Variable pitch feed screw

[kmartin]

Looking to continue a discussion between gletha & myself in an unrelated topic.

http://forums.turbocad.com/index.php/topic,7189.msg41864.html#msg41864

[kmartin]

gletha, your program lookss intriguing. How will it work with different bottle profiles? How will this be handled within your application?

[gletha]

You draw one helical element/bottle profile in turbocad starting at X0,Y0  and ending it at X?,Y0 then offset mill the profile. save the G-code then my program will do the rest. Right now I have it where the program will make the max of 16 pitch screw. To add more pitch to a screw it only take a short time to add it to the program.

[kmartin]

will the turns be indexed or continuosly spun as on a lathe?

[gletha]

A rotary table would be set up on a mill or router and the rotary table would be setup as the Y axis. The Y axis rotates and the X and Z axis moves to make the screw.

[kmartin]

I know there would be a rotary table  . I was curious as to whether the part would spin continuous like a lathe, or if one would index the rotary table, mill the length of the screw, index & repeat?

[gletha]

The part will index (move as if were the Y axis) I will see if I get time to set up mt mill next week and take some pictures. For now look at my windows paint picture of the setup.

[kmartin]

I recognize & understand your setup as I have been a machinist for 25 years. I am just new to CNC. I have a lot to learn. I have a book I need to get back to reading on the subject. 

[gletha]

When I teach G-code I use this as a starter. Very basic.

[kmartin]

Thanks. I can use all of the help I can get.

[gletha]

On my small mill when I 3D milling plastic I use a 1/8" Tip 2 Flute 2 Degree Tapered BallNose endmill with a stepover of .02 inch and a speed of 200 inches per minute. When I am 2D cutting out plastic, I use a .039 end mill and a feed rate of 3 inches per minute. Now on the larger cnc mills and cnc router I use end mills from 1/8 to 1 inch and fly cutters to 3 inch. But that is just me. When I an making the G-code and need to pick a toll, I use what I know works. When it something new I refer to the router tool books I have. Router bit suppliers will be more then happy to send you one. Onsrud is a good one to have all you need to do if fill out there catalog request form.

[kmartin]

Being that myrouter does not have a tool changer, I use a 1/4" 2 flute, solid carbide, high helix router bit from Onsrud, for most operations. Most of my parts are assembled with 5/16 - 18 stainless steel flat head cap screws. Instead of drilling those holes, I just interpolate them with the 1/4" bit. This saves me from having to change ou the tool bits. With that said, when I do have to do a tool change, I rarely us the "Z" tool offsets. I have physical stops on all of my tools to keep all of my tool lengths the same.

[gletha]

Is your cnc driven by steppers or servos? Are you planning on getting a rotary axis for your router or is your routers Z axis not have enough travel for a rotary axis?

[kmartin]

It is stepper driven. It is a 48 x 96 router with 12" under the spindle. Right now I only use half of my table. My plan when I got it 2 years ago was to put a 4th axis on one end & leaving it, that way it would stay indicated in after the 1st setup. I have a spare rotary table & stepper which I will be building my rotary axis. Now after talking with you, I will just unplug an axis instead of adding another board.

[gletha]

Make sure the stepper you will be pluging in has the same amp rating as the one you unpluged it from or you will need to change the amp setting in the stepper drive.

[kmartin]

That was a good bit of info, Thanks. BTW, I am Kenneth

[gletha]

Is your spindle air or water cooled? All my cnc are air cooled but I'm planning on getting another router in the next few months. I see there are alot that are water cooled spindles and I wonder if I should stick with air cooled or try water cooled. I know my air cooled spindle motors get hot. I would say you wouldn't want to put your hands on them after they ran for a while.

[kmartin]

I have a water cooled spindle. Runs up to 24000 rpm. My machine is Chinese. But I have had no real problems out of it. The only thing I dont like about it is the whole "Z" axis. I just dont like the way it wa built. I have bought all of the components to build a new axis, just a quite a bit heavier. I have tried machining aluminum on it & it was not pretty, my Z axis has a bit of flex to it. I cant really push it. I will be fixing that real soon though.

