milling problem

[ANESIMIN]

hi

how to maintain pieces with little thikness (3MM 4 MM) to machine  ;is there special vices?? we use to machine aluminium and pom C

an other problem occurs after  dismantling the piece (pom c) from the vice ;we dont find the same measurment . how can this happen? and how to avoid this.

is using the scotsh brite a solution?

[Guest]

Vacuum chucks/fixtures....

Sometimes if a part isn't complex, I'll use thicker stock and then a thin saw to cut off the part.... a little backside cleanup & done

In a pinch, double sided tape....I have also used heat activated glue sheets

It depends what needs to be machined

Edited July 21, 2018 by Guest

[ANESIMIN]

1 hour ago, JParis said:

Vacuum chucks/fixtures....

Sometimes if a part isn't complex, I'll use thicker stock and then a thin saw to cut off the part.... a little backside cleanup & done

In a pinch, double sided tape....I have also used heat activated glue sheets

It depends what needs to be machined

is there vices that can maintain 1 or 2 mm without domaging the pieces

[crazy^millman]

3 hours ago, ANESIMIN said:

is there vices that can maintain 1 or 2 mm without domaging the pieces

Not really where free state processes are the best approach. Clamping is just that it by it’s very nature is a force of compression to restrain the part using side force to hold it down. The very nature of physics is every force creates and equal amount of force. To keep the part restrained it takes an equal amount of force to make this happen and the problem is all metal has a certain amount of plasticity. That plasticity means the parts have a certain amount of flexibility and the thinniner they get they become more flexible. You are getting it it the point where it has lost it’s nature ability to resist bending, That is when you must switch from traditional compression from the side to either vacuum, adhesive or other means to machine the parts like window frame or tabs. It is not as easy is there a vice that can maintain it is a matter of the process has to be changed to suit the need. 

[Guest]

3 hours ago, ANESIMIN said:

is there vices that can maintain 1 or 2 mm without domaging the pieces

Ron summed it up nicely

I have a fairly complex part running on our HMC.....along the edges it's .035" thick +/-.001....

I cut them complete caged in the stock using tabs....we've run over 25k using this process....part loss is near 0%

That thin, it's ALL about process

Edited July 21, 2018 by Guest

[ANESIMIN]

14 hours ago, JParis said:

Ron summed it up nicely

I have a fairly complex part running on our HMC.....along the edges it's .035" thick +/-.001....

I cut them complete caged in the stock using tabs....we've run over 25k using this process....part loss is near 0%

That thin, it's ALL about process

what is the thikness of tabs ; how much tabs ; and how to clean them after machinnig

 

[Guest]

6 minutes ago, ANESIMIN said:

what is the thikness of tabs ; how much tabs ; and how to clean them after machinnig

On this particular part, they are .030" wide and .010" thick.....

A pair of tweezers and a quick wipe on some 400 grit paper takes the edge off...

[Newbeeee™]

I hate vices. Great for holding stock (thick) initially, or Chick (form jaws) for holding second op and finishing, but too many variables for a lot of work IMO

[tim_h]

On 7/21/2018 at 7:14 PM, JParis said:

Ron summed it up nicely

I have a fairly complex part running on our HMC.....along the edges it's .035" thick +/-.001....

I cut them complete caged in the stock using tabs....we've run over 25k using this process....part loss is near 0%

That thin, it's ALL about process

You are referring to a part cut with the "window" approach ?

So, approx.  what percentage of the perimeter is tabbed ?

Small parts ? or Larger parts ?

 

[Guest]

50 minutes ago, tim_h said:

You are referring to a part cut with the "window" approach ?

So, approx.  what percentage of the perimeter is tabbed ?

Small parts ? or Larger parts ?

The part is 1.25"  x 1.700" At its thickest, it's .190 at its thinnest, .035"..the outer lip is the .035" ±.001

I cut it out of .500" x 2.00" x 2.70" Stock...it has 3 tabs.....they're .030" wide and .010 thick..the part is processed, both sides complete, the last operations is machining the tabs...

This is the most I can show of the part as it's an ITAR project

 

Yes, the backside of those fixture rails are open windows letting me get at both side of the part.....the front plate is the prep plate, skin the face, add the mounting holes..That is a 400mm x 625mm tombstone 

It took nearly an hour a piece in our prototype shop/low production shop area, they used vises and such and fought the tolerances....

This process is just over 3 hours for 12 pcs....that's about 17 minutes per...the extra stock cost is easily negated as the cost of manufacture has gone WAY down

 

Edited July 23, 2018 by Guest