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Paraprop
07-29-2007, 03:53 AM
I am presently upgrading my mill to 4 axis.

On the spindle head (Z axis), I am going to add a diamond wheel grinder.

Right now I am not too sure how to scan an existing cam profile (from an engine intake/exhaust camshaft) into the system.

I am using a 2500 CPR encoder on the A Axis. so I would like to take a measurement for up to each of the 10000 steps in a 360 degrees rotation by a linear encoder head putting out a signal onto the encoder input of the DeskCNC controller card (same as used as feedback for the lathe spindle application). The output of this linear encoder (I still have to purchase it) has a resolution in the 0.001mm range. Then I would like to graph the resulting cam profile, eventually modify it and then produce a G code file to grind another camshaft lobe based on it. The grind is done just by rotating tha A axis and moving the grinding wheel on the Z axis. No need to move the X axis for it.

Is it actually possible to do so ? I could not find any hint on the docs. Available on the web. If yes, is there somewhere a similar application I could use for reference ?
Until now I can only find samples of scans done with the touch probe connected to the Lim input but I am afraid this method is not as accurate as if I go for the linear encoder even though I already got 2 sets of the IMservice touch probe. Also in the literature nothing hints about using the touch probe for parts rotating on the A axis.

41427

Thanks in advance for nay hint.

Paraprop

Daniel

NC Cams
08-17-2007, 11:50 PM
Andrews Products makes and sells a device (EzCam) that does EXACTLY what you wish to do. Audie Technologies does so as well as does Performance Trends. There was also the "Cam Doctor" sold at one time but they are no longer in business as far as I know.

They people currently selling machines do NOT however, provide any DIY "how to's" especially with regard to the software - some won't even sell the software without purchasing a machine.

Some of your ideas are valid - some, however, some will simply not work. The why's/wherefors behind both is far to complex to delve into in a message board thread.

For insight into cam reading "how to", contact the SAE and obtain some papers written by Jess Nourse. They were written in the late 60's or 1970's. The Nourse articles are/were what these same people used to create their cam reading machines.

There are also a number of other cam design articles that are mentioned in a "cam design" thread that is/was ongoing on the Zone. Do a search and it will come up near the top.

That's as much of a hint as I can offer.

toastydeath
08-18-2007, 12:23 AM
For a hobbyist, it is easier to grind a cam on a manual mill and grinding machine than it is to make a CNC to grind an acceptable cam. You're not going to get a smooth, long wearing surface with the intermittent step-cutting you're going to get from an ad-hoc CNC grinder unless you really know how to design a machine.

There are a lot of old books and articles on grinding cams via manual methods. These methods are certainly not as accurate as a even an okay CNC cam grinder, but they're going to give you a longer wearing and smoother running cam than what you're going to get how you've proposed to do it.

I would take the more inaccurate cam with a great surface over the slightly more accurate cam that breaks everything that comes into contact with it.

I might not know what goes into designing a cam, but I have a much better idea of what goes into building a CNC grinder, and it's not something that you're going to be able to easily finagle.

NC Cams
08-18-2007, 09:49 AM
There have been numerous attempts at making CNC cam grinders attempted over the years. I don't know of any that achieved commercial success outside of the Landis 3L. This machine is far, far and away too expensive however for the hobbyist to even consider.

We grind cams as a profession. We've tried to mill cams with 4th axis machines. WE even tried to create plate master cams with a 2D machine. After spending lots of time and money, we finally did it but it takes a VERY, VERY expensive CNC and one in very good condition to do it - a home brew CNC does NOT have the accuracy. The smootheness issues illuded to in the prior post are but a few of the problems that preclude the use of milled lobes for high speed cams - there are more and they are substantial....

There is a model size cam grinder that was made for/by a DIY'er - it was featured in a past issue of Home Shop Machinist and was a cover story as I recall. The machine did model engine size cams. I suspect it MIGHT be upscaleable to do Briggs or other one cyl cams but you'd still need to have a master cam created to grind from.

The cam arc and protractor design method used for the model engine cam will not create a profile that is smooth or dynamically stable enough to live in even a lawn mower engine. Again, the issues outlined in the prior post are harbingers of things that will happen.

Shameless plug: We do grind masters as a service to our clients. Although we haven't designed or cut any "model cams" like those used to on the HSM grinder, we theoretically could once we got the linkage geometry provided from whatever HSM adaptation is attempted.

Paraprop
08-18-2007, 10:36 AM
Thanks for your input.

Right now I would like to start with digitizing an existing cam profile with the DeskCNC controller.
Haven't yet received an answer from the manufacturer if it possible to use the encoder input normaly used for threading on a lathe, to read the cam profile data relative to each of the 10,000 rotary encoder steps per revolution on the A axis.

Indeed, there are a few hardware and software vendors who already do this and If I can access the data received by the encoder input of the DeskCNC controller, I may be able to do the same I guess.

For grinding I had already build a duplicator which worked quiet well. There was a follower on the master cam lobe and a diamond wheel on the raw cam. The whole thing was sliding on roller bearings and a weight pulled it towards the cam lobes.

Now the challenge is to do it on CNC. Even if it may not turn out well, it is a good learning experience.

Switcher
08-18-2007, 10:38 AM
There have been numerous attempts at making CNC cam grinders attempted over the years. I don't know of any that achieved commercial success outside of the Landis 3L. This machine is far, far and away too expensive however for the hobbyist to even consider.

We grind cams as a profession. We've tried to mill cams with 4th axis machines. WE even tried to create plate master cams with a 2D machine. After spending lots of time and money, we finally did it but it takes a VERY, VERY expensive CNC and one in very good condition to do it - a home brew CNC does NOT have the accuracy. The smootheness issues illuded to in the prior post are but a few of the problems that preclude the use of milled lobes for high speed cams - there are more and they are substantial....

There is a model size cam grinder that was made for/by a DIY'er - it was featured in a past issue of Home Shop Machinist and was a cover story as I recall. The machine did model engine size cams. I suspect it MIGHT be upscaleable to do Briggs or other one cyl cams but you'd still need to have a master cam created to grind from.

The cam arc and protractor design method used for the model engine cam will not create a profile that is smooth or dynamically stable enough to live in even a lawn mower engine. Again, the issues outlined in the prior post are harbingers of things that will happen.

Shameless plug: We do grind masters as a service to our clients. Although we haven't designed or cut any "model cams" like those used to on the HSM grinder, we theoretically could once we got the linkage geometry provided from whatever HSM adaptation is attempted.


Here is the link to the Home Shop Machinist "Building a Model Engine Camshaft Grinder" click the link below, & wait till the page loads the back issue database, then scroll down to & click "Volume 23 Issue 6, Nov 2004", it's the 3rd article on the list, by "Jerry Kieffer".