[gletha]

Are you linear guides the square type or are they the round bar type? All my router have the square type and they work good. But then again I only cut wood and plastic. Is it you z axis that is flexing or is it the frame that the axis mounts to?

[kmartin]

The guides I have on my router are the round type. The parts I have to build my new "Z" are the block type. The rods on my current "Z" are unsupported rods with a block on each rod house two linear ball bushings. It works fine for the most part. When I try to machine aluminum with it & can see the spindle assy flex, I am sure this is minimal when I cut my plastic parts, but being more rigid can only help with increasing my feeds, For the most part I dont cut any faster than 100 ipm.

[gletha]

My plan when I got it 2 years ago was to put a 4th axis on one end & leaving it, that way it would stay indicated in after the 1st setup.

That might be true for your rotary table if you want it always to be square to your axis. But the tail stock will need to be changed with every setup unless you part is always the same length. When I use a rotary table I think I have it at an angle to the axis as much as I have it square to the axis. I don’t use a rotary axis that much so I going to try to think back. The last time I used it was to make a router spindle holder and I used it square to the axis. Before that I used it to make a fan jet turbine and it was not square to the axis. I don’t have pictures of either project but the fan jet turbine I still gave the mold I made for the part I made. I could cast a part and take a picture of it if you want to know what a fan jet turbine looks like. The fan jet turbine was a RC scale or I could sat about 4” in diameter I think. I would need to find it in my shop and measure it to be sure. Just for fun I think I will cast it, take a picture of it and post it. Some one might want to make one for there self. I did the project made five years ago so now you know how much I use my rotary tables and I have two of them.

[kmartin]

Well the setup would be able to accomodate the longest feed screw I would need to make, as of now is 36". If I need a longer screw, I would make 2 pieces and assemble them after the fact.

[gletha]

What is the largest diameter you will need to make and what would be the max number of many lobs you will need? I want to clean up my program and add some features before giving it away that is why I'm asking.

[kmartin]

The max diameter would be 6 inches & the max number of lobes would probably be less than 10, most screws would generally have between 5 & 7

[gletha]

That is perfect my program lets you put a max number of 16 lobs in it. All I need to do is clean up the display and add a a stepover feature to make cleaner lobs. Turbocad only exploces an ark so far, then its a bunch of little lines. A stepover would then brake these line down to a smooth route. Like I say I like to use a .125 ball mill with a .02 stepover. It takes longer bit it make for a smooth finich. By the way I did step out to the shop to find the turbo fan mold and it not the what I thought it was. It's my first version but I will still cast it and post it. I wish it was the one with the compression fins. Like I said I made it five years ago for someone in Oakland TN. and I forget lastweek sometimes.

[kmartin]

Oakland is just outside of Memphis, do you live in TN?

[gletha]

I live in Louisiana. I do have ten food inspection machine I made in a plant in Oakland TN. All the boards in them I made on a small cnc. If you do a google search for hi-len youtube tegtronics you will see the machine. I also made the trim for the LED display on a cnc. I didn't make the cases I had them made.

[kmartin]

I have some ex-"step" relatives in LA. The live in Houma.

[gletha]

I told you wrong I food plant is in Rossville TN and I might have a trip comming up next month to Oakland. Wensday I was in Jacksonville, AR at a plant. This weekend I plan on putting the tail stock back onto my cnc lathe and then put the z axis back onto on of my routers. I made a mod to the router z axis to get two more inches of travel out of it. I should get done whth that work today. Then I'll clean up on the program I wrote for making the screws. I hope to get some time to glue up some mdf to make a screw blank so I can use it to make a screw and get some pictures. mdf is good stuff to make proto types out of the cost is almot zero but it make a mess with its fine dust.

[kmartin]

Rossville? Would that be the Kellogs plant? Anyway, if you make it to Oakland, let me know, maybe we can have dinner or something.

[gletha]

Yes that would be the Kellogg plant. If Kelloggs need any support with the inspection units I have Compass automation in Collierville lined up to buy parts from me the support them.

