! One question, should I true it prior to putting in the final welds or after the final welds?

Thanks,
Chris

Hi Chris

After, as it might move on you again when doing the final welding.
The blocks method can easily correct a fully welded gantry.

Cheers
Ross

Hi guys,

I was able to get 75mm x 50mm unequal angle iron for the Y rails thinking that was all that was available here in NZ... This was before I found the 65 x 50mm rails from another supplier, which I purchased for the X rails. My question is, since I have already drilled the 75mmx50mm can I use it and cut down only the 50mm side to the 28mm, or do I have to cut both sides down so that the 75mm equals 65mm?

Looking at clearance for the Y car, it seems there might be just enough room for an additional 5-10mm each side, but you guys would know better than I how much clearance there is.

Thanks,
Chris

The long leg of that angle should be "in board" of the carriage - so you should be fine on clearance issues. The upright, milled edge is outboard and not cause any interference. You should be fine with the x axis. The y axis car might need a little grinder clearance on the monocoup y-car - but that won't affect much.

Worst case, you keep the odd angle for the x and just remake the y.

What about weight issues? Any? Thanks Sean.

If your asking if the additional weight will affect the y-carriage - then the answer is not really.
You should be not really notice the additional weight if using any type of geared transmission/reduction drive. Direct Drive - Maybe, but not likely.

I added a 48" Z slide , dust collection and another Z in my carriage, with upgraded to 3/16" wall steel tube - and still didn't notice a difference. I was using 7.2 : 1 steppers and 30T pinions.

Cool, thanks. Was thinking that the rails would be too heavy for the gantry since I am already using 3mm tubing in the gantry, but sounds like it will be ok. It's a relief I don't need to cut them down.

Worst case, you may have to set your acceleration and deceleration profiles on the motor tuning in Mach 3 a bit slower (longer time) to accommodate the induced drag on the system due to the higher mass....but unlikely.

Best,
Sean

Have a bit of a problem, my long X beams are bowing slightly, about 3 mill in the center twist. When i clamp them together, they will straighten out, but what I was wondering was, if I bolt the rails to them, will they stay straight? Should I drill the rail holes through them while they are clamped together to straighten them or after the table is upright?

I'm bolting the cross members to the table with M10 bolts and a spring washer. So far it went together well. Drilled M11.5 in the crossmember, M10 in the beam.

Thanks,
Chris

Nevermind, I saw the post about welding the beam. Disregard.

Just curious, is there any way I could use 2x 4 core cables instead of 7 core for the e-stops, as it's very difficult to get 7 core here for anything reasonable. Will it affect any performance?

Many thanks,
Chris

I can't think of any reason why it'd make a difference, other than an extra cable entry/exit on each box. It really should work exactly the same as long as your individual cores are the same size as the 7-core would be.
How much 7-core do you need, in total?

I use cheap 2 core wires for light bulbs, & didn't even see the need to bundle them together. As long as its for AC & the correct voltage rating, if it can light a florescent lamp its good enough for the relay coil & switches which almost no current running in it.
Or if you must, you can get some Cat 5 cable with 8 twisted pairs in it. Just check if the Voltage rating fits the bill.

Well, my table is 3900 x 1550. So whatever much that is, not near my notes yet. Cat 5 would work? That would be awesome! Thanks!

On another note, I think my grinder broke while cutting rails. The teeth sound like they are grinding against each other on the inside. I took it apart and looks ok, not sure what the noise is.

I used 4 core shielded because the price was right. Ended up with about 1" diameter bundle of wires running from the machine to the control box. My router power is roof fed to keep it remote from control wiring.

Grinder bearings are trashed is my guess.

Actually, if your motor cables are shielded, you can bundle your router power cable with them. that is the whole point of having shielded stepper motor cables. E-stop circuit is 240Vac, even without shield, it takes a lot more than just VFD to corrupt 240V ac. Even a plasma torch cable did no harm to it.

