It is currently Sat Oct 20, 2018 2:41 am

 

hole quality

Plasma Cut Quality can often be an issue for many of us. Check here if you have plasma cut quality issues. Ask a question, look for advice, post a helpful tip here.
dsanford55
Posts: 19
Joined: Wed Nov 22, 2017 6:13 pm

hole quality

Postby dsanford55 » Sat Feb 03, 2018 6:52 am

i can't seem to find the the answer to my question searching thru the boards, so I'll ask.

I've got a HP 85 & LDR Motions, and running CNC Command software using sheetcam, cutting 3/8" plate at 19 in per min & 65 amps for the holes.
However I can't seem to get a good quality of cut for my holes.

Using a .375 lead in from the center, brand new consumables, and factory recommended settings from Hypertherm for 3/8" plate.

holes are somewhat beveled and not as round as should be.

any suggestions would be appreciated,
THANKS!!!!

mdwalker
Elite Contributing Member
Elite Contributing Member
Posts: 440
Joined: Fri Nov 14, 2008 10:20 am

Re: hole quality

Postby mdwalker » Sat Feb 03, 2018 8:44 am

Cut your holes at 60% of cut speed and see if that helps.

mdwalker
Elite Contributing Member
Elite Contributing Member
Posts: 440
Joined: Fri Nov 14, 2008 10:20 am

Re: hole quality

Postby mdwalker » Sat Feb 03, 2018 8:47 am

Another thing that can cause this is your torch height. Need to measure your actual cut height and see if it is accurate.

jimcolt
Elite Contributing Member
Elite Contributing Member
Posts: 2939
Joined: Mon Jul 20, 2009 11:18 pm
Location: New Hampshire

Re: hole quality

Postby jimcolt » Sat Feb 03, 2018 9:11 am

Email me directly and I will send the presentation called "Best Practices for Plasma Hole Cutting. There are a lot of techniques. [email protected] Keep in mind that you are using an air plasma cutter, not one of the liquid cooled, oxygen, high definition plasma's that can cut taper free, divot free holes on steel. They cost about 10x more than an air plasma....however save a lot of aggravation in secondary work. Here is a pic with top and bottom dimensions for different holes sizes cut in 1/4" steel with a Powermax air plasma:
dimensions.jpg

You do not have access to download this dxf file.
Become a Contributing Member to gain access to the thousands of files shared by our members. Click Here


dhelfter
Posts: 112
Joined: Wed Sep 09, 2009 11:18 pm

Re: hole quality

Postby dhelfter » Sun Feb 04, 2018 11:15 am

The presentation Jim Colt is speaking of is actually on your computer we supplied under the manuals/cut quality folder.

Thanks
Dan
LDR

tcaudle
Posts: 1038
Joined: Tue Feb 28, 2012 6:47 pm

Re: hole quality

Postby tcaudle » Sun Feb 04, 2018 3:28 pm

Once holes get small you need to cut them with the DTHCoff. How to do that? open SheetCMA and you will see in the OPERATION an input box named" Min Cut Length for DTHC" with a default of 1". That means it will automatically keep the DTHC from turning on at the beginning of the cut if the total lenght is LESS than 1". That only covers a hole of less than 3/8" diameter. I suggest you raise that to 3 io catch a circle of arounfd 1" diameter and below. DO NOT try to control the DTHC on/off at the beginning with a Cut rule....It won't work because the OFF run happens before the ON command and it turns it on anyway. When you slow down a cut your torch volts goes up. When you torch volts goes up the DTHC moves the torch DOWN to lower it back to the preset volts (dives) to stop that use the method above. Slowing down, picking the right leadin and turning off the DTHC on smaller holes will lead to better results. Make sure your touch off sequence is correct and the pierce height and cut height defined in the G-Code are actually being used at the torch.

