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JimDawson

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#1
A customer asked me to build a special high speed punch press for punching some plastic parts from a strip. I can't go into any product detail, but I can give the general specifications for the machine.

Target speed: 600 hits/min, more realistically 300 or so I'm guessing.
On-the-fly infinitely variable feed length from 1 inch to 6 inches
Easily adjustable for different punch patterns.....More on this later.
Because it's punching plastic, a push-pull feed system
1.8KW servo drives on both the feed and crankshaft drive.
Touch screen operator interface.
2 axis Galil motion controller

Just a teaser picture...I'll post more later

One of the side frames 12x20x1 A36 steel
1536272287686.png
 

vtcnc

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#2
A customer asked me to build a special high speed punch press for punching some plastic parts from a strip. I can't go into any product detail, but I can give the general specifications for the machine.

Target speed: 600 hits/min, more realistically 300 or so I'm guessing.
On-the-fly infinitely variable feed length from 1 inch to 6 inches
Easily adjustable for different punch patterns.....More on this later.
Because it's punching plastic, a push-pull feed system
1.8KW servo drives on both the feed and crankshaft drive.
Touch screen operator interface.
2 axis Galil motion controller

Just a teaser picture...I'll post more later

One of the side frames 12x20x1 A36 steel
View attachment 275030
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JimDawson

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#3
A quick overview of the electrical
The basic panel layout, DMM DYN4 1.8KW servo drives, and the rest of the hardware is from Automation Direct
1536336509398.png
The DMM 1.8KW servo motors, and other bits & pieces
1536336550754.png

The fanless micro computer w/Win10 and a 10 inch touch screen.
1536336584664.png
 

rgray

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#4
Watching with interest.
 

JimDawson

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#5
I had to drill & tap four 3/8-16 in the top of the frame to secure the top cover plate. The only machine I have with enough height to handle 22 inches is the old Harbor Freight drill press. It normally has a counter sink in the chuck for deburring, almost never actually drills holes.

1536365150828.png

So first beef up the DP table a bit, don't want to break it off when I set 150 lbs of iron on it.
1536365361195.png

I got the holes drilled & tapped and I didn't kill the DP :)

1536365413980.png
 

FOMOGO

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#6
Sounds like a challenging project. Nice work, making do with what you have on hand. Mike
 
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JimDawson

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#7
The next part is the connecting rod. Material = 4150, so we start out with a chunk 8 1/2 x 4 x 1 1/4.

1536592896371.png

First mount up a ''spoil plate'' in the mill vice to bolt the work to. The aluminum is just a piece of stock I had on the shelf, when done with this project, it will go back on the shelf and get used for something else.
1536593185284.png

Face off and drill & tap 1/2-13 mounting, the side holes will be used later. Since there are several operations, I spent quite a bit of time ''machining'' the part in my head to get the order of operation and work holding correct. I set the stock on top of the aluminum aligned it and clamped it down, and set the 0,0 at the top right edge. Then I scribed a line and witness marks to be able to locate the part again. This insured that the holes in the aluminum and in the stock agree in location. This 0,0 location will not change until the job is completed.
1536593404286.png

Since the entire outside needs to be profiled it gets bolted down at the bearing and pin ends. That allows access to the entire outside and for other operations. The bearing bolt is counterbored deep for a reason.
1536593510096.png

Then I took a 0.010 deep pass to mark the profile, then unbolted the part and over to the band saw to remove the bulk of the material to save spindle time.
1536594069987.png

Then back in the mill to run the roughing passes. The bolts don't have a lot of clearance, but I'm sure the part did not go back on exactly the way it came off, but it doesn't matter, the OD will clean up to size on finishing and everything else will be relative to the current location. Using a 1/2 rougher, full depth, with about 0.050 width of cut.

1536594397727.png

And the finishing pass, 5/8 Harbor Freight 4 flute. It's what was in the holder. :)
1536594594516.png

The crank end is 18mm thick, but the pin end is 1.25 so half of the difference needs to be removed from each side of the rod. So remove 0.270 in two pocketing passes with a 3/8 rougher. Now you see why the bearing end bolt was counterbored deep.