I'm not sure how to order the back issue, the store isn't working ( http://store.homeshopmachinist.net/ ).




Link to back issue:
http://www.homeshopmachinist.net/articleindex.php?pubcode=HSM&method=ISSUE


.

Switcher
08-18-2007, 10:43 AM
Google has a bunch of links for "Jerry Kieffer".

http://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=HPIA,HPIA:2006-29,HPIA:en&q=Jerry+Kieffer

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Switcher
08-18-2007, 10:49 AM
This shows the actual cam grinder.

1) http://craftsmanshipmuseum.com/images/camgrind1.JPG

2) http://craftsmanshipmuseum.com/images/camgrind2.JPG

3) http://craftsmanshipmuseum.com/images/camgrind3.JPG

---------------------------------------------------------------------------------------------------------------

4) http://craftsmanshipmuseum.com/Kieffer.htm

JERRY'S CAM GRINDER

In order to be able to make proper cams for his running engines, Jerry designed and built this camshaft grinder. He used the cast iron base from a discarded table saw. A Federal dial indicator was a $10.00 flea market purchase. The rest was made from bar stock. The power is supplied by the headstock/motor/speed control from his Sherline lathe. Total cost was under $60.00 not including the Sherline power unit. With it he can grind just about any model engine camshaft.

Specifications:
Max. cam length: 6.00"
Max. cam diameter: .750"
Grinding accuracy: .0003"

For his seminar at the April, 2004 North American Model Engineering Society Expo in Detroit Jerry will be detailing the construction and use of this tool.



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Paraprop
08-18-2007, 10:59 AM
Thanks for that Switcher.
Very kind of you.

Switcher
08-18-2007, 11:02 AM
I figure If that guy can make cams that small, maybe the machine could be scaled up to fit your job? :)

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Switcher
08-18-2007, 11:20 AM
More links (ideas). :)

1) http://www.strappe.com/grinder1.jpg

2) http://www.strappe.com/grinder2.jpg

3) http://www.strappe.com/grinder_notes.html


Scroll 1/2 way down the page:
4) http://www.strappe.com/hsm.html


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NC Cams
08-18-2007, 12:23 PM
The Keiffer mini grinder is essentially a scaled down table top version of a number of "rocking table" cam grinders.

These are/were made for the camshaft industry by Berco, Storm-Vulcan, Landis and a number of other companies who've long since faded from memory. It should not be impossible to scale up the Kieffer but, in doing so, you scale up the need for rigidity and accuracy - the larger the grinder the more substantial the error potential becomes - take my word, we've been down that path during our grinding and in-house master creation process.

The rocking table grinders all take a master and via a follower/linkage mechanism, trace the master onto the cam via the grinder. The conversion from simple design data to the master and then back thru the linkage geometry to the finished cam can be mathematically challenging.

Unless you have all the linkage geometries known and slop/clearances minimized, the design data and finished cam will not even be close to each other - moreover, the relationships ARE NOT 1:1!!!!!.

Heidenhain has multi axis rotary and linear encoders and counter cards that plug into a PC. The expense/complication comes in when you try to take data of the fly and turn it back into a meaninful cam follower motion curve. THIS CONVERSION FROM COUNTS TO DYNAMICS IS NOT EASY.

Even the seemingly simple task of finding the lobe center (point of max lift) can be challenging, especially if the cam has dwell at the nose or runout in the base circle (all cams do to some extent).

At one time Heidenhain offered DOS based ISA slot counters. Not anymore. They've gone to PCI which means you pretty much have to use Windows. Not only are the counter cards and encoders pricey but the development kit to write programming for Doze is not cheap. Hence, unless you plan to do a lot of cams, the cost to do what you're trying to do could turn out to be QUITE prohibitive.

We tried to do the same thing on the cheap as I was not bucks up when I started my cam company. Luckily, I struck a deal with a guy who made some table top measuring equipment and was able to buy some scratch and dent equipment that he'd developed for market. We then adapted it to some of our own fixturing and learned lots more about what counts when it comes to reading cams.

Even though I got a deal, it was expensive. I had little choice as I did not have programming nor much reverse engineering analysis experience, especially when it came to turning cam motion into engineering data - I could to the work once I got values but couldn't get values.

If you want/need a few cams measured, we offer the service and it is far less costly than making your own machine. However, being in Thailand does pose a transportation challenge.

Cost wise, your best bets are as follows:

cheapest: see if you can find a used "cam doctor". These were made at one time but have become a bit rare as the company is no longer in business. THey were the racers dream and relatively affordable at the time. Not suited for production validation measurement but better than a degree wheel.

Less cheap: Check out Audie Technologies. Not suitable for production QC validation and/or all-out killer reverse engineering but OK for racer analysis - probably as cheap as I'd go if I were an engine builder and was going to get serious. Have not used one but it is far better than a dial indictor and degree wheel.

High end, pro racer and production prototype suitable: Andrews Products Ezcam. These are superb, precise devices and they are doing world wide distribution of their machines. They are shop floor rated and also suitable for tool room inspections.

They have accuracies traceable and comparable to the Adcole - the Adcole is THE Rolls Royce of cam measurement devices. Ezcams are NOT cheap but considerably less than an Adcole and almost as good. Far better inspection device than a lot of aftermarket cam grinders and refinishers use even today.

Rolls Royce: get an Adcole.This is THE ONLY device recognized as useabla/suitable by the OEM's. PERIOD.

If you're bound and determined to make your own, do a search thru the SAE for any/all articles written by Jess Nourse. He wrote the articles that most of the cam measuring machine guys used to craft up their machines.

There are also a 3 article series written in the 1950's in Machine Design Magazine. One of the authors who wrote the article was Stoddard. This article, too, should be helpful in providing you with some of the math that you will need to take your encoder data and turn it into the measurement data you're seeking.

A simple tough point encoder WILL NOT BE SUITABLE to read a cam. Why? Tell me the true shape of an oblong American football when you only touch 3 points on the OD. Can't be done. Unless, you MEASURE the cam accurately, you can't simply touch random points and let some geometric mumbo jumbo program guesstimate via geometric curve fits what's happening inbetween.

With the encoder resolution you're talling about, you're going to be swamped with data. You can either process and interpret it properly or else why bother??? WIth the resolution you're talking, you're easily in the ball park of what Andrews Products machine already does.

All in all, it may be cheaper for you to buy one of the Ezcams and have a turn key one shiped to you than to reinvent the wheel. If you do buy one, tell Dave or John that you heard about it from NC Cams.

toastydeath
08-18-2007, 01:33 PM
If I was going to construct myself a cam grinder and I wanted to get close as possible to a good tolerance, I'd do the following. Please note this is crappy compared to a properly CNC ground and verified cam.

