Throttle Control Valve for GraverMax explained...

[mitch]

Since introducing the Throttle Control Module a few weeks ago*, I've received a number of inquiries about how it works. Operating under the assumption that for every person who asks there's at least a few who are also curious, I'm posting a comprehensive explanation here for all to see. I apologize for the length of this post, but I'm trying to cover about 10 questions and to really make things clear the answer requires a bit of background on how the GraverMax throttle system works.

(*Please note: The original thread was immediately bogged down, even hijacked, by some who wanted to focus on legal & political issues tangentially related to the product, and was quickly shut down by site admin. If anyone still wants to dredge that up, please send me a PM and I will be more than happy to entertain your questions & comments. Per the directive of our Benevolent Dictator, Alfanzo the Omnipotent, under no circumstances will such comments, concerns, or questions be tolerated in this thread. This discussion is solely dedicated to technical/mechanical matters, and furthermore, strictly devoted to the version of the product designed for the GRS GraverMax/Mate/Smith machines. If you have any questions or comments relating to the model designed for the other company's equipment, please feel free to send me a PM or, if you think others may be interested AND can keep it within strictly technical bounds, perhaps start a new thread focused on that specific topic. Your cooperation will be greatly appreciated.)

In general, the Throttle Command Module (TCM) is an improved aftermarket upgrade that allows older GRS machines to be retrofitted with what they refer to as a "Bias Valve" on their newer models. The main function of a secondary control valve in the throttle system is to allow fine-tuning of the throttle & handpiece response. The GraverMax & its evolutionary offspring require a certain amount of minimal airflow through the pedal even at rest for acceptable handpiece response (having a little flow at all times avoids unexpected surges that may occur when starting from zero). Until the introduction of the Throttle Command Module, this minimal flow was always achieved by simply adjusting the throttle at the factory to a pre-set level. In other words, the bleed valve in the foot pedal was rotated to a certain point, as if the pedal had already been engaged to a slight degree. Unfortunately, this method has some undesirable, unavoidable, side effects: The most sensitive segment of the bleed valve orifice, where the groove is at its finest, is wasted just to attain this minimum flow. Also, while the new "Progressive" foot pedals/bleed valves have an extra-fine extension to the orifice groove (see photo), this means the valve must be rotated even farther to achieve the necessary minimum flow, thus somewhat defeating the purpose of the finer groove. Obviously, a one-size-fits-all factory pre-set throttle cannot provide the optimum setting for the infinite variety of handpiece, pressure, & stroke speed combinations available to the user, either.

This also means that the factory pre-set flow must be low enough to accommodate the smallest handpieces with the lightest springs at the lowest pressures (higher flow rates would make them impact automatically). While this makes for a reasonably acceptable response with small handpieces @ low pressures, there will be an ever-increasing amount of lag time as you progress to larger handpieces @ higher pressures. To initiate impacting with larger handpieces having heavier pistons & springs, the higher minimum starting airflow must be reached with every cut by pushing farther on the pedal. (Before coming up with the TCM, I'd actually installed a stop screw under the heel of my pedal to take up the wasted travel, as much as 9°-11°, when switching to larger handpieces, but that was too cumbersome so I just started sticking a block of wood under the heel.) This unpredictable starting point is not only disconcerting for the user (like bad creep in a cheap trigger), but because the bleed valve travel has a fixed starting point it means the effective range of the throttle gets shorter & shorter with larger handpieces & pressures (see 4th photo)- a consequence of having to vent all of the throttle airflow through one valve.

The Throttle Command Module changes all this. Included with the installation instructions are detailed directions on how to re-adjust the bleed valve in the foot pedal to eliminate this factory pre-set minimum flow. Then the TCM is utilized to establish the optimum minimum flow for any handpiece, pressure, & stroke speed combination. In only a few seconds, the perfect setting can be dialed in, regardless of whether you're using a Monarch with an ultra-light spring and barely a whisper of air, or a Magnum at maximum pressures, AND YOU WILL ALWAYS BE OPERATING IN THE MOST SENSITIVE RANGE OF THE THROTTLE ORIFICE, with absolutely smooth, immediate response, and with 100% of the full throttle range available at all times. Your foot, your hand, & your brain won't have to adjust for different throttle starting points with different handpieces & pressures, the TCM makes them all the same. Also, if you have a precision regulator you can achieve a very fine "idle" with the piston lightly oscillating, but not quite impacting, for the ultimate in throttle/handpiece response.