Thanks for the input guys. I'll probably use either 4 core or cat5. Just having a hard time getting cheap 7 core in the lengths I need. Can only buy 50 mtrs.

The grinder was trashed, and started getting way too hot to work with, so I returned it and they exchanged it. They weren't going to, but eventually did. phew. I'll be much lighter with it this time. It's a bosch professional, and yes, I think the bearings must have gone last time. Trying to be lightiner, and grinding each side through. Doing it all the way through makes for a slanted rail.

Cheers,
Chris

Think rubbing/slicing off the rail instead of chopping when you use the grinder.

Thanks Ken,

Is it better to cut from one side or from both, resetting the height to ride on the flange?

Cheers,
Chris

I personally prefer cutting from 1 side & weld-shut the height once it is decided.
PS, the height will not be dead on... BUT do your best to keep them within 1~2mm variation (remember, think slicing/rubbing). The shims will do the rest in the later part of the build.

Ok, just finished cutting down my rails, they are hardly precision cuts, kind of jagged. I'm hoping the grinding will make them a bit more precise. The second X rail, I cut 1mm higher so I can have some leeway to grind it down a bit more precise.

Chris,
Did you put a grinder disk in after cutting down and make a few passes to even out the top profile.....like a surface grind making it really flat before you start profiling?

Hey Sean, thanks for the tip. Going to do that today. Unfortunately, one rail was cut from 28mm to 25mm slanting one side to the other due to the cutting disc not being perfectly level. May need to do that one over...

Just a quick question, if I want to weld 2 offcut angle irons together to make up a new Y rail, would that be advisable? I need to cut down a new rails one of my rails were cut to 25.51 mill.

Many thanks,
Chris

What process/system are you using to cut your rails down?, using the sled I made enabled me to achive a total variation along the full x length of 0.2mm!
see here:http://www.mechmate.com/forums/showt...3&postcount=45 and lower down in post 57.

That's sweet. Wish I had seen that one prior to doing mine. I used the skate. It's ok, and the last one turned out pretty good, but the other ones aren't that great. I'm going to need to grind them down with something to get them flat. Perhaps I ought to use something like this but with a grinder head, instead of the skate.

Hi Chris

Steady as she goes on the rails - 3mm variation is not good enough so ditch it and consider that as practice.

Treat the rail cut as two parts ..
1. remove the bulk
2. fine tune the height

As Alan has suggested the plate mounted grinder works great.
Set up on a straight surface, I used my X beams and then grind down the top of the rail square and to an exact height using successive passes.

When I say grind I mean sand.
Use a fresh grinding disk with a sanding disk as the cutting surface.
Start at about 40 grit or rougher then go up to 120 for a mirror finish to the rails.

My thread details the methods used. Sanding the rails will vastly improve the surface finish and significantly shorten the time you spend making the rails.

Regards
Ross

thanks, by ditch do you mean completely start over and buy new angle iron? Just curious, what is the lowest I cut the angle iron down to? Can I re-cut or sand them to 25mm or 24mm? if so, then I would be able to get them nice and even. I've been cutting on my X rails, but I don't think they are too flat either. I definitely underestimated the level of precision needed for these. The two long rails are 28mm for most of the rail, then they dip down to 25.5 and 27mm toward one end.

Been working low coz my xrails are quite heavy, hard on my back.

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Hi Chris

It is up to you to determine if 25mm is enough.
When the plans say specify something that's what I do.
"Ditch It' means recut one at the correct height.

If you have 3mm variation in height I suggest you have a real problem with your method.

1. Don't work low - get some tressles or saw horses and a few blocks of thick timber and lift one beam up on them at a good working height.
2. Look at this post http://www.mechmate.com/forums/showt...&postcount=186 and copy my setup.
3. Note you clamp the rail to the board and the beam and cut the rail from the back. It is impossible to get 3mm variation using this method.
even if the beam was bent over its length the rail is bent to match that and the cut remains at a consistent height.

Ross