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MonoNeuron
08-18-2009, 09:08 AM
I built this thing last year and all but finished it off but had a bit of trouble with the torch height controller.

I didn't work on it for about 6 months due to wedding plans and I've just recently got back into getting it back on track.
I will post a few photos up here for you all to see.

I tried to buy cheap rack and pinions but couldn't get them for what my budget allowed so I ended up with a 1/2" roller chain drive which turned out rather smooth.

I first tried toothed belt but the stretch was just too much for a 3/4 .200 belt and the whole head would wobble when changing directions quickly.

I have made a few changes to the design over the year and I hope this one will last.

I think I will still change out the belt drive on the X axis for a chain drive just to make it all the same

The chain is about $36 for a 10 foot length and the sprockets are about $20 each.

You can't go under about 18 teeth on the sprockets as you end up with a bit of cogging and over 18 seems to be pretty smooth.

One modification I will try is to machine the sides of the sprockets with a slightly greater taper or make them pointier.

Rich.

MonoNeuron
08-18-2009, 09:13 AM
More

MonoNeuron
08-18-2009, 09:15 AM
still more

MonoNeuron
08-18-2009, 09:20 AM
and still a few more

MonoNeuron
08-18-2009, 09:22 AM
And here is a link on YouTube with it zipping around.

:-)

Rich.

YouTube - Plasma Small

Kwakaman
08-18-2009, 12:51 PM
Looks like it's coming along nicely, Mononeuron. What size is your table?, it looks massive! Also what size steppers are you using, and what sort of travel / cut speeds are you looking at? Be very interested to know. I'm sourcing / planing a similar build ( perhaps not quite as large a table) and any tips would be handy.
Cheers Kwakaman. :cheers:

Mongkol
08-19-2009, 08:43 AM
Rich,
I am waiting for looking the first cut of yours.

Mongkol

millman52
08-19-2009, 04:24 PM
Mono, I like how you have things arranged. Looks very stable What do you remaining to make the sparks fly??

Dustin407
08-19-2009, 07:14 PM
Mono, Everything looks very nice and solid. It looks well engineered and should last a lifetime. Thanks for sharing the pics/videos of your build. Are you going to keep it outside in the rain?

MonoNeuron
08-20-2009, 05:33 AM
Thanks guys.
There are still a few things to mend on it at the moment. I think after I get it cutting properly I will still change out the X axis belt drive for a chain. I have just a little wobble when doing 90 deg turns (about 1mm or so but enough to notice)
I now have a problem with the torch not doing the touch off properly with the MP1000C.

I set the plasma torch tip just on the job then when I run the program the torch lifts about the same height as the offset instead of lowering down to do the touch off, then it raises about twice the height then fires and after the pierce dwell it goes down the offset amount to do the cut.

I just remembered I didn't have the ground clamp on the job (ID 10 T error)
This might also account for me not being able to turn on the THC button next to the torch on button in Mach3.

The ground clamp was connected to the table about 3 feet away so it still may have been grounding somewhere but probably not very well.

The last cut I did buried the tip into the plate and stuffed another tip after 5 seconds. That's 6 tips I've gone through now and cut about 3 meters of cut path. these things are supposed to last 1000 starts. LOL
I much prefer it when the torch is way too high than low. It's much cheaper. I think I will slow everything down so I can minimize the tip burying problem and hopefully catch it before it goes too deep into the plate and then I can see the tip volts a bit better and monitor what is happening without looking in 3 places at once. This is the stage where we become one with our machines.

Since I reinstalled the software I haven't been able to get the THC button in Mach3 to light up. (had it before about 6 months ago). I really dislike weird problems. I can't find the relevant pin in the software to change to see if it works either.
We'll get there in the end but it's a slow process. I had heaps less problems with the laser setup and that was a PITA.
Patience really is a virtue. :-)
Rich.