First, I'd construct myself two pantograph grinding machines, or possibly one, with two attachments. One would transfer a linear template, 1:1, to a master cam 10x the size I wanted on the finished cam. It would also have provision for reversing this process. The second machine/attachment would be the 10x reduction from the master cam to the product.

This allows me to produce things that I can check easily, i.e. a machine's accuracy and the linear template accuracy, without having to build a third, much more complicated machine to measure the cam directly. Once I know those items, I know the general ballpark of where the cams are going to land in actual accuracy. The direct measurement method is far, far more accurate than indirect methods, but being practical for a second, that's never going to happen as a hobby.

I would first cut and finish the linear template to +/- .001 or .002. This is easier than cutting a circular template in the first place, and the ramps, acceleration, and decelerations are more easily checked and created. Then, you rough out the desired profile on your 4th axis CNC, or by whatever method you want (I'd use a bandsaw and a file). Then, you finish grind the linear template onto the rotary template using your machine. Swap the linear template stylus for the rotary stylus, and grind your cam.

Then, reverse the stylus and the grinder. Grind the finished cam back onto a linear template, not a rotary one. Line the two templates up, and use two analog probe heads or LVDTs and the amp on differential mode to get the error in your cam, record it on a strip chart. Apply the errors you know your machine has to get the uncertainty in measurement.

Pantograph units can be made to fairly high standards, and the accuracy limit, practically, will be the template first and foremost, and second, the machine, if it was built properly.

Switcher
08-18-2007, 02:30 PM
Would something like this work (rough sketch below)?

The basic idea is to take a stepper/servo hook it up to Mach3, zero out the "A-axis", bring the follower down in the "Z-axis" till the bearing contacts the cam lobe, then zero out the "Z-axis", rotate the "A-axis" 360.0 deg. & let the stepper/servo record the travel in the "Z-axis".

Will Mach3 be able to record axis travel?

As far as actually grinding, use only the "A-axis" & "Z-axis" & manually jog the "X-axis" into position, I would think that you would use a 1A1 wheel that is wider than the lobe, so the grinding wheel shouldn't be critical in the "X-axis".

Remember this is just a rough idea. :idea:


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toastydeath
08-18-2007, 03:07 PM
I don't know anything about the DIY CNC controllers, so I can't comment on your measurement method.

The problem with the CNC grinding is that even commercial CNC mills and lathes do not have the kind of contouring accuracy and smoothness of operation necessary to do what you want. It just won't do it; a cam is more than just a lobed shape.

Seriously, you are going to break things and possibly injure yourself trying to make this a CNC operation when you just do not have the equipment available to you to build such a grinder. CNC cam grinders require very expensive motors, bearings, and other components to produce a smooth cam with an accurate profile, that a machine with ballscrews and inexpensive servos is just not going to be able to replicate.

You do have the ability, with your CNC gear, to do the research on and build a pantograph grinder or another manual solution, which will do what you want.

Please don't do something that's going to damage your equipment, or worse, someone.

NC Cams
08-18-2007, 04:19 PM
The use of a pantograph is complexity in search of a need. You do NOT need a 10x master to do tracer grinder grinding - ours are rougly 4-5x size and they run in 8000+ rpm racing engines.

The measuring of a cam needs to be done separately from grinding it. It is essentially impractical to make a do it all machine. The illustration in post 14 is a perfect representation of an inspection/follower system.

It is totally impractical to grind/finish a cam that way due to a lack of rigidity in the follower and/or grinding wheel systems. There are some serious forces generated in grinding and/or milling the lobe, especially if you want to generate a close to design intent profile from your data REGARDLESS OF THE SCALE OR SIZE OF CAM. Steel has the same modululus of rigidity no matter what the alloy, size or scale - just because it is smaller, that don't make it any easier to cut without deflecting it all over the place when you put a tool up against it.

CNC grinders are very difficult to coordinate, especially when you're trying to hold tolerances in 0.0001"s or there abouts - a lathe is easier to coordinate during threading than a lobe and that is NOT an easy task.

At least a lathe has to run at a constant velocity - a cam lobe, by its very shape and rate of change MANDATES a constantly changing velocity of both axis and that's the rub. Even at up to 0.0005" tolerance, a commercial product based CNC is hard to construct because the servos effectively can NOT rub their belly and pat their head at the same time and at the constantly varying speeds needed to duplicate even a mild lobe shape. Radical profiles are even harder to cut/grind properly.

Basically, it takes MASSIVE computer horsepower to have the servos keep up and to prevent follower error from occurring in the lobe profile when CNC grinding - especially if you want to grind at a rate faster than watching paint dry.

If you've ever seen a real cam grinder work, or better yet, what it takes to make a Landis 3L work, you'll see that I'm NOT blowing smoke.

Even the so-called "primitive" rocking table, master style cam grinders mentioned earlier are both accurate and efficient. Yes, they are not CNC but they do the job and can do so quite well once you learn the machine's idiosyncracies.

In fact, the Berco is still the "state of the art" when it comes to prototype cam grinding and many, if not most, of the aftermarket cam grinders have and still use them TODAY!!!!. Harvey Crane, Crower, Reed and a lot of other noted cam grinders can thank the Berco for helping them gain notoriety in the field of camshafts.

Toastydeath's comments about CNC contouring capability is SPOT ON. We know because we already tried that method, numerous times and on various CNC's. IT DOESN"T WORK!!!!!!!!!!!!!!! You'd be amaze at what happens to the "look ahead" feature of a CNC when you throw a cam lobe contour at one. Such notable machines as Haas, Fanuc and/ or Bridgeport puked when we tried to run cam contours thru them.

If you are bound and determined to do a CNC, don't even consider a stepper system. Why? they leave steps and they simply aren't fast enough. You can almost do as good with a 4th axis mill and do so at a fraction of the cost and complication and besides, the 4th axis mills still won't properly finish the cam.

BTW a Berco both finish grinds cams and it can copy/make its own masters via the copying of an existing profile from a finished cam or from a 1:1 precisely milled or ground model. THis leaves your inspection machine as the only separate machine you'll need.

You can have your masters made elsewhere or buy a 2D CNC mill and, after a lot of development and a ton of math and trig, craft up a CNC program that will CNC the model. Or, if you REALLY get good and spend lots of money, make a master directly with the same CNC.

Or, if you buy a master type grinder (Berco, Storm-Vulcan, Van Norman, etc), you can save the money on a master maker and simply buy CNC masters which is what we did and still do for a lot of our clients cams.

we eventually learned how to CNC our own but it took us nearly 5 years of development and buckets of money to figure out how and we had access to some of the finest cam mfg design and analysis and measuring software that money can buy. We also had some really good software code writers who looked at the job as a challenge - had they charged us shop programming rates, we'd have had to sell the business to pay the bill.

