Avoiding Machine Gotchya's

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Re: Avoiding Machine Gotchya's

Postby RoutnAbout » Fri Oct 14, 2011 4:11 am

Hi Osric, and welcome to the world of CNC and the forum. Lots of great help and knowledge here, so don't hesitate to ask questions as they arise.
Your correct, All of your feeds and speeds are set in your tool database. Once you create and go to save your toolpath, you have the option for what post processor best suited for your machine.

Hope that helps.
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Re: Avoiding Machine Gotchya's

Postby FixitMike » Fri Sep 07, 2012 4:25 am

Feeds and speeds are set in the tool data base. But when you import them into your toolpath they can be be modified. After you have selected a cutting method in the Toolpaths window, use the Edit button under Tool to modify the tool you have selected for that job.

Or, after you Select a tool, use the Tool Database screen to edit whatever parameter you wish, click Apply, and your edit will be applied to that tool in the database for all uses.
You can also use the commands in the lower left corner of the Tool Database screen to make a new tool.

Vectric also has instructions on how to enter a new form tool into the database.
http://www.vectric.com/WebSite/Vectric/ ... utters.htm
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Re: Avoiding Machine Gotchya's

Postby Win Brayer » Tue Apr 08, 2014 8:32 am

New to CNC. What is CV and how and why do you turn it on and off?
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Re: Avoiding Machine Gotchya's

Postby TReischl » Tue Apr 08, 2014 9:17 am

Win, if you read back a bit in this thread you will see a description of CV (constant velocity).

There is no way to turn it off/on via Aspire on the fly. If you are using something like Mach the command to turn it on is usually in the header for the cnc program. It also has to be enabled in Mach. In other words, you can put the command into the program to use CV, but if it is not enabled in Mach it will not work.

If you are new to cnc I would suggest that you check that it is enabled in your control software. It is extremely rare to turn it off, so as a new user I would not worry about it. As someone who has been working with cnc for thirty years I cannot recall the last time I turned it off.
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Re: Avoiding Machine Gotchya's

Postby Adrian » Tue Apr 08, 2014 9:18 am

It's a specific setting for the Mach3 control software. Most software has it but it's not always called the same thing.

http://www.machsupport.com/wp-content/u ... ngs_v2.pdf
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Re: Avoiding Machine Gotchya's

Postby PaulRowntree » Tue Apr 08, 2014 1:15 pm

As important as turning CV on/off is, it must be tuned to behave correctly. If you are using high feed rates, then the acceleration should be high as well to avoid rounding some corners. How large is 'high' depends on your machine. A sports car can go into a corner and change direction quickly, while a 18-wheeler at the same speed needs to start its turn earlier because its acceleration is lower than the car; the CNC is trying to make turns with constant velocity, but its ability to do so depends on how fast it can change directions.
As said above, you probably want to use CV, but you want to use it right too.
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Re: Avoiding Machine Gotchya's

Postby knowlzy0791 » Wed Aug 27, 2014 4:57 pm

As the military would say. Slow is smooth, smooth is fast
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Re: Avoiding Machine Gotchya's

Postby Piertechpierre » Thu May 07, 2015 5:45 pm

Hi,
I am new to the CNC machining. I bought VCarve Pro 8 and love the program. I made some kitchen cabinet sides, top and bottom and the CNC router will drill the 5mm holes 32 mm apart, cut the groove for the back and cut the outside shape of the cabinets. When I run the toolpath, everything runs properly and the program tells me it should take less than 3 minutes to complete the work. I then run Mach 3 and in the virtual mode it says the same and runs well. When I hook up the CNC (generic type) it barely moves. The G code has the x and y axis running at 3600 (mm/minute?) and the Z at 1200.

I have no clue what these numbers mean. Reading on speed, when I lowered the numbers to 100, it would take 2 hours to do one side.
I need someone's expertise to guide me in this wonderful yet frustrating world of magical woodworking.

I thank you in advance.
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Re: Avoiding Machine Gotchya's

Postby zeeway » Thu May 07, 2015 7:10 pm

Suspect you have Vectric software thinking you are working in inches, while your machine control software (Mach 3) thinks you are working in mm.