dsanford55
Posts: 19
Joined: Wed Nov 22, 2017 6:13 pm

Re: hole quality

Postby dsanford55 » Thu Feb 08, 2018 5:33 am

appreciate all the responses fellows...thx again

dsanford55
Posts: 19
Joined: Wed Nov 22, 2017 6:13 pm

Re: hole quality

Postby dsanford55 » Thu Feb 08, 2018 6:05 am

jimcolt wrote:Email me directly and I will send the presentation called "Best Practices for Plasma Hole Cutting. There are a lot of techniques. [email protected] Keep in mind that you are using an air plasma cutter, not one of the liquid cooled, oxygen, high definition plasma's that can cut taper free, divot free holes on steel. They cost about 10x more than an air plasma....however save a lot of aggravation in secondary work. Here is a pic with top and bottom dimensions for different holes sizes cut in 1/4" steel with a Powermax air plasma:
dimensions.jpg


Jim,
Been a few days since I posted... found the presentation you're referring to, thx

I'm going to draw some different sized holes for testing on the 3/8" and spend some time tweeking this pupy.
Thx again

dsanford55
Posts: 19
Joined: Wed Nov 22, 2017 6:13 pm

Re: hole quality

Postby dsanford55 » Thu Feb 08, 2018 6:07 am

dhelfter wrote:The presentation Jim Colt is speaking of is actually on your computer we supplied under the manuals/cut quality folder.

Thanks
Dan
LDR


Thanks Dan... you have all the bases covered as usual, just have to look in the right place...LOL
Thanks Dan!

David

BensPlasmaAu
Posts: 196
Joined: Mon Jan 13, 2014 10:37 am
Location: Boronia, Melbourne, Australia

Re: hole quality

Postby BensPlasmaAu » Thu Feb 22, 2018 1:51 am

tcaudle wrote:Once holes get small you need to cut them with the DTHCoff. How to do that? open SheetCMA and you will see in the OPERATION an input box named" Min Cut Length for DTHC" with a default of 1". That means it will automatically keep the DTHC from turning on at the beginning of the cut if the total lenght is LESS than 1". That only covers a hole of less than 3/8" diameter. I suggest you raise that to 3 io catch a circle of arounfd 1" diameter and below. DO NOT try to control the DTHC on/off at the beginning with a Cut rule....It won't work because the OFF run happens before the ON command and it turns it on anyway. When you slow down a cut your torch volts goes up. When you torch volts goes up the DTHC moves the torch DOWN to lower it back to the preset volts (dives) to stop that use the method above. Slowing down, picking the right leadin and turning off the DTHC on smaller holes will lead to better results. Make sure your touch off sequence is correct and the pierce height and cut height defined in the G-Code are actually being used at the torch.


A great tip Tom! I will also give this a go and see how things go.
Home built 3400 x 1400mm (11 and a bit X a bit over 4.5 feet)
Hypertherm Powermax 45
CandCNC Bladerunner IV
Some air dryer off the internet
Another water seperator I found unused on a shelf
Refrigerated air dryer

dsanford55
Posts: 19
Joined: Wed Nov 22, 2017 6:13 pm

Re: hole quality

Postby dsanford55 » Wed Mar 21, 2018 1:23 pm

tcaudle wrote:Once holes get small you need to cut them with the DTHCoff. How to do that? open SheetCMA and you will see in the OPERATION an input box named" Min Cut Length for DTHC" with a default of 1". That means it will automatically keep the DTHC from turning on at the beginning of the cut if the total lenght is LESS than 1". That only covers a hole of less than 3/8" diameter. I suggest you raise that to 3 io catch a circle of arounfd 1" diameter and below. DO NOT try to control the DTHC on/off at the beginning with a Cut rule....It won't work because the OFF run happens before the ON command and it turns it on anyway. When you slow down a cut your torch volts goes up. When you torch volts goes up the DTHC moves the torch DOWN to lower it back to the preset volts (dives) to stop that use the method above. Slowing down, picking the right leadin and turning off the DTHC on smaller holes will lead to better results. Make sure your touch off sequence is correct and the pierce height and cut height defined in the G-Code are actually being used at the torch.


I appreciate your input seems I should be able to tweek these even better, not sure.
The pics are viewing the top and bottom sides.
The top doesn't look bad at all and would work fine, the problem is the underside. I'm getting a divot for some reason.

