Tormach Perspective

[Tormach]

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

[barney9014]

Greg, You have a private message. Jim

[hockeypuck]

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?

[philbur]

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

Originally Posted by hockeypuck 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?

[pstockley]

You need to tighten the Z axis gib. The manual describes how to do this.

[zephyr9900]

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

[philbur]

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

Originally Posted by ProtoTrains 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

[Willyb]

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

[zephyr9900]

Originally Posted by philbur 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

[zephyr9900]

Originally Posted by Willyb 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.

Originally Posted by Willyb 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

[philbur]

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

Originally Posted by ProtoTrains 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

[dammachines]

Originally Posted by philbur 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