Project 1 from EmptyNester. Category: Custom Shop Tools - CNC Table

[acourtjester]

Just the added weight of the water and the tank needs to be considered when building the table frame. The size of the legs, cross bracing for stability and depth of the water. So guys put chemicals in the water to keep the funk down.

Have fun
tom

[EmptyNester]

Here's the layout for my table. I based this on other tables I had seen and trying to maximize size for materials. I also wanted to not overbuild it so that I could still move it around and handle it while building. (Since this is my first major steel project, I figured the table may be replaced quickly as I learn more. The stainless rails and carriages are the bigger investment and can be reused, if necessary.)

I only have the table about 2' high on purpose. I knew I'd have to lift any steel I want to cut from floor height, so I wanted to minimize the lift distance.



Based on recommendations from Ron at Precision Plasma (where I got my carriages) - I'm using 14 ga 2"x2" steel tube for the table and 16 ga 2"x2" stainless tube for the gantry.

The table used:
(2) 2"x2"x24' hot rool
(1) 2"x2"x20' stainless
(1) 2"x2"x1/8" angle (used for the bottom braces between the legs)
(1) 2"x1/8"x20' flat bar
(1) 1 1/2" x 1 1/2" x 1/8" angle
(1) 5' x 8' x 14 ga sheet
(3) 3" x 1/8" flat bar (for support slats)

The flat bar iswelded to the under side of the 2" sq table with 1" protuding toward the center. This gives me a good surface to weld a 14ga steel sheet to for the bottom of the water table.


Table Cutting List - (2) 14 ga 2"x2" square tube
Feet - Inches
6 - 4 table side
6 - 4 table side
6 - 10 center support
2 - 3 mid table support
2 - 0 leg
Total 23 - 9

2 - 3 mid table support
2 - 3 mid table support
2 - 3 mid table support
5 - 4 long end
5 - 0 short end
2 - 0 leg
2 - 0 leg
2 - 0 leg
Total 23 - 1

Leg brace cutting list - (1) 2" x 2" x 1/8 angle
Feet - Inches
6 - 6 table length brace
6 - 6 table length brace
5 - 0 table width brace
5 - 0 table width brace
Total 23 - 0

I also reinforced the corners of the cutting table with 28 1/2" pieces at a 45 degree angle underneath the table on each corner. I used 1 1/2" angle for that.

Corner Brace cutting list - (1) 1 1/2" x 1 1/2" x 1/8 angle
Feet - Inches
2 - 4 corner brace on the bottom of the cutting table
2 - 4 corner brace on the bottom of the cutting table
2 - 4 corner brace on the bottom of the cutting table
2 - 4 corner brace on the bottom of the cutting table
Total 9 - 4


I have basic construction done and have already "learned a lot" (code for "messed it up"). I post some pictures later.

[sportbike]

Looking good Nest.

I assume you are going with a gear rack drive for both axis?

What was the cost of teh gantry kit parts? Looks like a pretty nice package.

[EmptyNester]

Thanks.

I did get gear racks for both axis.

The gantry kit was $325. In hindsight, it seems a little steep and I may have gone other directions since I've learned more.

I've had a couple issues with the basic table construction. The first was the inconsistancy of my welds. It took me a while to figure it out, but it turns out that if I'm not sitting or standing upright with a good brace for my hand, my welds suck. But, it's a learning project.

The other problem I've had is that when I put the 2" flat bar on the bottom of the 2" square tube, it cause the tube to bow up (away from the welded side) by 3/4" to and 1" in the middle of the tube. I'm planning on putting a piece of angle on the top of the tube to extend the depth of the water table and to hold the slats. I'm hoping that welding that on will help reduce the bow.

[acourtjester]

HI Empty

I ran my plasma cable using a rotating pole in the corner of my table. It ended up with a shorter run, no worry of interference with the motor cables. My motor cables are run like yours. One picture shows my table corner with the rotating pole base.
Like this one shown here other picture.

[EmptyNester]

I reinstalled Mach and I was still having problems.

After looking through the Mach support forums, I found out that this is a common problem. The "IJ Mode" has to be set to "Incremental". That took care of it.

I'm anxious to give it a try, but may wait until the weekend so I have time to play.

[Rambozo]

You can have the IJ in absolute, you just need to tell SheetCAM to be that way, too. I actually like to keep everything in absolute or everything in incremental depending on G90 or G91. That mixed mode is a pain to work with, but I think Fanuc decided that was going to be their standard and everyone copied them.
There are also option where you can use radius for arcs with the R command. Here is a better explanation than I can give all about arcs.

http://www.cnccookbook.com/CCCNCGCodeArcsG02G03.htm

There are even some options in CAM programs to not use arcs at all. The CAM program will create all the arcs as a series of very small straight line moves. The programs get huge, but some controls can actually run them faster than having the control compute the arcs, especially with other options running like cutter comp, or rotation/scaling/offset commands running.

