Messages

651

General Mach Discussion / Re: Arcs and cutter comp

« on: April 12, 2013, 07:42:44 PM »

Mountainman,
If your machine has only a little backlash and can handle climb milling, then I would climb mill the part the whole time.  Conventional milling has the cutting edge sliding over the surface until the material is thick enough to peel a chip.  This wears the cutter much faster.  Climb milling starts with a full chip and the chip thins until it breaks off, which is much better. In most cases the finish is better too.

When programming manually from a CAD drawing I always program right on size and use cutter comp.  I always put the tool path in a subroutine and just set cutter comp, call the sub, adjust comp, call the sub.  I program the subs in incremental.  That way I can always position it anywhere, or even use it in multiple locations.  I also like to use undersize cutters on pockets to sweep the corners with the cut, not crash to a stop and change direction. This got me on good terms with the guy in the tool room because I actually asked for resharpened end mills, and he always made sure I got freshly sharpened ones.  He did a good job too, they always seemed to cut better than new ones.

One of the machinists said I was wasting time with rapid moves back to the start of the tool path and should program it the way you want to.  I pointed out to him that if we had lots of parts to do that would be a good idea.  With batches of ten or less you really can't justify the extra coding and testing to be sure it works.

Gary H. Lucas

652

General Mach Discussion / Re: HELP !!!! What Do I Need??

« on: April 11, 2013, 10:20:20 PM »

That was me,
However if the specials you need are already available they will likely be much cheaper.  I used Rhino for 6 years, and now have 6 years with Solid Edge, and likely to be changing to Solid Works.  The changes are only because of job changes, they are all very good software in their own ways.

Gary H. Lucas

653

General Mach Discussion / Re: HELP !!!! What Do I Need??

« on: April 09, 2013, 10:23:19 PM »

Jacqui,
It all sounds feasible to me, and I think the Tormach is a good choice.  Their tooling system looks very good, and repeatable tool holders is really the key to efficient machining.  I always keep an edge finder and a dial indicator mounted in tool holders permanently, because you always need them. Cam programs are usually described as 2D, 2-1/2D, 3D, 4D, and 5D.  2D is a program that can produce a gcode tool path using 2 axis, typically the X &Y. 2-1/2D adds the ability to also control the Z for things like drilling and pocketing, but not simultaneous with the other two axis motions.  3D gives you contouring of organic shapes ( the sexy curves stuff).  4D usually adds a 4th rotary axis to mill on the sides of parts that you rotate, or to simply re-position the part to do other sides without re-fixturing.  5D usually involves being able to also tilt the spindle in some direction.  Cost and the skill required by the operator goes up quickly!

I find that before I try programming a part there are two issues that need to be considered first.  What tools do I have available?  Sometimes you can do a part with simple tools, and sometimes you get a huge benefit from having special tools that may seem costly at first. For instance, a shaped tool that produces the groove that the lens fits into may warrant a special tool.  I used to have an endmill with a reduced section part way up the tool.  I used it to circle interpolate a round nub with an undercut to mount vacuum cups.  A local tool sharpening service modified an end mill for me.

Holding parts is often a huge issue.  If you are clamping a part down with clamps that stick up you may have to program interrupted cuts to go around the clamps, and Cam programs that can easily do that are much more complex and expensive.  Sometimes you write a program in multiple parts, with a pause to move the clamps.  I've even used double face tape on plastic parts. If you are doing multiples you may want a Cam program that can easily nest multiple parts on a single sheet.  Doing this manually can be very time consuming.

Since you are only trying to do one type of part, and not job shopping all kinds of parts, that should make your choice easier. I would take the time to figure out the tooling and holding questions so you can factor that into your Cam requirements.  If you are already using a 3D cad program to do your design work, things will be much easier.  If not you have a double learning curve. Cam programs need some sort of model to work with.  I once worked at a place where I programmed machining centers to machine castings made to 50 year old paper drawings.  I programmed everthing manually because making a 3D model of these complex casting would take days.  They replaced me when a left with a guy dragging along his own computer and MasterCam.  He didn't last long!