In addition to directions for correctly adjusting the bleed valve, the TCM has a couple distinct advantages over the factory bias valve which I believe offers the potential for making older equipment perform even better than newer models in this respect. One is the finer screw thread in the needle valve of the TCM vs. the factory unit- this makes it easier to fine-tune throttle/handpiece response. The other is that the needle valve is contained within a separate case- which serves two useful purposes. The case is insulated with open cell foam to suppress the noise of the escaping compressed air. This not only muffles the sound at the TCM, but since a significant amount of air is being diverted through the much quieter TCM, overall throttle noise is reduced as well. (The factory bias valve just vents into the uninsulated metal machine enclosure.) The separate case also allows the TCM to be located more ergonomically- i.e., while right-handed engravers usually put the engraving machine on the right side of their bench, it would be advantageous to locate the TCM within easy reach of the left hand. This is particularly handy if you want to maintain a really precise setting as your air compressor & handpiece warm up.

Finally, the Throttle Command Module can be utilized as a completely independent throttle in its own right. Instead of using the foot pedal for stippling, hammering, or other operations that require a constant speed for extended periods, you can just use the TCM to set it wherever you want. Not only does that relieve you of having to hold your foot perfectly still to maintain a constant setting, you can shut off the air supply from the compressor to the machine and the TCM will hold that setting while you take a break- for a few minutes or a few days.

The photos below illustrate the following, respectively:
1) A photo of the actual "bleed valve" from a foot pedal. The groove rotates past a compressed air orifice, and as the groove widens it allows more air to escape, actuating the handpiece. Note: This is a new "Progressive" model.
2) Smoke prints of the actual bleed valve grooves found in the old style & new "progressive" foot pedals. Note the fine tapered notch extension in the new version.
3) This is the new bleed valve with the approximate range of travel marked. The pedal rotates a maximum of ~23°, which translates to .200" of travel on the face of the 1.00" diameter bleed valve. This is the maximum amount of travel available with a small handpiece @ low pressure. As noted above, the extra-fine notch is a good idea, but as you can see it's mostly bypassed when the bleed valve is adjusted for minimum airflow at the factory.
4) This is the approximate range of throttle movement available when using a larger handpiece. Note the extra ~10° of travel necessary to initiate impacting with the heavier piston & spring, in addition to the factory pre-set minimum. This leaves only ~13° of rotation remaining to control the handpiece.
5) This is the range of the bleed valve that is used with EVERY HANDPIECE, AT EVERY PRESSURE & SPEED, when the Throttle Command Module is used to customize the throttle/handpiece response. Note the full use of the finest, most sensitive section of the valve groove.

For the time being, the Throttle Command Module is available exclusively thru Chris DeCamillis at www.engraversstudio.com

Thanks for taking the time to read this!​

 

[Brian Marshall]

Interesting...

I have spent way too much money over the years trying to keep every new model of every brand of whatever is out there for students to use when they arrive here. Anyone who has been here knows...

I've never not had whatever piece of equipment they were using at home, but of late I've decided that enough is enough, and I will only spend the money on small and important improvements.

If a new system or any other new tool comes out from now on - and costs over a hundred bucks - the manufacturer will have to supply it (lend it).

That is if if they want students exposed to it so they will buy it? I can't/won't do it out of my own pocket anymore. So far, Mitch has stayed under my new limit




Which leads to these questions - can one purchase and replace that one part (the plastic cylinder w/groove) to arrive at a "progressive" model footpedal? Do it yourself? Send it to Mitch to have it altered?



