Standard tolerance scheme for lasercut stainless
Standard tolerance scheme for lasercut stainless
(OP)
Looking at some suppliers I see people claiming plus/minus .003 to .005 on positional dimensions.
The question I have is "for a lasercutting machine, is that over the entire part? For the first 6 inches?
I'm working with a 16" wide sheetmetal part that mates to some plastic parts, and just need to verify my dimensioning scheme.
The question I have is "for a lasercutting machine, is that over the entire part? For the first 6 inches?
I'm working with a 16" wide sheetmetal part that mates to some plastic parts, and just need to verify my dimensioning scheme.
Chris Loughnane - Product Design
http://www.pdnotebook.com
http://www.twitter.com/DesignNotebook





RE: Standard tolerance scheme for lasercut stainless
Mike Halloran
Pembroke Pines, FL, USA
RE: Standard tolerance scheme for lasercut stainless
Chris Loughnane - Product Design
http://www.pdnotebook.com
http://www.twitter.com/DesignNotebook
RE: Standard tolerance scheme for lasercut stainless
Tolerances are a design function. Manufacturing processes have error.
As engineers we should understand the difference and use the terms correctly.
Now, to your question.
When your drawing is converted to a set of instructions for the machine, all the coordinates are converted to an absolute reference scheme based on the machine's known origin point.
The cutting head has no idea what feature it last made, or what feature it is going to make next, and it has no idea of the dimensioning scheme or tolerances on your drawing.
RE: Standard tolerance scheme for lasercut stainless
That's kind of like saying I'm talking about height, not inches.
Semantics either way...
Now, to your response.
That makes sense, but still confuses the issue a little bit. If a machine starts at the origin, and goes to one hole, then the next, then the next, etc. It seems that the error would add up between each.
Assuming it creates the features closest to the origin first (I think likely), that would make features further away have a greater possible variation in their position.
The only way I can think of them holding .003 (or .005) throughout is if, after each feature is made, the machine comes back to the origin and recalibrates it's position.
I doubt that the latter of those two methods is true, which gets back to my question... does the variation increase with it's distance, or is it the same over the entire workpiece?
Chris Loughnane - Product Design
http://www.pdnotebook.com
http://www.twitter.com/DesignNotebook
RE: Standard tolerance scheme for lasercut stainless
Perhaps they have more than one machine, and different machines have different capabilities.
So for the moment, let's pick a number. .003
What they think they are saying is that if they command the tool head to a specific position then the tool will go to that position with an accuracy of .003.
With only the information given so far, we don't really know if this accuracy is composite, or applies separately to each axis of motion.
The machine knows the tool position based on feedback from some sort of encoder. Maybe its error is a function of distance from the origin, maybe it isn't.
In all likelihood the people making the accuracy claims don't understand what they are claiming.
RE: Standard tolerance scheme for lasercut stainless
RE: Standard tolerance scheme for lasercut stainless
Chris Loughnane - Product Design
http://www.pdnotebook.com
http://www.twitter.com/DesignNotebook
RE: Standard tolerance scheme for lasercut stainless
Give them a drawing with tolerances, and buy (or don't buy) a part made to the drawing.
The resulting part passes inspection, or it doesn't. Binary function, returns one value, 0 or 1, no ambiguity to resolve.
Mike Halloran
Pembroke Pines, FL, USA
RE: Standard tolerance scheme for lasercut stainless
Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion
&
RE: Standard tolerance scheme for lasercut stainless
Which brings us back to my earlier point about people needing to understand the difference between tolerance and manufacturing capabilities and process deviation, error and distribution.