[wentyfalls]

Hi all,

Well I have just started my steel frame build. A couple of years ago i made a bad first attempt at a small machine that ended up with a pile of metal and a chinese controller board that did not work from the day it came out of the box.

So lesson learned I have decided to build a bigger and hopefully better machine with a steel frame and decent electronics.

So after considering importing a chinese machine, then looking at a CNC Router Parts kit (the freight to Australia was a killer) I then looked into a T-slot frame and finally settled on a steel frame which will probably have a T-slot gantry.

• The frame is 65*65*3mm primed steel tube
• The rails are 20mm supported round rails - I bought them from AusX mods, chris has been fantastic help.
• Two ball screws on the X (gantry axis)
• one ball screw on both Y and Z axis
• Stepper motors NEMA 24 495 oz on X and Y axis - 387 Oz on the Z axis - Aus X
• Gecko G540 controller AusX
• 2.2kW chinese water cooled inverter.
• Table size 1200*1400mm which should give me approx 1000*1200. With an overhang at one end to allow for dovetail joints

So my first bit is the bed, i am a bad welder and after reading MadVacs build log decided that avoiding warping due to weld heat would be a good idea.

My solution is to position the parts flat and square on the floor then epoxy (JB weld) a 50mm*3mm flat steel plate across the joints.

When the epoxy has hardened (min 24hrs) I drill and tap straight through the plate into the frame. Flip the frame and repeat on the other side - refer pics.

So far so good the epoxy is amazing stuff.

I hope to get the frame fairly accurate with the key issue being parrallel rails and the bed parrallel to the rails. My final step will be to machine the MDF bed flat

One issue I am having is finding a supplier of 1mm2 4 core shielded cable - does anyone know of any in Aus?

Apart from that I am content with progress so far, but would welcome any feedback.

Rich

[mhasting2004]

Welcome to the fray Rich.
On my build ( http://www.cnczone.com/forums/cnc_wo...biuld_log.html) I went the mainly bolt together route also but to get the rails square and level I just made some forms and poured epoxy as a nice bed for them.. gravity is a great thing for getting level surfaces.

Its been working very well for me so far.

Your nom de plume makes me think your in the blue mountains.. if your ever up Gosford way look me up and we can have a chat over coffee.

Cheers

[wentyfalls]

Welcome to the fray Rich.
On my build ( http://www.cnczone.com/forums/cnc_wo...biuld_log.html) I went the mainly bolt together route also but to get the rails square and level I just made some forms and poured epoxy as a nice bed for them.. gravity is a great thing for getting level surfaces.

Its been working very well for me so far.

Your nom de plume makes me think your in the blue mountains.. if your ever up Gosford way look me up and we can have a chat over coffee.

Cheers

Thanks for the welcome

You guessed correctly I am in the Blue Mountains - it is cold at the moment but I am still dedicated to the cause and in the garage each night.

I had a quick look at your build and it is very impressive.

My main driver for epoxying the joints has been due to limited tools - no access to a mill or lathes etc. Also if good welders have trouble with twisting then as a bad welder I would have heaps of problems. One minor issue is allowing extra time for the epoxy to go off in the cold

The epoxy leveling looks great - just a couple of questions.

1. where did you get your epoxy

2. I see how it levels a single rail, but how did you level each rail relative to the other. does that make sense?



Rich

[mhasting2004]

Hi Rich

1. I got some from the local fiberglass supply shop (plenty of boat builders up this way) and used West system epoxy but am using boat cote for a kayak I'm building right now. Not sure where up your way to get some but plenty of places in Sydney.

In the cold like now you could get some fast hardner or apply some heat (lamps etc)

2. If you look at the second pic in post 17 of my thread you can see the bridge I made form one side of the frame to the other with a bit of angle iron (actualll alloy from Bunnings). For this to work well you want a slow cure time and a very low viscosity epoxy.

I added epoxy to both sides and across the bridge so the amount of movememt of epoxy during leveling was minimum.

Once cured I used a piece of my gantry and a flat plate and sandpaper to get rid of the meniscus lip that will form around the mold edges. Again minimal cleanup necessary.

Cheers

[wentyfalls]

Hi Rich


I added epoxy to both sides and across the bridge so the amount of movememt of epoxy during leveling was minimum.

Once cured I used a piece of my gantry and a flat plate and sandpaper to get rid of the meniscus lip that will form around the mold edges. Again minimal cleanup necessary.