Brian Marshall
SJAS
Stockton, CA USA 95209
209-477-0550
instructor@jewelryartschool.com
http://jewelryartschool.com/

 

[mitch]

Hi Brian-
I know GRS sells a complete new 'progressive' pedal ($110? $115?) and would assume they'd be happy to retro-fit existing units (who needs two pedals, right?), but have no idea what they'd charge for that. I'm also not sure if one can simply order the new replacement bleed valve or what it might cost. I do know they are in all respects identical to the old type, with the exception of the tiny extension to the machined V-groove, so it's a simple matter of disassembling your pedal (an excellent time to CLEAN THE DISGUSTING COLLECTION OF DUST-BUNNIES OUT OF IT!) and swapping out the valves with no other mods needed.

As I stated above, I think this improved groove is a good idea, but only if you have the ability to take advantage of its full range- which means either using an aftermarket throttle control valve like mine, or if you have a newer machine with a 'bias valve', readjusting your foot pedal and using that bias feature every time you change handpieces, pressures, etc. time. (which, btw, takes about 5-10 seconds.)

I'm a die-hard tool customizer (my wife has watched me modify new powertools before i've ever even turned them on) and as such, have done a lot to trick out my engraving equipment. Most changes I like, some haven't been worth the bother, but this throttle control valve is truly something I wish I'd thought of years ago. Now the handpiece, ANY handpiece, starts exactly when I want/expect it to, right at the start of the pedal rotation. No more 'little farther, little farther, any day now...'- it's smooth & immediate every time. There's more than enough guesswork in my engraving- when my handpiece is going to respond to the foot pedal is one mystery i can live without.

 

[ARM]

Hi Brian-
No more 'little farther, little farther, any day now...'- it's smooth & immediate every time. There's more than enough guesswork in my engraving- when my handpiece is going to respond to the foot pedal is one mystery i can live without.

MITCH MOSCHETTI Esq
We just cannot ever buy experience.
Have started working bare footed with the FOOT PEDAL in the hope that we'd know and eliminate the guesswork for the response time from depression to commencement of the cut. And those have been agonising moments.
What we would like to U to confirm is whether this or the other TCM would improve the workings of the CLASSIC. CHRIS has advertised this on His site and we have not had time to fully discuss this with him.Would immensely appreciate your input here, which we value as well.
Thanks a stack
LORD BLESS
aRM

 

[Brian Marshall]

So, if the plastic bleed valve part is the only difference to a "progressive" foot pedal - do ya think that altering the old one I have here with a razorblade, a sawblade or a combination of the two, is possible?

Based on the image you put up, it doesn't look that complicated...

Or is this one of those "Don't try this at home things?" (That we always try anyway)


Brian

 

[Peter E]

I purchased my Gravermax within just a couple of months from the Gravermach being released.

I did get the "progressive" foot pedal as well as the "remote air regulator" which goes between the compressor and Gravermax.

When the Gravermach came out, I was considering selling my nearly new Gravermax and upgrading, but waited to try the Gravermach to experience the difference.

Glad I waited, as the next time I took a class at GRS all the workstations had been upgraded to Gravermachs.

The Gravermach with the "bias" control seemed to function exactly like the "remote air regulator" that I have with the Gravermax. It is very easy to adjust it so that the response from depressing the foot pedal results in precise, predictable power being delivered to the handpiece.

Also, the increase in "strokes per minute" from 4,000 to 8,000 was not significant as I have not had a need to use higher than the 4,000 limit of the Gravermax.

 

[mitch]

"Have started working bare footed with the FOOT PEDAL"

i've been working barefooted pretty much forever -largely due to non-airconditioned work spaces in the warmer months, but yes, it does help a bit with pedal control (it's also why i have a 1/4" thick piece of plywood on my pedal- so the uncomfortably sharp lip at the back doesn't irritate my foot).

speaking of working barefoot, that reminds me of a guy by the name of Daniel Brush who made (makes?) various objets d'art in NYC. there was a book out about his work maybe 10-12 yrs ago and it makes for interesting reading. while the pretty tchotchkes are, for the most part, lovely to behold, the real entertainment is to be found in some of the copy.

in particular, the part about working with a hammer & chisel to sculpt steel. he states that whenever he does that task, he suits up in bike leathers, heavy leather apron, etc., and still finds tiny chips embedded in his skin. in fact, they're typically so minuscule that he doesn't find them until they rust under his epidermis.

