Help, PVC pipe perforating machine design

[rustyk]

Need a little help with the design of a machine to drill holes in PVC pipe.

Pipe size ranges from 1-1/2" dia - 10" dia. Hole sizes range from 1/8" dia - 1/2" dia with the average size being 1/4" dia. Hole patterns are typically 2 rows of holes, one row at 135 degrees and one row at 225 degrees. The rows of holes are straight down the pipe centers usually being one of the following 1",2", 3", 4" or 6" centers, sometimes the holes are in line with the others but mostly the centers are staggered from each other. The material is PVC pipe sch 40 and sch 80, so it drills very easy. The pipe is 20 feet long.

I have been thinking about this for a long time and have had many designs in my head some good, some bad, and some just plain stupid. I have a 5x10 router. I have thought of building a 21 foot long x,y,z table type router setup that would hold 3,4, or 5 pipes and have a router or a drill head move along the pipe and drill the holes, only problem is that it would be to slow. I want to drill multiple holes at one time. Accuracy is not important +/- 1/4" is close enough.

I saw a real crude setup at a local septic tank manufacturer. They took 12electric hand drills and duct taped them to a 2x4 board mounted over a pipe on a table. The board that held the drills was held in place by two boards at the ends running back 4 foot and hinged to the table (the drills did move on an arc but it seemed not to matter). Overhead springs held the drills up. Plug it in, pull down and hang on, it was funny to watch this guy drill pipe, but it did drill 12 holes at one time and fast.

I laughed at the setup at first but while driving back to our shop I realized that this guy had a good idea, just terrible machine building skills. I have thought of building something to drill 10 feet at a time, one row on 6" centers. This would mean mounting 20 drill spindles on a z axis on 6" centers(this would cover all the centers except 4" without removing drill bits) I have thought of building a frame that would hold one pipe on an adjustable height angle iron base The frame would be several feet above the pipe to allow travel of the z axis with no racking. A person would index the pipe for the different rows and slide the pipe in or out to get the ceners needed. Z axis travel by means of stepper and ball screws or maybe hydraulic.

Make the spindles? buy the spindles? What would be a good way to drive drill spindles? Timing belt, 90 degree gear set on a shaft

Anybody ever seen one? Unfortunately Google doesn’t help on this.

Any ideas to help me?

Thanks

[DareBee]

It is the spindles that are killer on this job.
I have R&D'd almost identical machines.
Air drills are no good for most people needing this many spindles because you will need a 50hp compressor to get enough CFM for continual use.
Even electrically it takes a LOT of amps to handle the start spike of 20 6 - 8 amp hand drills.
Anyway
It is crappy design but the only inexpensive method is the Clamped-on-hand-drills.
I have looked for off-the-shelf "cartridge" drills to no avail. You can get the bodies for Milwaukee mag drills and such but they are massive and very slow RPM.
The best machine would use an "autodrill" type of spindle http://www.auto-drill.com/automatic_drill.htm. I find that even the least expensive of these I was looking at 3 - 5k EACH.
A much more complex approach is to make a "Z axis" platen and a set of spindles with drivetrains of some sort.
Designing and building a good industrial duty platen is a difficult enough let alone after you throw 1000# of spindle and drive trains up there.
My application was very close C to C which limited my choices. The most economical, robust and simple was to use Sherline 6507 spindle. For your application it might be easiest to use the Sherline spindles complete with drive motor.
Remember you want speed on these drills 2 - 3k RPM would be best. You also have to operate this unit - bevel gears at 2000rpm = big headache.
Have fun

[mxtras]

I always start an engineering project with a list of constraints and a budget.

What is your budget on this?

Scott

[Geof]

Originally Posted by rustyk ....I saw a real crude setup at a local septic tank manufacturer. They took 12electric hand drills and duct taped them to a 2x4 board mounted over a pipe on a table...... I laughed at the setup at first but while driving back to our shop I realized that this guy had a good idea, just terrible machine building skills. I have thought of building something to drill 10 feet at a time, one row on 6" centers. This would mean mounting 20 drill spindles on a z axis on 6" centers(this would cover all the centers except 4" without removing drill bits) Any ideas to help me? Thanks

Go with this. You know it works, the hand drills are an off-the-shelf item and everything else is easy to fabricate.

