So it begins... Cnc plasma table buid

[GoodB0Y]

Ok... Hi

So I've been reading and reading and then did some more reading and I think I have a good plan. But I'm hoping you guys can steer me in the right direction and help me not do anything dumb

I've decided on a table with a cutting area of 32/48.
Hgr20 for the y axis and sbr16 (not the best I know but 2 rails one on top and one on the side) for the x axis. I'll be running a blowback plasma cutter and I've settled on linuxcnc for control.

Now I might be crazy or this might be weird but It'll be made out of aluminum tubing and won't have legs. It'll sit on my welding table and be stowed away against the wall or a chain hoist to the ceiling when not in use. Don't freak out! I have 12 foot ceilings and sturdy hoist mount lol. But This is of course because I have a ton of stuff in my shop already like mig, tig, sand blasting cabinet, powder coating oven, jd square tubing bender, ect ect...and of course my projects... So space is limited lol. My rough estimate is 35lbs of frame and gantry 15 20 for motors rails and wire ect... If it's more then I'll deal with it but that's the goal lol.

My first step or what I want is to get the gantry and z axis done as this will determine alot of the design afterwards... Wish I could draw pretty pictures in cad for you guys but other than a couple scribbles and measurements most of it is my head haha...

So to my first question:

What is the minimum or good height for my gantry? Of course it's up to me and I've seen pretty much everything but I'm leaning towards 4 or 5 inches to bottom of the gantry with the z axis having the ability to pull the torch 3 or 4 inches above the cutting table.
Thoughts???


Any other criticism? (Please be kind)

Got some parts on the way... Sbr rails for the y axis, 8mm rods, bearings, lead screw nut for the floating torch head z axis and a dial indicator which I've always wanted but never really needed till now

Gosh I'm a blabber sorry haga

[plasmanewbie]

Enjoyed reading your post, I can tell that your pumped! I love the table top style idea Nothing wrong with that, gotta have it suit your space, budget, workload, etc. If i were to build a table I would make the gantry low, reduce the inertia on sharp direction changes, If you dont need a lot of clearance for cutting pipe etc than why not, also compact and tidy for your stow away design. Look forward to seeing your setup come together. Have fun.

[GoodB0Y]

Appreciate the response and encouraging words!

You reinforced my thoughts... Although I don't want to limit the abilities of the table I think realistically 4 inches of height will be enough.

Now I gota purchase the gantry beam... Going with 2x4 and I'm wondering if anyone has any experience tapping.125 aluminum?

I don't mind going thicker but I think I can do.125 or what like 3mm?

The sbr rails have lots of holes and I'm not carrying alot of weight. Can.125 be taped realistically?

Oh one more question

I've read some have had issues with too short of travel on the probing/floating head. Meaning that a small or short travel during probing can cause problems... Anyone have any comments on that? Trying to keep everything tight and compact and I don't want to waste travel distance. I'm thinking just less than half an inch or 10mm... Yes?

[adbuch]

Interesting project! I think the gantry to table distance will depend on several factors. If you want to cut into the side of square or rectangular tubing, then you would want to have enough clearance to handle this. Also - may you will want to use it for occasional cnc routing - if so plan for enough Z travel for the different scenarios you may encounter. If this table is only to be used for cnc plasma cutting - then the lighter the gantry - the better - easier to accelerate/decelerate as well as less stress on the motors/gears/belts.

Dvaid

[acourtjester]

Ah yes another DIY guy, Great One thing is your are doing the research be for jumping in the pool. There was a guy on YouTube who lifted his table to the ceiling to get it out of the way too, I have seen other who swing theirs up against the wall. One thing I will mention is to be aware you need a way to get rid of the dust from the cutting. You can use either water table or downdraft. Plasma dust in nothing you want in a shop, I use a water table and drain it after cutting. With a small table that is not bad. Down draft you need a way to exit it from the shop (large flex tube to the outside) plus a fan system. I assume you are using a hand torch so that helps with the Z height, 4" is OK for travel about what you will be cutting. LinuxCNC will work fine I am using it on the last table I build (keeping for my own use). QTPlasmaC is the GUI that is great for Plasma, I took me a short time to setup the Z travel, to get it right but not a big deal. If you watch this video the torch almost hits the upper limit when it retracts, but I made changes to fix that (software setup, Pncconf ). I can send you info to help with the install, I used a dedicated PC but some used a dual boot setup.

