Bridgeport Manual to CNC conversion...

**V8kid** · 10-03-2020

Whoa! Have 3 months gone by? After finally getting the house ready for sale it was time for me today to have a bit of time in the man cave and Muzzer was mostly right in that it was easy to bore out the yoke on the faceplate - here a tap and there a little tap and with patience it dialled in spot on. The original Bridgeport acme bush had a 3 thou clearance but I decided to make the ballscrew 1 thou clearance and its a nice snug fit

However I should have read Muzzer's post more carefully as his machine is slightly different to mine and sods law the casting walls on the yoke were thinner on my series1 Bridgeport making the fixing holes problematic.

The X axis was no problem as the casting thickened around the securing flange allowing 3 fixings but the Y axis was iffy. I managed to offset grind one of the ballscrew ( V hard material would not drill) fixing holes and just manage to get 2 off diametrically opposite 6x1mm fixings with a 0.5mm wall thickness on the outside but I held my breath whilst I did it.

Only have stainless fixings in stock so will have to order HT Allen screws before assembling.

Cheers and ta for the pioneering work Muzzer

**Muzzer** · 11-03-2020

Heheh, good to hear it went well! You don't actually need a lot of screws. If you look at the yield strength of an M6 machine screw, you'd break something else before 2 of them failed.

What's next? Have you got the rest of the parts for the X and Y drives? I forget what your plan is for the Z axis - I might have to look earlier in the thread to see what you planned....

**V8kid** · 12-03-2020

Already converted to X&Y CNC using existing Acme screws and Steppers on Mach4 with Ethernet smoothstepper. Works OK but..... Hoping the ballscrews will give more speed and accuracy.

For the Z axis I obtained a spare head casting and machined the front flat so I can get the ballscrew closer to the quill and extended the slot downwards so I can get 2 fixings on to the quill. Need the X&Y axis up and running to machine the necessary Z axis slipper, Not sure how well this will cope with drilling large holes may have to do that manually.

How did you reinstate the oil feeds to the yoke? For the X axis I drilled into the old bush keyway which should distribute the length of the yoke but for Y axis just put a drip onto the ballscrew at the back side. Not sure how much lube is required.

Cheers

**Muzzer** · 14-03-2020

IIRC, there were oil pipes for each of the X and Y acme nuts and I was able to reinsert them into the ballnuts. The X can be fitted when the table is still off but I fitted the Y with the table and saddle in place (forget why) and I recall a little bit of messing about inserting the pipe into its ballnut, via the hole in the front of the knee.

Nice solution, getting a spare head casting. I wasn't impressed by the crude approach used by Elrod, South West Industries etc that relied on a Z axis yoke sticking way out from the quill to clear the features on the standard head. When combined their massive castings (you could have kept a rabbit inside the housing Elrod "designed" and supplied for his conversions), the end result is enormous and expensive - but not even very robust around the ballnut and quill.

I designed my own Z axis drive using a 16mm ballscrew that replaces the threaded feed adjustment rod. This allows a ballnut yoke with a minimal overhang and the installation is compact and neat.

Unless you plan to do a lot of heavy drilling, you don't need a big motor for the Z. As a starting point, if you ignore friction, the torque and force are related like this:
Torque x angle = force x distance where angle is number of radians in one turn (2*pi), distance is the ballscrew pitch (metres) and the torque (Nm) / force (N) are your input and output.

So for my 2Nm Leadshine closed loop stepper and 4mm ballscrew, the stall force would be ~2 x 2 x 3.14 / 0.004 = ~3000N, which is equivalent to the weight of about 300kg (or three fatties). That's a lot of force and would be a test for most ballnut installations. Any pulley reduction ratio would increase that further - in fact mine is 1.8:1, resulting in about 1/2 tonne of force.

In practice, you lose a fair bit of your motor torque along the way, especially if you don't align your ballscrew carefully, but even so, you can see that a lot of these conversions you read about are stupidly overspecified in terms of stall torque, reduction ratio etc. There's one good reason for fitting limit switches...

Keep us updated on your progress!

EDIT - missed out a factor of 2 on the left side of the fag packet sums. Answer was right, though.