If you are not using a 3D modeling program I suggest you look at Rhino3D.  Lots of artistic people using it, and the user forum is a fantastic resource.  There are also several Cam programs that run from within Rhino.  MadCam and RhinoCam, are two of them.

Hope this helps,

Gary H. Lucas

654

General Mach Discussion / Re: Hard Limits & Home positions

« on: March 26, 2013, 08:18:36 PM »

Brett,
800 oz/in steppers, 80 volt drivers @ 68 volts, 20mm x 5mm pitch ball screws, moving about 100 lbs on THK ball slides with ball spacers.  Yeah, I think a crash could break something!  Hence the reason I will not try running it without end limits, and they are going to be set far from the ends until this thing is completely debugged.

Gary H. Lucas

655

Tangent Corner / Re: Ballscrew End Machining

« on: March 25, 2013, 10:28:46 PM »

I would bet you they do the annealing with an induction coil placed over the end.  You can very rapidly heat the end so that the heat won't travel very far down the shaft.

Gary H. Lucas

656

General Mach Discussion / Hard Limits & Home positions

« on: March 25, 2013, 10:19:17 PM »

I am building a machine with 2 NC limit switches on each axis.  The plan was to simply connect them all in series with the E-stop button to prevent a crash against the end stops.  To get jog away from a limit switch would require holding in the reset button until you've cleared the limit.  My question is, would it be possible to also use those same switches as home positions if I home each axis separately?  I'm thinking I'd just hold in the reset button during homing, so it wouldn't go into E-stop when the limit is hit. However I don't believe the switch resolution is going to be good enough to home the machine and then use that to locate a fixture, so this may all be a waste.

In the past I ran a pair of Fadal machining centers that had home positions, and you had to home the machine for the tool changer and such to work properly.  I also ran a Spindle Wizard CNC knee mill, but on that machine I never bothered homing it. I just picked up the work location with an edge finder and set tool lengths to the top of part and away we go. If there were lots of operations and lost position would really screw me up, I'd just write down on a post-it the dial readings for each axis when at 0,0,0 of the work location.

My tool holders are repeatable for length.  So my plan is to keep an edge finder permanently set in one holder, and use that to pick up all work locations. I am also considering bolting down a small block to the table that I can call home by picking up the top and two sides, then set all tools off of it.  That way on a long job where a power failure would lose my positions I could reset the machine by picking up the home block with the edge finder again. This machine does not have dials so I can't use the post it method!

Thanks,

Gary H. Lucas

657

Show"N"Tell ( Your Machines) / Re: Ex-Cell-O Spindle Wizard to retrofit

« on: March 21, 2013, 07:28:15 PM »

Wow,
This gives me flashbacks, I ran one of those for 4 years!  The Excello is an excellent machine, like Bridgeport, only better built.  The belt speed change is more robust than a Bridgeport too. I pulled the motor off and replaced the belt too. As I recall the motor is bolted to a top cover and you just remove four bolts and lift it off.  I wouldn't toss the variable speed drive, even with a VFD.  There is NO substitute for gearing to get lots of low speed torque.  That little gear motor that drives the speeds up an down in steps set by the setscrews actually works quite well.  You could make it give you just two ranges if you wanted, high and low, and you get to pick what those ranges are.

The table drive is not ball screw.  It has an anti-backlash nut with a spring loaded mechanism to tighten a second nut against the first.  It seems to work okay, but a fair amount of friction so it will never move real fast.

I hope you got the NMTB 40 spindle, because it is way better than the R8.  I would also recommend you put a drive on the knee immediately.  That sucker is heavy, and with a five inch quill travel you WILL spend lots of time cranking that sucker up and down for tool changes!  If you have NMTB start looking for short integrated chucks, and screw machine length drills.  I found a really nice NMTB short chuck, and went to buy more, they had discontinued making them, I got he last one!

Good luck with your project.

Gary H. Lucas

658

Mach4 General Discussion / Re: New people welcome !! Come in here and introduce your self!

« on: March 20, 2013, 10:56:07 PM »

Hi Gary,

Welcome to the forum.

Sounds like a very interesting machine you and your grandson are building. 

Tweakie.