[SegoMan DeSigns]

Welcome to the forum.

My 2 cents here:

If you are keeping the plasma table stored above the welding table how are you gong to make parts for the project you have clamped to the welding table? I would do it over a vacant space on the floor and have fold up legs (if needed) to prevent your head banging them.

Is a fold down from a wall option a workable solution?

Your gantry height is dependent on a couple of things, are you wanting to cut tubing? I went with 8" from top of slats, when slats are removed I can cut 12" tall tubing for lights logo ect. The higher the gantry the less chance you have from a tip up collision.

Be sure to allow for gantry & Z skate width + some spare room for cutting sheets of material..

[GoodB0Y]

Some good points...

The video acourtjester posted helped alot.... I was and still might do something similar. But I'm trying to do the floating head and z travel on the same rail... We'll see if I can get it done lol. Also the gap between torch height and the probe is tight! That's what I was hoping to accomplish! Thanks for that and the offer of help I might take you up on that when the time is right.

Should have added that I'll be running a water table with 2.5 inches of water... I tried to powdercoat without a booth for a bit and ya that was dumb lol. I still find powder coating dust on stuff from 4 years ago lol.

Good points SegoMan. Nothing is written in stone and legs folding or removable will always be an option... And agreed that the gantry defines the limit of what can be cut. I like your ideas and will certainly consider them. My goal is maximum cut dimensions so I plan on having my y axis travel (cart) travel right to the end plates. I believe that will get the torch right to the edge of the water table... 2 inch of tubing plus just over another inch with the hgr20 rails on the side. That's 3 inches beyond the water table edge and in theory alow for a cart 6 inches wide....I think that should be stable enough but I'm open to suggestions on that.

shop or garage tools and equipment are always better the bigger they are haha. I had a terrible time determining the dimensions of my powder coating oven. I ended up with 2x3x6... My blasting cabinet was the same wanting bigger but limited on room and budget. My welding table was another... So the plasma table is a compromise... But I'm happy with its dimensions. Just hope it doesn't weigh a ton lol

[tnbndr]

I'll throw 2 cents into the pool. I think once you have a plasma table, you are going to use it more often than you think and you will get tired of lifting it up and down, filling and draining a water table etc. I would build it on a retractable caster system and push it out of the way when not in use.



This is the system I put on my 1200 lb Weldsale table.

[GoodB0Y]

Agreed... Folding legs and casters would be a good solution!

[GoodB0Y]

So... Is 2 inches of water pan enough?

With the material and design I'm working with its 2 or 3

And can I run the z axis stepper from a belt? Like inverted rather than a coupler?

I've been looking for timing pulleys but I'm not sure if I can mount a pully to the lead screw If I could use a belt to drive the z axis I can save 3 inches in total height... The coupler and stepper add 3 inches in height.

On a side note I did pick up the metal for the gantry beam and some 3/16 sheet for the cart/z axis. The gantry is 2x4 sharp edge 6061 aluminum 40 inches long. Amazon delivered the sbr16 rails and 8mm rods with bearing blocks and holders. I've got a really good idea how to do my z axis with floating head and it looks like the total cart width will be 4.5 inches. That'll get me edge to edge with the torch. Hope to have something to share on that soon.

Honestly I've built a ton of stuff... Autonomous Drones, mini bikes, powder coating... I even stuffed a dodge motor into a ford (cummins swap) but this is going to put me to the test! Haha

[adbuch]

I think you can do it just about any way you want - inverted z motor, etc. - as long as you can figure it out and get it to work. Lots of possibilities here.
David

[GoodB0Y]

Will any timing/belt pully fit on the end of a lead screw? I googled it but couldn't really find an answer.

And is 2 inches enough water?

[adbuch]

Will any timing/belt pully fit on the end of a lead screw? I googled it but couldn't really find an answer.

And is 2 inches enough water?

Yes - the end of the lead screw can be machined down to and flat added to accept pulley, gear, etc.