ooooooookay........ hmmm, i routinely chisel steel wearing nothing but a pair of shorts and flip-flop sandals. the chips fly off to my left as i cut in a right-to-left lateral direction. i can count on one hand the number of times i've been impaled by a flying chip- with all five fingers left over. then there's the small matter of if the chips are so tiny they escape initial detection, how did they ever pierce his skin??? we've all had our hands showered with red hot grinding swarf without incident or injury. how does this guy get penetrated by a microscopic speck at room temp- let alone through the protective gear???

you know, i kinda suspect the authors of the book swallowed this fish story hook, line, sinker, rod, reel, & boat...

 

[mitch]

So, if the plastic bleed valve part is the only difference to a "progressive" foot pedal - do ya think that altering the old one I have here with a razorblade, a sawblade or a combination of the two, is possible?

Based on the image you put up, it doesn't look that complicated...

Or is this one of those "Don't try this at home things?" (That we always try anyway)


Brian

hmmm, an interesting question. next to worst case scenario, you mess it up and take a mulligan with the other end of the V-groove. worst case scenario, you end up buying a replacement with the improved groove already in it. i suppose one could even experiment by flipping the bleed valve back & forth between the new tapered, extended groove and the old straight V for comparison.

as i mentioned in the pics in my initial post, the max range of travel on the face of the valve is .200", so you could use that to establish scale for the other dimensions and go from there. maybe for really, really fine work- if you never need max power- one could experiment with a long, ultra-fine groove extension? however, i doubt a new one is very expensive, so like so many things it's probably cheaper, easier, faster to just buy it (but that's soooo not like how the typical engraver's mind works, is it?)

 

[Brian Marshall]

Mitch,


Yep, read the book. Daily bowls of pea soup for lunch, and morning meditation whilst sweeping the shop?

My shop could use the daily sweeping, and I do like the occasional bowl of pea soup - but every single day for decades?

On a tough day, falling asleep instantly - I have woken up in bed with maybe a dozen chips in the sheets - and while they irritate the wife a LOT, I never even notice them... until she starts in on me.


Brian

 

[mitch]

to Peter E.-
"I did get the "progressive" foot pedal as well as the "remote air regulator" which goes between the compressor and Gravermax (emphasis mine).
...
The Gravermach with the "bias" control seemed to function exactly like the "remote air regulator" that I have with the Gravermax. It is very easy to adjust it so that the response from depressing the foot pedal results in precise, predictable power being delivered to the handpiece."

Any 'remote air regulator' that lies between the compressor & the GraverMax cannot function as a throttle control/bias valve- it's simply not in the throttle line. It may be able to affect the overall system in such a way that it feels the throttle response is somewhat improved (and i'm not doubting your impression in this regard), but in order to directly adjust the throttle response, you must have the ability to bleed excess air from the line feeding the foot pedal between the rotary valve & the foot pedal. whatever happens upstream of the entire machine cannot specifically manage airflow to the pedal.

When they say the precision remote regulator "will allow your handpiece to start at precisely the same foot pedal position time after time", they must be referring to a consistent starting point from one cut to the next, not from one handpiece to another. (Fluctuating pressure from a standard type regulator can result in an inconsistent pedal/handpiece response.) Don't get me wrong, having a precisely controlled air supply is definitely a positive thing, and WILL help ensure consistent throttle/handpiece response at that particular handpiece & pressure combination's natural actuation point in the pedal stroke, but it simply isn't positioned to manage the throttle airflow independently and therefore can't adjust different handpieces/pressures to the same starting point in the pedal rotation. My Throttle Command Module & the GraverMach Bias valve can because of where they're installed in the system.

 

[mitch]

"Daily bowls of pea soup for lunch..." and wasn't it cheerios every day for breakfast? yeah, now i remember the daily shop sweeping ritual and how it described him buying only the purest gold then melting it & generally messing around with it for hours to 'purify it' further before making a big deal out of making a simple round ring. and the two years he let a granulation project sit before finally firing it, etc., etc., etc. oy...

