Bridgeport Manual to CNC conversion...

Yeah seen those vids, its a nice tight job he did there. I modified my quill connector so that there is more meat below the screw - this takes the down thrust and eases the strain on the bolt a lot.

Tenths LOL, I love those discussions :) Having said that, i am really pleased how accurate my old girl is, plenty for my needs. Lately i had need to asses my probing accuracy, its only a basic probe with the three-point contact setup but i get repeatability of around +/-0.03mm which i think is pretty good for a conversion.

All good fun :)

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Originally Posted by Davek0974

I was looking at those machines too ;) theres some good stuff on there at present.

The worst part with a BP conversion is the Z axis/quill drive - it has to be canted out in front of the quill and all the force must go through a single bolt into the quill - that bolt was never made to take anything more than a quill-stop :)

As the screw is driving the quill from one side there is a lot of axial twist moment on the screw which is not good, they work but i don't know how long for.

At the end of the day with a BP you take a machine worth maybe £3k, spend £8k on it and its worth maybe £3k - there is no return value here.

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The return is you have an accurate machine which weighs 875Kg, has a small foot print, low current, spares are cheap second hand because so many were manufactured, many conversions have been done on Bridgeports and ballscrew drawings are available, if it breaks you can fix it.

Of course, there is a value but you will never make money on a conversion.

Sadly the very flexibility of a Bridgeport is the downfall of a conversion - recently lost a fair bit of stock and time following a simple tool breakage, it was not working well, the homing position was off, just wrong, it took a while to discover that the small tool breakage had nodded and tilted the head by a few degrees in both axes!

It was only a small tool but must have bucked the head as it snapped, a fixed head machine with a table as big as the BP would be lovely but the height goes up due to having all the Z travel in the head not the knee and just won't fit :)

Lesson learnt - re-tram the head every time something happens!

Yes parts are plentiful, power is usable, rpm could do with being higher - currently running 1:1 3Hp motor at 4000rpm, I think she would take 5000 but the motor would not be happy so needs raising to maybe 1:1.5 ratio or so but then bottom end suffers and rigid tapping may not be possible, I was going to fit a servo drive up there but could not figure a suitable size unit that would give speed and torque needed.

Its a lovely machine though, helps even more as i spent so long using her in manual mode as well, get to know the sounds and feel of it so you can spot a CNC tool-path thats a bit over the top ;)

Any reason not to go for this?

https://www.ebay.co.uk/itm/Bridgepor....c100005.m1851

Seller indicates its 2150mm to highest point. The newer interacts are too tall.

Thanks

Looks reasonable, what can be seen of the ways looks good, will have ball screws, my only thought is the z travel but it can be worked with.

The head on these cant be tilted over can they? Just realised, I can just about do 2150mm but the garage door is lower, fail.

A smaller Harrison 600 has popped on another forum. Worth looking at, even for some manual milling (and perhaps CNC conversion)?

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Originally Posted by komatias

Yes, done it to something similar.

https://www.youtube.com/watch?v=M_VAXZbv6hc

has cost me around £3000 in total by now but only using steppers plus the cost of the machine. £1500 for the ballscrews as I went full hog with high preload and C3 accuracy. Also went with £300 worth of angular contact bearings to suit. Would have gone servo's if funds had allowed then.

Do not sell the DRO, I find it invaluable as you want to be able to switch between cnc and manual and also helps calibrate steps per unit.

From what I read the kit ballscrews are not as good as you are made to think, hence I went with my own ballscrews.

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Hi, Where did you get the ballscrews from and did it include a larger yoke?
Cheers!

I dunno about komatias but I got mine from AliExpress, machined to my own drawings for a nominal cost, like $5 per ballscrew - that saved a lot of messing about and they did a good job. The std ballnut diameter is slightly bigger than the std leadscrew nut, so I machined my yoke out on the (Bantam) lathe. Unless your machine is in almost new condition, you may struggle to justify expensive ballscrews, as there will be slop and backlash even once the gibs are adjusted. The ballscrews account for only a part of the total.

Using an MPG means I don't need the X & Y handwheels, which (in my case) added a lot of unhelpful moment of inertia to the servos so I removed them and have a better servo response. I still have the original DRO I fitted years ago but this simply tells me how worn the machine is. If you can achieve backlash below 20-30um (0.001"), I'd say you are doing well. However, the actual accuracy will be worse when you are machining as opposed to cutting air, as there will be additional forces at play - but the willy wavers tend not to get into measuring that, as it spoils the fun.

In the end, this is what I went for and is now for sale.

https://www.ebay.co.uk/itm/Bridgepor...torefresh=true

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Originally Posted by Muzzer

I dunno about komatias but I got mine from AliExpress, machined to my own drawings for a nominal cost, like $5 per ballscrew - that saved a lot of messing about and they did a good job. The std ballnut diameter is slightly bigger than the std leadscrew nut, so I machined my yoke out on the (Bantam) lathe. Unless your machine is in almost new condition, you may struggle to justify expensive ballscrews, as there will be slop and backlash even once the gibs are adjusted. The ballscrews account for only a part of the total.

