Sunday, March 24, 2013

Automation and a Dodgy Left Shoulder

When I was a younger man I did not own industrial quality machines and I was prone to wearing out parts on the machines I used in my work. These days I'm older, yet I have industrial quality machines and now I'm wearing out parts on myself.

When I first began this blog I posted about the acquisition of a 1959 Covel #10 surface grinder. The old grinder has been a great machine. The cost associated with purchasing, moving the machine, and upgrading this machine are to a point where I really have more invested in the machine than it's relative market value. However as a result of this investment I know what I have,  a machine that grinds accurately and flat over the length of it's capacity which is always a question mark with any used surface grinder.

However the Covel came as a manual grinder which means all the moving parts have to be activated and run with physical action on the part of a human operator and the worst of these activities is traversing the table left to right constantly. This requires many repetitions just to grind the surfaces of one part. This finally took a toll on my left shoulder. One Friday morning  several weeks ago I began experiencing a stabbing pain under my left shoulder blade. I figured a bit of rest and some over the counter pain medications would fix such luck. In fact things got worse and it became evident that I would not be doing any grinding for while. I needed to give my shoulder time to heal.

Being persistent I starting teaching myself how to grind with my right arm only. I could do this but it was a slow process, futile really. I decided that while my shoulder was recuperating that maybe it was time to shop for an automatic surface grinder. A quick bit of research revealed that an automatic surface grinder with any chance of reliability was going to cost something close to automobile purchase type money.

Given the time commitment required to move one machine out and another machine in, and considering the investment I had in the Covel grinder I decided it might be worth an attempt at automating the Covel.

I read on many of the online metal working forums a lot of speculation about how one would go about automating the long axis of a surface grinder, however there was no documentation from anyone that had actually pursued and accomplish this to any degree of reasonable use so I contacted an automation company and proposed my plan for accomplishing this task and ask them if they thought it was a feasible idea.

They agreed that it was feasible, recommended a few changes to my plan and also informed me of other information I needed to gather in order to make reasonably informed decisions as to what components would need to specified and purchased. It seemed my gamble was going to cost somewhere around $1000.00 and there was no guarantee of success. Considering the price of an automatic grinder or worse yet, a new shoulder, I decided I would take the gamble and began the research required to fill in the blanks of how to undertake this transformation. The picture below shows all the major components required.

A 1/2hp  3 phase inverter rated induction motor, a 40 to 1 gear box (speed reducer), GS2 Variable Frequency Drive, not shown are the miscellaneous wiring devices, various pulleys and belt required.

The motor control configuration was sorted out after a study of the VFD manual....actually an extensive study. I have two other 3 phase motors in my shop powered by VFDs, however I would be asking this one to perform more complex motor control than anything required on the other machines. The picture below shows all the components mounted to the machine and also a belt/pulley guard fabricated for safety sake.

Basically everything operated as expected even though some parts of the system did in fact require considerable tweaking along with some tweaks to the vfd programming. Check out the video below of the newly automated grinder actually working.

Much to the relief of my left shoulder the automation of the surface grinder tables works great and operates very reliably. My gamble paid off. Now to get busy and make up for lost time.



  1. Very cool, Ron. Necessity (and pain) are the mothers of invention! Hope the shoulder has fully healed.

    Are you only advancing the progress of grind with the wheel and the rest is automatic now? I assume this is the index across the blade.


  2. You're correct Neil, I only have to advance the saddle across the width with the hand wheel in the middle. At some point in the future I may also automate that process but that becomes a bit more complicated as it has to be timed with the longitudinal movement and the amount of increment is different whether you are rough grinding or doing the final passes for the final finish.