SheetCam and commandCNC

How can I improve on these 17/32" holes in 1/4" plate ?
Any suggestions?

inside offset operation:
" Min Cut Length for DTHC" (6)

45 AMP cut settings

A) 60% decreased cutting speed for 1/4" plate
B) lead in: .375 perpendicular (default center cut setting for circles less than 1")
C) over cut: .2
D) NO lead out


outside offset operation:
" Min Cut Length for DTHC" (6)
45 AMP cut settings
A) 1/4" 45 AMP
B) lead in: .375 (default center cut setting for circles less than 1")
C) over cut: .2
D) NO lead out
popper hinges.jpg
popper hinges 1.jpg

You do not have access to download this dxf file.
Become a Contributing Member to gain access to the thousands of files shared by our members. Click Here


motoguy
Elite Contributing Member
Elite Contributing Member
Posts: 1075
Joined: Tue Aug 25, 2015 12:05 pm
Location: Central MO, USA

Re: hole quality

Postby motoguy » Wed Mar 21, 2018 1:53 pm

I found the best, most reliable method for cutting small holes was to put the holes on their own layer. Then disable THC for that layer, and manually set the cut speed for that layer (30,40,50,60% of book speed, depending on what you're trying to accomplish).
Bulltear 6x12 w/ Proton Z axis & watertable
CommandCNC/Linux w/ Ohmic & HyT options
Hypertherm Powermax 85 w/ machine torch
Solidworks, Coreldraw X7, Inkscape, Sheetcam

dsanford55
Posts: 19
Joined: Wed Nov 22, 2017 6:13 pm

Re: hole quality

Postby dsanford55 » Wed Mar 21, 2018 5:17 pm

motoguy wrote:I found the best, most reliable method for cutting small holes was to put the holes on their own layer. Then disable THC for that layer, and manually set the cut speed for that layer (30,40,50,60% of book speed, depending on what you're trying to accomplish).


thx for the reply.
I've got the holes on their own layer, so that's covered. And the THC for that operation is set in SheetCam, so that's covered. These were cut @ 60% of book speed so I think I'll try backing that down to 50% on the next series of cuts and see what taht does.
Thx!

motoguy
Elite Contributing Member
Elite Contributing Member
Posts: 1075
Joined: Tue Aug 25, 2015 12:05 pm
Location: Central MO, USA

Re: hole quality

Postby motoguy » Wed Mar 21, 2018 5:27 pm

I have also gotten away from a big overcut. I used to Arc in an arc out. Now I come in perpendicular, and have about a kerf sized over cut. .06 or so on 1/4". That is not much of an over cut, but combined with the slower travel speed, it seems to clean the whole up nicely without leaving an out of round shape where the / cut digs into the edge.
Bulltear 6x12 w/ Proton Z axis & watertable
CommandCNC/Linux w/ Ohmic & HyT options
Hypertherm Powermax 85 w/ machine torch
Solidworks, Coreldraw X7, Inkscape, Sheetcam

dsanford55
Posts: 19
Joined: Wed Nov 22, 2017 6:13 pm

Re: hole quality

Postby dsanford55 » Thu Mar 22, 2018 6:13 am

motoguy wrote:I have also gotten away from a big overcut. I used to Arc in an arc out. Now I come in perpendicular, and have about a kerf sized over cut. .06 or so on 1/4". That is not much of an over cut, but combined with the slower travel speed, it seems to clean the whole up nicely without leaving an out of round shape where the / cut digs into the edge.


I think decreasing my overcut is a good idea. Looking at these pcs. when I cleaned them up the problem area was in the same place on each of the pcs. Seems when using the perpendicular lead in, when the torch starts it's cut on the radius, there's a divot. Leads me to think reducing the cut speed back to 50% or less will probably solve the issue.
This machine is just fascinating, I love it, just a learning curve. LOL

dsanford55
Posts: 19
Joined: Wed Nov 22, 2017 6:13 pm

Re: hole quality

Postby dsanford55 » Thu Mar 22, 2018 7:44 am

sitting here drinking coffee and surfing through these threads also discovered I'm using the wrong nozzle for 1/4" 45 Amp cutting operation.
Jim has some terrific posts and pics, discovered this on another thread.
Going to order some 220941 nozzles, looks like thats part of the problem too.


Return to “Plasma Cut Quality Forum”

Who is online

Users browsing this forum: No registered users and 9 guests

Easyscriber engrave attachment for Hypertherm torch's