MonoNeuron
08-20-2009, 07:29 AM
The table size is about 3 meters by 4 meters with about 100mm of Z travel.
The speed it moves doesn't really matter except for the rapids from one cut to the other and homing so the cut speeds are standard for whatever size plate you will be cutting with it.
I think Hypertherm set their fastest cut speed at 12 meters per minute which is about 1/2 of what the table can do with a bit to spare. I think it's outlined in the video.
X = about 30 meters per min
Y = about 20 meters /min
Z = can be whatever floats your boat with the way it's set up. Slow or Hyper Fast.
The spring balancing the head was just about a perfect fit and was a good find in the rubbish bin of my shed. Do our sheds really have a rubbish bin???. Aren't all things good to a "collector"

The only real drawback I can see with the table is the material handling issues. I would like a fork lift to carry stuff around but I don't have any concrete to drive it on and I don't have a jib crane to lift large plate on and off the table. It's something of a dilemma for me and while I try to come up with an idea the thing lives outside in the cold of winter and sweltering heat of summer. We only get 9" of rain per annum so rain really isn't too much of a problem here. I must get all my loans paid off and find somewhere to put it.
I would ask my step brother to let me keep it at his multi million dollar business premises if I knew he wouldn't take all my plate for free ????? when he ran out.
It's a quandary I will have to ponder for a little while yet.
All my sheds are full of "toys" :-)

I also have an idea for a material removal scraper for when parts fall through the table onto the floor and it will be something like a grader blade on tracks. I have mentioned this before and it's just getting the time to do it.

SWMBO has just got another job which involves night shift and I get to look after the shop on those really nice warm sunny days when she is sleeping, so I can't venture into my realm and potter. I only get to work outside when its a dust storm or raining. I take it all in my stride though, as I must. We actually had 9 dust storms last year and have had 3 this year. The drought is really affecting the whole country. But that's another story.........

Rich.

MonoNeuron
08-28-2009, 03:13 AM
I went back through all my literature yesterday and sat down and had a good read and finally came up with the result that I had left 2 wires off the sensor card that sends the voltage to the controller. Another ID 10 T error on my part.
I wired it up and changed the Z axis touch off switch pin to high and now I can get it to go through the motions and cut without burying itself into the job.
It's a good start.
I now just need to get the THC LED to switch on and off in Mach3 and all will be well.
Then all I have to do is go through all the setting up for speeds and feeds and amps and air pressure to get it to cut right.
I can then strip it down and fix the little things I have wanted to fix for a while and maybe repaint it and add some name to it (like RT Plasma) or something like it named after me and the little woman as it sounds a little bit like Arty Plasma.
I have so many plans for it and the first job I think will be to make a better enclosure for all the computer and drive stuff and get it out of the old washing machine tub. :-)
Rich.

MonoNeuron
09-06-2009, 09:29 AM
Tom came to my aid last week and suggested I put my license file in the Mach3 folder to register it. I am so damn stupid sometimes!!!!
The THC LED now turns on and off.
I was looking for something really hard and obscure but it turned out to be deceptively simple.
I wish I could fix most problems that easy.
I did a few test cuts and the torch bounced up and down really fast while cutting on the first cut but never touched the plate. I then set the anti dive switch to on and it performed really good. I now have a working plasma cutter......Clap clap clap etc.
it's a relief after all this time but I'm still not out of the woods yet as I have to get it all set for the different thickness plates and then set up the fine cut tips etc etc.
This will be the fun part.
Also I have to test the gantry for square cutting as I want this to be as good as I can get (within about 5 thou over 3 feet would be ok :-) )
I will also test the repeatability of the chain drive but I reckon it will be pretty good too as all the accuracy really is in the stepper motors.
I will set the pierce height to 0.120" and the initial cut height to 0.080" for the 80 amp consumables and take it from there.
I then have to do all the finer things like motor covers and parts scraper and bolting it down etc etc etc.
Now the fun part begins.............

millman52
09-08-2009, 07:59 PM
LMAO Things that make you go HMMMMMmmmmmmmmm!!

glasswoodmetal
09-10-2009, 02:52 PM
I a newbie here. I am trying to make a cnc plasma cutter. I do metal sculptures for reasons yet to be discovered. I had this idea to make my own plasma cutting cnc since I can't afford to buy one. I already made the x y table. it's about 3 foot square. It's crude, but I think it will work.

I also got two motors and a controller from a wheelchair. The motors are 24 volt.

I am guessing the controller would be quite difficult to program or impossible.

What are some cheap options for controller and software for cad to plasma cutter?

Are the free motors a cost savings or will they make finding a controller difficult?

Basically, where do I start? Controllers, software, or Motors?

Thanks,

Glenn

MonoNeuron
09-11-2009, 09:48 AM
Hi Glen and welcome to the Zone.

Probably the easiest way for you to go is with a stepper motor system as they are basically trouble free and very easy to set up if you follow the wiring diagrams.
You have a range of drivers at your disposal like the Xylotex, Gecko, SmoothSteper etc and it is up to you how much you want to spend.