Thus, you really only need a CNC mill which can be used for pretty much anything, a dedicated measuring machine and the cam grinder. If you spend a bit more money and buy a really good mill with 4th axis capabilities, you can rough lobe mill the cams on the 4th axisl wherein the mill removes the majority of the metal.

However, the mill can NOT mill a lobe accurately enough out of hardened material to work properly in an engine - again, been there, done that. SOft metal milled to rough shape them? Yes, finish them NO.

If you really want to make a DIY bench top cam grinder, the Kieffer grinder in Home Shop Machinist is an EXCELLENT example of a home made DIY model engine cam grinder. I'm not a fan of the SWAG'd profile design method he's shown but the grinder is an excellent scaled down variant of a rocking table grinder.

If you're willing to make a CNC grinder, why oh why would you use a "bandsaw and a file" to rough out ANY part of the cam???? See prior comments about 4th axis milling and/or 2D milling of lobes and/or masters.

Paraprop
08-18-2007, 11:47 PM
Switcher, Toastydeath and of course, NC Cams.

Thanks a lot for your input. Normally in the 2 years I registered on this forum, 70% of the time I get No reply, 28% of the time 1 reply but this time I really get what I was looking for.:)
Most probably it is because (given my Swiss origin), my english is poor and my sentences can be easily misinterpreted. Also I have never been gifted for writting. Maybe some may also choose not to reply because they are scared that all the info which goes to Asia will be used to make cheap competition to the US market. :confused:

I graduated in electronic engineering and work for a multinational company here. That allows me for a nice living.

My hobby is to build PPG's (powered paragliders) and tune 4 stroke kart engines. Mechanical knowledge/experience is the weakest point in all these activities but that is what makes it so interesting as I am learning a lot out of my projects.

Another CNC project I work on at the same time is a wooden Propeller CNC router. (Right now I hire a person who makes them by hand on a self build duplicating router). The income out of it allows his familly to leave and helps me to partly finance my hobby (my wife at least believes me that it is so...)

After 2 years of dreaming, finally I went ahead and build my first 4 axis mill

All axis are servo controlled and use 1000 CPR encoders. The 4th. axis can be fit with a 2500 CPR encoder which I got already.

The mill is running on linear guides and ball screws.

I think to make the concepts work, the setup should be OK.

pls. see some pics. below.

Later on, I may migrade to a more sturdy "Bridgeport Clone" from Taiwan for the tough mechanical work and build a router of adequate axis length for the prop making and used this one for Aluminum engine parts.


I have already had good experience with the Dynamometer interface, Port flow analyzer and valve spring analyzer kits from Performance trends.

I had a close look at their cam analyzer and tried to equip myself step by step with the same components so that if I get stuck at a point or another, I can buy their data aquisition module and software, connect my 2 encoders into it and finish the job but I want to try it on my own first. (the 2500 CPR encoder comes from their system specs.)

NC cam, you mentioned Performance trends in the first reply but not anymore in the last one. They do also advertise their solution as a retrofit for the Cam Dr. hardware. What is your opinion about their solution for my purpose ?

Again, I am not into Nascar. You saw my Honda GX200 engine Cam in the first posting.

If I do not manage to read the data out and convert it into a G code by my own, I may ressort to get the Performance trends kit and hook my encoders onto it. I will have the advantage of having a very accurate homing position and also can read the data at constant speed which the hardware proposed by performance trends cannot do.

From your opinions, at least a very accurate rough grinding could be done by using my rotary axis with 10,000 (servo steps) per rotation and a good diamond grinding wheel mounted onto my Z or even Y axis (may be more rigid in my present case).
The machine will have all it's time to do the grinding at very slow speeds if required. Given that I will use the same resolution for grinding than for measuring, e.g. 10000 points for the 360 degree rotation of the small lobe, do you think that will still leave noticeable marks on the lobe ?

From there on, I could then figure out a rocking table grinder for the smooth finishing only and of course in that case I'll have also the need to make lobe templates somehow....


NC Cam,

Another proposal. When was your last time that you did have nice holidays in Thailand ? you mentioned that you where looking into retirement and hand over your shop in another thread. I am sure once you will do this, you will have the need for some other activities. Why not combining the holiday offerings of Thailand and a bit of hobbying on your favourite subjects here with me ?

Paraprop
08-19-2007, 12:17 AM
Below I wanted to share a few pics of my earlier cam measuring and grinding setups...

And sorry for that in my last mail, I forgot the pics of my CNC prototype mill

NC Cams
08-19-2007, 10:44 AM
RE: cnc cam grinding = the reason why CNC cam grinding is so hard to do on a DIY basis involves some of the vagaries of the cam profile and the not so readily apparent geometry and math issues involved in reading them.

Essentially, the cam profile is a locus of points that have infititely changing radii that go thru each/any 3 or 5 or whatever curve fit you choose to use. There in lies the problem.

Whereas anyone who knows trig and calc and geometry can take any 3 points and find a/the fixed radius that will go thru them, the constant changing radius of curvature screws up the look ahead feature that the CNC mill code writers use. Why? becasuse the next point you come to changes the instant center of the radius from the previous point and the CNC can't handle that. The CNC wasn't programmed to look for or how to handle that situation so it pukes when it comes to it - which happens as soon as you come off the base circle.

We tried it with Fanuc, Haas, Bridgeport and other generic G code interpreters and they all crapped out when you got off the base circle and started up the ramp and into the main event. No matter what, the computer had problems.

Landis, with their 3L figured out proprietary methods for doing it. The software requires a special computer to run their CNC 3L grinder and its code. Moreover, they figured out how to take 1 deg data and make it smooth and step free when grinding either a master or the cam itself. To get the free software, you spend about $2million for the grinder.

The file they use is text readable and it is purely 1 deg lift data and some other stuff needed to cut/grind the lobe. SO we figured, no problem, we'll do the same thing with their data. WRONG. We did cut a shape but it was so full of errors (motion discontinuites), flats and herky jerky motion that the follower system sounded like a machine guy while it was running. The profile was suitable, quite suitable for a rough milled lobe shape but TOTALLY unsuited to that of/for a finished cam.

Steppers do essentially the same thing. Getting servos to work is also problematic for the same reason - the smoothing function and/or look ahead seems to NOT want a discontinuous, constantly changine radius of curvature. Moreoeve,r the surface velocity is always changing in an automotive cam profile which also causes fits to/with many servo driving algorythms. In a sense, this is why master type cam grinders are so viable. The masters are makeable, readable, and correctable - if you can handle the complex math and trig involved.