Cheers

Thanks m

the epoxy bridge looks good. Ive got some casting resin in the shed, i'll see what it is like and if it sets hard enough.

What cable did you use - I got a quote for 4 core (3 core and earth) sheilded 1mm2 cable today - $6.50/m + $14 shipping. It is more than I thought but is hardly the most expensive part of the build.

Rich

[mhasting2004]

Like most of my machine (probably 95%) the cabling was scavanged from discarded gear from work. Data is via large shielded multicore SCSI cable along the cable tracks or split down to 3/4 core shielded to each sensor.
All data is optically isolated and sensors run at 24VDC

The only cable I needed to buy was single core hookup wire for power distribution inside the cabinets and som twisted / shielded 4 pair data cable that I doubled up (used two wires for each leg of the motor coil) for the motors.
I got both of these at a local electrical supply shop. (sorry cant remember the cost)

Best to actually go and have a look at what they might have on the racks as you want something that is relatively flexable and so spliting pairs and multistrand are the definetly go over heavier/ fewer cores.

[wentyfalls]

I had considered shielded microphone cable from Jaycar, but it was not quite able to carry the required current, parralleling the cable is worth looking into, if I can fit all the wires in the e-chain.

[wentyfalls]

Well last night I went to continue my epoxy_plate_and_tapped jointing method and disaster struck....

The epoxy did not stick - I had tried some permatex epoxy from Super Cheap auto and I don't think it worked as well as the JB Weld.

Then, I think my tap is blunt because I got three bolts stuck and then sheared them off trying to remove them.

So having seen the success that mhasting2004 had with his epoxy flood levelling system I am going to try welding the joints as accurately as I can and then finish off with the "hastings flood method".

So today I bought some new welding rods and will be doing lots of practice tonight.

I only have a stick welder but we'll see how it goes.

As long as the weld is strong and I dont warp it too much, a grinder and paint will hide a multitude of sins - or an ugly weld.

I kind of like the way that these builds evolve as you get into it and have to adapt. It is good for the brain (when it doesn't keep you awake thinking about it)

Rich

[CarveOne]

Some recommendations for a stronger epoxy joint if you are not doing this already. Epoxy will pop free easily if on a smooth surface.

1. Clean the surface to be glued with a solvent like acetone. (with proper safety precautions of course)

2. Sand the surface to be glued with 100 or 80 grit grit sandpaper to rough up the glue area and give the epoxy a good "toe hold". Lots of small scratches down into the metal is best.

3. Repeat #1 in case the glue area has gotten contaminated with oils again during sanding.

This is more work but the payoff is much stronger joints.

[mhasting2004]

one more epoxy tip that I only learnt recently....

Use plain vinager for clean up of tools and hands (BTw always were proper PPE ie gloves etc) works a treat and is non toxic and a darn site cheaper and does a better job than Acetone.

Do use Acetone to clean joint as CarveOne states though and it can also be used to thin the epoxy up to about 5%.

In my setup the epoxy is not for any mechanical hold, it is there as a shim only and is under compression.

For a bolted frame ala Mad Vac what I would do (and I believe this is his method also from memory)

• Mix a thick slurry of epoxy that is slapped in the joint (epoxy and milled glass fibers).
• Hold in place with tape to stop it all running out
• Assemble joint
• Snug up but not tighten the bolts.
• Let set. (24hrs)
• Go back and tighten bolts to proper torque
• Drill and pin the joint. Don't rely on bolts to hold position unless your spending big on shoulder bolts everywhere... and even then.

The welding that I would do is making the flange ends on all the frame parts (pre drelled as its easier to do first) rather than the cheek plates shown it the first pics. Ie am over sized plate welded to the end of the tube with 4 bolt holes. Actually 5 holes... put one in the center so the air thats heated up in the tube can escape while you weld

Try and use bolts under tension rather than sheer.

This will ensure a solid frame that is not under stress.

Cheers

[wentyfalls]

Thanks for the tips guys

I followed the instructions to the letter and cleaned all surfaces including the mixing tray with paint thinner.

I am pretty sure that the permatex product is just not as good as the JB Weld.

However, I have "made my bed" - so to speak, and welded the frame.

When it comes to truing it all up at the end i'm relying on the "flood leveling" and will also epoxy some blocks of aluminium on the frame of the bed, then machine them down with the spindle and then attach the 25mm mdf bed.

