rebuilding my table a few questions.

[timberfab]

Planning a refresh / rebuild of my current Custom CNC Table

Have a few questions for the group.

1. What size and series 80/20 extrusion is your gantry made of?

2. Where are your limit switches mounted? Table or gantry?

3. Do you have home and limit switches on your table? Do you like them, use them?

4. Magnetic break away. do you have one? Can I see some pictures of it?

5. How deep is your water table? Do you have an air bladder for adjustable water levels? Can you post a picture of it?

6. Is your gantry offset from the center of your gantry carriage so that you can use more of your table size?

7. What Gauge material is your water table made of?

[SeanP]

1. What size and series 80/20 extrusion is your gantry made of?
Mine is a steel frame

2. Where are your limit switches mounted? Table or gantry?

3. Do you have home and limit switches on your table? Do you like them, use them?
Don't have either on mine, just zero up on material and work away, no problems at all.
I do have solid stops to square up on first, limit switch on Z

4. Magnetic break away. do you have one? Can I see some pictures of it?
https://www.youtube.com/watch?v=fRi8LzY4aTg

5. How deep is your water table? Do you have an air bladder for adjustable water levels? Can you post a picture of it?
I went for 100mm at the deepest to 80mm at the shallow end, seems fine to me, slats are 75mm x 3mm, I do have a air bladder it's a must I would have thought, have a look at the link in my signature below.

6. Is your gantry offset from the center of your gantry carriage so that you can use more of your table size?
No I mist that trick when I made mine up, it's not a big problem as I can get a full sheet on plus the gantry.

7. What Gauge material is your water table made of?
2mm hot rolled, butt joined and welded, I did have a few pin hole leaks when making it up, ran a good smear of polyurethane sealant on the underside, no problems at all, painting the base inside the tray is a waste of time I think, maybe up the sides.

[suttoncnc]

2. Where are your limit switches mounted? Table or gantry?

3. Do you have home and limit switches on your table? Do you like them, use them?

I use my machine primarily for machining aluminum. It is a dual purpose machine. So, I do use solid state hall effect sensors to determine home position. I am using 2 motors to drive the gantry and my gantry is 60 inches wide, so the homing routine "squares" the gantry because I have a sensor on each side of it. This assures that my parts are accurate. I have Mach setup so that it homes VERY slowly while it hunts for the sensors, this gives me a very accurate homing position. My sensors are located on the table and not the gantry itself. My limit switches are totally separate from the homing sensors. The limit switches are simple mechanical switches tied into the emergency stop circuit and halt the machine if any of them trip. This is useful to prevent the machine from crashing and doing damage to the stepper drive gear train. Before installing them, I had several HARD crashes and the rack and pinion setup suffered some damage.

[timberfab]

thanks for the replies. any one else?


For additional information, this is my 3rd custom table. It is 6ft x 12ft runs CandCNC Bladerunner with DTHC feather touch, MACH3, SheetCam TNG Development, CNCRouter Parts PRO Rack linear motion and a custom Z-axis.

[muzza]

I have 3 cutting setups but this is based on the new one we are currently building which should be finished this month and is a culmination of what I've had and done on my others.

Gantry is light gauge steel.

Don't use limit switches except on the Z, use hard stops

The pan is made from 2.0 mm hot rolled with a 75 x 50 x 2.5 mm RHS support structure with outriggers to an angle frame and can be totally lifted from he table should I need to. It tapers from 85 mm deep an the ends to 100 mm where it joins a centre drop section which is 125 mm deep with the tank return protruding 10mm to minimse sludge entering the tank and a flush mounted drain to waste for cleaning. The slats are 65 mm x 3 mm and slot into 4 frames so that any one slat area can be easily raised to retrieve small parts or take the lot out in 5 minutes to clean out. I usually keep my water level about 20mm below the top. If I'm cutting a lot of aluminium I can dump the water, remove the whole water tray and reinstall the slat frames and slats in about half an hour.

Bladder tank has just over 1000 litres of useable volume and is made from 2.0 mm hot rollerd with 25 x 8 strengthening ribs internally welded and a removable end folded in 3.0 mm hot rolled so it's easy to periodically clean the sludge buildup inside of the tank. Cover panel has a 25 x 10 neoprene compression gasket with bolts at 200 mm spacing.
We've tested this at 20 psi (about 5 times working pressure) and although it bellied quite a bit between stregthering ribs there was only 1 pinhole at a nipple weld which has been fixed.

Gantry is done so the whole grated area of 4.0 metres x 1.6 metres has torch access as the table has 100 mm perimeter drawing ventilation.

The question was asked recently on bladder construction so I've attached a few pics
Murray