torch reference question.

[cruz]

hi everyone,

this might be a extremely stupid question but here goes:
I have a plasma table with a floating head.
When i want to cut something, i zero out the Z-axis by using a small 2mm plate.
I adjust the height of the torch until the 2mm plate just goes between the torch and the plate i wanna cut.
Then i set the Z-axis height as 2mm.

but sometimes a plate has a bow in the middle, the torch then pierces too close to the plate and almost always destroys the cutting nozzle.
I know there's a setting in the sheetcam post processor for the reference distance,
but doesn't that require ohmic sensing?

Or does that setting still work when not having any ohmic sensing?
The only height reference the table has comes from the proma THC, but isn't that only for during cutting when there is an arc?

A other issue that might be relevant:
i cant use the volt setting giving by hypertherm for my powermax105.
i need to use way less volts then said by hypertherm, otherwise the torch cuts WAY too high.
i need to use about 24 volts less then what the book says to have a somewhat correct cutting height.

would appreciate help or info.

thank you

[tnbndr]

A true floating head as I know it would follow any contours of the sheet as typically several rollers carry the torch head at a fixed height but it actually follows (floats) with the sheet contour.
You appear to just have a fixed height torch.
Your need to provide more information on torch, software,etc before anyone can be of much help.

[cruz]

I've attached a picture of the head setup maybe that helps, sorry for the dirty water

The reason I'm thinking it's a floating heads is because the whole torch assemble can be lifted along the guide rail you can see on the picture.
That whole assembly is then connect to the Z-axis motor, but i can always glide the torch and its mounting plate up and down.
Also the torch is mounted to the mounting plate with a magnet, for not damaging the torch when colliding.
if the torch mounting plate with the torch moves from its position, the machine/mach3 goes in emergency stop.
software is: inventor autodesk for CAD
sheetcam for CAM
mach3 for controlling the table

[robertspark]

Picture?

[acourtjester]

The question I have is what model Proma do you have (there is a 150 or a SD). To add a picture you click on the "Full Edit & Preview" below the box you enter your post in (where you type your question) sthe screen changes to have a "attachments" tab below. click on that, and a screen change shows a small box "add files" when you click on that you will see a folder on you hard disc. Move to where you have the picture stored and click on it, If the image can be uploaded you will see a box with the picture name and on the right the status with a green check. you then
select where in you text you want to add the picture and click on place inline. this will place the picture name in the text area. then click on submit. If you do not get a green check in the status it will not place the picture, you will need to reduce the size of select another picture.

[tcaudle]

IHS (aka "touch off") is a required step for automated cutting. The whole concept of THC is to account for warped or non-flat material. With the 105 you only have about .010 tolerance up or down from the recommended .060 cut height before there are problems. Pierce height is typically a little over 2X cut height. The THC does not do IHS (inless its a toial stand alone model that has the sequence built it. Two things are required: A way to sense the material and the code to use that sense and position the torch each time the correct distance above the material no matter where the material goes. Now, there is a difference between a floating torch head and a floating torch HOLDER (mount). The latter lets the torch float independent of the Z carriage in the vertical plane, and is typically mounted with a switch that acts as the sensor. Its a mechanical touch off (versus ohmic) . A lot of tables just have the one sensor. So the touch off sequence moves to the pierce point, lowers the torch slowly unitl it trip sthe sensor switch (by pushing the torch up and tripping the switch. It then lifts the torch by the SWITCH OFFSET amount (varies with the touch of switch mounting ) and re-zeros the Z position (torch on top of material) once it knows where it is it lifts to pierce height fires the torch then plunges to CUT HEIGHT and starts the cut.

While ohmic sensing is more elegant it has drawbacks. It can and will miss from time to time and you have to have a backup sensor that keeps the Z from mashing the torch into the material until something breaks.

Trying to cut with a table with no IHS is a exercise in frustration because if there is even slight variation in material height it messes up the pierce and often trashes the consumables

[cruz]

here's the picture

and oh yeah
Model of the THC: Compact THC Controller 150

[cruz]

also i'm using the "mach3 plasma" post processor.
this is the current touch off sequence (after i've zeroed the z-axis like i explained in my first post):
- torch goes to the rapid clearance height
- torch goes to the pierce point
- torch goes to the pierce height and pierces
- torch goes to the cut height and cut the part/shape
after that the torch goes back to the rapid clearance height and start everything over.
it doesn't reference the plate height during the whole cutting process.

whats weird to me is that it doesn't seem to have any "reference tool" built in . only the proma compact 150 but that's for during the cutting right?

is this something which can be added to the machine easily?
something where the torch physically touches the plate than updates that as the zero for the Z-axis.
so that each pierce happens at the the perfect height.

i don't want ohmic sensing because of the watertable, the ohimic sensing might reference the height from any water om the plate.

i'm just giving all the info i know i think might be relevant, if you want more picture i take some tomorrow.

thanks everyone

[tcaudle]

That is because MACH3 Plasma is for a table with no THC and therefore NO IHS. That system appears to have a proximity sensor at the top for something. Is there no instructions from the vendor? These are basic things that should be covered in a products instruction manual.