David

lead screw with flat.jpg

lead screw 2.jpg

lead screw 1.jpg

[acourtjester]

Here is how I did it on a early table. I used about 3.5" of water on my table.
"Will any timing/belt pully fit on the end of a lead screw? I googled it but couldn't really find an answer."

motor drive install (4).JPG

[GoodB0Y]

Thanks for the picture... That helps.

Looks like the end gets machined? I was thinking just a mount to the screw shaft... Idk I may not want to go that route.

I've managed to shrink the z axis down enough... Changing the spot that the lead screw mounts, trimming the coupler and motor shaft has given me almost an inch less total height. Think I'm pretty happy with it. 4.5 inches of travel with the floating head on a single rail and 11ish total height

Ya 3 inches seems pretty standard. Just trying to keep the total height of the machine down.

There's always a trade off lol

[acourtjester]

I think you may not fully understand the Floating head mechanism, it only need a small amount of movement to work. You just need a section that can slide up and down that is from the switch trip travel. In the video above if you watch the lower mount parts they only move maybe 0.050". that trips the switch in the upward direction, the Z axis stops and then retracts downward with the Z axis movements to the up direction. I only have a long mechanist due to using a machine torch, using a hand torch the whole floating section could be 4". If you watch a video from the JD garage group theirs is very short.
I think this video will show what you are looking for with the Z axis and the floating head switch as on mechanist.

[GoodB0Y]

No I understand...

My z runs on two liner rods with 4.5 inches of travel and another roughly .5 for the floating head portion (ability to adjust the float gap). I used 8mm rods with two bearing blocks per side for the torch/bottom portion and one bearing block on each side for the floating head.

The top floating portion will pull the torch up and have light springs to assist on the down motion..although I bet that I won't need springs as it moves very freely... But I can have springs if needed

Or maybe I have it wrong lol

[GoodB0Y]

I have a rough z axis built just to see if it was going to work and if I could do it lol... Lots of stuff and precision fabricating has to be done in a tight area!lol... But I think I got it... I'll post a picture for comments when I have it finished. The only thing that worries me is mounting the stepper as it needs to be perfectly aligned...

[acourtjester]

You have a small about of misalignment that will be tolerated with a belt assembly, but do use pulleys with lips on them
Ok I was not sure if you did understand, great you do. I have never used springs on the floating head assemblies, as the torch weight is enough.
One thing you need to watch is the affect the hanging cable has as the torch moves around.

[GoodB0Y]

Ya I was thinking the 3 steppers and belts would be a little forgiving with alignment but actually they'll be the easiest as they will be mounted on easily squared surfaces... The z axis is a little harder for me. I bought a machinest square for the small stuff and thinking some thicker aluminum 3/8 x2 for the z stepper. Drilled and taped for 5mm bolts on the ends where it's mounts to the plate then the holes for the stepper itself ugh!

To answer my own question yes you can drill and tap 3mm in aluminum. I did it for my gantry linear rails and it seems to hold very well... My side beam for the rails will be.188 or almost 5mm just because the rails will be supporting the gantry

[GoodB0Y]

And if I could be honest for a moment... After I got the rails mounted to the gantry and the cart and z axis built...

I probably spent 20 minutes just sliding it back and forth! Haha! Linear motion is such a cool thing! I'm already thinking of what I can do with linear rails

[GoodB0Y]

So it looks like my gantry with all 4 steppers, linear rails, aluminum beam, end plates ect should weigh 27lbs...

The builders at linuxcnc and another site say that nema 17s (larger versions) should be enough...

True?

[acourtjester]

They are used by some but the table and assemblies are small, like 3-D printers and laser engravers. If you are starting a new build I would used Nema 23 motors and drivers that are sized for them. They do make different size Nema 23, the lower OZ/In that are shorter. But you may already have your motors. The one difference is the shaft sizes and this would also mean the pulleys bore size, (8 MM or 1/4"). Nema 17 or smaller. If you go to small the speed with suffer.

[GoodB0Y]

Ok thanks I appreciate your help

A 17 should be ok for the z axis cart?

And I'm thinking of 300oz.inch x 2 for the gantry drive.
Think that'll be ok?

[acourtjester]

Looks like the guy at JD garage is using a 17 on the Z, would not be mine but it your table.