Sunday, September 5, 2010

My Current (Messy) Workshop and Some Info on My Planned Taig Mill Mods

I had planned to vent in this installment over some of the people in my life that are holding me back and constantly standing in my way, but shooting pellet guns with my son today seemed to serve that purpose fairly well, at least for the current time.

Anyway, I'll attempt to upload some pics of my current workshop to accompany this blog and I'd also like to set a baseline reference for not only my goals for the Taig "Micro" mill project (that I have dubbed "Operation: OVERKILL"), but also for the reasons I've decided to modify it instead of upgrade to a larger machine.

Here's a pic I just took of it a few minutes ago:

Figure 1: My Taig Micro Mill in it's natural habitat.

As you can see, I'm a bit cramped for space.  Yes, I know it's quite a mess and I should clean up the swarf or chips spread around it and my other machines, but controlling that has been a problem too.  I'm constantly making more swarf with at least one machine, so I figured as long as I keep my precision tools put away in their respective places in the chest, keep all important paperwork and tools or accessories out of the way of the swarf pile, and keep each machine's slides or ways and leadscrews well-oiled, the chips can accumulate until they're close to getting in the way, at which point I will (and previously have done) clean them up. 

Here's some more pics of my cramped work area:

Figure 2: This is my slightly modified Harbor Freight
7x10" mini-lathe, part #93212.  Even more extensive
modifications are planned for the majority of parts
that were originally included with this lathe and the
14" bed extension kit (center to center distance) that
I purchased on sale from than
I have in the works for my Taig mill.

Figure 3: My Sherline 4400 3.5x17" lathe rests under
the plastic cover that is currently serving as a stand for
a set of prints.  Note that lighting in this room is poor,
so I have multiple individual desk lamps and shop lights
to aid in that department.

Without going into much detail I can say the series of modifications planned for my Taig, while considered overkill by nearly all others, are relatively simple compared to the mods and upgrades I have planned for my HF mini lathe. 

The Taig mill is pretty much good to go "out of the box" for most applications, but my projects will require more rigidity than it currently has and I also need to save as much time as possible when working, so the ability to take larger cut depths, use faster feed rates, and even use tooling with shanks and cutting diameters over 1/2" to assist in cutting down work time and increasing the mill's capabilities are imperative for the finished product.  A larger mill would be the answer to anybody else in this particular situation, but 1) I don't have the room, 2) I don't have the budget, and 3) owning and operating a Sieg product (the Chinese manufacturer of the Harbor Freight lathe I own) and seeing the tolerances held (or lack of) during their manufacturing processes, the only mill available new in a size I could use in this space is made by Sieg and would require considerable work to even produce repeatability without any regard to accuracy or precision.  Quality is synonymous with both the Taig and Sherline names, but Sieg doesn't exactly have a similar reputation. 

There's always the possibility of purchasing an older used machine of quality construction to meet my needs, like an Atlas or other bench-top milling machine, but I believe that unless I know the owner of said machine quite well and know how the machine was used and treated then it would only be gambling if I were to acquire such a machine; unless the previous owner was an anal and conservative person like myself, I would most likely consider the machine's prior use to be abuse (and I honestly don't know any people locally that are anything like me).

So I need to speed up the progress of my projects while retaining the same or better quality that the factory issues each Taig mill with, but how am I going to modify it to accomodate these needs?  Ha ha ha (with the sound of gears turning in the head of an evil genius)...

As a student in the Machine Tool Technology Program at Ashland Community and Technical College, I have access to a vast array of industrial machines: a Centroid CNC mill, an Okuma CNC mahining center, an Okuma CNC turning center, a wire EDM, surface grinders, cylindrical grinders, a host of different lathes, an army of Bridgeport Series-2 milling machines, and even other machinery that I can use to make the components for my "Operation: OVERKILL" modified Taig.  This explains the means but still omits the details.

Although I've designed and engineered most of the critical components for this project, all my sketches and prints are drawn by hand.  I've been pretty stubborn in that aspect because I both own CAD software and have access to even better industrial versions at school, and I also know that using a CAD program can all but eliminate errors from miscalculations and provide more depth and insight into some of the more obscure parts and components that will be needed for this, but I've always been an artist in the sense that I love to draw with a pencil on graph paper.  I will attempt to draw a completed sketch showing all major components with a CAD program as soon as I get the chance, to not only post here but also to determine the lengths of some angled parts and other dimensions that I would otherwise need to either calculate or measure before building, but I honestly wouldn't hold my breath for that.  This isn't a rush job, but I am aiming for a completion date before I finish this machine tool program at the end of the next semester (the end of the Spring 2011 semester).