There is so much to learn when you are first starting out that it can seem a bit daunting with all the information available at your disposal but if you take apart the machine into smaller finite pieces then it seems to make more sense after a while.

What you need.....

1 - size 23 stepper motors. (many and varied but aim for about the 1 - 4 volt range and up to 2.5 amps should be enough) You can drive stepper motors at about 20 times their rated voltage but you can NEVER go over their rated amps or you will burn them out. Steppers can be found in photocopiers and older large printers.

2 - stepper driver. As above or search on eBay for ones. Don't get sucked into buying full step drives as they are very noisy and vibrate the motor way too much to be useful. Aim for the 8-10 microstep drives (gecko has a cheap option and Xylotex are quite good also)

3 - Power supply. A simple transformer, Capacitor and bridge rectifier is about all you need. (A wiring diagram is on the Geckodrive.com website)

4 - Software. Corel draw - can be had on eBay for about $70 and up. SheetCam - for the G-Code conversion software and Mach3 - for the controller of the machine and switches etc. All very good programs and the cheapest (there are some free ones out there but they are not as functional)

5 - read, read, read these forums and get your teeth into what you are about to undertake. As I said earlier, break down each part into a separate item and you won't get into too much trouble. Read the wood router forums on table design then look at the plasma forums for the specifics you want.

6 - Ask a lot of questions BUT only after you have had a good search through the forums for what you want. If you can't find it then ask where to find the post you are looking for. Most people don't like to post the same answer 15 times. If you still can't find the thing you are looking for then ask away and you should receive a response very quickly.

This is such a fantastic repository for information and their shouldn't be too much that isn't already covered.
Above all have fun. This is so bloody addictive especially when you press the button for the first time and send the machine off on it's merry way. Sometimes not the direction you want it to. :-)
It becomes easier the more you read which should take you a few weeks to get to grips with.
I wish this site was here when I first started as it would have made life SO much easier for me and I wouldn't have wasted thousands on the wrong stuff.
Warm regards
Richard.

glasswoodmetal
09-21-2009, 08:48 AM
I am building a plasma cutter CNC from as much used material as possible -- not only because I have no money, but also because I like to reuse stuff. I have to admit, I have been cheating lately.

The table pictured below is about 90% recycled (mostly for free). The bolts and threaded rod were bought, as well as the skateboard bearings.

I tested the y-axis with my screwgun, and used the oxy-acetylene torch for the cutter. It looked almost like a plasma cut (except for the speed).

My lead screw came from a hospital bed. It is way too short. I ordered 2 lead screws from ebay.

I was trying to make my own circuit from parts, but gave up on that and bought a controller from the web. Yesterday, I hooked it up to the PC. It was exciting to see the motor spin.

Now I have to bolt everything together.

http://www.tikibuilder.com/IMG_8144r.jpg
http://www.tikibuilder.com/IMG_8152r.jpg

RUN-A-MUCK
11-19-2010, 07:10 PM
More

MonoNeuron,

Where / what are the V rollers that are riding on top of the angle iron rails? Are they the expensive presision ones, or did you find a cheeper version?

RUN-A-MUCK

glasswoodmetal
11-19-2010, 08:41 PM
I used a new set of skateboard bearings. $10 for 8. I tried used ones, but they were wobbly.

That was many generations ago. I have a more modern version in a video on my website Tiki Builder - Glenn Moore Tiki Artist Home Page (http://www.tikibuilder.com). I have experimented with a lot of bearings, lead screws, and tracks since the video on the website.

The machine has since been dismantled and scrapped. I want to try it again when I get more time and money. I am convinced that the machine must have reasonable linear motion tracks and blocks, and there are some on the web that are moderately priced.

My vintage esab 875 also created major problems. The old-tech high frequency arc starter wreaked havoc on the pc and controller. I tried the recommended grounding everything to the extreme, but still had problems with the arc jamming the motors. The final fix was to place the controller in a microwave oven case, ferrite cores on the wires, and shielded db9 cables for the motors.

Regardless of how crude a cnc has to be, I recommend to anyone that ever considered it to perservere at least until you get one cutout or drawing or whatever the goal is. I will remember for as long as I live the first time my machine started, cut out a circle and stopped.

millman52
11-19-2010, 08:53 PM
MonoNeuron,

Where / what are the V rollers that are riding on top of the angle iron rails? Are they the expensive presision ones, or did you find a cheeper version?

