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

[EmptyNester]

After using my PP50, I found that my hand isn't nearly as smooth or coordinated as I'd like. So, I'd like to build a CNC table.

Having mostly finisihed the Hovercraft project after a year and a half - I wanted to do something that would be quicker. But, almost any project would be quicker than that!

My goal is to do the project for as little money as possible since this is more of a toy than a needed tool. And, to limit initial cash outlay, I wanted to do the project in stages so that I wouldn't have to sink too much money in all at once.

In my work life, I write embedded control software (currently for medical devices), so I'm comfortable with the electronics and software side of the project. I figured I could save the most money on the drive control if I went the E-bay route and I'm fairly confident that if the parts are functional, I'll be able to get them to work.

I have about 8 hours in on the electronics and 8 hours in on the table (just started this week).

I got a four axis drive kit Wantai Motor with:

• (4) Nema 23 428 oz dual shaft motors
• (4) 4.2 ampp stepper controllers
• (2) 36 vokt, 350 watt power supplies
• (1) breakout board
• (1) parallel cable

I didn't necessarily want the dual shaft motors since I don't plan on adding encoders, but this kit shipped from a US warehouse. So, I went with this for $406.

The first thing I did was to do a quick/temporary wiring job to make sure all the components worked. Using the demo version of Mach, I could spin all the motors, so I figured that was good enough to continue with the project. With that done, I picked up my steel on Monday.

I'll post the drawing I did for my table when I get a chance (it's in Visio and I only have that at work).

I'll post pictures and prices since I'm trying to build a "hobby level table" at "garage project prices".

I'll go into more detail on the electronics side, since that information is harder to find when you try to do research on the internet.

[Rambozo]

There is a free Visio viewer you can use. I use Visio all the time for quick drawings. However, with each new version it seems to be moving more and more away from technical drawings. Back from before Microsoft bought it and the was a specific technical edition.

[EmptyNester]

Here's the table as its current state in the garage.



I've been going back and forth on how much support is enough for the water table. After talking to my brother in law (long time fitter) and my daughter (materials science engineer doing her post junior year internship in a metalurgy failure analysis lab) - they both think I'll have sufficient support.

The urge is to to support the table bottom more, but with water 3" deep there will be about 400 pounds of water. That's less than 1 pound per square inch. My reasoning (right or wrong) is that the table to leg weld it more of a concern for stress failures than the sheet that is the table bottom.

I'm willing to take a chance. That's the fun part - it's never interesting without the chance of a dramatic failure!

[posixPilot]

Google sketch up is a good alternative to Visio for this type of drawing, since does dimensional material do well (I.e. lumber, tube, etc.). And it's free to boot!

Cheers
Mike

[EmptyNester]

I finished construction of the basic table. I haven't done the mounts for the rails yet.

It has both wheel and anti-vibration feet on it. This will let me move it around the garage by myself. It's worked well for moving it in and out of the garage.

This picture is while I was draining the table after the water test. Unfortunately, I have some work to do on fixing leaks.



What was interesting is the two leaks in the photo below. If you look closely, where the arrows are pointing, you can see a gap in the heat affected zone. This is just where the leaks are.



For the drain I just used a 1/2" black pipe coupling on the bottom of the water pan and threaded a ball valve on it.

[zoama]

For the drain I just used a 1/2" black pipe coupling on the bottom of the water pan and threaded a ball valve on it.

May as well put a garden hose adapter on it http://www.amazon.com/Anderson-Metal...094267-8385652 (link is only for illustration)
You could fill it the same way... slowly with no fountain.

[EmptyNester]

Zoama,

You've become my idea man! That would work out well for filling and draining.

(I just got the mandrel for my hovercraft muffler. That's was another great idea from you. - Thanks)

[Rambozo]

That is so not what I meant when I said I wanted a pool table.

[EmptyNester]

Since I have a sqaure tube frame, I decided to use angle to make an adjustable mount for the gantry rail.

I cut a wood pattern so that I could cut slots in the angle. It would allow bolting the angle to the square tube legs. The slots are vertical so that the entire piece of angle can be moved up and down to level the gantry rails to each other.

At the top of the angle, I put another piece that had a slot in it. This is to allow movement of the gantry rail closer and further in relation to the other side.

[EmptyNester]

When I welded the carriage, I didn't think about the cross tube between the two x-axis.

I ran a weld bead along both the top and bottom of each joint. The top of the top joint is where the y-axis bolts on. The weld bead would have prevented any adjustment in length of the y-axis (it's a slotted plate).



A little bit of grinding and the situation was fixed.

[SeanMurphy265]

I would add some support in the middle, but if you not cutting over 1/4" it will probably work fine.

[EmptyNester]

I would add some support in the middle, but if you not cutting over 1/4" it will probably work fine.

I probably won't be doing anything heavy. (I just wouldnt' be able to lift it.) I'm planning on more decorative/artsy stuff.

If you look at post #12 you can see the cross pieces I put in. Would you put in support in addition to that for heaver work?

[SeanMurphy265]

I probably won't be doing anything heavy. (I just wouldnt' be able to lift it.) I'm planning on more decorative/artsy stuff.

If you look at post #12 you can see the cross pieces I put in. Would you put in support in addition to that for heaver work?

I think it depends on how heavy you go! You have your 4 vertical corner tubes now, but if you add one piece of tube in the middle (vertical) on all four sides that would greatly reduce the capacity of the table. My table is heavier 5'x9' and I used 3/16" and 1/8" tubing; I can slide the table fairly well. I'm going to add some castors in the rear to help move the table.