One modification might be to mount the drills in some manner to the spacing can be changed.

One additional suggestion is that when you buy the hand drills you get a lot of spares. You will have to get the mounting clamp for these custom made and it would be annoying to have a drill burn out and then find that model is not available.

[rustyk]

Originally Posted by mxtras I always start an engineering project with a list of constraints and a budget. What is your budget on this? Scott

I have the capability to build just about anything if I know what to build, however on this one I am lost on the design.

I don't think OSHA or my insurance would like me to have electric drills taped to a board so what I need to do is improve on the same idea.

I would like to keep it as cheap as possible, but 10,000 would be a good start.

The method I use now is a hand drill and temporary employees. Cost per hole varies with what I have to pay the employee and how much interest the employee has in actually working.

I would still have a labor cost using a machine but should cut the time it takes to do an order of pipe. Handling, packaging, and placing the pipe in and out of the machine or fixture wouldn't change but the time it takes to drill the holes would drastically change.

[Geof]

Originally Posted by rustyk ....I would like to keep it as cheap as possible, but 10,000 would be a good start.....

I think that is a very realistic figure. I think it should be quite easy to build a multistation drill press using hand drills mounted on a long tube with adjustable spacing including hydraulic clamping for the PVC tube and hydraulic downfeed for the drills within this budget. The operator would slide the tube in from the side, clamp, drill, unclamp and rotate to next position, clamp, drill, etc.

[DareBee]

Just like Geof says only I would be more inclined to use Pneumatics are even manual operation with linkages and levers.

How about instead of moving the drills you move the pipe into the drills. Kinda like a sliding table on a table saw.

[paulC]

Some thoughts.
If you were to mount the drills a 12 inch centres, you could move the pipe 1 to 6 inches so as not to have to move the drill mounts. 11 plunges for 1" centers, 2 for 6". Have a indexable v shaped carrier as the base that moves 11 inches max. Maybe have the carrier hight adjustable for the pipe size. this would be easier than moving the drill structure up and down. Once you get it working manually you could add some form of automation controled by a PLC.
You could have an sprung inverted V shapped clamp move down with the drills to hold pipe in place.
Later add method to rotate pipe automatically. This would need rollers spaced along the carrier to make it easier for whatever method you choose.
Paul

[blksmith]

why not use a 10hp or so motor to turn a jack shaft with pulleys driving however many drill press heads and use small hydraulic cylinders to operate the feed. small half hp drill press are cheap and are easy to modify.

[martinw]

Originally Posted by rustyk Need a little help with the design of a machine to drill holes in PVC pipe. Accuracy is not important +/- 1/4" is close enough. I saw a real crude setup at a local septic tank manufacturer. They took 12electric hand drills and duct taped them to a 2x4 board mounted over a pipe on a table. The board that held the drills was held in place by two boards at the ends running back 4 foot and hinged to the table (the drills did move on an arc but it seemed not to matter). Overhead springs held the drills up. Plug it in, pull down and hang on, it was funny to watch this guy drill pipe, but it did drill 12 holes at one time and fast.

Dear rustyk,

IMVVHO, the septic tank guy got pretty close. You do not need accuracy, so why pay for it?

I really do not think you need CNC here unless you want real volume production.

With a small number of jigs, and a whole bunch of $80 hand drills, you could be off and running.

BTW, the way round the current surge is to start the drills up in sequence, not at the same time.

My two cents

Best wishes

Martin

[harryn]

I would be tempted to hard mount the drills / spindles, and move the work up to the drills. this is probably lighter and easier to move.

Once you get this far, you might as well go the next step and just drill all 20 ft in one plunge. It would be tempting to spray some water on the bit while drilling to reduce melting. It might even be possible to just punch a hole like that.

As mentioned earlier, if the drill motors are mounted on an adjustable mounting arrangement, you could deal with the different pitch easier.

[mxtras]

I see the biggest complication being the selection of a direction - more than how to accomplish this.

It seems like there are quite a few ways to nail this for far less than $10,000.

I do like the idea of raising the pipe to meet the drill.

As far as the melting - that's simply tooling configuration combined with speed/feed. Easily solved with some level of speed control/definition.

Do you have a general layout in mind yet?

Scott