1536595042648.png

Then pocket out the center web another 0.250 deep just to remove some mass, and do some other cleanup in preparation for machining the radiuses with a 1/4 ball end mill.

1536595290550.png

Machining the radiuses, don't want any sharp corners that would cause stress risers.
1536595403549.png

And the first side is finished. Now it gets flipped over and the same operations are performed on the other side.
Then once that work is done, the bearing and pin holes will be bored.

1536595519777.png
 

BaronJ

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#8
Hi Jim,

If that were me drilling the holes in the top of that hunk of metal, I would have put it on the foot of the drill and dropped the head down to suit !
Reminds me of drilling out holes that were too small in a propshaft spider that was already welded up.
 

JimDawson

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#9
Hi Jim,

If that were me drilling the holes in the top of that hunk of metal, I would have put it on the foot of the drill and dropped the head down to suit !
Reminds me of drilling out holes that were too small in a propshaft spider that was already welded up.
That would work. The problem with doing that on that particular drill press is that the head won't drop without extensive modification. :)
 

BaronJ

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#10
Hi Jim,

Oh thats a bugger ! My floor standing drill press at the time was a "Fobco Star" 1/2" with a column that passed through the drill head. That made it easy to lower it, right to the floor if needed. I originally had three of them, two floor standing and one bench mount. I kept the bench mount one !

The number of times I wish I had kept one of the others. Annoyingly the floor standing ones were a couple of years newer with 16 mm chucks, and bigger tables.

Edit: Sorry it is the bench one with the 1/2" chuck.
 

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#11
OK in the previous post one side of the connecting rod was finished, so now is time to do the other side. So first mill a con rod shaped pocket into the aluminum. 0.125 deep and a loose press fit. This locates the part exactly back relative to 0,0 without having to dial anything in after it's turned over. The screwdriver pockets are so it's possible to get the part out of the aluminum block, you need to pry it out.

1536637997775.png

The same operations were performed on this side as the first side. I left the ''island'' on the crank end because I didn't have enough meat in there to counter bore for a screw. So I used flat head screws on this side for tool clearance.

Also you now see why the side screw holes were there. All they have to do is hold the part down, the pocket holds it in location. The next step is to pocket and bore the bearing and pin holes.
1536638620284.png

While the con rod was running, I was setting up to fab up the feed rollers in the lathe.
12 x 4 inch dia 8620. This was another bit of a screw up on my part, originally I designed the rollers to be 3.800 dia, and ordered the material. After a design review I decided to make the feed rollers 2.75 diameter so I'll be making a lot of chips to get this down to size.

Does this look like too much stick out? :grin:
1536638933498.png

Yeah, I guess it is. :cautious: Note: The chuck jaws are at the absolute limit of extension where I will run them. So support it in the steady rest to face and center drill. For center drilling I normally face a small area, in this case about 1 inch dia. Then center drill and then finish the face after the center is in place.

1536639032076.png
 

JimDawson

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#12
Finishing the connecting rod

First I profiled the big end bore to remove the material as efficiently as possible without having to turn the entire volume into chips.

1536805526970.png

Then I drilled the pin end with a 1 inch drill then to out a bit more by profiling the bore. Final diameter is 1.250
1536805651306.png

Then bore to size. Using a 3/4 inch 2 flute endmill for a boring bar. Nice and stiff and sharp. You just have to get the tip of the set at the correct angle. Works great, I use endmills in the lathe for boring bars also when doing shallow bores.
1536805917673.png

And the finished rod with the bearings pressed in, bronze flange bearings in the pin end. I reduced the mass of the 8 1/2 x 4 x 1 1/4 raw material by about 65%.

1536806301957.png
 

FOMOGO

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#13
That came out great. Thanks for the walk through of all the operations. Mike
 

JimDawson

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#14
Thank you Mike. It's my pleasure to try to show some tricks & tips.
 

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#15
The next part of the project is to make the driven feed rolls.

The original design called for 3.800 dia rolls so I ordered a foot of 4'' dia 8620. Well I changed the design so now the feed rolls are 2.625 dia. Had to make a lot of chips. This stuff cuts nice, tough, but didn't give me any problems once I figured out the feed & speed and depth of cut. I could only take 0.050 off of the diameter per pass on my lathe.