RUN-A-MUCK

The wheels are like these or maybe ARE these: V-groove wheel #2 (http://www.cadcamcadcam.com/v-groovewheel2.aspx)

glasswoodmetal
11-19-2010, 09:07 PM
They are regular sealed skateboard bearings -- I put them like this:

locking nut - Bearing - washer - Bearing - Washer - angle iron - Bolt

the angled ones look cool, but I was on an extreme budget - used, cheap, or free. I only bought new if I couldn't find it used.

At one point, i took wheelchair bearings and tried to grind a groove with a cutting disk on a body grinder. I couldn't get it accurate enough.

MonoNeuron
11-21-2010, 05:16 AM
I have a small metal lathe that I made my rollers for for the X and Y axis but I ended up buying the size #3 rollers from VXB bearings on the web for the X axis.

The Y rollers were made from molybdenum disulphide Nylon which is black in colour and has pretty good wear resistance and lubrication properties. $90 for a 2" stick 3 feet long 3 years ago.

I made the rollers for the X axis but didn't machine them very accurately and they wobbled about 0.005 which is unacceptable for me and I couldn't be bothered remaking them so I bought the #3 size and slapped em on.

I wanted the high tensile nylon rollers due to their zero electrical conductivity which I thought would make the table a little bit more resistant to stray electrical currents. Does this make a difference??? Maybe not but I feel better about it .:-)

When I get it up and running I am going to make new side plates for the gantry to spread the load across the rollers a bit better as it seems to want to topple over forwards when stopping for corners or sharp turns. All small design faults that can be rectified with a little effort.

I also ended up changing out the x axis belt for a chain drive and it is so much better. I also had a really good look at the motion of the drives and found the Y axis drive belt from the motor to the drive gear would stretch a fair bit indicating that there is way too much weight for the poor little thing to be able to drive the gantry fast so doing corners or circles would make them come out wrong. Circles were more like rounded corner squares

I have ordered 3/8 roller chain for this and plan on gearing it down about 4-5 to 1 reduction to take a bit of strain off the motor.
I also swapped the Y axis motor to the X axis which is a 5 phase size 96 1.4 volt and fitted a 5 phase size 96 2.8 volt high speed motor to the Y axis.
The performance gain is very noticeable.

I also now have problems with the torch height controller not going up and down again. I though I had it all worked out but I didn't.

I think I have a ghost in the machine...............
But I am getting there slowly.
I really am jealous of the people who build these thing and they just work......
Rich.

RUN-A-MUCK
11-22-2010, 04:47 PM
How well do the angle iron rails work? I have seen other people use that concept, but I haven't seen any report about how effective they work.
I want to build my table as cheep as I can, and I could save a bundle if I can use angle iron for the rails. I know it's not "precision" but are we talking about a huge error or 2-3X what the precision rails would do.
There must be some way to put them down straight.

millman52
11-23-2010, 08:10 AM
How well do the angle iron rails work? I have seen other people use that concept, but I haven't seen any report about how effective they work.
I want to build my table as cheep as I can, and I could save a bundle if I can use angle iron for the rails. I know it's not "precision" but are we talking about a huge error or 2-3X what the precision rails would do.
There must be some way to put them down straight.


I used Cold rolled round bar with bearings 90 deg. apart for my table, it has worked fine. see sketch below It's more work to install but is easily replaceable if wear develops.

the angle iron for a rail should work ok. There is a bit of roughness to the finish of hot rolled steel but I'd think once the black mill scale wears off you should have a decent running surface

MonoNeuron
11-23-2010, 08:35 AM
The angle iron is surprisingly even in shape and if you get a length that hasn't been mishandled then they are also pretty straight. I used a vernier across the top of my rails when I was welding them in place just to see how much it would vary when I clamped it down to weld and it was within 0.002". Well within the tolerance of a plasma cutter.

You can set up some Ni-chrome wire along the length of where you are going to weld it to make it straight or you can make a small jig and clamp it to the side of the rail you are going to weld it on and pull the angle iron against it and tack weld it in place. You don't need 1" welds along the length as a lot of small tacks work very well and also doesn't distort the frame any noticeable amount.

I just made two small jigs from 1" angle iron and used them to set up a guide for welding.
I did notice one of my top rails on the gantry has a small wave in it but it is about a 2 hour job to replace it and I might do it one day but the bottom rail is straight which tends to balance out the wave by about 1/2.

