1st build: Router/Plasma

[krebsatm02]

I've been looking into building a plasma table for a couple years now, mainly too help me justify the cost of buying a plasma cutter. Well I haven't been serious up until a month ago when I found this site. Much to my amazement I found out you also hook up a router with out too much more trouble.

Goals: To build a quality 4' x 8' table with only plasma at first since a router will cost a bit more for the extra contoller.

Plan:

1st: figure out if the motors I have will be adequate, and find out there specifacations.

2nd: figure out the drive system and what compents I will use

3rd: purchase drivers and other parts (rack and Pinion, bearings, etc...)

4th: build table

So I've been scrounging around work and through friends and have found a couple motors I think will work well.

Components:

Motors: I already have 3 servo motors which I think will be suitable, problem is I don't know a whole lot about them. Two of them are identical motors from Globe motors. One has a good encoder and the second looks like someone dropped it on the encoder. The third motor is smaller but has a gear reduction. It also has an encoder which looks fine. My plan is to use the to identical Globe motors for the X and Y and the unknown motor for the Z.

I've hooked up the motors to the power supply that came with the unknown motor. The power supply is rated at 24 volts and 5 amps. It spins the unknown motor very well, and the 2 globe motors about half as well. The only info on the globe motors is 75 VDC, so I'm assuming they'd spin much better with more voltage. I'm in the process of aquiring more info about the Globe motors, but they said the motors are propreitary to Datatek storage systems and won't give me any info.



Controllers:

I guess I'm going to either go with Rutex or Gecko since I'm using the servos. I really haven't found any other choices that go up too 75 volts.

Drive system:

I know for the X axis I want to use rack and pinion. Haven't decided what I want to use for the Y, possibly rack and pinion also to keep it uniform. For the Z I've found 3 acme screws at work that came with the unknown motor and powersupply.

X axis track:

I work in a machine shop at a university and we have about 60 ft of left over 1" X 1" 6061 aluminum square tubing. I've found a few pieces which haven't been molested and are very straight. I've been thinking of turning them up on edge so instead of using them flat they would be like a diamond so crud would fall off easier. It makes mounting them a little more complicated, but I've got access to a TIG welder and can come up with something.

Gantry (Y axis):

With the motors also came a 5 foot long 4" x 4" square carbon fiber tube that was used on a robot to run a backup storage system. I'd like to use it for the main beam of the gantry as it is very strong, rigid, and light weight. It came with a couple rubber coated bearings that ran up and down it that I can use to attatch the Z axis too. Anyone see any problems with this?

Z axis:

I'll use the acme screw for the drive system on the Z. At first it will be in operable, but when funds recover I'll add the controller so I can hook up a router and what not.


I'm researching the motors, controllers, and powersupply at the moment and thats what I want to tackle first. I've been reading on how to build a power supply and it doesn't look to hard. All the other compents that need to be built shouldn't be a problem as I have access to mills, lathes, and a TIG welder at work. At home I have a MIG, chop saw, torch, and other tools...

Looking forward to finding out information and start building! Thanks for the help. - Doug

[jcc3inc]

Sir,

If you will email me, I will send you pix of the router system which I made. While it was Primarily a test bed, It also does work as a router. I have used some novel (I think) ideas in the construction.

As you are probably aware, the force required in plasma cutting is only frictional drag + mass x acceleration. For routing you will have to add the router cutting resistance. A higher HP router will need considerable additional force, plus introducing vibration and deflections of your structure.

Regards,
Jack C. jccinc-at-owc-dot-net

[PaulH]

Why don't you post your pictures here in the gallery where all of us can benefit from your experience?

[jcc3inc]

PaulH,

See my pix in Skate Bearing Design.

Thanks,
Jack C.

[krebsatm02]

ok got the specs back on the motor:

537a194 - Kt=3.21 ozin/amp, R=8.9 ohms, at 78 VDC: 40 ozin, 2700 RPM,
1.55 amps.

From just briefly looking before I go to work 40oz/in seems pretty powerful, is this correct?

Also, what does the Kt=4.31 ozin/amp mean? Is this an effieciency rating, or am I way off?

[chuckknigh]

40 oz in is actually on the small side. Depending on your purposes for the machine, it may be sufficient, but it's hard to go wrong with MORE POWER! (Tim Taylor grunt)

Just for reference, the HP LaserJet printers (models 1, 2, and 3) each had a single steper motor that ran the printer functions. It was 100 oz in...in a printer!

-- Chuck Knight

[krebsatm02]

Originally Posted by chuckknigh 40 oz in is actually on the small side. Depending on your purposes for the machine, it may be sufficient, but it's hard to go wrong with MORE POWER! (Tim Taylor grunt) Just for reference, the HP LaserJet printers (models 1, 2, and 3) each had a single steper motor that ran the printer functions. It was 100 oz in...in a printer! -- Chuck Knight

Hmm... maybe he wrote the wrong number down, maybe he meant 400? It seemed like a pretty big motor to me compared to others I've seen. Does it seem like it should be more? It's 55.035 Long x 2.110 in diameter with a .240 shaft diameter.

After looking into this more it seems as though I'll have to have a worm drive hooked up to use a rack and pinion. I'm looking for information on worm drives right now, but anyone have a ballpark figure of what they cost?

Thanks - Doug

[jcc3inc]

Doug,

I'd like to advise against a worm drive; we used worm-and-wheel on a few machines we made, and found them to be unsatisfactory.
1. Efficiency is low, maybe 20-30%
2. We had problems with lubrication

We went to spur gear reduction, about 20:1 and found this to be a far better approach.

One of your motors seems to be a Pittman; it would be fine if it is in the right range of speed/torque. We used motors of a similar size on our plasma machines (4 x 4/8 feet). 250 IPM was no problem for us. I used linear DC amplifiers (very simple design) and never had any problem; the drive force for plasma is mostly F = MA with little frictional drag.

Regards,
Jack C.

[Henning Bitsch]

Hej

I have buldt a plasma cutter on a old manual router tabel with SKF skrues,
And i have bought a complet drive system from Maxnc the max 15 LC2 with dobbelt stack motors it is working ok , i have a small noice problems ,right now i am working on a heigh control system. I wold like to have some windows baced software replacing the Maxnc software.

Henning

[2muchstuff]

Got any more of that carbon fiber tube.