We finally figured out a way to do it. Actually, we stumbed across a guy who was a motor head and did motion simulation work for government projects. He figured out how to do it but it took some proprietary software that we had written by some of the now deceased authors who wrote some of the articles previously mentioned - software that, outside of the industry, simply does NOT exist nor has it even been written about. Although the guy did/could get the 1 deg data to cut a master, it too had steps and herky jerky motion. It took the proprietary software that the cam gurus wrote nearly 20 years ago to make it viable.

Like I may have said, the guys who wrote the software we used are some of the same guys who wrote THE seminal articles that EVERYONE who's made aftermarket measuring equipment has used as a/the primer to craft up their software. These guys were brilliant when it cam to camshafts and software. To some extent, ALL of the aftermarket hot rod cam guys who used computer programs owe their livelihoods and fortunes and reputations to the tools that these guys left behind in their publications.

RE: Performance Trends + I can't speak badly about their software as I've never used it. I did have a conversation with them once and asked them if they could add some features that we, cam makers need/use when it comes to reading/inspecting cams.

In short, they fetl their customer base did not need the features, hence they declined to help. For this reason alone, we looked elsewhere for software and have not looked back at their products.

In light of the fact that Andrews Products makes cams (perhaps worlds largest supplier of aftermarket and OEM H-D cams), the outfit knows what's involved in MANUFACTURING a cam to the tightest of specs. His measuring software is really, really good - this is the software we use as does a number of other manufacturers of cams .

Not only does it read the ENTIRE profile (especially the ramps) but it can identify bend and runout and where it is. This feature is lacking in some of the racer grade software that others offer. I highly recommend the Ezcam to anyone looking for a very good PROFESSIONAL measuring system...

Re: 2D mill clone for cam and or master milling: that type of mill is NOT accurate enough to cut a precision master. The software might be adaptable but the typical mill has too much hysterisis.

Do an "Extrak" search on the Zone. I outline chapter and verse what we went to/thru to get our Bridgeport to cut a reasonably close master. And even so, it does NOT do an adequate job in several areas.

RE: retirement in Thailand = I"ve already had my share of travel and with the world situation the way it is, I"m literally fearful to travel outside the country - I think too many folks are pissed off at ANY American, regardless of any intent the traveler may have.

Moreover, I have some health issues that may eventually require long term care which is something I take in to consderation when I go/move someplace - you just can't walk into ANY hospital for the treatment that I may/will need. Besides, I'm not wealthy by any stretch and, since I'm self employed in a high tax region of the country, I don't have a lot of expendable income, not anymore. Although my guys do a good job in helping, and espeicaly grinding, they are not equipped to run the business in my absence nor do the engineering required.

NC Cams
08-20-2007, 10:03 AM
Re: fotos of your early generation cam grinder = You essentially have made a "rocking table" cam grinder. But, instead of the grinding spindle staying stationary and the cam rocking, you're rocking the grinder spindle and keep the cam spindle table stationary.

This may or may not be adequate. We keep the grinding wheel stationary as it is BIG (18" in our case) and rocking that much mass at speed is NOT easy to do. In our case, we mount the cam spindle on a table and the cam spindle table rocks into and away from the wheel.

The use of a double gear system to transfer motion from the master to the victim cam (or vice versa) leaves a lot to be desired. Gears must have backlash. In your case, you have two sources of backlash which can manifest itself into error/profile deviation at the to-be ground cam profile. THe wheel does/will push the cam away as you load it to grind. It will push away the amount allowed by any backlash and the instantaneous timing and lift will deviate from intent - either a lot or a little.

The Kieffer (Home Shop Machinist) style of mounting the master and the cam coaxially is essentially IDENTICAL to what our Berco does (and a lot of the other pro cam grinders for that matter). This way, there is a 1:1, slop free connection between the master and the cam to be ground. In your case, even as little as 0.002" backlash at a gear will manifest itself as profile deviation in the profile. Depending on where it occurs and how bad it is will determine if you will have problems and how bad/much. Two gears doubles any error potential.

Before the "its not that critical comment" even gets made or even thought, I seem to recall that this application is for an ultralight aircraft application. For the simple reason that someone's LIFE may depend on whether the engine runs and lives or not, this application is even MORE critical of having the cam ground PROPERLY and ACCURATELY than any race crap that we migh ever do.

Paraprop
08-20-2007, 11:26 AM
No need to worry about the application.

A PPG (Powered paraglider) is first of all a glider which does not need any engine if it gets lift from thermals or one jumps from a mountain, However when you do it from a plain, you appreciate an auxilliary propeller engine which helps you to go upwards. Once up you can stop the engine and glide till you reach back to the soil or you can restart when you are getting low. Mostly they use 2 stroke engines as they are much lighter for the same power but also very unreliable. I am working hard to get my 4 stroke powerfull and light enough to be an alternative.

for the gear system, I will recheck if there can be some backlash in it when the grinding wheel pushes. Actually the 2 cams are connected one to the other at their shafts after having used the gears for indexing.

Given your expertise in the matter, would you mind to comment on the result of a typical grind on the enclosed curves ?
green and dark blue are the master intake and exhaust lobes respectively.

Till now we never managed to exactly the same lobes but mostly the difference is just after lift of in the elbow of the curve.

Any suggestions appreciated.

CarbideBob
08-21-2007, 05:45 AM
Oh, you haven't lived till you've tried to build a CNC profile grinder.
Couple of things to think about. The contact point of the wheel on the profile is not always on the wheel centerline. It moves up and down on the wheel so you have to comp for the wheel dia. and calculate where the contact point will be. The in and out motion of the wheel will not be the same as the profile measured with a point gauge. A mechanical (rocker & follower) design comps for this automatically but on a cnc you've got to do the math while your profiling.
Because of this and to generate a smooth profile you need very fast responding servos, very low friction axis, a very fast cnc controller, and super high resolutions.
You'll want 250,000 counts/rev or better on the rotary axis to get a smooth profile. Since no one makes an encoder that is actually accurate at this resolution level you also need to map out the encoder errors and comp for it on the fly.
This is why these machines are sooo much more expensive than a conventional cnc.
Bob

NC Cams
08-21-2007, 08:51 AM
Looking at the LIFT curve doesn't tell you anything about the quality and/or dynamics of a cam profile.

Looking at the VELOCITY curve (first derivative of lift) tells you IF you have an error in the profile.

Looking at the ACCELERATION curve (second derivative of lift, first of velocity) tells you how bad it is.

Looking at the JERK curve (third derivative of lift....) tells/shows you haw badly/rapidly you'' be applying the acceleration forces to the V/T - this has an affect on how fast the system will detiorate under any "jack hammer" loads that can occur.

