tooling for repeat punching of holes accurately on Ironworker

[Machine Shop BDS]

Hey All, we need to punch 3/4" square holes in lengths of aluminum channel 1" x 2" x 20' accurately as we also need to punch a cover plate to match. using our Edwards 55ton ironworker,

As I mentioned it needs to be accurate if each position is out by .0002" that could add up to an 1/8" misalignment on the last hole.

This tiger stop https://www.tigerstop.com/products/tigerstop/ would be perfect but its way out of my budget

I'm thinking of a tapered locator to hold the position on each cycle, wondering if any of you may have built or seen a good method or tool available.

Thanks in advance

Regards Chris

 

[Nmbmxer]

...position is out by .0002" that could add up to an 1/8" misalignment on the last hole.

I would start with your MMC positional tolerance stack-up for both parts and work backwards. Sounds like incremental positioning is not going to work, a pin that is sized to be able to easily drop into the hole will give you compounding errors if you don't ensure it's pushed firmly to the stop each time, and the hole size tolerance makes it worse still. Also see the attached chart for what the NIST considers metal tapes accuracy, 20ft falls into a 1/16" tolerance. So even verifying if your first and last holes are right will be challenging. Half of your tolerance (if you want 1/16 true position) is used up if you measure each part of the assembly with a different tape measure. I'd slot one or both parts personally.



I had a job that needed repeating hole patterns on a channel that was much to large (12') to fit on the Prototrak mill that we wanted to use for positioning the part in X&Y. I made a large fixture that had popup dowel pins every 24" and you would clamp the part against the first pin, then drill a table full of holes. Then drop that pin and pop up the next one, reclamp and repeat the drilling. Determine how many holes you can add up before you can't meet tolerance and then move to the next accurately place locator. Or slot the holes.

 

[Ries]

I think its way more work than its worth to try to do this on an Edwards. I would send it out to somebody who has a cnc turret punch. I have a Geka, which is much sturdier than the edwards, and it has pretty decent steel scales on the built in heavy duty length stop, but it wont hold .0002 over 20'. I cant imagine a machine, any machine, without actual dro style scales holding that kind of tolerance over 20'. You could build a 20 foot table for a home built stop system based on the old biesemeyer stops- I built a 12 foot stop for my bandsaw I use for stainless, which comes in 12' pieces. But its based on an adhesive backed steel measuring tape, which doesnt have the accuracy you want.
Ironworker holes are, by definition, sloppy, as the clearance between punch and die is oversize to allow for a range of thicknesses. Unless you have a custom square punch and die ground exactly for your thickness, you are gonna be talking about slop way more than .0002 between 2 or 3 hole sequences. I just think you are trying for something that is not do-able without the right tool, and even with a tiger stop, there can be some slop in square holes. https://www.mikestools.com/biesemeyer-miter-saw-table-systems_1447.aspx

 

[Superbowl]

Drill round holes on your mill for all 20 ft using the DRO to measure between holes. Then make a square punch with an integral centering button.

 

[john.k]

I used to get the side members of hydraulic presses punched by a local fabricator ..1/2 " x6" steel..........he used to get the punched holes accurate to 002 ,often to 001 .....this is for the dozen or so holes in each side of the press uprights...........all he had a was small punch and shear ...small Omes ,I think......certainly no turret punch.

 

[memphisjed]

Tiger stop is the fast easy (cheapish) option. Angle line would be how the mid size shops would do it. Tiger stop will have wiring into the ironworker to automate the process, which is pretty sweet. Tiger stops are bad ass.
You can build a multi stop with aluminum extrusions and a sled/stop on simple v bearings. A ratchet dog on sled catches t-nut tabs in extrusion. These stops are set with a tape measure so no stack up error. Pipe bending machines use this design. Works well enough.
Angle masters are the cnc machine for doing these normally.

 

[Fish On]

Hey All, we need to punch 3/4" square holes in lengths of aluminum channel 1" x 2" x 20' accurately as we also need to punch a cover plate to match. using our Edwards 55ton ironworker,

As I mentioned it needs to be accurate if each position is out by .0002" that could add up to an 1/8" misalignment on the last hole.

This tiger stop https://www.tigerstop.com/products/tigerstop/ would be perfect but its way out of my budget

I'm thinking of a tapered locator to hold the position on each cycle, wondering if any of you may have built or seen a good method or tool available.

Thanks in advance

Regards Chris

Does the hole placing need to be positionally accurate to the drawings to that tight of a tolerance, or is it just that the channel and cover plate need to match?