 

[Peter E]

Your explanation sounds perfectly logical Mitch.

When turning on my Gravermax, once the compressor has filled the tank, I then turn the knob on the "remote air regulator" till the handpiece vibrates and makes the tapping sound as in the instructions provided by GRS. Add a bit more air as the instructions state.

Then, fine tuning is done by depressing my foot pedal, and making another fine adjustment on the remote air knob, until when I depress the footpedal, the handpiece has power immediately just as it does on a Gravermach using the "bias" control.

If the adjustment is off, a noticeable HISS is heard before the handpiece is activated, or if off the other way, the handpiece will have a slight vibration.

I have one handpiece attached to each port, and going from one to the other, DOES require re-adjusting the "remote air regulator".

To me, it seems to have the same effect as adjusting the "bias" knob on the GraverMach, as the handpiece is activated precisely.

 

[mitch]

Ok, Peter, after going over the instructions for the Precision Remote Air Regulator on the GRS site (http://www.grstools.com/PDF/LIT-272_PrecisAirProgFoot.pdf) I get what you're getting at. Basically what they recommend is tuning the throttle response by using the lowest possible pressure before the handpiece automatically starts self-impacting*. This method will work just fine if you're okay with always using any given handpiece at its minimum working pressure (which I concede is probably fine for most people most of the time). You can do this trick with the standard regulator, but because they allow more pressure variation you'll need to leave a greater margin of error and settle for a bit more pedal lag.

However, if you want both the flexibility of using higher pressures (for more vigorous chiseling, esp. w/ bigger hdpcs) AND the ability to fine-tune the throttle response, you'll need some means of adjusting the air bleed in the throttle line itself.

*If you've ever forgotten to turn on the compressor you've gotten a brief- and annoying- demonstration of this concept. You're working merrily along and all of a sudden the handpiece develops a mind of its own- spastically oscillating in blatant disregard of throttle input- until it peters out (no offense) altogether. The whole while you're sitting there thinking "WTH is wrong with this POS now?!" oops- operator error... The basic functioning of the machine relies on sufficient volume & pressure of air to force the piston against the anvil in the handpiece, then air is gradually bled off by the throttle valve to allow the spring to push the piston away. With the pulses of air from the rotary valve, this creates a situation of dynamic equilibrium where the air pulse drives the piston into contact with the anvil, then is momentarily eased and the spring pushes it back, and so on. The throttle control valve (pedal and/or supplemental) serves to allow more air to bleed off behind the piston, allowing it to withdraw farther in the bore, thus getting a bigger run at the anvil on the next stroke. In other words, more throttle = longer piston travel = more piston momentum per stroke = heavier impacts.

 

[Christian DeCamillis]

Peter,

I am using the gravermax with the precision regulator and I adjust it as you describe. The TCM that Mitch makes is also attached and when you turn the bleed air off on the pedal it makes a big difference in how the valve works. It makes the start up much smoother as well as the start position being predictable. You can even let the piston idle if you want to.

I also have a mach and yes with the regulator you can adjust it well. I have never gotten the bias valve to make any difference with it until I shut off the bleed air from the pedal as Mitch tells you to do with the TCM when you install it on the gravermax. Then the bias valve operates as it's described to at least in my opinion.

What Mitchs valve will do if you use it along with a precision regulator is make the performance of your max virtually same as the newer models with one exception. The newer machines pulse the air a little more crisply. For me that makes no difference, in fact I prefer the the less crisp hits for my own reasons. The other thing the new machines do is perform better at the lower and higher speeds. By adjusting the motor speed controller in the max I can also change how it performs at lower speeds. and make it go faster if I wish.

The other difference between older and newer is that the new one are much quieter. What I did to solve that issue was to remove the screws that hold the motor so it doesn't vibrate and resonate against the metal body and frame. I put some rubber type foam under the motor and now I have a very quiet machine. In fact even with the cover off it's almost silent.

These are things that I have done to enhance the performance of my older machine. I would suggest to people who might want to do some of these things to first check with the manufacturer to see if they would recommend doing it or not.

 

[Peter E]

Thanks for the explanations Mitch and Chris.