[cruz]

That is because MACH3 Plasma is for a table with no THC and therefore NO IHS. That system appears to have a proximity sensor at the top for something. Is there no instructions from the vendor? These are basic things that should be covered in a products instruction manual.

the sensor is for when the magnetic breakaway torch holder moves because of a collision.
it then sets the machine in emergency mode, you have to put the torch holder back in its place and reset mach3.

nope nothing about it in the manual (long story about after service from the vendor).
can a IHS be added to the machine without too much work and modifying the machine?

[djreiswig]

If your z axis raises up slightly when you run the torch down and into the material then you should be able to add a switch to sense this and detect the material. I'm not sure what controller you have, but if you have a spare input you can assign your new switch to z-home in mach3. Then you need to find a post for SheetCam that does IHS and program the switch offset measurement. Then you should have what you need.

Ohmic works fine with a water table. After the first reference, the post flow keeps the water off of the material. Only issue is if your material is painted or very rusty.

[cruz]

If your z axis raises up slightly when you run the torch down and into the material then you should be able to add a switch to sense this and detect the material. I'm not sure what controller you have, but if you have a spare input you can assign your new switch to z-home in mach3. Then you need to find a post for SheetCam that does IHS and program the switch offset measurement. Then you should have what you need.

Ohmic works fine with a water table. After the first reference, the post flow keeps the water off of the material. Only issue is if your material is painted or very rusty.

oh okay, if i wanna use the ohmic sensing, do still need the switch for the Z-axis?
what i'm trying to ask is:
when i wanna implement ohmic sensing what would the setup be?
- upgradeing the retaining cap to one with the ohmic sensing wire connecting.
- what else? i assume i need to wire it in with the Z-axis in someway?

in terms of adding a IHS without too much work or making changes to the machine wich would be easier ohmic or floating head with the switch?

[djreiswig]

For ohmic you will need some sort of module. If you have CandCNC electronics you can buy their FeatherTouch. Otherwise there is a waterswitch some people use.
The switch method is probably the easiest to implement. It isn't as accurate if you do a lot of thin material that will flex when the torch touches it. If you use ohmic you still want the switch, but it gets wired as estop in case the ohmic fails, it keeps from crashing the torch into the material.
If you tell us what kind of controller you have it will help us to help you figure this out.

[acourtjester]

There may be some that disagree with this but if you are using a BOB board with Mach 3 you can wire all the home/limit switches in series. And have a floating head switch attached to the torch mount to detect the metal surface, these are wired as normally closed.This would use the G28 command for the Z axis in the g-code. When the torch moves down (homing action G28 Z) and touches the metal the torch moves up and trips the floating head switch. The g-code will then zero the Z DRO and go to the pierce height. If you add a ohmic sensor (feather touch) it gets wired as a separate switch (Z home position). But reacts when the torch touches the metal surface and works the same, but the floating head switch now worked as a safety if the ohmic sensor does not work. If you use the water switch unit it uses the G31 Z command and is wire in as a Probe and works as a Normally open switch, the floating head switch still works as a limit/safety. I have done this with tables I have built. And yes you will need the adapter on the Hypertherm torch for the contact wire, and work better if the common return is connected to the metal being cut, both the plasma work lead and the BOB common connection. Here is a floating head switch with a slide like yours.

floating head parts.JPG

floating head parts (15).JPG

floating head parts (12).JPG

[cruz]

oh yeah forget something quite important:
the torch assembly has a second proximity sensor on the base of the torch holder.

the first picture shows both the sensors, the one above is for the magnetic breakaway torch.
the second sensor to the left of the guide rail is the one i forget mention.

IMG_20190106_173420.jpg

IMG_20190106_175847.jpg

when the torch is in the down position the senor rests on the plate beneath it and the led of the sensor is on,
when you slide the torch up the led goes out and in mach3 the digitize signal is on then.

IMG_20190106_175953.jpg

here are some pics of the bob and some other pictures.

IMG_20190106_173009.jpg

IMG_20190106_172950.jpg

IMG_20190106_172905.jpg

[tcaudle]

That is because MACH3 Plasma is for a table with no THC and therefore NO IHS. That system appears to have a proximity sensor at the top for something. Is there no instructions from the vendor? These are basic things that should be covered in a products instruction manual.

the sensor is for when the magnetic breakaway torch holder moves because of a collision.
it then sets the machine in emergency mode, you have to put the torch holder back in its place and reset mach3.

nope nothing about it in the manual (long story about after service from the vendor).
can a IHS be added to the machine without too much work and modifying the machine?

You already have it . You just need to figure out the bottom touch off sensor and how to wire it and set it up as the mechanical Touch off.