It is the acceleration forces generated by the cam that excites and applies force to the valvetrain and these are what you need to concern yourself with.

Your curves are very classic curves, however there is clearly some visible ripple (aka error) that exists in various places. This ripple, depending on how bad it is at the 3rd derivative, will have more of an effect on your valvetrain than you can imagine.

This simple ripple could be the result of as much as 0.001" backlash in a gear drive cam spindle or it could be wheel balance or prior profile error or machine slop or on and on and on.

YOU WANT 1:1 motion ratio with NO BACKLASH POTENTIAL ANYWHERE when you grind a cam. You can either do all kinds of things to correct for the vibration after its ground into place or, better still, DON"T LET IT GET THERE IN THE FIRST PLACE.

BTW: we've seen and ground cams that have NO visible chatter/fluctuations in the cam profile and these were found to create havoc in the system during operation. I simply would not accept nor ship a profile that had clearly visible deviations in the lift curve as bad as you have - surely, the ripple/deviations in the 2nd and 3rd derivatives would be far, FAR worse. Your lift curve can't/won't tell you anything about the dynamics potential of the cam profiles you're working with.

When you strive for cam grinding perfection, you'd be amazed at how easy it is to grind really GOOD cams. The hard part REALLY is getting rid of the slop/deviation creations in your grinder. Once you do that, things almost take care of themself.

How do you do that? First get a GOOD, precise sensitive cam measuring machine. Letting Excel or some other software do curve fits to choppy input data is like putting bondo on a rusted out fender - it looks good but the underlying metal is not sound and of essentially poor quality. The whole job will eventually suffer when this "band aid" peels off which it eventually will.

Once you see/find that you have errors, you then systematically go about identifying the root cause(s) and fixing them. Along the way, you'll learn even more about grinding cams than is taught in ANY textbook I've ever stufied on the subject.

I thought I knew a LOT about cams - I did until I started running my cam grinder. Then I learned that the high school educated grinder operator who showed me how to run the machine was clearly far smarter than I - especially in the non-published vagaries of cam grinding. I learned that the classic admontion about instructors was true = namely, those who KNOW, do it, those who think they know teach and/or write about it....

You're to be commended for doing what you've done - real creative stuff. You simple need some advancement and/or "clean up" and some tune ups to your proces. It is a way to an end, it only lacks sophistication and the necessary preciseness and perhaps a bit of dynamic clarification.

Paraprop
08-21-2007, 09:29 AM
NC Cams,

Thanks a lot for the instructive information you provide to me.
below I have enclosed 3 different camshafts, 2 curves each

first and second are
Original from Honda Velocity & Acceleration
Original from Honda Velocity & Jerk

third and fourth are
Master tuning cam Velocity & Acceleration
Master tuning cam Velocity & Jerk

fifth and sixth are
copy of tuning cam Velocity & Acceleration
copy of tuning cam Velocity & Jerk

Pls. note that Master and copy tuning cam are the same as on previous pdf. doc.


Are the curves clear enough so that you can make some comments or should I show the information in a way which is more convenient ?
If yes, pls. advise how you would like to see them.

Thanks in advance

Paraprop

NC Cams
08-21-2007, 04:53 PM
All the profiles have randomly located issues in them. The velocity curves are visibly rough and choppy and the jerk curves are more than choppy enough to make you seasick. We'd simply NOT ship/do something this rough.

The issues could be grinding related or they could be the result of deficiencies in the measuring proces. I'd be remisss to criticise either or since I've not measured the cams on my equipment - hence, I can't speak for the veracity of the mesturements or the dynamic predictions that would evolve from your mesaurements and/or equipment. If they are, in fact properly done and correct, I've seen and made much better.

I can say the we'd simply not grind or ship cams with the velocity deviations that are evident in the ramp and other areas of the master and copied cams. Our stuff tends to be MUCH smoother and continuous.

These issues could be the result of backlash in a gear driven system or runout or tooling deficiencies or any number of other little or substantial things - I can't tell from here but there are clearly "issues" that we'd not accept or tolerate.

We've ground cams using a supplied part as a master. Do we simply trace it as I suspect was done here? NO. We read the cam and then do selective fixing and/or smoothing. Is this effective? Our first "daytona" cams were just such copies. The client reported that our "copycat" cams made more power than the originals.

When you copy something, it is very hard to NOT copy and or to expound upon deficiencies that may previously exist in the part. If you first remove these deficiences,you can turn an adequate part into agood one. Sometimes, it is actually better to design something from scratch as there may be too many issues involved or it is simply too hard to fix what's wrong.

I don't know enough about your power requirements ("I want more" is not enough info) or the specifics of your valvetrain and/or engine. You may be looking for something from an engine in an RPM range that it was NOT specifically designed to operate.

Example. A 12000 +/-500 rpm peaky bike engine may NOT have the best power curve when you really want/need a broad, flat torquier curve that offers more grunt over the 6000 to 10000 rpm band.

Looking at a simple lift curve won't tell you how to address those needs. You may be in need of a totally different tuning strategy (shorter cams, wider or narrower lobe centers, whatever). At that point, a "custom" as opposed to a copied race bike cam may much better suit your needs.

We offer custom cam design, manufacturing and design services. We'd be happy to quote these services as needed to tailor your engine's power curve more appropriatedly to your needs.

These services could include inspecting sample cams and making specific recommendations based upon a TOTAL review of your valvetrain (springs, weights, etc) and desired operating needs. Feel free to contact me via PM for a quote for our services.

FPV_GTp
08-21-2007, 06:42 PM
I am presently upgrading my mill to 4 axis.

On the spindle head (Z axis), I am going to add a diamond wheel grinder.

Right now I am not too sure how to scan an existing cam profile (from an engine intake/exhaust camshaft) into the system.

I am using a 2500 CPR encoder on the A Axis. so I would like to take a measurement for up to each of the 10000 steps in a 360 degrees rotation by a linear encoder head putting out a signal onto the encoder input of the DeskCNC controller card (same as used as feedback for the lathe spindle application). The output of this linear encoder (I still have to purchase it) has a resolution in the 0.001mm range. Then I would like to graph the resulting cam profile, eventually modify it and then produce a G code file to grind another camshaft lobe based on it. The grind is done just by rotating tha A axis and moving the grinding wheel on the Z axis. No need to move the X axis for it.

Is it actually possible to do so ? I could not find any hint on the docs. Available on the web. If yes, is there somewhere a similar application I could use for reference ?
Until now I can only find samples of scans done with the touch probe connected to the Lim input but I am afraid this method is not as accurate as if I go for the linear encoder even though I already got 2 sets of the IMservice touch probe. Also in the literature nothing hints about using the touch probe for parts rotating on the A axis.

