Rounded outside inner corners

[TrinityFabworks]

I'm having a hard time getting sharp clean corners on an outaide cut with and inside angle. Is there a trick to it? Does it have anything to do with acceleration values?

[motoguy]

What control setup and software? If you're using MACH3, check into the CV settings:

https://www.google.com/url?sa=t&rct=j&q ... ef9mRIyb8V

Yes, it will also be tied into accel settings. The higher the accel settings, the less of an issue you should see. However, your accel capabilities will be whatever they are (usually hardware limited). The CV settings can allow you to workaround this.

If you're not using MACH3, perhaps photos of the issue?

[TrinityFabworks]

What control setup and software? If you're using MACH3, check into the CV settings:

https://www.google.com/url?sa=t&rct=j&q ... ef9mRIyb8V

Yes, it will also be tied into accel settings. The higher the accel settings, the less of an issue you should see. However, your accel capabilities will be whatever they are (usually hardware limited). The CV settings can allow you to workaround this.

If you're not using MACH3, perhaps photos of the issue?

Thanks for the help, I will look into it! How do you find out what your maximum acceleration values are? Do you just go with the trial and error method until you find out where you're losing steps and then back it off a little bit? How can you tell that your motors are losing steps?

[Old Iron]

The faster you cut the more exaggerated the corners round off.
Post your equipment and the speeds you're cutting. Also if your table is belt drive or rack and pinion.
If you're cutting really fast then, look into slowing the gantry down at corners sharper than 45 degrees.

[tcaudle]

if you slow down on corners expect the THC to react and dive. If you have a THC you can turn on and off from software then setup a Cut Rule in SheetCAM to turn it off on corners and slow down at the same time

[TrinityFabworks]

if you slow down on corners expect the THC to react and dive. If you have a THC you can turn on and off from software then setup a Cut Rule in SheetCAM to turn it off on corners and slow down at the same time

I am unfortunately running mach3 with a proma 150 thc. I wish I knew a way to be able to turn the thc off on small corners like that with mach3. I know how to make the cut rules, but quickly found out that they have no affect on thc on or off in mach3. It seems like there should be a way to achieve this.

[robertspark]

https://www.plasmaspider.com/viewtopic. ... hc#p107508

+ use a code snippet before corners of a certain size to turn the thc on and off.

[TrinityFabworks]

I've read that thread before, but it doesn't look like they came up with any solutions. Is there a proven tried and true way around this?

[robertspark]

I've read that thread before, but it doesn't look like they came up with any solutions. Is there a proven tried and true way around this?

I don't understand your reply, I mean you replied earlier:

I am unfortunately running mach3 with a proma 150 thc. I wish I knew a way to be able to turn the thc off on small corners like that with mach3. I know how to make the cut rules, but quickly found out that they have no affect on thc on or off in mach3.

That thead tells you how to turn the THC on and off with Mach3 via macro.

what it does not tell you is how to use the sheetcam cut rules and or code snippets, but your earlier reply says:

...
I know how to make the cut rules, but quickly found out that they have no affect on thc on or off in mach3. ...

So if you KNOW how to use the cut rules and snippets you should be able to setup sheetcam to inset the THC ON and THCOFF macros in the correct positions.

Originally you asked:

I'm having a hard time getting sharp clean corners on an outaide cut with and inside angle. Is there a trick to it? Does it have anything to do with acceleration values?

And you got replies stating that acceleration is key to plasma cutting more so that maximim velocity because as long as you machine is able to achive a rapid speed equal to your expected maximum cut speed relative to the material you want to cut there is little benefit in going any faster if you have a home shop.... yes if you're making widgets in a commercial setting I'm sure rapid time matters, but then you'd probably have a hypertherm commercial system then

If you have issues with corners then you either need to improve your machines acceleration (use higher voltage to your steppers if that is possible (check your drive voltage rating, consider the gecko rule of thumb [32 * SQRT (L) = VMAX] https://www.geckodrive.com/support/step ... asics.html ), consider alternative stepper motors, consider alternative drive mechanism), if these items are not possible then consider slowing down for the corners and accept that you'll get a bit of bottom dross and that you'll probably get a larger kerf on the corners given there will be an amount of overburn where the arc cuts more material that is possible with an optimum cut velocity.


Look I am not a fan of Mach3 .... yes it works .... so does a model T ford... but I wouldnt want to drive one daily today .... Mach3 is no longer being developed .... it has its issues .... if you are happy to live with them then great just accept that its a model T and whilst it will get you from A-B it won't do it as well as something which is being developed and has been built with plasma in mind ..... given you are running windows and a Proma THC150 (again I'm not a fan of but it does the job) consider something cheap like UCCNC.... It has the macros (run in sync with motion [no divots]) built in). cncDrive have a REALLY good offering at the moment, a combined motion controller and breakout board which is 24V (high noise immunity) and is ethernet connected with free, yes FREE UCCNC software licence......
https://www.cncdrive.com/AXBB.html
https://www.cncdrive.com/UCCNC.html
http://www.shop.cncdrive.com/index.php?productID=965

[TrinityFabworks]

I've read that thread before, but it doesn't look like they came up with any solutions. Is there a proven tried and true way around this?

I don't understand your reply, I mean you replied earlier:

I am unfortunately running mach3 with a proma 150 thc. I wish I knew a way to be able to turn the thc off on small corners like that with mach3. I know how to make the cut rules, but quickly found out that they have no affect on thc on or off in mach3.

That thead tells you how to turn the THC on and off with Mach3 via macro.

what it does not tell you is how to use the sheetcam cut rules and or code snippets, but your earlier reply says:

...
I know how to make the cut rules, but quickly found out that they have no affect on thc on or off in mach3. ...

So if you KNOW how to use the cut rules and snippets you should be able to setup sheetcam to inset the THC ON and THCOFF macros in the correct positions.

They say right in the thread that the macro isn't a reliable way to do things with mach because it has to stop motion first. I have written cut rules before for thc on and off in Sheetcam until I realized that it wasn't going to work the way that I had hoped.

[Nacs Fab]

What control setup and software? If you're using MACH3, check into the CV settings:

https://www.google.com/url?sa=t&rct=j&q ... ef9mRIyb8V

Yes, it will also be tied into accel settings. The higher the accel settings, the less of an issue you should see. However, your accel capabilities will be whatever they are (usually hardware limited). The CV settings can allow you to workaround this.

If you're not using MACH3, perhaps photos of the issue?

What did you end up setting your CV At? I remember you looking into this issue a while back, could you screenshot that CV settings area in your Mach config? Thank ya!

[motoguy]

What control setup and software? If you're using MACH3, check into the CV settings:

https://www.google.com/url?sa=t&rct=j&q ... ef9mRIyb8V

Yes, it will also be tied into accel settings. The higher the accel settings, the less of an issue you should see. However, your accel capabilities will be whatever they are (usually hardware limited). The CV settings can allow you to workaround this.

If you're not using MACH3, perhaps photos of the issue?

What did you end up setting your CV At? I remember you looking into this issue a while back, could you screenshot that CV settings area in your Mach config? Thank ya!

I went to CommandCNC around a year ago, and haven't used Mach since then. I remember checking "disable CV on corners less than" (or something like that) 44 degrees. Just played with the angle number until I found a setting that gave the results I wanted.