enlarging vacuum holes

[spock]

A customer has asked me to quote drilling out about 15,000 vacuum holes in thermoform mold tooling.(Alum. material) Currently .016, they want .020 dia.
Problem is, I did not build the originals nor do I have prints. every hole would have to be put in manually, after "eyeballing" location of original. Many are on angles or start in radii.
Does anybody out there have any experience doing this, is it feasable? I have some experience putting the .020 holes in new tooling, but never have been asked to open up existing.

[One of Many]

I have a made at least 5 years of thermal form tooling, and I have never seen a tool that would ever need than many vacuum holes. Nor could I imagine the minimal gain if changing them by a mere .004 unless very rapid cycle times shaving tenths of a second are that critical.

Would they be inspecting every hole for tolerance?

Can you open these holes from the back side of the die, taking advantage of the "possiblity" of drill re-entry taper is less significant compared to the exit where it counts?

Sometimes, whatever it takes to please the curiosity of whom ever requests a change like this, it must be done.

I'd consider doing it the simple way by hand with a little WD-40. Using a piece of drill blank in the original hole could give you an idea how to orient your drill bit in a dremel over the existing hole. The larger drill should still follow the original hole. If you can find a drill long enough, use the other hand to hold in place a drill bushing on/near the business end of the drill and let it seek its own path, yet be ready to compensate with the dremel end. Careful you do not slip out of the drill bushing and spear yourself with the drill.....not that I'd know anything bout that.....er anything....well, uh....?

I doubt it is worth over complicating for the purpose of vac holes. They would really need to justify their case if they really expect drilled vac holes +/- .004 and the cost to produce the same of that many holes.

DC

[MrMold]

Although I don't profess to be an expert in Thermoforming. I have built a fair number of tools. You'll need a steady hand and a fair number of drill bits. I'd lay off the coffee that day. You'd be suprised how fast they go. Don't be too concerned with a few broken bits, it's going to happen. I'd probably use some kerosine or mineral spirits. As for what the customer is trying to accomplish and the insane number of holes..........well if he's paying for it let him worry about that. I suspect other problems with the tool or process.

[spock]

The reason for the change in hole size is to increase vacuum (of course). The customer is contemplating a change to a "stiffer" material, (polypro) and they think they will need the increase in vacuum. As for the number of holes, this is spread out over several sets of tools.
The drilling has to take place from the mold surface side, these are deep tools with .25 holes drilled in from the back and the .016 breaking in to connect the vacuum to the source.
I like the dremel idea, I am going to do some experiments and see how they go. On new tooling I use the sensitive spring loaded chucks, which work well. But these are mounted in a b.port type mill, and using this system means I am would be constantly realigning the mold tool with the spindle. I have my doubts as to whether I can do that or not, (or if it is even worth it).

[One of Many]

Poly has it's own issues since it has a such a memory and will not likey stay put on dies with fine detail or sharp corners as it cools. Poly's higher forming temp, also retains heat a lot longer than many thermal formed materials. If they like the way the part looks in ABS, it is not realistic to expect the same detail out of poly-anything.


It may be possible to use water chilling lines in the tool, in an effort to freeze off the material rapidly to circumvent some of the relaxation. The problem with rapid chill is that this can force the need for heater cartridges in the tool to return it to forming temp in a reasonable amount of time. That is a vicious circle and best be worth the additional complexity!

Larger holes do not increase the vacuum pull on the material directly. It increases the speed at which it pulls over time. This is where a combination in lack of surface area that the vacuum can work on, along with specific material attributes, are a detriment to the desired result. Course Sandblasting the tool surface may help keep the material from sealing off so that the vacuum available does act on a larger area by capilary action between the die and material.

DC

[spock]

One of many,
thanks for the info. I will try to pass that along, maybe they will change their mind! one can only hope.....
I have been sitting on this quote for several days, not sure whether to turn it in or turn it down. If a job like that goes well, all is fine but if it is a slow, tedious disaster it would stop up workflow for who-knows-how long. Thanks again for the input!