Amana 1/8" roundover - #49694 tool file issue

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phil from seattle
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Amana 1/8" roundover - #49694 tool file issue

Post by phil from seattle »

I am having trouble getting this bit and the 49694 bit tool file from Amana to work correctly with VCPro. I downloaded the Amana tool database and it has an odd diameter (.3767" vs .375" from the Amana datasheet). I suspect that is to avoid a mark when rounding over a square edge, though +0.0012" seems like an odd amount for the diameter. But for the life of me I can't get it to work correctly in VCPro.

So, based on the attached picture, I want a tool path that is 1/16" inside (or outside) the edge I am rounding over. I drew that vector and a 2D Profile Toolpath On it produced a correct preview and actual cut.

As I understand it, in the 2D profile and an Inside or Outside machine vector, you select an allowance offset from the diameter to get the correct tool path. In this case, if you ignore slight diam difference, -0.125" for an inside cut but that gets me way off the cut line that should be 1/16" from the edge I want to round over. See the picture. I tried 0.125 + 0.0012 and0.125 + 0.0006 (half that) to the offset and that still didn't do what I wanted. Playing with it I found I could get very close to the correct tool path by using 0.1103" as the allowance offset. Shouldn't the allowance offset be bigger for a bigger diameter??? I would think the precise allowance offset should be 0.12585 (0.3767-.0125)/2 (Diam - minor diam)/2.

Now, I pulled down the whiteside .tool file for their 2050 equivalent 1/8" roundover bit which has a diameter of 3/8" (0.375) and plugging in the predicted offset (0.125") works correctly. So why does a diameter of 0.3767 cause a problem?

FWIW, I drew this up for a class I'm teaching. I need to sweat the details if I'm teaching and this just isn't making sense to me. If it was only for me, I'd just draw the actual tool path and be done with it. I wish the On option in Machine Vectors allowed an offset allowance, would make life a lot simpler.

Ver 11.003 (Build 7591.8655.1334)
edge offset.png

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Adrian
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Re: Amana 1/8" roundover - #49694 tool file issue

Post by Adrian »

Just about to go out so I don't have time to check through the whole post but are you aware that toolpaths are calculated from the centre of the bit? That's the most common error when using bits like this as people often expect the cut to be calculated from the edge of the profile.

Also I wouldn't trust anything in that Amana database. I've lost count of the number of issues the errors in it have caused with posts on the forum.

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Re: Amana 1/8" roundover - #49694 tool file issue

Post by Leo »

I would draw that as a form bit and create my own tool data base entry.

You can use the information in the drawing you posted, BUT, personally I would measure the bit with calipers to verify the dimensions.

Once you have an accurate tool in the Vectric database you can preview the cut in toolpath preview.

Feeds and speeds have as much to do with your machine as it does with proper chipload.
Amana does not know your machine, therefore, the Amana feeds and speeds are only a suggestion.

As to the 1/16 offset
You can do an offset in Vectric, then use the offset vector and use "ON" for the toolpath.
In the toolpath preview the cut "?should?" look good.
Adjust as needed.
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phil from seattle
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Re: Amana 1/8" roundover - #49694 tool file issue

Post by phil from seattle »

Adrian wrote:
Fri Dec 03, 2021 9:01 pm
Just about to go out so I don't have time to check through the whole post but are you aware that toolpaths are calculated from the centre of the bit? That's the most common error when using bits like this as people often expect the cut to be calculated from the edge of the profile.

Also I wouldn't trust anything in that Amana database. I've lost count of the number of issues the errors in it have caused with posts on the forum.
Yes, I am aware of that but the toolpath for Inside and outside 2D profile is 1/2 the diameter away from the vector. Offset Allowance changes that and that is what I having trouble with for the roundover bit.

phil from seattle
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Re: Amana 1/8" roundover - #49694 tool file issue

Post by phil from seattle »

Leo wrote:
Fri Dec 03, 2021 9:51 pm
I would draw that as a form bit and create my own tool data base entry.

You can use the information in the drawing you posted, BUT, personally I would measure the bit with calipers to verify the dimensions.

Once you have an accurate tool in the Vectric database you can preview the cut in toolpath preview.

Feeds and speeds have as much to do with your machine as it does with proper chipload.
Amana does not know your machine, therefore, the Amana feeds and speeds are only a suggestion.

As to the 1/16 offset
You can do an offset in Vectric, then use the offset vector and use "ON" for the toolpath.
In the toolpath preview the cut "?should?" look good.
Adjust as needed.
Yeah, like I said, if it was just me, I would use On with a specifically drawn offset vector. Wish you could use Allowance Offset with On.

I would assume (probably my first mistake) that the Amana tool is correct. Yes, measuring is always a good idea but that is outside the issue here. The Allowance Offset to get to the correct tool path is way off. I actually did draw up a tool database entry and it had similar problems so I went for the Amana one.

Not sure why F&S matter about tool path. I am aware of it's importance in general, though.

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Re: Amana 1/8" roundover - #49694 tool file issue

Post by Rcnewcomb »

Wish you could use Allowance Offset with On.
But which way would you want it to offset?
Right=positive, Left=negative?
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Re: Amana 1/8" roundover - #49694 tool file issue

Post by adze_cnc »

phil from seattle wrote:
Fri Dec 03, 2021 7:35 pm
So why does a diameter of 0.3767 cause a problem?
Because you don't know whether, when Amana created that form tool, they made the flat longer or the radius of the arc longer or a combination of both.

Taking the profile from their DXF file (replacing their arc with my own because theirs was rubbish) I created a new form tool. Plugging in a -0.125 offset in a profile toolpath gave me a "perfect" round-over. Whether the DXF matches the reality of the bit I don't know. I'd have to do what Leo suggested above and measure it for myself.

phil from seattle
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Re: Amana 1/8" roundover - #49694 tool file issue

Post by phil from seattle »

Rcnewcomb wrote:
Fri Dec 03, 2021 11:13 pm
Wish you could use Allowance Offset with On.
But which way would you want it to offset?
Right=positive, Left=negative?
sure, why not. It makes the math a lot easier for me.

phil from seattle
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Re: Amana 1/8" roundover - #49694 tool file issue

Post by phil from seattle »

adze_cnc wrote:
Sat Dec 04, 2021 12:11 am
phil from seattle wrote:
Fri Dec 03, 2021 7:35 pm
So why does a diameter of 0.3767 cause a problem?
Because you don't know whether, when Amana created that form tool, they made the flat longer or the radius of the arc longer or a combination of both.

Taking the profile from their DXF file (replacing their arc with my own because theirs was rubbish) I created a new form tool. Plugging in a -0.125 offset in a profile toolpath gave me a "perfect" round-over. Whether the DXF matches the reality of the bit I don't know. I'd have to do what Leo suggested above and measure it for myself.
Yeah, I can see that. Still, it doesn't explain why an allowance offset of .1103" was needed to get the tool path to be correct.

And, FWIW, I put calipers on the bit and it was .3756". Given that my calipers aren't super high end, I would call it .375 and be done. I doubt they are really accurate to 4 places. What's a fraction of a mil between friends...

Any, I'm not going to lose any more sleep and will just toss the amana tool DB entry.

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