Rich

[wentyfalls]

well I went to Bunnings the other day loooking for a resin/epoxy that is pourable enough to use to levell the surface for my supported rails.

They sell two products both made by Diggers.

A fibreglass resin and a clear casting/moulding resin. I could not tell which one was the best and all I really need is one that flows well.I would expect the casting resin to flow well but it is twice the price of the fibreglass resin.

So I emailed the manufacturer and they sent me some specs on the two products and they are basically the same strength and viscosity as each other and they said that apperance was not crucial then the fibreglass resin will do the job.

It is nice to get good service despite my slightly odd questions

[wentyfalls]

Hi

i have been pondering my build and will need to make some gantry brackets that connect the y axis rail/bearings to the gantry (moving gantry).

They are fairly simple 120mm * 10mm aluminium plate, but there are a number of holes are required and they will need to be spot on.

The holes would be easy to machine with a finished CNC machine, but fiddly if done by hand.

Do you think it is possible to make temporary brackets out of MDF or ply that are strong enough to allow me to machine some aluminium ones. My design has a sunken bed so the gantry almost sits directly on the Y axis bearings.

If not, does anyone have any tips to achieve good accuracy- especially on the end where I will need to drill and tap into the 10mm ally to make the 90 deg joint

I hope I make sense, I'll post a picture when I get a chance

Rich

[CarveOne]

Hi

Do you think it is possible to make temporary brackets out of MDF or ply that are strong enough to allow me to machine some aluminium ones. My design has a sunken bed so the gantry almost sits directly on the Y axis bearings.

Rich

Yes, it's worth a try. Just keep the feed rate reasonable in order to not over stress the Z axis. Use a center cutting end mill. Use slow plunge rate.

[wentyfalls]

Yes, it's worth a try. Just keep the feed rate reasonable in order to not over stress the Z axis. Use a center cutting end mill. Use slow plunge rate.

Thanks CarveOne,

I'll follow your advice. After I posted my question I had a dig aroud the forum and there are even examples of guys milling Aluminium with all mdf constructed machines. Albeit at a slow rate.

I think ill do the same with my z axis and spindle mount

We'll see how it goes.

Of course i am thinking way further in advance than my build rate

[CarveOne]

If your CAM software can do peck drilling and ramping operations those will help. A small squirt of WD-40 or other spray lubricant will help prevent galling, and place a sheet of plastic over your MDF table top if you want to keep the lubricant off of it.

[wentyfalls]

Hi all,

Well i have made a bit of progress this week and managed to complete the frame, give it 1 coat of paint and levelled the rails on the Y axis.

To levell the rails I followed mhasting2004's method (ill call it the Hastings method)

I first welded som plates into the bottom of the legs, tapped them to M8 and screwed in some bolts as temporay levellers. I'll get some anti vibration feet soon (the spec of the ones i want is M8)

Then I levelled the whole frame up as close as I could with a spirit level and it came really close. I had visions of severe twists due to the welded frame.

Next I built a dam around the rails and had a connecting bridge. I used timber and a piece of 3mm mdf folded into a 'V' for the bridge.

I used polyester fibreglass resin (Diggers brand from Bunnings) and as it is clear I thought i'd paint the rails first so the painted surface would show through the clear resin. This was a minor issue.

The paint disolved in the resin (see pic)

Also as there was no roughed metal for the resin to stick to I dont think the bond between resin and rail is very strong.

Any way attached are the pics.

The final colour of the resin is a blue black blend of the paint and undercoat that actiually looks ok.

I will bolt the rails through the resin into the frame so the resin to frame bond strength is not crucial.

We'll see how it goes. So far it is satisfactory.

Rich

[wentyfalls]

Well somehow my resin levelling per the previous post has been a massive failure

I put a spirit level and straight on it today and somehow the resin has managed to defeat the laws of physics (to me anyway)

1. One side is flat but not level - Pic 1

2. The both sides are not level to each other - Pic 2, I shimmed it with a 1.5mm thick piece of wire to get it level.

3. The other side is curved - Pic 3 shows a straight edge and you can see light under it!

Any suggestions anyone.

One option I am considering will be to remove the resin and mount and shim the supported rails directly to the steel using a wire method similar to the one described in MadVacs build log.

[joel0407]

My build is only in the planning stage but I would suggest aluminium extrusion bars.

[joel0407]

And buy a new camera. LOL