[kmartin]

So it sounds athou your program is coming along quite well. I will have to get started on my rotary indexer ASAP 

[gletha]

I got my Z axis back on my router. I still need to do some wiring and get the covers on. I do that next week along with getting the tail stock back on the lathe. I took to many brakes today. Look at the picture I drew two diameters a 4" and a 6". Look at the travel each 1.8 degree step. If not 1/2 or micro stepping a stepper motor has 200 steps per turn at is 1.8 degree per step. I sure you may know that, I thought I would add it anyway. On a 6" diameter screw each step would me .09". Using a .125" ball mill I like a .02" step over. That is what I use to get the finish I like. With all that said, I want to build a simple 6 to 1 ratio rotary table to get the .02" step over just to see what it finish would look like. I'm thinking it might have a zig zag to the finish. This is something I hope to have completed in the next few weeks.

[gletha]

I order the parts today for the rotary table. I going to be using a timing belt. I can't wait to see how much backlash or spring the belt gives. I will be using a gates 150XL037 timing belt, 80 tooth pully, 10 tooth pully and a 270oz stepper motor. I said I was going to make a 6 to 1 but at The last minute I went with 8 to 1. I plan to make the rotary table and tail stock out of aluminium. I'll be posting pictures and the TC files as I am building the rotary table.

[kmartin]

Sounds like fun. I guess I need to get started on my table at work also.

[gletha]

Instead of converting your rotary table, give me a little time to get this one made. It might work for what you want to do. I should have less the one hundred dollars in it. You should keep your rotary table as is unless you have a spare.

[kmartin]

I have two here. But I will wait to see what you come up with. I too have thought  about building an indexer from scratch.

[gletha]

Correction the large pulley will be 60 tooth. It will be 6:1 rotary table. I drew up the rotary table and hope to get it cut out sometime next week. I'm still waiting on the timing belt to come in.  When I make sure it all fits together and works. I’ll post the drawing and part list. My first screw will be made from mdf. I'll glue up a few strips of mdf so I then can turn it to a screw blank.

Part so far:
XL 10 tooth pully the bore size is 3/16" I will enlarged the bore to 1/4"
XL 60 tooth pully 5/16" bore
Timing Belt 150-XL-037
Aluminum rectangular Bar 1" thick 2"wide 1' long
Two aluminum Plate 12"x12" 1/4" thick
Four 30160CTN bearings

[kmartin]

I am very excited to see the end result.

[gletha]

I got all the part in now so I should be posting some picture in the next few days. I glad I haven't posted my TC drawing yet, I have already made changes and I haven’t cut the first piece yet.

[kmartin]

I got all the part in now so I should be posting some picture in the next few days. I glad I haven't posted my TC drawing yet, I have already made changes and I haven’t cut the first piece yet.

Isnt that how it always goes. To me that sounds like a normat day at KIK Custom Products. :-)

[kmartin]

Have not heard much on this thread in a while. How is everything coming along Gletha?

[gletha]

It has been a week and I must say I got all the parts but I haven't done any machining to make the rotary table yet. I hope some time next week I'll get it machined. I been working on vacuum pods. I got a 4"x4"x12' bar of aluminum the cost was almost $1,200 to make the pods. I'll start a new thread and call it vacuum pads.

[kmartin]

I have been looking into building some vacuum pods or a vacuum table for my router.

[gletha]

I did some work on the rotary table. "some as in not much"

[kmartin]

looks like fun, uh, wait a minute, it looks like what I did at work today 

[gletha]

Here is the parts list so far

McMaster 57105k11 10 tooth pully. The bore size was 3/16" so I enlarged it to 1/4"
McMaster 57105K33 60 tooth pully 5/16" bore
McMaster 1679K129 Timing Belt 150-XL-037
McMaster 9008K531 Aluminum rectangular Bar 2" thick 2"wide 1' long
McMaster 9246K13 Aluminum Plate 12"x12" 1/4" thick
2 bolts 5/8" being turned into shaft. one for turn table and one for the tail stock.
4 sealed bearings.

[kmartin]

How are you coming along gletha? I have a question. How are you tensioning the timing belt? I did not notice a tensioner or slots on the motor mount.

[gletha]

I trying to see what the finish will look like using a belt driven rotary table. I don't think it is something I would use. If the belt stretches then you could say it failed. There isn’t an adjustment. I hope to get some pictures of it doing something soon.

[gletha]

Update: I've been real busy but still have plans make a Var. pitch screw it just might be another week or two.