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  1. #1
    Join Date
    Aug 2005
    Posts
    49

    Tormach Perspective

    I regret that I cannot get into these forums more often, but it looks like the machine users are doing pretty well to explain the machine. I would like to address a few of the ideas that I often hear, either in discussions with people on the phone or on various forums like this one.

    Idea #1 “The PCNC 1100 is designed to a price point”
    Not true. During the design reviews, and with various companies and engineers involved, there was always a consistent guideline. We were working to establish the lowest possible cost while meeting specific criteria for precision and reliability. The price was flexible, the technical objectives were not. Over the three-year development period, numerous designs, companies, and prototypes were rejected. Rejection was nearly always based on quality, precision, or reliability. The price kept going up, but we never budged on the fundamental requirements. The price is as low as we could manage, but the machine was designed to a performance level, not a price level.

    The idea continues today. On a small machine, the industry standard 6” vise is just too big, but a 4” vise is too small. We wanted to provide a vise that was “just right” for a small mill. We tried to find import vises that would fit better, but the quality and precision was inconsistent. If it isn’t absolutely square, flat, and true, a $100 machine vise is not a cheap vise, it’s an expensive paperweight. The vise we settled on is a custom-made 5” vise, made in the USA, and almost $500. We wanted to offer a lower cost vise, but as with the mill itself, precision and performance came first.

    Idea #2 “The price will go up now that Industrial Hobbies has closed shop”
    I cannot guarantee the price will not go up, but I can assure people that our pricing is cost based, not market based. Market based means you look at what others do and price as high as you can yet staying below alternatives. Cost based means you look internal at your costs of production, essential profit, and other factors, and then price accordingly. Our objectives are outline in our “about us” page (http://www.tormach.com/about.htm). It’s pretty simple really; by keeping costs as low as possible and following cost based pricing we maximize our objectives toward the concept of Personal CNC.


    Idea #3 “Building a CNC mill from a manual mill and parts kit is more work, but the end product can be similar to a PCNC 1100.”

    Which is closely related to…..

    Idea #4 “The PCNC is a conversion of a manual mill.”

    This is way wrong. The PCNC 1100 design was started from scratch with original castings. We had initially considered building a CNC based on a manual machine frame but found the results unacceptable. There are just too many things to explain here, but I suggest people who wonder about this look into design details like Turcite, milled and ported lubrication lines, hand scraped ways, ballscrew quality, cartridge spindle, VPI motor windings, resin casting versus sand casting, and compare QC inspection sheets. We are quite familiar with most of the manual machines that have been used by hobbyists, from buying sample mills to walking the floor in the Chinese factories. Let me put it this way: we make a lot of machines in China. We’re doing it at the lowest possible cost and I know our cost of manufacturing. Our manufacturing cost of the basic frame of the PCNC 1100 exceeds the retail price of the manual mills that people are converting.

    Converting a manual machine into a CNC machine can be a great hobby and personally rewarding. Never the less, just like building a boat, or kit car, the rewards come from the process, not the product. You simply cannot find a good rationalization by looking at cost, resale value, or the performance of the end product. This was not true before we created the PCNC 1100, but it is now.

    Greg Jackson
    Tormach LLC

  2. #2
    Join Date
    Nov 2005
    Posts
    4
    Greg, You have a private message. Jim

  3. #3
    Join Date
    Oct 2006
    Posts
    20
    My Tormach has a intermittent Z axis problem, it drifts down after the machine is shut down for the evening, only one time out of four, any ideas?

  4. #4
    Join Date
    Jun 2006
    Posts
    2512
    If all else fails read the manual.

    I don't remember the page number but I think it’s under the maintenance section.

    Regards
    Phil


    Quote Originally Posted by hockeypuck View Post
    My Tormach has a intermittent Z axis problem, it drifts down after the machine is shut down for the evening, only one time out of four, any ideas?

  5. #5
    Join Date
    Oct 2005
    Posts
    215
    You need to tighten the Z axis gib. The manual describes how to do this.