**Muzzer** · 02-04-2020

Not sure who used the Panasonic servos but in my case, I used DMM Tech servos for X and Y, as mentioned on the controller thread http://www.mycncuk.com/threads/13520...the-controller I was living in Vancouver at the time, so I drove over to the DMM Tech building and picked them up in person.

DMM Tech seem to me to be somewhere between hobby and industrial. No disrespect to them intended but they really aren't in the same league as Panasonic, Yaskawa etc but there again, they don't claim to be. And the pricing is an order of magnitude less. As I've spent many years myself developing similar products, I took one of mine apart and it wouldn't get through a proper design validation test - but it works fine in my workshop environment for my purposes so I'm happy.

There seems to be a Korean supplier on ebay who recycles servos, motors etc that have presumably been swapped out (preventative maintenance) after reaching their service lifetime on mainstream industrial machine tools. That seems like a good option for getting hold of good quality ("proper") gear at sensible prices. Can't recall the name, mind. Perhaps somebody here knows.

**Chaz** · 02-04-2020

Originally Posted by Muzzer

Not sure who used the Panasonic servos but in my case, I used DMM Tech servos for X and Y, as mentioned on the controller thread http://www.mycncuk.com/threads/13520...the-controller I was living in Vancouver at the time, so I drove over to the DMM Tech building and picked them up in person.

DMM Tech seem to me to be somewhere between hobby and industrial. No disrespect to them intended but they really aren't in the same league as Panasonic, Yaskawa etc but there again, they don't claim to be. And the pricing is an order of magnitude less. As I've spent many years myself developing similar products, I took one of mine apart and it wouldn't get through a proper design validation test - but it works fine in my workshop environment for my purposes so I'm happy.

There seems to be a Korean supplier on ebay who recycles servos, motors etc that have presumably been swapped out (preventative maintenance) after reaching their service lifetime on mainstream industrial machine tools. That seems like a good option for getting hold of good quality ("proper") gear at sensible prices. Can't recall the name, mind. Perhaps somebody here knows.

People's experience of DMM seems very much hit and miss. Some love them, some hate them. The Panasonics cost more but they are great bits of kit. I wish I knew how to use them better but it is what it is.

My next option/ avenue would be to look at the 'common' cheap servos from China. It might be a 'get what you pay for' but for me something like DMM, with the mixed feedback) is simply too expensive. Id either go Panasonic and know I get what I pay for, or go cheap Chinese (which many are using but I have no first hand experience yet).

**Chaz** · 02-04-2020

I've been using Panasonic. I tend to use a guy on ebay called GPWizard (or similar). his stock varies but can sometimes source what I need.

**Chaz** · 03-04-2020

The Yaskawa stuff looks very similar to Panasonic. Look at the front panel, very similar if not the same layout. Wouldnt be surprised if there is some commonality here.

For what its worth, my Father In Law used to be in charge of one of the largest ports in the world, running all their electrical systems. Think of moving millions of tons of goods per month. They used Yaskawa variable speed drives extensively, a serious outfit.

**Muzzer** · 03-04-2020

I've not seen the "absolute bus type" (990MDCb) version of the Newker in the flesh but it sounds as if it uses some sort of serial bus to pass absolute motor positional data back to the controller and presumably also does away with the conventional step/dir signals in the process.

Must admit I'd prefer not to have to home the machine each time at power on but the feature comes at a cost. I just accept that both the Newker and the Acorn need homing each time but I'd be interested to hear how the costs for the 2 alternatives compare if you enquire with Newker. Presumably you would need to buy their motors as well as the controller itself for the system to work.

**JAZZCNC** · 03-04-2020

Originally Posted by Muzzer

I've not seen the "absolute bus type" (990MDCb) version of the Newker in the flesh but it sounds as if it uses some sort of serial bus to pass absolute motor positional data back to the controller and presumably also does away with the conventional step/dir signals in the process.

I've been in touch with Newker about Bus type Absolute setup for my VMC and the absolute controller is NEW1000 MiCb-4 series. The absolute drives are dual axis so for a lathe you'll only need one drive.

I've got the manual if anyone wants to see it but it's too large to upload to Forum so contact me directly thru PM.