DIY cnc Plasma finally underway

[welding shed]

The start of my plasma table it will have a little over 4 x 2 cutting area, myplasm components aside it will be a cheap no frills build.
still waiting on several bits one being a much shorter ball screw for the x and i need to chop down the rail on it also.

cnc plasma 3rd pic.PNG

cnc plasma 2nd pic.PNG

CNC PLASMA FRAME.PNG

[TJS]

Water table ? If so: Don't make the mistake I made. I made an angle picture frame with sheet welded in the center(edges of the angle..albeit my table is larger) to make the table. Get a piece bent up on a brake and weld the corners up. Use stainless.

[welding shed]

Thanks tjs my bodged attempt at the water table is here ive got to bully it into shape as well as patch it up but it should be ok.

[acourtjester]

Good show many DIY types here (Me too built a few tables from scratch), you will be very happy when you finish things up. Feel free to ask questions about things to help you along. Go ahead and assemble the parts you have to see if they need to be changed or not. That way you making progress and you will be able to change or upgrade later. You said you have had other CNC projects so you have the big picture and understand the software end too.

[welding shed]

Thanks pal

[tcaudle]

Using ballscrews for linear motion for a plasma table typically does not end weell

There are two reasons:
1. Linear speed is the motor RPM (typically around 800 RPM max be for it stalls under load) DIVIDED by the TPI of the lead screw. If you use a typical one of say 5 TPI you get 160 IPM. Means you have to cut thinner material at feedrates a lot lower than called for and deal with the increased kerf width, increase slag and diving torch. Numbers get worse if the TPI is higher.

2. Seems like a simple solution is to gear the interface between motor and ballscrew up to spin it faster BUT there is a physical limitiation call "lead whip" that occurs. The faster you spin a long screw the more it bends the screw form centrifugal forces. The smaller the screw the sooner it happens.. It will be obvious when it does because your table will vibrate and it can get violent.

One of the reasons you see most plasma tables built with rack and pinion or belt drive is because the ratios work the other way

Ballscrews are GREAT for routers and milling machines where accuracy is more important than speed. Since the myplasma supports neither you have some issues to address.

An ultra light gantry and a direst drive pinion to rack (smallest diameter pinion you can use ) will give you the speeds you need . Of course driving both ends of the gantry is best to prevent racking

[welding shed]

An ultra light gantry and a direst drive pinion to rack (smallest diameter pinion you can use ) will give you the speeds you need . Of course driving both ends of the gantry is best to prevent racking

Thanks' for the great advice folks
I see people out there running screws on the smaller machines and think i would be happy with those cuts but they don't show the limitations you pointed out so i might as well eliminate those while I'm at this stage.

I've now sourced rack and pinion.but i did originally want to stick to the solo X axis beam(60mm extrusion) but i fear now with it going to have rack mounted and the stepper moving along it as opposed to being fixed at the back end it might create issues, so i have to chew on whether to do away with that and go for a rail plus RnP either side.

Im also going to replace the tb6600 drivers i bought with DM556T

Thanks again darren

[acourtjester]

You do not need to have 2 motors to drive an axis, all the table I have built use a cross shaft to drive the axis on both sides with one motor. the cross shaft passes through the rail to drive both sides, works great. I have never had the out of square tables with dual motors sometime have.

2 tables 4x4 and new 4x8.JPG

DSCN1646 A.jpg

DSCN2120.JPG

DSCN1668A.JPG

[welding shed]

Nice idea,I haven't come across that one before.

[SegoMan DeSigns]

Sprocket heads Rule!

I had to do mine different than Tom's due to the weight of my gantry (400 lbs). I did not want to much side load on the motors so the X axis has its own chains with tensioners that the gantry bolts to, then the jack shaft that feeds the chains has a spring loaded ant-back lash and gear reduction,

IMG_20220705_001054743.jpg

IMG_20191109_165357214.jpg

IMG_20191220_183805509~2.jpg

The SxS was added to assist in acceleration and drifting around corners.

[djreiswig]

The SxS was added to assist in acceleration and drifting around corners.

It's the little details that make all the difference.

[weldguy]

Great looking build, be sure to post some pics when you have it completed!

[welding shed]

Great looking build, be sure to post some pics when you have it completed!

Thanks, I will do ,ive had to slow down...I've now settled on rack n pinion.. a closed loop stepper set up.
Gas has arrived so im just trying to finish off the water pan.