  6. #6
    Join Date
    Feb 2006
    Posts
    1072
    I've tightened my Z gib four times in one month of intermittent use (probably 20 hours tops on actual machining.) I'd like to know what other users' gib experience has been (sorry about perpetuating the OT on this thread, but I've seen people jumped on for starting new threads about existing subjects )

    Randy

  7. #7
    Join Date
    Jun 2006
    Posts
    2512
    I've tightened mine twice in maybe 80 hours use in 9 months. One thing I did notice is that it is possible (at least on mine) for the top adjusting screw to get down the side of the gib rather than staying on top, so the adjustment becomes a bit confused. When this happened I removed the two adjusting screws and pulled the gib to check it out. This is when it became clear that the screw was finding its way down the side of the gib. With a bit of careful reassemble everything was OK, although I will need to keep an eye on it in the future. I think the adjustment method is relatively insensitive and the head falling slowly under its own weight is not in itself a problem. The main issue I found was that there was a balance between the head "nodding" forward due to a loose gib (which impacts on the perpendicularity of the spindle to the table) and the risk of missed steps due to an over-tightened gib.

    Regards
    Phil



    Quote Originally Posted by ProtoTrains View Post
    I've tightened my Z gib four times in one month of intermittent use (probably 20 hours tops on actual machining.) I'd like to know what other users' gib experience has been (sorry about perpetuating the OT on this thread, but I've seen people jumped on for starting new threads about existing subjects )

    Randy

  8. #8
    Join Date
    Nov 2004
    Posts
    284
    Hi Guys

    Obviously Tormach are using the Gib adjustment to hold the Head Assembly up when the Mill is powered down. It would be interesting to know how much tighter the Z Axis Gib needs to be adjusted to hold the Head assembly compared to say the Y Axis Gib? If there is allot of difference than this could possibly answer why you are required to adjust it so frequently. Another possibility is that the Gib might have some high spots and it is taking time to wear in?

    One possible fix would be to install a counter weight system to compensate for the weight of the Head assembly. That way the Gib could be adjusted the same as the other Axis and hopefully not require as frequent adjustment. A simple cable & pulley system with a weight hanging behind the vertical column would work very nicely. Some of the smaller Mills are using Gas Socks for counter balancing. I would prefer the weighted method.

    Has anyone actually seen instructions on the correct way to adjust a Gib on a Dovetail setup? I just go by the feel of the Axis but I would like to find out the correct, technical way?


    Willy

  9. #9
    Join Date
    Feb 2006
    Posts
    1072
    Quote Originally Posted by philbur View Post
    I think the adjustment method is relatively insensitive and the head falling slowly under its own weight is not in itself a problem.
    Thanks for the datapoint, Phil. My head has never been "loose" but it would slide down under its own weight, at least part of the Z travel. Each time I've adjusted the gib, it has taken less than 1/4 turn of the top screw to firm up the head. I check it by placing an old bathroom scale upside down on the top of the head door and pulling down on it. I've been adjusting to the low side of the 40-80lb that the manual recommends.

    I'm very happy with the machining and resultant surface finish, so maybe I'll just leave the gib alone for a while and see what happens. As long as the head doesn't slide down far enough to land on the vise, things can't be all too bad...

    Randy

  10. #10
    Join Date
    Feb 2006
    Posts
    1072
    Quote Originally Posted by Willyb View Post
    One possible fix would be to install a counter weight system to compensate for the weight of the Head assembly.
    Bob Warfield posted a photo of a Hurco VM-1 frame showing its counterweight mounting chains in the "Quill and head problems?" thread in the IH forum (it's on page 2 of that thread.) He hotlinked the pic from his own website so I won't repeat it here.

    Quote Originally Posted by Willyb View Post
    Has anyone actually seen instructions on the correct way to adjust a Gib on a Dovetail setup?
    Well, in the case of the Tormach head, the correct way per Tormach's Operator's Guide is to adjust the gib so that it takes 40-80lb downwards pull on the head to move it with the machine unpowered.

    But you are right--on my Sherline lathe and mill I have always just adjusted the polymer gibs by axis motion feel.

    Randy

  11. #11
    Join Date
    Jun 2006
    Posts
    2512
    The head will only come down slowly when the machine is switched off, so just place a block of wood on the vise/table before you turn it off for the day. I do that anyway as a general precaution.

    I guess you are aware that the head may fall rapidly if you electrically disconnect the steppr motor.

    Phil

    Quote Originally Posted by ProtoTrains View Post
    Thanks for the datapoint, Phil. My head has never been "loose" but it would slide down under its own weight, at least part of the Z travel. Each time I've adjusted the gib, it has taken less than 1/4 turn of the top screw to firm up the head. I check it by placing an old bathroom scale upside down on the top of the head door and pulling down on it. I've been adjusting to the low side of the 40-80lb that the manual recommends.