First face and center drill for the center. When doing something like this, I just face a small circle around the center, no need to face the whole end, the saw cut was pretty straight. Just need a flat surface to keep the center drill from walking around.


Then turn down to 3'' dia for roughing out.
1537062236632.png

Then over to the band saw to cut into part sized pieces. Once back in the lathe, do the work on the front end and bore for the shaft. The bore will now become my base surface. The bore and counterbore are concentric, but the OD is subject to the runout in the chuck (about 0.003), that's why to OD is only roughed out at this point. For the finished piece, the bore and the OD must be concentric.
1537062625740.png

Then flip it around and machine the step on the back. The OD of the step does not have to be perfectly concentric to the bore, it just holds a couple of set screws, chuck tolerance is good enough.
1537062866214.png

Once I have the part to this point it's ready to key, I didn't get any pictures of that operation. I have a Dumont broach set and a broach press. Here is a picture of the broach press, configured as a mini press brake in this picture. Built from a Chinese wood splitter. Not much of a wood splitter, but makes a great long stroke 7 ton arbor press.
1537063765501.png


Then over to the mill. This is the shaft that the roll will run on in the machine. First mill the keyway.
1537063910186.png

Then D & T the set screw holes. I set up the spindex because I wanted one hole over the key, and the other at 90°. The part is located off of the edge of the vice so the spindex only needs to kinda hold the shaft. I just shimmed it to the right height. This is the first time I have used the spindex, I've had it for 25 years :) Had to clean it up a bit before I could use it. I's been sitting in the back of the bottom shelf of the tool cabinet for a long time.
1537063977410.png

Then back over to the lathe with the shaft in the collet chuck. If I didn't have an accurate collet chuck I would have either used the 4-jaw or turned a stub arbor in the 3-jaw to have a concentric shaft to mount the part on for finishing. This is the best solution because the roll is mounted on the shaft that it will be running on in the machine, so the best concentricity that I can get. This chuck has about 0.0002 runout (after I reground the bore). Now I can finish the OD.
1537064691007.png

Once the OD is turned to size then knurl so it grips the material. The two rolls are slightly different sizes, I want to outfeed roll to pull a little faster than the infeed roll. About 0.5% difference in the circumference. This should prevent any tendency for the material to buckle as it feeds through the press.

The shaft tried to walk out of the chuck during this operation, so I moved the tailstock center into position for a little added support. Running at 70 RPM with a slow feed. Using heavy sulfur cutting oil. I start with about 1/2 the knurling roller on the part and feed towards the headstock, then feed until about 1/2 the knurling roller is off the part on the other end. Then stop the chuck, reverse the feed, and run back to the start point. If needed, go a bit deeper and run again. I did these in two passes. Don't retract the knurling rollers from the part until you're happy with the result, it will screw up the pattern. I need to buy some new knurling rollers, these are junk, the center hole is about 0.010 off center. The holder is fine.
1537064987282.png

And the finished parts
1537065645814.png
 

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#16
Next is the real heart of the press, the ram. This press is unique in that the die is integrated into the press rather than being a seperate part as in most presses. This is a single use press so this works out well. This means that there is no margin for error and the tolerance stackup has to be minimized. I have been doing surface grinder quality work on the mill, have been holding +/- 0.0001 on the critical dimensions. The good news is that properly set up, my machine will hold those tolerances.

The first step in the process is to get the fixture block set up, the same chunk of aluminum I used to fixture the connecting rod, I just used the other side.

The nut for the wrist pin nut is the item to be made, 2 inch 1018 shafting. The fixturing holes are already drilled & tapped.
1537461694308.png

The nut mounting holes done.
1537461778012.png

Then pocket clearance for the nut so it can be attached to the rear ram plate, this way it can be drilled & tapped in the same setup as the pin hole in the ram plate, this insures that everything is concentric.
1537461983413.png

Aligning the ram plate on the machine 0,0. I just scribed lines in the proper place to set the 0,0 point, nothing critical here because the piece is oversize at this point.
1537462186118.png

Then drill and C-sink the mounting holes. Using flathead screws for tool clearance.