[acourtjester]

yes that does I have 2 sizes 60 amp and 80 amp the 60's are the .040 (1mm). If you have tip cleaners for a OA torch try to get close with one of those and then mic it for the size. But most likely you should just go with the smaller one and see how it works. there is not a great supply of different sizes for t e torches. I buy 1mm for a P-80 torch & WSD-60 torch, I have and the everlast unit I have is rated at 60 amp plasma (PM256 multi) and I have not tried to cut thicker then 1/4" steel on the table.
I'm sure there are guys with much more experience then I have with plasma tables.

[EmptyNester]

I'm embarassed to say - I don't know what size the tip is. They weren't marked. My eyes aren't great at that small a measurement, but the one I used for that cut appeared to be about 0.06" (I have others that I think are 0.04"). Does that sound right?

Pressure: 65 PSI
Amps: I think it was 30
Speed: 60 IPM
Pierce height: 0.2 in
Cut height 0.04 in (though, there could be some slop in my touch and go switch offset because it looked higher than than when doing a "dry run")

What difference does the tip size make other than the kerf width?

[aaxiss]

Kinda sounds to me like a bind. You started in the center of the table think you may have some sad in the center maybe s and the extra pressure on the gears is causing the gears to click a bit?

Just a thought

Sent from my Nexus 7 using Tapatalk 2

[EmptyNester]

Thanks for the feedback guys.

I found a reference so I could start learning G-code. It looks like the G-code never turned off the torch, so I'm guessing it was due to the noise on the interface from the motors when they cut the corners and doubled speed and made quick direction changes.

I didn't put a ferrite on the BOB -> THC cable yet. That's probably the first step. If that doesn't do it, I guess I can delay the torch off in software (probably start with 250 ms and take it up from there). I'd prefer to address the noise, but I think I could end up cutting/wasting a lot of steel getting scope captures to figure out what's going on.

I think that the cut rate was way too slow. I had been trying to find a good chart to give me a starting point for cutting speeds and amperage settings based on thickness. I finally found a decent starting point on Eagle Plasma's web page:
http://eagleplasma.com/4x4system.html

It recommends 240 ipm @ 30 amps for 16 ga. I cut the 18 ga at 10 ipm @ 35 amps.

[EmptyNester]

Taking all the advice, I checked all the motor settings. It turns out that the Y axis had a different acceleration that the X/A. I didn't think that would make a difference, but I set the Y to match the X/A anyway. They are all set the same except the max speed on the Z is much lower.

I then taped a 1:1 image down and manually positioned the torchhead at multiple points on it. That all seemed to line up properly.

I tried to cut again, and I remembered to turn the THC on in Mach before I started. I also up'ed the cutting voltage by about 3/4 volt. This is what I got:



It's a perfect match to the pattern. My best guess is that the torch did move the metal because it was too low before the THC was turned on. I guess that was a lesson in the value of the THC.

My wife is happy with the result, so I can be assured of continued "enabling"

One other thing that is interesting is that having up'ed the voltage 3/4 volt, it seemed I had more spatter on the top at pierce points. So, I'm impressed with the precision of the control. It makes an argument for setting cutting voltage in "counts" instead of volts since it has seven times the resolution.

I did have an interesting though on the THC. All I've used it on is 16 ga. I'm wondering if any aspect of the voltage behavior (other than being at a different voltage) will change on thicker metal.

Thanks all for the help.

[sportbike]

My wife is happy with the result, so I can be assured of continued "enabling"

My wife was discussing finding a new hobby the other day....up pops a plasmacam and she was like "that's neat". I talked to her a bit about a plasma table and she was actually into it. She is an accountant, so this is totally different than her "normal" day, which is why I think she is sort f into it.
I told her that if she wants to get into Metal Art, I fully support her and will do what I can to enable her to get started.

If this takes off, I may be building a plasma table and hell, even breaking ground on a new garage by the fall... wouldn't want my wife to have to work out in an old drafty garage would I?

[ShaneJackson]

You have mastered the force young Jedi. You have demonstrated mind control... making her want a new shop and a plasma table.

[travis]

took my wife to see a plasma cutter demo at a car show shes like you "need' one of them then i show her the price on a blue boxed and the price on a powerultra half the price 3 in 1 shes like save for it lol

[EmptyNester]

My wife was discussing finding a new hobby the other day....up pops a plasmacam and she was like "that's neat". I talked to her a bit about a plasma table and she was actually into it. She is an accountant, so this is totally different than her "normal" day, which is why I think she is sort f into it.
I told her that if she wants to get into Metal Art, I fully support her and will do what I can to enable her to get started.

If this takes off, I may be building a plasma table and hell, even breaking ground on a new garage by the fall... wouldn't want my wife to have to work out in an old drafty garage would I?

Excellent work! All I can say is "keep working it"

Today my wife had said she wants a new railing on the front porch. The existing one is wood and she wants to stick woth wood. I said that I can leave a framed opening in it for a laser cut design. Now she's really excited and trying to think what she wants.