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What to do with old plasma table

There is another axis stacked on the Z but it is not powered it only slides, it usually has springs to keep the torch at the bottom of the travel so when the the Z drives down it goes until the float switch trips, then retracts a certain number of steps allowing you to dial in your pierce/cut height to the .001" of a inch.

This is a decent explanation.
 
CarterKraft said:
There is another axis stacked on the Z but it is not powered it only slides, it usually has springs to keep the torch at the bottom of the travel so when the the Z drives down it goes until the float switch trips, then retracts a certain number of steps allowing you to dial in your pierce/cut height to the .001" of a inch.

This is a decent explanation.
Click to expand...

Interesting. I imagine that works fine for smaller cuts, like in the video, but ohmic sensing is better for longer cuts, since it is sensing real-time and can adapt for big gradual bows in large plates?
 
patooyee said:
Interesting. I imagine that works fine for smaller cuts, like in the video, but ohmic sensing is better for longer cuts, since it is sensing real-time and can adapt for big gradual bows in large plates?
Click to expand...
Once the torch has fired and cut established (time delay from torch fire) the torch will switch to THC and use the raw arc voltage measured by the Torch Height Controller to keep the torch at the correct height with OUT contacting the plate.
 
One problem that I ran into with my table using ohmic sensing is sometimes the torch tip would hit a bit of slag or something that would insulate it. Z would keep going down until my magnetic torch breakaway kicked in. I have now added an air blast when touching off and a floating head with a limit switch that acts as an overtravel alarm. Just finished the project (Still have to improve the wiring situation) but so far so good. It is much less violent now if it happens.


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Eric642 said:
One problem that I ran into with my table using ohmic sensing is sometimes the torch tip would hit a bit of slag or something that would insulate it. Z would keep going down until my magnetic torch breakaway kicked in. I have now added an air blast when touching off and a floating head with a limit switch that acts as an overtravel alarm. Just finished the project (Still have to improve the wiring situation) but so far so good. It is much less violent now if it happens.


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Click to expand...
Nice work on that setup.
 
CarterKraft said:
I found when I was trying to wrap my head around all this stuff was to actually use the manuals for the stuff I was looking at to help teach me the stuff I didn't understand, that made a lot more sense to me and I was able to better follow what I was trying to accomplish.
This is the Myplasm/Promo instructions
THC stuff is around page 22


MyPlasm CNC System - Proma-Elektronika

proma-elektronika.com proma-elektronika.com
Click to expand...
I'm confused about ohmic sensing. I've seen references to using the torch tip as the probe but then I've also seen a separate, stand-alone probe referred to as an ohmic sensor. (Often they're green.) Are these just two ways to do the same thing, or something entirely different?
 
patooyee said:
I'm confused about ohmic sensing. I've seen references to using the torch tip as the probe but then I've also seen a separate, stand-alone probe referred to as an ohmic sensor. (Often they're green.) Are these just two ways to do the same thing, or something entirely different?
Click to expand...
The only one I am familiar with uses the actual torch shield/tip to do the sensing.
If using a Hypertherm there is a separate shield part number with a 1/4" spade terminal for attaching the sensing lead, as seen in the above example by Eric.

1709932030112.png

Plasma, waterjet and laser cutting systems from Hypertherm

Hypertherm makes industrial cutting systems, software, consumables and accessories. Information available in 11 languages.
www.hypertherm.com www.hypertherm.com
 
I'm going to have to buy 2 motors no matter what. I want another for my y-axis and I'll need one for my THC. Would it behoove me to use my current nema 24 from my y-axis on my THC and then get two higher torque nema 24's for my Y-axis? Or is there a reason not to mix motor sizes?
 
patooyee said:
I'm going to have to buy 2 motors no matter what. I want another for my y-axis and I'll need one for my THC. Would it behoove me to use my current nema 24 from my y-axis on my THC and then get two higher torque nema 24's for my Y-axis? Or is there a reason not to mix motor sizes?
Click to expand...
I was thinking about that when this started, using one of your current motors for the Z would be pretty smart I think, IMO the Z is the least critical axis to drive, not much weight and accelerations are low.

I used a much smaller nema 23 motor on my Z but used the same drives for all, that gives me flexibility of having swap ability etc. between them.
 


At this point of this video, what are the capacitors and rectifier he is referring to? I don't see those in the system diagram.

Also, in this part of the diagram, I'm pretty sure the component on the left is the power supply, but what is the larger component to the right of it?

1709934666743.png
 
patooyee said:


At this point of this video, what are the capacitors and rectifier he is referring to? I don't see those in the system diagram.

Also, in this part of the diagram, I'm pretty sure the component on the left is the power supply, but what is the larger component to the right of it?

1709934666743.png
Click to expand...



Just from looking at this image I'd say the smaller device on the left is the 24v DC "field" power supply powers the limits/home switches ohmic sensor etc. the larger box on the right is the power supply for the axis' drives. 48v in this case, usually 36v-70+ depending on drives/motors chosen.

edit: watched the clip. these are two types of power supplies AC>DC
The capacitor/rectifier setup is for a unregulated "linear" power supply like this Unregulated Linear 1440W/72VDC/20A Toroidal PSU
The enclosed boxes are switching power supplies and don't need any of the extra components.
I am using switching but its common to use the linear for the stepper/servo drives.
 
any sort of 3d part will fail just because of heat exposure
lifter station, the idea is great, but it will not last long
 
patooyee said:
I'm going to have to buy 2 motors no matter what. I want another for my y-axis and I'll need one for my THC. Would it behoove me to use my current nema 24 from my y-axis on my THC and then get two higher torque nema 24's for my Y-axis? Or is there a reason not to mix motor sizes?
Click to expand...

I'd go 34's on x and y and flip a 23 to z and you'll have the other as a spare.
 
bgaidan said:
I'd go 34's on x and y and flip a 23 to z and you'll have the other as a spare.
Click to expand...
If I go 34's on Y I have to change all my bracketry. You don't think that going from a single 178 oz/in 23 to 2x 270 oz/in motors would be a sufficient upgrade? That's 3x the power that I used to have. While it was less than ideal, the single 178 did what I needed most of the time. The only time it didn't was when there was something physically wrong. (Which was often. :) )

X is the only axis I never had a single issue with. I see no need to change motors there.
 
Here is an evolving shopping list that I'm making. Feel free to make suggestions or fill in the blanks.

Shopping List
 
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patooyee said:
If I go 34's on Y I have to change all my bracketry. You don't think that going from a single 178 oz/in 23 to 2x 270 oz/in motors would be a sufficient upgrade? That's 3x the power that I used to have. While it was less than ideal, the single 178 did what I needed most of the time. The only time it didn't was when there was something physically wrong. (Which was often. :) )

X is the only axis I never had a single issue with. I see no need to change motors there.
Click to expand...
I think that's solid plan, I thought we were still guessing about motors.
I feel like I put bigger motors on my 3x3 table...

Edit: my X/Y motors are 425oz/in, not sure the closed loop are worth it just yet. I am running them open loop still, haven't worried about cause it works open loop just fine.

STEPPERONLINE Closed Loop Stepper Motor 1 Axis CNC KIT 3.0 Nm/424.92oz.in Nema 23 Motor & 0-8.0A 24-48VDC Closed Loop Stepper Driver CL57T V4.1 Amazon.com
 
CarterKraft said:
I think that's solid plan, I thought we were still guessing about motors.
I feel like I put bigger motors on my 3x3 table...
Click to expand...
Haha, we were until shortly before that post. I found that there only seems to be 3 sizes / strengths of 23 motors. After I started looking up photos of them it was obvious that I had the smallest ones, which are 178. 270 is the middle size. I forget the next one up but it requires a bigger driver, so I figured I'd skip that so as to keep all my drivers the same.
 
patooyee said:
Haha, we were until shortly before that post. I found that there only seems to be 3 sizes / strengths of 23 motors. After I started looking up photos of them it was obvious that I had the smallest ones, which are 178. 270 is the middle size. I forget the next one up but it requires a bigger driver, so I figured I'd skip that so as to keep all my drivers the same.
Click to expand...
There's some good discussion of acceleration/IPM in this thread that might help you lock in to a motor size drive ratio etc.

 
SomeGuyFromOlympia said:


This is what I was referring to
Click to expand...


One nice thing about not doing this for a living is that I can afford some down time to experiment a little, especially when it comes to printing stuff like that, that is nearly free to me. I am printing a version of that floating head right now. (It's a remixed version that bolts directly to the plate of the Openbuilds z-axis that I ordered.) I'm trying it with ABS first and, if that doesn't work out, will use PETG. Both of those materials withstand heat way better than PLA. There's also some carbon fiber filaments that get annealed after being printed that might be worth trying, we'll see how far my patience takes me.

At this point, I'm being really conservative with my spending until I find out what my tax bill is going to be. So things in this thread may go quiet for a bit but it will not die. I am 100% committed to getting this table back up and running at this point.
 
patooyee said:
One nice thing about not doing this for a living is that I can afford some down time to experiment a little, especially when it comes to printing stuff like that, that is nearly free to me. I am printing a version of that floating head right now. (It's a remixed version that bolts directly to the plate of the Openbuilds z-axis that I ordered.) I'm trying it with ABS first and, if that doesn't work out, will use PETG. Both of those materials withstand heat way better than PLA. There's also some carbon fiber filaments that get annealed after being printed that might be worth trying, we'll see how far my patience takes me.

At this point, I'm being really conservative with my spending until I find out what my tax bill is going to be. So things in this thread may go quiet for a bit but it will not die. I am 100% committed to getting this table back up and running at this point.
Click to expand...
I'm using some ca glued pla torch mount, its just a "get it working" place holder but so far so good.
 
I'm getting ready to order Myplasm. Anyone got an idea what a voltage divider is for / what it does? Do I need one?
 
I think the voltage divider goes inside your plasma unit and gives an output so you can run a torch height control.
 
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