1537462304637.png

I screwed the part down and took a shallow profile cut to get an outline and drilled & tapped the nut mounting holes. Then over to the band saw and cut out the part and attach the nut. Again nothing is critical at this point because the part is just roughed out.

1537462549385.png

The finished part. The sides, bottom, and pin hole location relative to each other are the critical dimensions. 1 inch shoulder screw.
1537462765188.png

Then I made an identical plate for the front side without the nut.

Then I made two spacer blocks that will hold the spacing of the two ram plates correctly for further operations. These will be used later to mount the bolster plate.
1537463043293.png

Now I can drill & tap the holes for the linear bearing blocks and the bottom plate. I used a couple of 1/4 '' flathead screws to hold the assembly together.
1537463348760.png

The bottom plate, also drilled & tapped for the punch holder. I have been able to drill the dowel pin holes and have everything line up, good repeatability.

1537463519729.png

And the finished ram assembly.
1537463624054.png
 

JimDawson

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#17
Next the punch holder that attaches to the ram.

Still using the same aluminum fixture block, I had it pre-drilled & tapped to accept this part. This is a chunk of 4150, same material as the connecting rod. Clamped a larger chunk to the fixture drilled & c-sink, and drill & ream the dowel pin holes. Then did a shallow profile cut to mark the OD, then cut it out on the bandsaw. Then bolted it back down to the fixture for finishing.

1537499358649.png

Then drill, straighten, drill & ream the 7 punch holder holes. Straighten? After drilling the pilot holes at about 0.170, I went in with a 0.187 endmill to insure the holes are straight, then drill with a 0.236 drill prior to reaming. Then ream with a 0.2495 reamer to fit the 0.250 punch shanks.
1537499882726.png

Once the holes are reamed then flip the part over and mill the clearance for the punch heads.
1537500010036.png

And there it is..... the ram installed in the press. The action is silky smooth, I'm happy with the way it came out. Everything fit as planned.

It's really too bad that all of the really cool work is going to be hidden inside the covers.

1537500332131.png
 

JimDawson

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#18
I kind of started this thread in the middle of the project so here are some pictures earlier in the project.

Here is the stand that the press will be installed on. 2x2x1/4 square tube. Took me about a day to fab this up.

1537500831040.png

The press frame showing the crank housing and motor mounts.
1537500985532.png

Fitting the feed system and linear bearing rails
1537501107395.png

The rear view with the motors in place.
1537501175350.png

The crankshaft, made from 3 inch 4340.
1537501477920.png

Once the steps are done on the right side then go in and nibble out the the left bearing journal. Just plunge a bit with the tool as you are moving the carriage back & forth a bit while plunging in with the tool bit. The crank journal is left at 2.125 inch to be able to turn the eccentric.
1537501609074.png

Once the journal is roughed out and tool clearance turned, then go in with the right hand radius tool to finish and put a generous radius in the the corner.

1537501968204.png

Then setup the steady rest and drill & bore the motor end. This will press directly onto the motor shaft. Got a little hot when I was drilling it. :)
1537502119505.png

Once cut off in the band saw, I built a plug to go in the end so I can clamp it in the 4-jaw without squishing the end. The threaded end is so I have something to grab onto to pull the plug back out.
1537502363978.png

Then set up in the 4-jaw to turn the eccentric. To insure the part is pointing directly at the tailstock, both bearing journals are measured to make sure they are in the same plane. This is done by dialing it in then bumping the part with a dead blow hammer until it's lined up properly. The offset is supposed to be 0.375, but 0.3755 is close enough. Took about a half hour to dial in to this point. The bearing journals are 30mm and the crank journal will be 40mm, that way the the connecting rod will slide over the bearing journal onto the crank journal with 0.010 clearance.

1537502885164.png

The center drill is on the spindle centerline. looks a little weird :)
1537502967673.png

Starting the eccentric

And finishing

And the finished crankshaft. I didn't get a picture of slitting the sleeve that presses onto the motor shaft. The crank bearing is a tight slip fit on the crank journal. It has to find its own center so could not be pressed on. The bearing journals are a light press fit as are the crank housing bearing bores.

1537503673195.png
 
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