Surface grinder concept/project

[BillTodd]

 Quiet in here   

I purloined and few bits from a scrap wire-eroder that have inspired a couple of project ideas - (it was working and only scrapped because it needed to be moved and the only way to get it out of the workshop was in bits)

From the U/V wire-angle mechanism I have an incredible two-axis slide unit - cross roller guides, 1mm pitch ball screws  , preloading gears  has to have been designed for micron precision or better . But more on this later...

From the head unit I have a couple of Rexroth double row ball linear guides . These are far too good to use on the plasma cutter I had planned , hence this surface grinder idea.

A while ago , on YouTube, Stefan Gateswinter' showed off his new Bema surface grinder (https://www.bemagmbh.de/en/range-of-services/lever-operated-flat-grinding-machine/)  I liked the compact size and novel layout.  I also had a pair of US made servo linear axes modules very much like the ones used on the Bema , I just needed something for the table to slide on.

The design is a bolted aluminium construction  , using 25mm plate for the base and 10-15mm plates to stiffen where required . The table will have a travel of about 11inches (280mm) with the head traversing 14" (350mm) or so.  It should have about 12" (300mm) above the table .

I'm not sure about spindle ATM. I have an old Black&Decker grinder spindle (yes I know B&D but it is from the days when they made a better class of tool)

I'll probably use a chain driven table (Like Bema) but may motorise the Vertical and traverse since it will be easier than adding handles .

If I can find a suitable head unit, the Z will have a 0.1um Mitutoyo scale also courtesy of the wirer :-)


Coming soon ... microscope and/or Nano-mill 

[shipto]

I have been thinking recently about putting linear rails on my converted surface grinder. although I would put the rails upside down rather than the way. This way I figure there would be less chance for the grinding dust to sit on the rails and damage the bearings.
I know you could cover them but I still feel there is the risk. I do like that design though.

[BillTodd]

I'm sure it would work fine.   The table is supporting the whole length of the rail  so it operates like a mill where the bearing is directly under the cutting force

I've gone for the stationary rail which keeps the table lighter and easier to traverse manually.

The dust cover is a problem, I can only find flat bellows ( rather than the inverted U shape I would prefer), so I am thinking about light air pressure to reduce dust ingress , perhaps using a hoover motor as a pump.

[BillTodd]

Update on the spindle assembly.

Like the Bema model, the entire head can revolve . so to see what it would look like, I added a cup wheel the the rear of the spindle , it could be used in a horizontal vertical fashion a little like a Blanchard .

[ltlvt]

I would love to get my hands on a Vintage Mini Surface grinder. But in my area if it gets machined it must be for an Oil Well. Nothing small around Oil Wells.

[BillTodd]

It's just the as difficult to find a small grinder over here,  the few that are around are old a often knackered.  Indeed, it was the lack of small grinders in Germany that led Stefan Goteswitner to buy his "crazy expensive" Bema , and inspired this project.

The market for small grinders must be too small for manufacturers to make s profit, although, t am surprised the Chinese haven't had a go :⁠-⁠)

[Joules]

Over the years I  have looked at Warco's little surface grinder and many years ago ordered one they had on offer, but the offer was recinded a few days after my order placed !!!   The price of them now is such that they are beyond my budget.  I did try to get bogstandards Warco grinder but I was one down on the buyer list.   I now limit my surface grinding to what I can fit on a D bit grinder, far from ideal but better than nothing.

[jackary]

This is my small surface grinder. I made it from the bottom half of a Dore Westbury Milling machine and fitted a modified large Lathe toolpost grinder for the grinding wheel.  The table runs on small ball races spaced and adjusted to just touch the underside of the table. After much adjusting/experiment it now works very well.
Alan

[BillTodd]

Nice Alan,

What size motor is that?  The blue one modelled abive is 200w but I have a not too much bigger with more power (500+watts ?)

[jackary]

Hi Bill,
I think its a half HP 3phase motor. I had a lot of trouble with  the original 1 HP USA motor that came with the grinding head. It created terrible vibrations on the ground surface. I bought a new uk Half HP motor on Ebay but that was not very much better. I then swapped it with my Clarkson grinder motor and that solved the problem. I suppose this motor was specially balanced for grinding but I can not see any special reference to it. I will look at it tomorrow and give you better details.
Alan

[jackary]

Hi Bill ,
Here is a photo of the motor on my grinder
Alan

[BillTodd]

Cheers Alan,

I'll model the larger motor, 200w doesn't seem enough, although I suspect the limit will be the available VFD , which might be also 0.5hp like yours.

[JHovel]

I have a small CC tool and cutter grinder that I uses as a surface grinder.

[BillTodd]

Hi Joe,

Nice little grinder. What make is it?

[JHovel]

CC Engineering Industries Limited, Sydney Australia
I was given it in a very dilapidated and worn state and restored it including re-scraping every single sliding and flat surface on it. Lovely little tool in use now. Here is a link to one on the original cast iron base recently sold at auction: https://www.grays.com/lot/0006-5048538/mechanical-workshops/cc-engineering-industries-surface-grinding-machine
They made several T&C grinders, arbor presses and assembled other tools like chainsaws that were highly import taxed, from parts supplied by others, fabricating or casting the required local content to permit a "Made in Australia" label to accommodate the laws of the day. This was true for many imported goods, like almost all automobiles and trucks/lorries, until the mid-'80s. So our "local" car manufacturers were GM, Ford, Volkswagen, Citroen, Toyota, Leyland, and many others. The labour content of those was sufficient to be local goods. They even assembled Rolls Royce cars here.
There is a story of a wealthy farmer in the 50s writing to Rolls Royce asking to made a more suitable car for Australia, with wide running boards, since the current models of the had nowhere to put dead sheep found in the daily use of the car on the farm....
Many other companies had assembly plants here like Bosch, Hoover, Metabo.  They are all gone now since the repealing of import duties. No tools or cars or electrical goods made in Australia any more.... except very specialised stuff like mining machines, trains etc, mostly with imported parts, because all of the feeder industries for those parts are gone too now, of course.

[BillTodd]

Experimenting with a Raspberry pi pico servo.

This sort of thing used to be difficult. Now  all you need is a £5 microcontroller and a few lines of python and you have a servo controller.

Here , the pico's PIO  (programmable input/output) is configured to be two quadrature counters (it can easily have 8)  , one handling the motor position, and one counting the handwheel input. One of the pico's PWM outputs is amplified, filtered and sent to the servo amps (on the right).


 

I feel the need to make a pico DRO  ....