Toleranced parts and how people get by

[minimillaidan]

ok so it s always crossed my mind and I ve posted on here and other platforms about cutter comp many times now.

some people may say change the record it s coming and you ll have to wait for it... But it always made me wonder how people get by without cutter comp.

Now in my day job I work on some really expensive MOD parts very tied up tolerance and crazy looking parts, I find myself using cutter comp basically every day to achieve the desired/ required size sometimes within microns!

Say you have a slot on a milled part that requires a tightish tolerance +-0.02mm how are people achieving this sort of tolerance without the cutter comp option on masso???

I understand you could fudge tool sizes potentially to achieve this but out of interest wondered how people are achieving toleranced parts?

hope to hear some good replies with how people get on with their masso controller and who knows masso may incorporate the cutter comp option in near future (fingers crossed)

 

[model-and-toolmaking]

I too, find it frustrating. On one of my machines I run production parts. They have +/-.001" tolerance. What I have to do is have iterations of each program ( with slight changes in tool diameter). It sucks. I think they have been spending their resources on the new touch screen controller (which seems pretty cool).

I have another mill for tool and die work. I had to remove the Masso3 from it and put in a controller that has wear comp. I will probably use the Masso on a plasma cutter.

 

[minimillaidan]

Granted the new touch screen set up is great... but was it really needed! They should have dialled all the functionality of the controller in first not just cutter comp.

the shame is that you have had to use a different controller rather than your masso in order to do more accurate work.. this shouldn t be the case. I love masso as a product just think this option would make it next level! Rather than these gimmicky items but suppose that s what people buy into these days....

 

[zombieengineer]

@minimillaidan / @model-and-toolmaking

When you get down to the +/-.001" tolerance there error could come from multiple sources including how concentric the tool is with respect to the spindle.

Does a method exist where you can measure the width of the tool in a similar fashion as the Tool Setter? The best I can find is something based around a laser beam photo interrupter.

Next question: How do you determine which side to offset the tool path?

This would require some knowledge of which side of the tool path is actually going to engage the work-piece. This might be something that can be done on a PC where you could analyze if the tool is performing a finishing pass (the axis of the tool is traveling within a previous machined slot but only cutting on one side). From a coding perspective this would be something of a nightmare to implement as this involves calculating intersections of volumes.

EDIT - Should have done some research first ( https://www.autodesk.com/products/fusion-360/blog/cutter-compensation/ ) - Basically you are asking for Masso to implement G40 / G41 / G42 g-codes.

 

[model-and-toolmaking]

Yes, the G41/G42. The code needed to implement it should be available; it is not new technology.

One easy way to measure what a tool will cut is to cut thru a thin piece of EDM graphite. And then look at it on the optical comparator. If you do not have a comparator you can make a cheap one with a digital microscope and a tablet. Just mount it on a mill, tape a thread across the tablet screen, move the table to line up on one side. Set zero, move to the other side. (Move in the same direction to limit backlash.)

Tool sizes can be off there nominal size by quite a bit. Especially cheap carbide endmills. Micro endmills are hard to measure without optics. Most 3/8 carbide endmills I have found measure .372 to .374. Tool flex or push off ( in the tool, holder & spindle ) and runout all play a part. This may not be an issue if you deal with +/- .005" tolerance.

Wood routers, plasma cutters and the like may never need tool wear offsets. I do not know what % of Masso controls end up on precision machine tools. They seem more popular on routers and Plasma cutters.

 

[testyourdesign]

@model-and-toolmaking

I have a workaround that is not quite as fast as the In-Control type cutter compensation but it still allows me to be reasonably efficient using Masso. I normally keep a laptop next to my mill and simply adjust the affected toolpath using the "Stock to Leave" feature under the "Passes" tab in Fusion360. With the built-in WiFi option in Masso, you can edit the individual operation in Fusion360 and post the new code directly to the machine very quickly. In my situation, I normally have 6 to 10 tool changes in a typical program so in-control cutter compensation would not be as beneficial as posting a single operation when reworking the first part to adjust a particular feature since it would have to run through all the operations to make the adjustment. This might not be suitable for everyone but it works great for me.

Another option one could consider is to create additional tools in the Fusion360 library and adjust the tool diameter to compensate for the cutter compensation value you need. With a custom library that has preset Plus or Minus Size tool diameters, you could simply swap out tools for one that is slightly larger or smaller by the amount you need to adjust. I found this to be less efficient than using stock-to-leave but if you know your tool is always a few hundredths or thousandths under nominal then you could simply set it in the library and forget it.

If you want to learn more about the cutter compensation features in Fusion360 then check out this blog post on Autodesk web site. That post helped me get a better grasp of how Fusion360 handles this requirement.

Hope this helps.

Cheers, Stephen Brown

Masso Club Member #1