Fixture Design

[Jay Kyle]

Hi,

I'm trying to plan a fixture plate design of small parts on my mill. The raw stock start out as 1" round bar by 6" long. When I design a plate to hold multiple pieces, should I design for maximum part density on the fixture plate - which means using small tools, or should I open up the spacing between parts a bit to allow for larger tools. I'm looking for schools of thought on this one.

 

Thanks

 

Jay

[Guest CNC Apps Guy 1]

Depends on quantities. If every second counts, you'll want to use larger tools. If unattended run-time is your goal, then smaller tools and higher part density would be the route I'd go.

 

JM2C

[Jay Kyle]

Thanks JM2C,

I hate to be always asking questions but I'm still in the newbie mode. This is good advice.

 

My parts need to go through 5 operations, so next question is: When designing up the fixture, should I design it so all 5 ops are on the same plate, and I just cycle parts through the various stages on the plate; or one plate per operation and I swap plates each time I run the batch through. Batch sizes range from 100-500 parts. My table size is 40"x20" so the plates would be too big to manhandle.

 

I guess the same would apply for multiple 2-Jaw Kurt vises on the table.

 

Jay

[Guest CNC Apps Guy 1]

My own personal preference is that you get complete parts every cycle. It's not always possible or feasible, but when it is possible and feasible, I think it's a good idea. Several factors went into me forming that opinion;

1) My WIP (Work In Process) count will be higher when I do not complete a part per cycle

2) Inspection/inspector will be getting a steady consistent flow instead of being innundated with a bunch of parts at once.

3) If a mistake is caught in the later stages of the part, because your WIP count is lower, you'll loose fewer parts and waste eless money

4) You can setup the entire job instead of doing some here, doing some there, etc... The reason why this is important, think about your job for a sec... you're programming something and somebody interrupts you for say 15 minutes. Ok, you loose that 15 minutes, that's a given, but, how long does it take you to get back into your "groove"? Depending on what you're doing, that 15 minutes could have cost you 30 minutes. Granted that's probably extreme but hopefully you see my point. If you can do a complete setup, you only have to set tools once, you only have to set fixture offsets once, you only have to load the program once (unless it does not fit in th control).

 

Hope this helps the cause.

[Chris Rizzo]

What James says.

 

something else big to think about is part change time. design to keep the spindle running. If you've got to change several hundred parts, don't do it in the machine. Build a few identical fixture plates so one can run while your fiddling around changing 500 parts outside of the machine.

[Guest CNC Apps Guy 1]

What Chris says, spindle running = making money. Spindle sitting = costing money.

[Thad]

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.... then smaller tools and higher part density would be the route I'd go.

 

JM2C

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Thanks JM2C,

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Now *that's* just plain funny!

 

Thad

[Colin Gilchrist]

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JM2¢

 

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[Colin Gilchrist]

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