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Punch press design

Billbwi

Plastic
Joined
Jul 13, 2022
Doing design work for a punch press for rubber walk mat coping. I will be punching 1/2 inch square along the edge of an extruded rubber core. The slots with be 1 inch center to center. Punch press is a simple die shoe with cutting dies attached. My question is what would be the best linear feed mechanism to maintain an accurate 1 in center to center on my cutouts? Would a pressure roll driven by the press do the job if so any diagrams that would help in the design? Without getting elaborate and over budget is there a servo drive or encoder that would be better? Thanks billbwi
 

sfriedberg

Diamond
Joined
Oct 14, 2010
Location
Oregon, USA
Rubber could be a bit tricky, as it's much stretchier/compressible than metal strip.
Have you already considered some basic techniques such as
1) punching multiple holes at a time (with spacing guaranteed by the punch holder), followed by
2) feeding the material until the last hole punched (in one set) registers with a locator in the die base?
Normally, rigid material would be fed with sufficiently weak force and with adequate edge guides that when the last hole punched encounters the registration locator, the material does not buckle. With rubber, that's a bit harder, but if you are already thinking about "smart" feed, you could feed forward until you hit the locator, then reverse to establish a specific (small) tension on the material. This tension would be a process parameter you would establish during tryout that gives you consistent hole positioning.
 

rogertoolmaker

Cast Iron
Joined
Jan 3, 2016
As mentioned in the previous post above feeding rubber may be more than a challenge depending on the durometer of the rubber. If you decide to attempt to feed the rubber, pulling rather than pushing the sheet. Please post the part dimensions. The size of the part has a lot to do with the type of feeding equipment. Look at Rapid Air Hitch Feeds.
Roger
 
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M.B. Naegle

Titanium
Joined
Feb 7, 2011
Location
Conroe, TX USA
Benchmaster used to make a mechanical die press100_3384.JPG with a feed roll mechanism that was used for perforating strips. We used to service and sell them for leather belts that had holes along the length. It's been awhile since we had one in the shop, but if I remember right it was set-up to keep punching as long as the lever or pedal was engaged (no single trip), and the rolls would index an adjustable amount between each trip via a friction drive. Their rolls were a closed side design, but I wonder if you could do something similar with a open roll and feed table which the operator could assist through? Trick with feeding soft or stretchy goods through a machine like this is keeping the side that isn't being feed moving at the same rate as the side that is being fed. If you let it just hang out the front of the machine, the operator will constantly be stopping and repositioning, so having some kind of table with guides will help.
100_3378.JPG
100_3386.JPG
 

Billbwi

Plastic
Joined
Jul 13, 2022
That is exactly the set up I need. The rubber I have to punch is stiff enough to feed thru with knurled pressure rolls. I was hoping there was a way to attach the roller feed to the press flywheel. I might have to go with a separate feed that can be monitored by an encoder or servo motor
 

Strostkovy

Stainless
Joined
Oct 29, 2017
How long is it? If it can be mounted on a belt driven sled I would go that route.
If not, I would use a pneumatic clamp/shuttle system, where you have a stationary rear clamp and a mobile front clamp.
The front clamp is closed during punching. The rear clamp then closes, the front opens, and then the front returns back to its neutral position. The front clamp closes, the rear clamp opens, and the front clamp shuttles forward into an adjustable stop.
 








 
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