[cruz]

That is because MACH3 Plasma is for a table with no THC and therefore NO IHS. That system appears to have a proximity sensor at the top for something. Is there no instructions from the vendor? These are basic things that should be covered in a products instruction manual.

the sensor is for when the magnetic breakaway torch holder moves because of a collision.
it then sets the machine in emergency mode, you have to put the torch holder back in its place and reset mach3.

nope nothing about it in the manual (long story about after service from the vendor).
can a IHS be added to the machine without too much work and modifying the machine?

You already have it . You just need to figure out the bottom touch off sensor and how to wire it and set it up as the mechanical Touch off.

any suggestions on how to do that?
i'm not so known in the world of cnc programming en making changes to the cnc table.
is it a software or hardware job?

i bought the table from a vendor, who gave me (naive and unknowing) that the table is top notch and ready to cut top quality parts for years.
but the table is at best a hobby table with: - open stepper motors that run very rough
- a very basic thc
- no limit switches on the table
- a bob with a parallel port
and so on.
anything but industrial table ready for years of quality cutting
and now his website is offline...
guess it's my own fault for buying without knowing too much about it.

[djreiswig]

Tried posting before but it didn't stick.
You need to assign your switch to z home port & pin.
The input should be on when the torch touches the material and the z runs down past. You may have to change the active high/low setting. Then you need to figure out the measurement between this point and where the torch is just touching the material. That is the switch offset.
You will need a post that has a G28.1 reference move. At the top of the post is a place to enter the switch offset (in mm).

[cruz]

Tried posting before but it didn't stick.
You need to assign your switch to z home port & pin.
The input should be on when the torch touches the material and the z runs down past. You may have to change the active high/low setting. Then you need to figure out the measurement between this point and where the torch is just touching the material. That is the switch offset.
You will need a post that has a G28.1 reference move. At the top of the post is a place to enter the switch offset (in mm).

i'm sorry but i don't quit understand everything.
when you let the torch and torch mounting plate just rest,
the bottom sensor is on the little metal plate just underneath it.
i've marked the picture to explain better what i mean (English isn't my native language).

IMG_20190106_175847.jpg

i'm probably not understanding something, but how am i supposed to find out the switch offset then?
also when putting the value in the sheetcam post processor, i have this text: post.ModalText(" G28.1 Z")
where exactly should the value (switch offset) be put?

sorry for not quite understanding this, i'm really not known i all this stuff, i assumed the table was turn key ready

[djreiswig]

Jog the torch down until it hits the material. Then slowly keep jogging until the sensor light goes out. Zero the DRO in Mach. Now slowly jog the torch up until you can just slide a sheet of paper under the torch. Look at the DRO. That figure is your switch offset. There should be a place at the top of the post that says switch offset. You put the measurement there but it has to be in mm.
Which post are you using?

[cruz]

Jog the torch down until it hits the material. Then slowly keep jogging until the sensor light goes out. Zero the DRO in Mach. Now slowly jog the torch up until you can just slide a sheet of paper under the torch. Look at the DRO. That figure is your switch offset. There should be a place at the top of the post that says switch offset. You put the measurement there but it has to be in mm.
Which post are you using?

oooh okay, that simple nice
right now i'm using the "mach3 plasma" post processor from sheetcam but it says it's for machines without THC, so i'll have to find another post processor.
looking at all the post processor there are alot where you can put the switch offset at the top of the post processor.
got any idea which one i could use?

[djreiswig]

Not sure. The THC part of the post is a different part. Not really related to the IHS. You would need a post that has the proper output for your THC unit.
I think there is a Mach plasma with thc post. I would try one and compare the code for the same job with your current post and see what the difference is.

[cruz]

Not sure. The THC part of the post is a different part. Not really related to the IHS. You would need a post that has the proper output for your THC unit.
I think there is a Mach plasma with thc post. I would try one and compare the code for the same job with your current post and see what the difference is.

okay .
one more question:
to assign the sensor to Z-home, can i use the automated setup given by mach3.
can i just select Z-home in the tab input signals and choose automated setup, and then just move the Z-axis so that it mach3 finds all the required data
like port and pin number.
or does it need to be done manually? if so how is it done?

i can't thank you enough for all the info you've already given.

[djreiswig]

You said the sensor changes the digitize input now. Just go into ports and pins and see what digitize is set to and set z home to that port and pin. Then disable the digitize input to be safe. You might have to change the active setting so the z home is on when the torch runs down and activates the switch.
I've never used automated setups in Mach.

[cruz]

You said the sensor changes the digitize input now. Just go into ports and pins and see what digitize is set to and set z home to that port and pin. Then disable the digitize input to be safe. You might have to change the active setting so the z home is on when the torch runs down and activates the switch.
I've never used automated setups in Mach.

okay, i'll try that tomorrow.
i'll let you know how it went.
thank you