Working On A Drag Knife for Vinyl! #117 - Bassett, VA

[Tom Ayres]

Problem solved. I figured it out Pete, the proxy schematic is backward and of coarse I wired it based on the schematic. It just didn't make sense, the voltages were everywhere and never went to 0v. What a pain. NOW I can mount the z proxy. Thanks for your support Pete.

[pblackburn]

No problem

[Tom Ayres]

A shift in gears...
Back in the beginning of my interest in building a MM, thoughts of what the ideal machine for me would be and what it would be capable of doing ran through my head. I have a Legacy ornamental turning lathe, which I've had for 18 or so years and is a pain to operate, its inaccurate and doesn't really impress, but the conceptual designs it spurred were. But the process to use it takes so long I just stop using it. An indexer for the MM was a must, so now that I have it running (not finely tuned yet) I wanted to plan something that would either attach to the top from the top or have it cut below the spoil board. I have been watching occasionally others who dare to go there and know it is possible. I'll approach this like Pete has, paced and methodical. But not until #117 has paid for itself.

(ideas soon follow)

[Tom Ayres]

I need vacuum hold down eventually and ran across this pump http://www.ebay.com/itm/110786692393...84.m1423.l2649 on Ebay, is this good enough for a total area of 5' x 6' (half of my table)?

[ger21]

Do you know any of the vacuum specs?
CFM?
in of Hg?

If you plan on holding through a spoilboard, then you ideally want about 20-25in Hg, and 200-300CFM.
ShopBot guys using vacuum cleaner motors get by with 8-10in Hg and 300-400CFM.

If you use a "pod" system, you can get away with less CFM, but will want at least 25in Hg.

[Tom Ayres]

Based on a very limited amount of usable info on the net it seems to be somewhere in the 200-210 cfm at 30-35in Hg per pump. Not sure if I understand that listing anyway it says its a double pump, does that mean 2 pumps or 2 stage? who knows, I guess I'd have to do more research. Thanks Ger.

[ger21]

You can't get more than 29in Hg, and anything over 25 at that CFM would be very expensive. Make sure you're they're using the same units (in Hg), as 30-35 is not correct.

[pblackburn]

Vacuum is a funny thing. Not the idea of using it but the workings of it. I work with vacuum furnaces. We use big Stokes pumps with the assistance of blowers to hold 30 inHG of vacuum. Vacuum will be decreased exponentially once an area is open. Small leaks can cause a big lack of inHG. So the better the seal the better the performance and less heat generated by the pump. The harder it has to work; the more heat generated by the pump; the less life expectancy of the pump. Our pumps run at 230°F nominal with no leaks but we are pulling and maintaining deep vacuum.

If you have a product line that has a profile that will be run a lot, you can create a vacuum layout to hold that part with minimum lose using minimal hp and minimal money. It is all about design. Ideally you would want a customizable holddown that could be easily manipulated to handle all your parts without the adding downtime to product line changeovers for new part setups. This can be mechanical, electrical or electro-mechanical. Any time the machine is down or using wasted energy that it should not have to be using, you are losing money!

So it is all about your product line and the design you pick. Take time, do your homework and enjoy the fruits.

[KenC]

For sanity check, total vacuum is o bar. if anyone tell you they can get -2bar, they must be from another dimension. not even this universe.

[pblackburn]

Ger is right 30iHG is what we call deep vac maintaining 5 microns or less. Most of your vacuum generators you can buy are 25inHG. To give an idea or the science and cost of the generators, Schamlz makes a vac generator that fits in the palm of my hand that uses compressed air to make the vacuum. They cost $2400.00 per unit.

[pblackburn]

Vacuum Conversions

[Tom Ayres]

Sorry I must have pulled from the wrong information, even I know that 29in Hg is near perfect vacuum. (Must have more coffee) Let me dig deeper. Like I said info is scarce. I get back to you guys.

[pblackburn]

Tom, that probably happened with people not understanding gauges and misreading them. A lot of problems with people reading any gauge is a gauge is the most accurate at its mid-range. So a vacuum gauge is at 30 inHG it is at its far point. Since you cannot reach 60 in of vacuum, a manufacturer cannot do deal with this impossibility. It is impossible to make a truly accurate gauge to read 30 inHG in its mid-range. It will however be accurate at 12-15 inHG.

[KenC]

Pressure isn't the only factor in vacuum usage. there are 2 major combo, high vacuum + low flow & High flow + low vacuum. My vacuum table is high flow low pressure, the high flow is the to ensure the pump can such enough air (mostly to overcome leakages) to maintain my target vacuum (or partial vacuum to be exact). High acuum+ low flow is mostly for applications where leakage is minimum & deep vacuum is needed.
I remembered I wrote all my numbers & information somewhere, can't remember where in this forum. BUT if you dig enough, you will see them.

[Tom Ayres]

Well that's not going to work if I'm reading it right it only creates 0.20 bars at best. On to the next find...

[IMMark]

Tom (or others),
There is some interesting reading, ideas and builds on this forum;
http://www.tk560.com/phpBB2/index.ph...50f519bcce01a2

regarding vacuum builds.
Best of luck
Mark

[Tom Ayres]

I agree

[darren salyer]

The forum Mark linked to is now bookmarked and I'm sure will lead to many hours of what my wife calls time wasted on the internet...
Tom, I have a Legacy mill too, and have the same frustrations.
Its been on CL since I finished the MM, and I'd like to build an indexer for mine as well.
What I'd REALLY like to do is build one like Art(turningaround).

[Tom Ayres]

Do you know the link? I'd like to see which you're speaking of.

[darren salyer]

Marks link in post 496.
Sorry for the confusion.

[pblackburn]

How is the learning curve coming along?

[Tom Ayres]

Its coming along. I haven't been able to spend any time in the shop since Saturday morning. My son has been competing in robotics in Richmond. His team got to the quarter finals where they got eliminated. Oh well there's next year.

I'm planning to get out there tonight to do some more tweaking of the MM by getting that little 'Black' button on the y car to work for a zero routine and multiplexed to run a probe routine as well, oh, and add a "Blue" screen to Mach for z zero and center finding. Once that is done then I'll feel like I can start messing around with other aspects, like creating stuff.

[KenC]

A remote Zero finding button/s on the gantry is very practical add-on.

[Tom Ayres]

I thought so too, should make the function a bit easier.

[darren salyer]

That is an understatement, Ken.
Kinda like a car, you don't really notice the options until you drive a car without it.
Putting a zero button on the Y-car was one of the best add ons I did.
Neck and neck with the laser zero finder.

[KenC]

Laser zero finder is another must have.

[Tom Ayres]

Where do I get one of those?

[darren salyer]

I documented part of it in my build thread. A laser crosshair from China for less then 10 bucks and Gerry's Mach 2010 screenset will make your material setup much easier.

[Tom Ayres]

How do you compensate for tooling with the laser? Is that in the 2010 screen set?

[darren salyer]

yes there is an offset that you input into the script after you measure it.. Mine is about 4" Y offset and about 2" offset. Pressing the laser button inputs those #s into the DROs, then pressing the move to zero button positions the bit where the laser was, if that makes any sense?