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Re: Avoiding Machine Gotchya's

Postby Adrian » Thu May 07, 2015 7:30 pm

If you have no clue what those numbers mean you need to take a step back and spend some more time studying. You're going to get yourself in a right mess and really frustrated if you don't get a good handle on the basics.

http://www.vectric.com/media/docs/suppo ... ic2013.pdf
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Re: Avoiding Machine Gotchya's

Postby ChrisInEstes » Thu May 07, 2015 8:36 pm

Speaking of Mach3 & CV...

I never had a rounded corner problem till I started using faster feed rates and slower spindle speeds. I was making dust (and sometimes smoke) but had nice square corners. Now I make chips and have rounded inside corners, but square outside corners. I guess that's progress, eh? :lol:

Yeesh, all the Mach3 CV stuff is complicated. I've spent hours searching & reading about the CV settings, and still haven't figured out what all I need to change, or even what to start with.

Somebody please buy the same router & control box I have, get it set up properly, and then let me know the settings. :mrgreen:

OK, here's a specific Mach3 CV setting question that I haven't found an answer to. CV Dist Tolerence Units. Mine is set to 180. But, 180 what? What are the "Units"? Inches? Thousandths of inches? Stepper steps?

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Re: Avoiding Machine Gotchya's

Postby tayler_mann » Tue Jun 09, 2015 3:36 pm

I run my machine to my Onsrud designated chip load period. I am not sure what you all consider speed but I use my Onsrud 56-600 bit for acrylic and with the chip load my feed rate comes out to around 210 IPM (53 MPM) I believe. I never have problem and I have flawless cuts that almost look polished. My spindle speed also can not go any slower than 19,000 so I am limited to how slow I can actually go. Even when machining plate aluminum and blanks I will run around 80-150 IPM with a .187" - .2" cut (I would like to include I am slowly getting away from the Imperial units :) ). Here is a link from Onsrud to get the designated chip load from your router bit and make the most of the $30-45 spent on your tool. The chip loading is towards the end of the document. I also agree with the tape comment. If your vacuum isn't strong enough....BUY ANOTHER VACUUM! I have had horror stories told and seen by what happens when tape lets go. For some reason one time I was cutting an 0 out of 1/2" aluminum and was relying on tape to hold it to the table after it was done cutting it. For some reason it cut the outside of the "0" first and than proceeded to cut the counter (inside of the "0"). After it's last past as the machine was moving up on the Z it grabbed the "0" and flung it not through one side but both sides of a wall with 5/8" drywall and insulation. If that would have hit me I would for sure either not be here today or I would have been seriously injured.

http://www.onsrud.com/files/pdf/OC-12-ProductionCuttingToolCatalog.pdf
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Re: Avoiding Machine Gotchya's

Postby Adrian » Tue Jun 09, 2015 3:59 pm

Something a lot of people forget when working out feed rates is the size of the pieces they are cutting. A machine can be set to cut at 300IPM but if the parts are 4" square (for example) it's not going to get even close to running at that speed.
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Re: Avoiding Machine Gotchya's

Postby tayler_mann » Tue Jun 09, 2015 7:59 pm

This is very true as well. Unless you have your acceleration set at extreme amounts which in turn will cause in a higher inaccuracy tolerance. Also at high speeds you have to remember to set your acceleration angle. You can lose square corners past 110 IPM if you are set to >22.5. I know from past experience. The first time you push your machine its nail biting.
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Re: Avoiding Machine Gotchya's

Postby Need More Tools » Sun Jul 12, 2015 6:25 pm

Hello Everyone! I have been reading about people using double sided tape. That to me just sounds a bit dangerous. I built a pneumatic clamping system on my home made cnc table. I also use tabs or make my stock a bit thicker and run thru my drum sander to release my part I am after. The clamping system is easy. installed two pieces of t-track the length of my table and I have one board with two t-bolts that slide the length of the table. The other end I have 4 pneumatic cylinders attached to a piece of aluminum. place my work on the table and make sure its sitting flat on table against the aluminum rail and slide the board with the two t-bolts against the work and lock down. Then apply air to the cylinders and we are locked in place. If I fear of cutting to close to the aluminum I just put in a piece of scrap wood between the aluminum and the work. I may have 100 bucks in the whole system and bought it all except had the air compressor. Safety is key here as I always have someone over wanting to watch something being cut or carved. I don't want my machine tore up or my friends. Any questions please feel free to ask.
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