 

[dkmc]

.0002
on an ironworker

 

[memphisjed]

.0002
on an ironworker

It is not .002 tolerance, it is stack error issues. If your jig is set to 4.001 inches by the time you get to hole 100 you are .1 out of position. Common error to see with people using offset jigs or even repeat spacing programs in steel parts.

 

[dkmc]

It is not .002 tolerance, it is stack error issues. If your jig is set to 4.001 inches by the time you get to hole 100 you are .1 out of position. Common error to see with people using offset jigs or even repeat spacing programs in steel parts.

You best count the zeros

 

[memphisjed]

.0002
on an ironworker

Read out by end of bar. It is all stack issue. I have never seen a single stop/jig work for this type of work, yet they keep happening, boss people and suits keep saying they work. You can do it if you layout one bar, and then watch as error grows, then position hole where it needs to be manually once tolerance point is reached. Could be 2’ of using jig, could be 4. Multi-stops set with a tape measure can run a full stick. Lots of incremental moves are not equal to lots of modal moves.

 

[Limy Sami]

.0002''? ........on an ironworker? ............good luck with that - you'll need it

 

[michiganbuck]

Is the assembly going to be disassembled?
If not might or rarely you make holes oversized, locate the parts, and then use a filler to locate the exact location with some release agent on what holds it together. But this would make them match pairs. likely not what you are shootomng for
I think a next-hole gauge would be lucky to hold .005.

 

[Machine Shop BDS]

Does the hole placing need to be positionally accurate to the drawings to that tight of a tolerance, or is it just that the channel and cover plate need to match?

the channel and cover plate marching are the important part

 

[Machine Shop BDS]

Hi All, many thanks for all the good points, appreciate your reply and time. I think Superbowl has a good suggestion, basically making one template out of steel and some how fix in place parallel to the channel to be punched and have a location pin to locate in the template to punch each position,

A few commented on the accuracy of the iron worker, I don't see this as an issue as it does not matter if the hole position is out by as much as .020" its just that it cannot stack up and accumulate , so by using the template set by a DRO or CNC this should work pretty good, will put some thought in to how to set this up.

I welcome any further thoughts or ideas.

Regards Chris

 

[Rocketdc]

I mounted DRO fences from proscale.com to my ironworker on my punch and shear stations. They have stops that you can set in the fence that flip away if you need to set multiple repeatable positions. They're not heavy duty, but if you're reasonably careful you can get good repeatable accuracy and I think you can get fences up to 20' for around 2K. I only use the flip away stops to quickly locate the DRO stop which locks in much better, the flip aways only have a set screw into the aluminum fence, not strong enough to use as actual stops.

 

[Machine Shop BDS]

Rocketdc, thanks that is a nice setup! does it have the same mode as a DRO where you can locate a specified amount of holes and distance apart?​

 

[Rocketdc]

Rocketdc, thanks that is a nice setup! does it have the same mode as a DRO where you can locate a specified amount of holes and distance apart?​

You might be able to set those inputs into the DRO, not sure. I would ask the company, they have different models. I was looking at lots of different options from the tiger stop down to basic flip stops and these DRO's weren't much more than the tape on scale, basic flip stops, except these encoders are a bit more accurate and repeatable. Tiger stop is nice, just can't justify the expense for the amount of use it would get and it's not as flexible as this setup.

I set mine up with an extension that bolts onto the existing stops that mount on the punch table so I can slide different length fences on depending on what I'm doing or remove the whole thing entirely with a couple of kipp levers. Having a long fence permanently attached to the table is cumbersome and takes up a lot of room so I keep a short 36" fence on for day to day use.

 

[Fish On]

the channel and cover plate marching are the important part

Ok, so ironworker tolerances are fine.

For avoiding tolerance stacking, just index all holes from the end of the bar. Instead of a pin jig from the prior hole, set up a 10' or 20' fence (depending on feasibility of flipping the part) and use flip stops from the end of the bar.

Doesn't even have to be flip stops. Could be fixed stops that are next to the bar, where a tab is clamped onto the bar to catch each stop.

What's the hole spacing, and how many parts do you have to run?

 

[Overland]

I have a DRO on my 21"x80" lathe. Trax from memory.
The unit is bolted to the carriage with a roller arrangement that runs along a machined surface on the side of the bed. Some form of encoder I imagine. I've checked it repeatability several times by running the carriage up and down the lathe to an indicator, and it is very repeatable. I would think it would be fairly straight forward to mount this to run along a rail on your fence and keep track of the position.