Tweakie,

I've looked at some of your posts, you have done some amazing stuff!

I've got a long history of my own building automation projects.  My dad was an electrician and bought an Atlas lathe for our home shop when I was about ten.  He also worked for Mettler and brought in  swiss machinist to mount the new chuck, and give some machining tips.  He also taught me how to weld about then.  This past Saturday I took him out to breakfast from the assisted living place then he came over to the shop at my employer to watch me crank the handles on the clapped out bridgeport I keep there.  Right next to it though is my sweet, like new 1952 Southbend 10" lathe mounted on a stand with a collet drawer built in!

I was telling him about Tyler (grandson) turning the dials to position holes and that he picked up quickly how to use the edgefinder, count turns and stop at the right numbers.  Dad said something about my grandson running the machine and maybe getting hurt.  I said what about when I was 10 and you taught me to use a lathe and weld?  Then he repeated the story he always tells about me welding on a job out in the driveway.  A car stopped to complain about the arc blinding people coming down the road.  The guy just about had a puppy when an 11 year old kid raised the helmet to see what was going on!

I'll try to post some pictures in a little while.  I need to dress her up a bit, looks a bit naked right now.

Gary H. Lucas

659

General Mach Discussion / Some questions about Mach3

« on: March 19, 2013, 10:11:22 PM »

I am building a multi-purpose machine and I have some questions about how Mach3 operates which will influence how I wire it.  I have two milling/lathe spindles that are interchangeble.  Once is DC motor driven, the other is stepper motor driven, and therefore positionable.  I also have another stepper motor which is to be used for an extruder for 3D printing. I have a USB 4 axis breakout board.  I intend on driving the stepper spindle and the extruder from seperate drives, but using the same step, enable, and direction signals, which are switched by a multipole relay.

My questions:
What powers up the stepper drives?  Just enabling the E-stop circuit, or is there a standby mode where you can be programming and such but the drives are off?

I want to use the machine as a Vertical Mill, Horizontal Mill, Vertical Lathe, Horizontal Lathe, Shaper, Cutoff Saw, 4 axis robot with pneumatic gripper, and 3D printer.  The vertical mill and the horizontal mill need to switch the Y and a Z axis.  The lathe axis get switched around too.  When I want to 3D print the A Axis signals need to go to the extruder etc.  Is the best way to do this to create a profile for each machine type?

Thanks,

Gary H. Lucas

660

Mach4 General Discussion / Re: New people welcome !! Come in here and introduce your self!

« on: March 19, 2013, 09:55:38 PM »

Hello,
My name is Gary Lucas. I'm building a project with my 9 year old grandson.  As a joke I refer to it as the Ifactory.  I currently work in the waste water industry doing 3D design of equipment skids.  I also have a heavy electrical background, along with PLC programming.  I also worked as a programmer on Fadal machining centers and made parts for a few years on a Bandit CNC.
I picked up some very robust precision THK GL20N ball slides with ball screws and then came up with a somewhat unusual arrangement of the three Cartesian axis.  Travels are 18" X, 18" Y, and 18" Z.  I Also purchased a manual Sherline mill/lathe that is providing the milling spindle and a lathe spindle (I have two) so I can configure it as a CNC Vertical 4 axis Mill, CNC Horizontal 4 axis Mill, CNC Vertical Lathe, CNC Horizontal 3 axis Lathe.  My configuration can be extremely stiff over small distances so I should be able to use it as a planer or shaper as well.  I am going to mount up a hacksaw as well for cutting off material.  I also have a fifth axis, (switchable with the 4th) which runs an extruder for 3D printing.  It also has a heated build table for the printer.  The whole thing is mounted on a surplus 24" square 205 lb. surface plate that was hand scraped, and is dead flat.  The table is supported by an aluminum T-Slot frame and has a full enclosure with sliding doors because I can't let a 9 year old get hurt!  Currently it is mechanically about 95% complete, the tremendous amount of electrical cabling is all strapped down, and the two electrical panels are completed built and all the heavy power wiring is done.  Hopefully I'll power it up in about two weeks.  Working on Mach3 configuration this week.