I'm not too worried about it but it might make a difference to long critical jobs as it's only about 1 foot of it that is warped.
I think the rails will last a very long time with a spot of lube on them occasionally.

Rich.

millman52
11-23-2010, 01:27 PM
Wear will almost be non issue. The V bearings have a bit of wiping action as the mating sides rotate along a v rail. This is a good thing with routers etc where wood dust may tend ot pack or stick to a rail. With plasma cutting it will be abrasive dust the would tend to act a bit more like grinding compound. Even still wear will be minimal.

I was afraid of wear on my cold rolled mild steel round rail but almost 3 years of pretty hard usage has put but very minor flat spots along the full length of the round bar. Completely non issue. The oposite side of my table has a piece of cold rolled flat bar that standard ball bearings roll in contact with. it has done nothing but create a black line. No apreciable wear. All in all I'm convinced mild steel rails as long as they are straight & true are as good as any for a plasma table. Especially one that isn't going to used 8-16 hrs per day every day of the week. In that case you'd probably want to think about using hardened precision rails that are installed to be a replacable wear out type of part.

RUN-A-MUCK
11-24-2010, 09:42 PM
Thanks. I was hoping to be able to use CRS Steel to really reduce my table costs. Sounds like that should be fine.

MonoNeuron
12-30-2010, 04:45 AM
I just had a read through this thread again and I was thinking about the cold rolled steel bar. Even if it did wear 20 or even 50 thou on top it still wouldn't matter if you had a torch height controller to compensate for wear.

The only time you would have problems is with side wear and seeing as though most of the weight of the gantry is coming from gravity pushing down, the only time you would get wear would be from quick turns at 90 deg and such which wouldn't have too much bearing on the overall problem. If you only used 1 guide rod on one side and just had the other side rolling along a flat bar just to keep the height the same then the only wear you would have would be on 1 bar which would be easily replaceable.
Especially if it was clamped down and not welded.

ANY rolling action is better than ANY sliding action.

Make the guides out of anything you have handy that is straight and hard.

two cents worth.
Rich.

MonoNeuron
09-30-2014, 01:49 AM
Just an update on this machine.
I never did get the thing working to my satisfaction. If it was 1/2 the size then the roller chain would have been fine. It worked really well for 1/4" steel and up but thinner stuff had to be pushed faster which introduced way too much wobble in all the axis.
I also had another problem which had me a bit worried. The missus was having a shower one day and was saying she was getting an electric shock from the taps. I didn't remember screwing any screws in the walls for ages and probably hitting any wires ( home under renovations ) so I jumped in after her and indeed was getting shocks from the taps but only when the heater in the room was on warming the area. We got the sparkies around and they tested for a while shaking their heads solemnly and then told me we have 90 volts at 9 amps running through the house. Crikey. We could have been killed! Turns out we lost the neutral line on the power supply pole so all the power was going through to ground and electrifying the house.
I was using the plasma cutter that morning and then it wouldn't run again after that and after 3 months of emails and testing ( I work 7 on 7 off, 12 hour shifts so don't get a lot of time to test stuff especially outside in winter) , we found the Hypertherm 1250 motherboard had fried a critical circuit and was now toast. I got this replaced by the supply company through their insurance and they were pretty good about it. Probably better off replacing a mother board than having 2 funerals.

About 1 year to the day the same thing happened again but I didn't have the plasma cutter set up at that time so it didn't get fried. The fault was intermittent so they put a monitor on the lines and 2 weeks later found that the neutral connection at the pole was loose causing intermittent faults. The connection thread was burnt from the previous fault and the wire couldn't be tightened properly. Such is life I suppose.
After all the problems and numerous faults with all electrical things in the house I ended up stripping down the plasma table and will rebuild it in the future when I get time. Which isn't much now a days.

I will go with rack and pinion drive for the next build which I think is the only way to drive a plasma table due to the speeds involved and having to do 90 deg sharp corners that puts a lot of load on the set up. I bought a few sticks of rack from and eBay supplier in Melbourne called "CNC and Cupcake World" and they have 1 and 2 module and some gears to suit and all have hardened teeth. And a very good price to boot.
When I built the original table the rack and pinion available was far too expensive to buy for domestic use so I tried to find an alternative but really, none were suitable for a big table.
See you all in the future for the next plasma, laser and 3D printer builds.
Rich.

kermit582
10-10-2014, 08:06 AM
just wondering if you could turn plasma cutter down and then slow table speed?