    I'm very happy with the machining and resultant surface finish, so maybe I'll just leave the gib alone for a while and see what happens. As long as the head doesn't slide down far enough to land on the vise, things can't be all too bad...

    Randy

  12. #12
    Quote Originally Posted by philbur View Post
    I guess you are aware that the head may fall rapidly if you electrically disconnect the steppr motor.
    Yup, or if you're dumb enough to loosen the stepper to ballscrew coupler!!

    Rather frightening - and probably not the best for the machine...

    Dave

  13. #13
    Join Date
    Jan 2004
    Posts
    56
    Respectful Observer's Perspective-
    Tormach - Good start - but you guys need to keep it going by continuing to improve/evolve your product line. Here are my questions/concerns/suggestions all rolled up.
    1) Weight - 1,100# is that a feature or a resultant? Have you maximized the stiffness to weight ratio? To most hobbyists - 1,100# is a detriment not a benefit. Show us the FEA. Prove that you need the weight or loose some!
    2) No servo option - ?
    3) No DIY control option - for the hobbyist?
    4) No Gecko control Option - ? - I'm not in any way associated with Gecko, but from what I've read you would have a much more credible product and unquestionable image with a Gecko Logo on it!

  14. #14
    Join Date
    Feb 2006
    Posts
    1072
    Quote Originally Posted by dammachines View Post
    Yup, or if you're dumb enough to loosen the stepper to ballscrew coupler!!
    Or if I put a JATO bottle on top of the head and light it off...

    Hey guys, I just said unpowered, i.e. "Push the red button, Frank" for any MST3K fans.

    Randy

  15. #15
    Join Date
    Nov 2004
    Posts
    284
    Take a look at the "Design Analysis Report” on the Tormach Web Site.

    http://www.tormach.com/document_libr...0Design_v1.pdf

    It is a detailed explanation on the design of the Tormach CNC Mill and how it was built from the ground up. Your only other options are to purchase either a converted manual Mill or convert one yourself. There is no machine that is perfect but I truly believe Tormach have done a great job with it's design and from what I have seen, it performs as advertised.

    Willy

  16. #16
    Quote Originally Posted by dansutula View Post
    1) Weight - 1,100# is that a feature or a resultant?
    The 1100 in the machine name refers to the 1100 watt (1.5HP) motor, not the weight.

    So probably not a feature - though it seems many hobby machine vendors tout the weight of their mill as a measure of it's rigidity...

  17. #17
    Join Date
    Oct 2006
    Posts
    20
    Hello,
    Can someone please explain why my Z only slides once in a while ( one out of 5 )

  18. #18
    Join Date
    Feb 2006
    Posts
    1072
    Quote Originally Posted by dammachines View Post
    The 1100 in the machine name refers to the 1100 watt (1.5HP) motor, not the weight.
    Actually, it could to the weight also. In the PDF that Willyb pointed out:

    Size was a very important aspect. We began with a design point of about 1000 lbs and a shipping crate that can be moved with a pallet jack...As the design cycle progressed, our machine grew in weight from about 900 lbs to 1130 lbs, but we kept the physical dimensions that we started with.
    So the weight is a feature. The PCNC1100 is much more of a baby Haas (our prototype shop at work has a TM-1, and I've looked at it long and hard...) than a beefed-up benchtop mill in many ways.

    Randy

  19. #19
    Join Date
    Feb 2006
    Posts
    1072
    Quote Originally Posted by hockeypuck View Post
    Hello,
    Can someone please explain why my Z only slides once in a while ( one out of 5 )
    Varying room temperature, how much the Z axis has moved lately, whether you've given it a shot of lube lately, etc. would be my guess. My own Z doesn't slide down consistently, but sometimes the conditions are just right, I guess. When it gets to sliding down too often, I readjust the gib...

    Randy

  20. #20
    It's been a while since I've read that paper. -- Probably read it on a daily basis while I was waiting for my machine to arrive though

    I just know that in a conversation with Greg I said something about the weight being the name and he explained to me that the name referred to the motor size, not the machine weight.

    I've only seen a Haas in pictures so I can't compare. Though I've seen pictures of benchtop mills too and it is obvious that it isn't one...

    Dave

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