41427

Thanks in advance for nay hint.

Paraprop

Daniel

Hi

speak to this guy at http://www.sportdevices.com/
they had some cam-profiling device that enable scan camshafts , i couldn't find a direct link to the page .

cheers

Paraprop
08-23-2007, 09:36 AM
Given that the first cam of the 3 is a Honda production cam, I should be reassured that part of the results shown should come from the lack of accuracy of my measurement method right ?

NC Cams
08-23-2007, 10:56 AM
Perhaps.

IT could be technique, lack of proper preparation or even a bogus part although the Japanese stuff I've measured is darn near jewelry in quality.

It is not easy to read cams. You don't just throw them in the machine, spin it around and wah'lah, get the data.

It took us WEEKS of experimentation with known good/pre-read cams to find the proper way to read a cam. We also spent a lot of time eliminatng deficiencies in our equipment and yes, even the software.

Unless you have a known good baseline cam to use as a yardstick/reference, you can't really know if you can or should trust your measurements

M-man
09-01-2007, 04:03 PM
WHat are the tolerance of the profileshape on a normal cam?

NC Cams
09-01-2007, 08:47 PM
There is no such thing as generic tolerances for the profile shape of a "normal" cam.

They vary from profile to profie, engine to engine and manufacturer to manufacturer. Some engines are more sensitive to others with regard to lift deviations and others are more sensitive to abnormal changes in the velocity, acceleration and/or jerk rates.

You could have a BIG lift difference but a small acceleration and/or jerk deviation and the engine won't know the difference. Yet, with the opposite condition, you'll tear stuff up.

We supply the velocity plots to our payiing clients ONLY and ONLY when the client specifically requires it in a certified cam data chart - it is included in the quoted price of a/the cam cam analysis service and this is not necessarilly inexpensive.

Analysis price goes up if/when the cam has "issues" and we have to figure out if it is a reading problem or a manufacturing problem or simply a bad design - after all, you're paying for "right data" and a bad analysis does no one any good.

We do not offer such technical info outside that which we supply when we analyze a clients cam on a contract basis. Very few if ANY of the commercial cam grinders even supply velocity or acceleration data as standard or even optional fare to their clients - no matter what you pay for the cam.

We don't supply it to our NASCAR clients unless they are a VERY good customer and need it for problem solving purposes. in short, you ain't gonna get free cam tolerance specs on a M/B. No cam maker in their right mind gives this data out.

Why do you think that Audie, Andrews and/or Cam Doctors were created???

Answer: because cam makers have ALWAYS been notoriously close mouthed about ANTHING that has to do with the shape, dynamics and/or tolerances of their profiles. Period. Paragraph.

vmax549
09-22-2007, 08:39 AM
Paraprop I have been doing what you want to do for years. It is within the realm of your Deskcnc system with the 4th axis and TP100 probe. Basically you will center the cam under the spindle and then locate a starting point on the cam . Next locate the depth of the base circle and set to Zero. Then rotate the Aaxis .025deg at a time while probing down with the spindle at each .025deg rotation. This will give you a point cloud of the cam lobe tied to a reference point on the camshaft. Next load up the points cloud in the Cad program to do the smoothing between points, THere will be a ton a points to deal with.

The grinder can be a simple wheel mounted stationary next to an x/y table that uses your Aaxis to rotate the cam for grinding while the y axis provides the interpolation to grind the profile.

Now everything HAS to be aligned with procession as far as the center of the probe to the centerline of the cam for probing and the center of the wheel to the center line of the cam for grinding. Being you are doing it straight line without a rocking arm it is fairly simple with no translation needed for the arm movement.

I would suggest you build a seperate grinder. DOn't use your mill to set up for grinding. The micro dust will eat your mill alive in no time.(;-)

Is it NASCAR perfect NOPE, will it do what you need? Absolutely Been doing it for years in small engines turning into the 10k range without problems.

We KNOW kart racing engines(;-)

(;-) TP

Paraprop
09-22-2007, 09:11 AM
Vmax549,

Thanks a lot for these motivating news.

How do you fool the DeskCNC software to digitize out on the A axis ?

Are you using 3D mode ? (2D does not seem to work)

Do you switch the A to be the X axis and define Ymin and Ymax to be 0 ?

Then set Z "min" to be the base circle and Z max a bit more then the Max lift ?

Good comment about dust. Indeed it is not a problem to mount the grinder onto a dedicated ball screw setup.

Indeed my kart engines do not go much over 8000 RPM


Paraprop

NC Cams
09-22-2007, 11:37 AM
The method proposed by VMAX549 will ONLY work if you are cutting a flat tappet cam with the bottom of a bottom cutting cutter. Reason: this is pretty much how a flat follower "sees" the profile.

However, if you have a roller cam or a finger follower cam, you won't even come close to duplicatiing the lift profile that you're intending to achieve. To cut the lobe you have to compensate for the fact that there is a geometry difference/offset that has to be accounted for between the cam and the radius'd follower. This is why a roller cam and a flat tappet cam of comparable durations are SO, SO much different in shape.

FWIW: we tried the 0.25 deg method and, yes it will cut/shape a cam. Yes, the engines will run BUT said cams tend to generate/impose a LOT of superfluous vibration into the valvetrain - so much that you can actually HEAR a difference in the how the system sounds while running.

The sound that the 0.25 deg "flats" (that's what you're effectively cutting) make resemble a "machine gun" to some extent. Imagine what that superfluous shaking does to a valve spring at high RPM.

NASCAR performance? To the go cart racer, their local race track win is as satisfying as any NASCAR win and, due to the $$$ consequences, a bit MORE highly valued.

This is why one of the top go cart cam grinders uses the exact same method to grind the go-cart cams he makes as he does for the high dollare V-8 cams he grinds for pro racers.

VMAX549's admonition to craft up a grinder is well said advice. The HSM pictured device should be scaleable to do what you want to do with relative ease.

Noticeable difference? If you do not consider an end of race drop off in race performance due to killed springs inconsequential, then there is no difference between a ground cam and a 1/4 deg cut cam. However, in our work with 5hp Briggs race engines, this sort of diminishment of performance and/or its affect of part durability was deemed unacceptable.

BTW if anyone saw the inspection traces of a 1/4 deg cut cam as opposed to the exact same profile generated with a ground cam, even a neophyte could readily see the difference between the two. It is very easy to choose/pick the smoother ground shape from the cut shape. When given the A vs B "blind taste test"' choice, absolutely NONE of our clients EVER chose the cut cam over the ground one when we offered them the choice 'tween the two.

The key phrase in VMAX549's post are, ".... do the smoothing between points, THere will be a ton a points to deal with...." It is easy to get/generate 1 deg lift data and have Excel graph out a smooth lift curve that SHOULD occure. It is HARD to turn that into a SMOOTHLY transitioning lift profile on a hard metal cam that does not drive the valvetrain into spasoidal fits of herky jerky motion.

ANY cam grinder learns that lesson after a while as pretty much all of them made model cams and/or masters using the interval flat cutting method over the years - most have simply gone away from it for reasons of quality, durability and speed. It has become easier and FASTER to CNC grind them when you have access to the "right" equipment.

BTW, We do it (make cams) day in and out for small, medium and large single and multi-cylinder engines that work in stock, race and prototype applications.

vmax549
09-22-2007, 12:00 PM
Paraprop, I am using MACH3 cam software. It has a direct probing cycle G31.
Deskcnc uses the bed of nails approach I believe. Ask DeskCNC for advice there. Or you can do it another way, that is to switch the Y axis to the Aaxis and reset the steps to get A rotation when the Y movement is called for. Then you need to calculate the circumference of the Max lobe radius from the centerline to be able to set the A axis envelope so it represents the circumference of the lobe. Not quiet as easy but can be done.

Another thing to consider is to probe a point between the two teeth on the cam gear that has the timing dot. Probe it using the Aaxis for rotation, set the center between the teeth to zero that will give you the reference point needed so the two lobes will be timed to the gear correctly. When you grind it, do the same thing again to set the zero point of rotation.

The smoothing of the points in the point clouds is neccesary to ensure there is not the railroad tie effect in the profile(;-) once smoothed the CAM Doctor(WITHIN reason) nor the engine could tell the difference .

Just For what it is worth (;-) TP

Paraprop
09-22-2007, 11:35 PM
NC Cam,

Thanks. Indeed I will only grind simple flat tappet cams. I cannot cut it with a flat cutter because I have to weld up the original cam lobes with a Rc 62 TIG welding rod else the cam lobe would not last. (my apologies if I used the wrong unit as it is a year ago that I sourced these welding rods).
I guess that using a properly aligned grinding wheel with a movement perpendicular to the cam axis should yeld the same result than a flat mill cutter.

Given that I can go yp to 10000 points per 360 degrees, I can theoretically achieve 0.036 deg. large " facets" around the lobe. That is about a 7 times finer finishing.


I do well understand your point about the quality of the end result and won't argue there. You had well highlighted the issues in the threads covering cam grinding. Nevertheless, those parts being manufactured in Thailand, they do cost very little in comparison to the U.S.

On the other hand getting a specialist in the U.S. to make me a special grind will set me back about 80 to 130 $ + shipping + 20% import duty + 7 % VAT + duty clearance agent fee. At the end, it is more than an entire new engine costs here. Quantities needed are limited too.

Paraprop

NC Cams
09-23-2007, 10:55 AM
Several coments:

Simply welding HARD metal onto a lobe is not necessarily adequate for cam profiles. Reason: you have to crank the engine under marginal lube and high loads to start them. The metals have to have high scuff resistance during this guaranteed period of marginal lube. The ONLY weld material that we've ever seen work on welded cam lobes is Wahl Colmonoy #5 or the next harder alloy - I think it is #56.

Single pass welds won't hack it due to weld diliution of parent metal. You need dual pass welds at a minimum. Proper post weld stress relieve is MANDATORY. Yes, the welded cams do work - but for how long. We've found that it is not an isssue of if the weld will spall but, rather, when. Low stress applications may be more tolerant - all our stuff is high stress. Sooner or later, ALL the welded stuff we've worked with starts to come apart or, worse yet, the cams break due to the welding affects on the parent metal.

For this reason, alternative methods involving steel billet cams were developed for restorative or custom prototype applications that offer better performance, all things considered.

WHether it be steel billet or welded OEM cams, ultimately, a proper post machining/welding heat treatment is absolutely essential/critical.

Yes, you can THEORETICALLY get 10000 points MATHEMATICALLY. However, your ACTUAL machine resolution probably will not/can not be that fine. You'll be lucky to hold 0.000010" and more likely 0.0001" at best.

Again, we've been thru this already with high buck servos and steppers as well. High resolution servo's will work if you run them slowly to keep follower error low.

We've YET to see steppers NOT yield step free finishes on cam profiles. Interestingly, we've also seen them leave 'steps' on OD ground journals. Steps that are visible to cam inspection measurements as well as the naked eye.

Comments re: so called "custom grinds": We are one of the very few cam grinders/designers who does NOT offer "cookie cutter grinds". All our grinds are SPECIFICALLY designed for the specific client using THEIR parts, their operating conditions and their valve train geometries. However, just like tailor made clothing, tailor made cam profiles are not inexpensive.

So called "special grinds" offered by name grinders are essentialy "off the shelf" generic grinds that are, at times 20 years old or even more. Depending on the legacy of the design and the design philosophy used at the time, they can be OK or perhaps superb or, sadly, parts breakers.

Frankly, we've had chances to inspect/measure some of these gems and found some to be quite lacking in sophistication and/or development. Some aren't much better than stock profiles. Some are works to be proud of. There is no way to figure out which is which by looking at catalog specs.

For your application, I'd be a bit weary of anybody's $130 "custom ground cam", especially a reground or welded one.

camshaft
05-01-2009, 10:05 AM
We have been regrinding cams with Berco rocking table cam grinders since 1970. We began with automotive cams and moved into industrial camshafts. As cores became difficult to find we started manufacturing, and are now the leading manufacturer of new replacement cams, cam lobes, cam sections, and cam muffs for the industrial engine market. We started out using Cam Doctor but we've used an Adcole exclusively for about 13 years. We bought a new Landis 3L several years ago, and we have traded up since then. We now have two CNC cam grinders. Occasionally we have to manufacture a cam that is too big for our CNC grinder (for instance a cam for the Cooper GMV compressor - about 18" dia). We have been able to achieve good results using a CNC vertical mill.

Clay at Kams, Inc. - cam and cam follower manufacturing and regrinding for industrial engines. (http://www.kamsinc.com/camshaft-remanufacturing-regrinding)

Paraprop
05-01-2009, 10:58 AM
I still haven't come any further with my project except that in the meantime I bought a cam measuring setup from Performance trends.
It is a great time saver for cam evaluation and also for comparison after I do finish my cams on the old self made duplicator.
As soon as I have a moment, I will look deeper into the softwares data files and see if I can use the data to make the G code for the CNC cam grinding.

mrehmus
08-15-2015, 01:16 AM
Try this one: G-CAM Web application to build CNC GCode to grind cams: https://sites.google.com/site/tsmeweb/resources