The main thing that would scare me is the the gantry (depending how you mount it). If you get too much weight on the table it could distort your gantry. I have seen where some people have made their gantry where it could stand alone instead of mounting it to the table.

I called precision plasma about their Z axis and they would not sell me one. Since you bought a kit will they sell you a Z axis?

[EmptyNester]

I cut the slats and put them in the table.



I had orginally put in slots every six inches. When I looked at it, I decided that was too far apart. So, I went to four inch slots. As a result, I didn't have enough steel to fill them all.

I just painted the gantry rail mounts, so I'll be able to mount them and the gantry rails in a couple days.


Question:
I had been thinking of painting the slats with heat resistant paint. Anyone have any experience with that? Is it a good or bad idea?

[EmptyNester]

I've had the drive electronics set up for a while. I just hadn't gotten around to taking any pictures to post.

I used an old PC case to house everything. I had thought about using the power supply in it for 5V and 12V, but decided it was too big and too much of a pain since it needed the power control logic overridden (no PC to power it on and off).

This is a 4 axis kit from ebay. It came with two power supplies for the motors. They are mounted on the top and bottom of the case. I arranged them so that one of the x-axis motors was on each power supply. It seems like it would balance the load a little better.



I mounted the four motor controllers in the middle.

I left the original PC fan in. I got a small 12V power supply (upper left corner) to run the fan. I have additional fans and will add them if necessary.

Right under the fan is the break out board. I have it mounted so the parallel port connecter goes out an existing hole in the case.

I have a five volt power supply (again, from e-bay) mounted in one of the drive bays. It's used to run the logic voltage on the stepper motors and the motor side of the break out board.

I decided to use isolated power supplies for the BOB. I had an old 5V wall wart from an iPod, so I used that for the PC side of the BOB.

I couldn't find any reasonably priced connectors that I liked for the drive cables. So, I went the cheap route and got a couple terminal strips. Given that I'm not going to be taking everything apart often, I think that will be fine.



I've already had it all running the motors. That was the first thing I did when I got the kit. They had a 14 day return period, so I wanted to make sure that they worked.

[EmptyNester]

Thanks all for the advice.

---

Sean - Since I don't have a dial caliper I wanted to figure it out by the math. It turns out that I did the calculation right, but then just plugged in the wrong number (duh). Once I used the right number, it seemed as good as I could measure it without a dial caliper.

The math I used is:

Distance per revolution (circumference) = Pitch Diameter * PI
(the pitch diameter was specified on the web page at McMaster)

Distance per rev = 0.625 * PI

Distance per rev = 1.963 inches

With 200 steps/inch and using 1/16th microsteps - I have 3200 steps/rev

Steps/in = steps/rev / inches/rev
Steps/in = 3200 / 1.963
Steps/in = 1630.158

--

Ram - one gap in my understanding (of the may) is cutting speed. I had originally thought that would be based on the stepper speed, but then realized that would work right. I'm guessing that's something you set in Sheetcam?

--

Jester - thanks for the tip - I hadn't thought about that. The motors are pretty stiff when powered off, but I'm guessing that the floating head and the torch will add some significant weight.

--

I just finished "adjusting" the Y axis carriage. With a couple blocks of wood and a crowbar, I was able to get it square. It now runs perfectly on the tube.

Just a couple more wires and I should have all axis running.

[EmptyNester]

I now have the table put together and right side up. I still have to weld what was on the under side.

This is only my second big welding project, my welding skill is progressing but I really have a problem with consistency.



I'm planning on putting 2" angle around the cutting area so that I can get up to 4" depth for the water table. I have 3" flat stock I'll use for the supports and just put it in notches I'll cut in the angle.

I'm planning on puttiing heavy duty casters on with a leveling foot with each one. That way I can move the table around without help and still be able to get it stationary and level. I kept it low to the ground so I wouldn't have to lift metal as high to get it on the table.

I'm not sure if I'll need to add support in the middle. The inner dimensions of the table are 52" x 76". I expect to lose a couple inches due to carriage dimentions. I assuming I'll have about 50" by 70".

Rege

[EmptyNester]

I got my carriage kit from Precision Plasma ($325). I originally saw it on EBay, but then went to his web site to find out more.

I liked the iPlasma tables he had, but buying a pre-built table wasn't in the budget.

The kit contained the carriage plates and all the bearing and hardware necessary, as well as plans for a portable cutter (just carriage rails, no table).



Two of the completed carriages are below, one X and one Y.



Based on the plans that came with the carriage kit, and a discussion with Ron at Precision Plasma, I went with 14 ga 2" square tube for the table and 16 ga 2" stainless for the gantry.

[acourtjester]

Great start empty
I built a table my self and it was a great project, there is tons of info on the web about CNC tables you may look at CNCzone for one. One thing you need to remember is the size of your water table and the volume of water it will hold and its weight.
Look under hobbyist projects you will find mine (DIY CNC table plasma cutter) and seanMurphy256 posts about builds. PM if you have any questions I will see if I can help.

Have fun
Tom

[EmptyNester]

Great start empty
One thing you need to remember is the size of your water table and the volume of water it will hold and its weight.

Tom,

I have seen Sean's, but I'll take a look at yours.

Is there some specific concern about structure and weight of the water? The water weight should be about 400 lbs.

Thanks,
Rege