I'd nearly forgotten to cover the major issues I have with this mill (WTF?!?).  The biggest problem I've had with it is due to the weight of the spindle motor hanging from the left hand side of the headstock.  This can cause the spindle and headstock to be misaligned with the travel of the Z axis, leading to all sorts of issues when precision work is required.  I believe that either the headstock extrusion or the dovetailed headstock mounting plate on my Taig are out of spec and I could probably have them replaced through Taig if I were to call or email them and complain, but these aren't just simple fixes for me with my intended goals. 

The next issue I have with this machine is the constant need to align the headstock and the Z axis to the table.  Even in the middle of an operation it seems to slightly come out of alignment, completely screwing up what should be nearly perfect finishes and closely held tolerances.  The single nut on the stock Z column's pivot seems to taunt me, so I have developed a NEED to add additional support for the Z column in an effort to bitch-slap some sense into that little bastard, eliminating this problem for good. 

Other issues that have taken precedence on my long list of upgrades include the lack of a variable speed spindle control (the factory six-step pulley system limits the spindle to six unusable speeds, none correct for any job at hand when working with any kind of metal), the lack of rigidity in the Z column for using essential mill tooling like flycutters, boring heads, face mills, shell mills, and large diameter slitting saws or arbor-mounted cutters (among many others), the small 13/32" or 10mm ID capacity of the largest ER-16 collet, and various other small problems I've found by having to use allen keys to adjust the motor mounting plate to change belt positions and trying to keep the Z axis and headstock in alignment.  My design fixes ALL of these issues at the cost of simplicity and adjustment points.

Though I do tend to overcomplicate things and often design components much stronger than they need to be, I've always felt that it's better to be safe than sorry.  A mill, for example, cannot be TOO rigid, but it can be not rigid enough.  To increase rigidity on my mill, I'm adding a MASSIVE shunt wound DC motor to the rear of the Z column's steel square tubing.  Massive may be an understatement for a machine of this size, but I won't have any issues due to a lack of power with this 1/2HP 90VDC armature 100VDC field 1725RPM GE motor at nearly 6.75" in diameter and 11.75" in length (excluding the 5/8" by almost 2" long output shaft). 

This motor will ALWAYS remain stationary and permanently attached to the Z column while the headstock will be free to move about its length of travel.  Design challenges for this arrangement nearly made me take an alternate approach to this mod, but I believe I have the major issues worked out.  Using Thomson ball bushing linear bearings secured in the upper motor mounting plate and other shaft support plates to provide support for 1/2" diameter shafts and easily accessible timing pullies keyed to their shafts along with a few thrust bearings and other more complex components will allow for this configuration, but my efforts to design more rigidity into this machine will ultimately lead to a loss of adjustability: in this case I'll lose the ability to mount the headstock at a 90-degree angle to the Z column.  I have yet to use my Taig in this configuration, but I'm sure I'll build a new headstock or some sort of 90-degree gearbox if I ever find a need for it.

Here's a pic of the motor I'm using:

Figure 4: At 34lbs, this 90VDC armature 100VDC
field separately-excited shunt wound 1/2HP 1725RPM
GE motor should add both rigidity and an excessive
amount of torque to my Taig mill if it's ever needed
(the KB Electronics KBPB-125 speed control can and
will limit the torque output to acceptable levels for
use with a smaller milling machine).

To test both the KB Electronics KBPB-125 variable speed DC motor controller and this motor after it was received, I built this small control panel for ensuring all circuits on the control were in proper order:

Figure 5: A temporary control panel I had built to
test the motor pictured above and the used KBPB
variable speed DC motor control unit I had purchased.

I don't need all the features on the speed control unit I'm using just as I don't need all the torque provided by the motor pictured above, but it's nice to know that they're both there if and when the time comes they are needed. 

I have the motor mounting plates drawn up in the latest version of Esprit at scho(I prefer to use MasterCAM over Esprit but each has its own unique advantages and ideal applications-Esprit just happened to have features that allowed for quicker creation of complex parts like this one with multiple unknown dimensions and datum points) and ready to CNC mill and engrave once I get the proper material to construct them from, so I'll see if I can save those as .pdf files or .jpgs to post here.  Of course each individual component will be proudly displayed and boasted upon via these pages as soon as possible once they're each completed, and the finished product will have multiple reviews on nearly every aspect as soon as possible over short- and long-term usage, too. 

Many of the smaller components for this project can be built on the machines I own, but I'll take advantage of the access I have to the CNC equipment to make as many parts for this as I can.  As anal and picky as I am, I need to have each piece look as professional as possible.  We don't play "slop" in this house...

Anyway, more to come later-I need to tram my Taig again, dammit...

1 comment:

  1. Almost like a game of spot the item when I was searching for th sheline lathe... just kidding.

    You're modding while I'm still trying to learn how to square a piece of stock...