Help with pneumatic or hydraulic presses 2

[Bradbyname]

Hi guys
For the past couple of years we have been drilling a 4mm hole on one side and a 6mm hole on the other side of an ABS plastic box which is 4mm thick.

Worth noting also, is that after this i plan on making one which will stamp out 1mm thick aluminium sheet.

I am looking into making a press to make both holes simultaneously but i am unsure as to what i should be using for this. I have read up on hydraulic rams which i see can provide tonnes of pressure, but then on the other hand there are pneumatic cylinders which are more appealing to me as i would like to run this off our compressor, and they're quicker!.

If anyone is experianced with these and you could share your knowledge with me it would be greatly appreciated. no doubt by reading the above, you can tell ive walked into a brick wall


Kind Regards
Brad

 

[MintJulep]

Designing a good punch press is non-trivial, and there are plenty of commercially available punch presses that you could buy for far less money that it would cost you design and build one of your own.

 

[kingnero]

Also, if they are hollow plastic boxes, it probably won't work as there is no "back" pressure.
I guess you're talking about 4mm wall thickness?
The box's planes will most likely deform too much in order to have a clear punch-through.
However if you could work around this, punching the holes is a doable idea.

 

[Bradbyname]

Thanks for the reply, however the comemrcial presses i have seen do not press in two directions at the same time.

I do own a lathe and a mill and quite a bit of tool steel at my disposal, and i have a good understanding of machining the two end die. Granted the cost of the pneumatic parts may be close to what i could have picked up a cheap hydraulic press but that does defeat the object when you enjoy creating the products from scratch

 

[Bradbyname]

Thanks Kingnero.
Yes i intend on making a jig which the boxes slot over to provide the back support on both sides.

 

[ajack1]

The “normal” way to do this is to use a couple of cam pierce units in a conventional press have you considered this option?

Pages 26-31 show some options but there are many different companies make cam units or you could even design your own.

 

[Occupant]

I have done this, however, with air over oil cylinders (the manucturer escapes me at the moment) and as ajack1 already said there any number of cam units available to redirect the motion.

 

[Bradbyname]

Thanks ajack, occupant. The cam is a good idea if i choose to utilise one cylinder - which from a price point this is likely.

Occupant, the problem i am having is working out how much force i would need in order to punch the plastic boxes. I have seen some 1/12" cylinders which would generate the equivalent of 63KGF, but that doesnt sound like enough. the bigger cylinders with a 200mm bore, seem extremely expensive in the region of £800.00

If you could shine any light from your past experiance of using air, it would be greatly appreciated

Kind Regards
Brad

 

[moon161]

Are the holes concentric? If so, you could make them in 1 process w/a stepped drill.

 

[MikeHalloran]

Punching ABS is not going to give you clean holes; they'll have a lot of die break, and cracks.

You could investigate 'drill cylinders', basically half a drill press.
... or just physically disassemble a couple of Chinese drill presses and put air cylinders on the feed.

Or use air cylinders and slides to advance a couple of big soldering irons with hollow tips. The resulting holes will be ugly, but stress-free.

Or go ahead and tool up to punch and bend the box from metal.
Or pay a small-lot manufacturer to do so; if you can buy 500 or so this becomes attractive.



Mike Halloran
Pembroke Pines, FL, USA

 

[Bradbyname]

Thanks for the info Mike, drilling may well be an option. I do buy these boxes in quantity, but we try and do as much in house as possible to keep the costs down obviously. hence why i am looking in to this. even if it cost me a small fortune to design an automation system for it it would well be worth the trouble in the long run.

The short answer would be to take up injection moulding and mould the boxes as we so require. However that i feel will be one to contemplate in the future!

 

[SnTMan]

Depends on quantities, and the ablity to cleanly punch ABS, but..

I can't believe it takes a great deal of force to punch a 6mm hole in 4mm of plastic. A hand operated punch should do the job.

Regards,

Mike

 

[MadMango]

Quantities and rate will determine what should be used. You might want to also consider a custom broaching tool as well, coupled with a simple arbor press.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[potteryshard]

Rather than punching, it might be easier to use a plunge router with a pilot guide. A template could drop over the side (or whereever) of the box to locate the hole(s).

 

[Bradbyname]

We currently use a pillar drill which is quick in itself. Its just changing the drill bit and repeating the process on the other side i am trying to eliminate. after the comments above have highlighted that the ABS may crack and have a poor finish i feel more inclined to design a mechanism to advance two motors back and forth on a rail

But thanks to everyone for their input. its certainly given me plenty of food for thought

 

[berkshire]

Bradby name,
If changing the drill bit is a problem, just set up a second drill press alongside the first, have them both running and move from one to the other.
Or if you do not like moving around, invest in a Burgmaster Turret Drill.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor