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.  |