Admittedly, I have not done much in trying to understand the mechanics of my Gravermax and foot pedal. I was surprised to see what was "inside the box" when I needed to clean the rotary valve!

It would be interesting to try out the TCM to see the difference.

 

[mitch]

This has proved to be most enlightening. Out of curiosity, I played with my machine a bit and found that while I ordinarily use a standard 720(?) handpiece @ 30psi, I need to drop that to around 22psi to 'tune' the handpiece with the pressure regulator. Of course, that's with a readjusted bleed valve in the pedal, so with factory pre-set pedal leakage it would be a bit higher?

This raises a few more questions:
Does this handpiece actually operate at ONLY ~22psi and any & all throttle venting only serves to bleed it down to that functioning pressure, regardless of input pressure?

Or do higher pressures provide more punch on the downstroke?... and you just need to bleed more air at the throttle to actuate the piston?

So assuming a handpiece can be tuned by adjusting overall input pressure, this means a couple things:
Due to the unavoidable fact that there needs to be some initial airflow thru the throttle (to avoid pent-up surges when starting from zero), without a secondary valve the bleed valve needs to be rotated to provide that necessary minimum flow. As I showed in my first post, this results in the finest segment of the bleed valve orifice- esp. the progressive version- being largely or even entirely bypassed/wasted.

In order to take full advantage of the finest segment of the bleed valve and its full range of travel, one must readjust the pedal valve to zero flow, then rely on a secondary valve- either my Throttle Command Module or GRS' bias control- to provide the minimum required flow.

So, if you're just going to tune the handpiece response by regulating input pressure from the compressor, without readjusting the bleed valve in the pedal, does the factory bias valve actually do anything? And going back to my question above regarding 'do higher input pressures actually translate into more engraving power, or is the excess pressure just thrown away until it reaches the natural operating pressure of the handpiece anyway?', does the GRS bias valve achieve anything if higher pressures don't provide more punch at the point?

 

[Christian DeCamillis]

Mitch you bring up a good point and you are right on about the pedal valve bleed needing to be turned off and the secondary valve to do the minimum. which is what you express be done in your installation instructions. this is what my experience showed when I used the bias valve on the mach without the bleed air shut off it seemed to do nothing more than act as a fine adjustment. When i shut the bleed air off it performed the same as your valve did on the max. So the bias valve does do a lot on the new machines if the bleed air is shut off.

I must say though that this is what I experienced. I always suggest that people check with the manufacturer before changing something in case the change could cause some other issue that i don;t know about.

Bob Finley there in Emporia aka. Unbelievable artist craftsman a genius of sorts. who does some incredible deep relived carved and even 3d carving on his knives and such that he also makes, told me that when he cuts deep and needs to hog out area's that are deep. By deep I mean 60ths. or more. that's about 1.5mm for those in the metric world. He turns up the pressure or over pressures past the optimum pressure for running the handpiece normally. He like some of the older handpieces for this. he said he gets more power. I tried it and it works or it feel like there is more striking force. on the down stroke. but you need to put the pedal to the metal and there is a lot of air bleed of course. But the power seems much stronger. i don't know if there has ever been any measured data on the force but it does seem to work.

 

[pilkguns]

Bob Finley there in Emporia aka. Unbelievable artist craftsman a genius of sorts..

Definately a genius. Holds a number of patents, as well as drag racing National Records. Super guy. And an unsung hero of the engraving tool design world.

 

[Arnaud Van Tilburgh]

There was a TCM under the Christmas tree for me. I installed it easy like the manual shows. Used it already for stippling cutting lines and shading.
But as I’m now moving my shop to another location, I only can start over again before Wednesday next week.
I will ASAP write a review on the TCM, in particular showing new work and bulino using it.
I’m one of the rare ones that use a Graversmith, but I can tell you that I love that machine, and even more with the TCM

To be continued, :big grin: arnaud

 

[airamp]

HI,

I would like to know how the TMC works with the Lindsay Classic ??

I have asked before but never got a answer??

Will it slow down the piston with short stroke and low pressure more that stock??

How would you set it?

AirAmp