Using an MPG means I don't need the X & Y handwheels, which (in my case) added a lot of unhelpful moment of inertia to the servos so I removed them and have a better servo response. I still have the original DRO I fitted years ago but this simply tells me how worn the machine is. If you can achieve backlash below 20-30um (0.001"), I'd say you are doing well. However, the actual accuracy will be worse when you are machining as opposed to cutting air, as there will be additional forces at play - but the willy wavers tend not to get into measuring that, as it spoils the fun.

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Thanks for the info I have already converted my Series 1 to CNC using the standard acme screws and also removed the handles 'cos I was getting fed up with getting the occasional thump. By the way I'm with you on appropriate accuracy for outlay I paid £130 for my Bridgeport as it literally had fallen off a lorry and the head casting was cracked. Another £150 in used spares got me going and I've spent another £700 on the CNC conversion. So value.

One thing that puzzles me is the wall thickness on the standard Bridgeport yolk. I can see there is enough meat to machine out from 32mm to 40 mm but there does not appear to be enough wall thickness for the securing bolts without breaking through the wall. How did you manage?

I guess I could buy a 2505 ballnut and dismantle the X axis to see better but I'm pushed for time as we are moving house in the spring so any info would be highly appreciated.

Cheers
David

Not sure where you get the 32mm figure from. The yoke bores are designed to take bronze cylindrical leadscrew nuts, as opposed to being directly threaded. On my Series 1 BP clone, the original X&Y leadscrews were 1-1/4" ie ~32mm OD. The actual leadscrew nuts themselves were pretty much 39mm OD and the DFU2505 ballnuts are 40mm OD, so I only had to bore the yoke bores out about 1mm on their diameters.

As for fixing, there's really no need to use all 6 holes. I only fitted two M6 screws and there was enough meat for me to drill and tap the holes. If you look at the tensile load that would cause an M6 bolt to fail, you'll see that this wouldn't be the first link in the chain to break.

Here's a bit about the actual boring: https://mightyshiz.blogspot.com/2018...or-larger.html

And fitting the thing back on the machine. Note that the Y axis ballnut may foul something (I forget - possibly the knee lift?), which required some angle grinder action on mine.
https://mightyshiz.blogspot.com/2018...allscrews.html

Murray

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Originally Posted by Muzzer

Not sure where you get the 32mm figure from. The yoke bores are designed to take bronze cylindrical leadscrew nuts, as opposed to being directly threaded. On my Series 1 BP clone, the original X&Y leadscrews were 1-1/4" ie ~32mm OD. The actual leadscrew nuts themselves were pretty much 39mm OD and the DFU2505 ballnuts are 40mm OD, so I only had to bore the yoke bores out about 1mm on their diameters.

As for fixing, there's really no need to use all 6 holes. I only fitted two M6 screws and there was enough meat for me to drill and tap the holes. If you look at the tensile load that would cause an M6 bolt to fail, you'll see that this wouldn't be the first link in the chain to break.

Here's a bit about the actual boring: https://mightyshiz.blogspot.com/2018...or-larger.html

And fitting the thing back on the machine. Note that the Y axis ballnut may foul something (I forget - possibly the knee lift?), which required some angle grinder action on mine.
https://mightyshiz.blogspot.com/2018...allscrews.html

Murray

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Excellent thanks Murray I appreciate the work you put into documenting that. I'll spec the end machining myself as my drive arrangements are a little different to yours and whilst I'm waiting on China Post will bore out yoke.

Yup 32mm was a mistake on my part.

Never used a faceplate before fortunately one came with my Triumph lathe so it promises to be good fun.

Cheers
David

FYI, I used Machine Parts Store on AliExpress https://www.aliexpress.com/item/8537...27424c4dIg5u4J
Service was good, the machining worked for me and the price was right.

Let us know how you get on!

Thanks for all the advice I have now ordered from an eBay supplier in China as I did not get any replies to my request for quotes from AliExpress and am going ahead with C7 spec 25mm ballscrews and double ballnuts. Cost was £179 inclusive of eBay fees of £24 which the vendor detailed separately and was clearly upset about!

I guess machining the yoke will be fun as in order to align the bore I will have to centre both the tailstock and headstock ends of the existing bore and I can envisage them fighting with each other for alignment. Anyhow it keeps us out the Pub.
Cheers
David

Wasn't too difficult to set it up in my case. There was a machined surface that I bolted against the face plate and I got the bore dialled in quite accurately with a bit of care.

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

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....

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

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.

Hi,
where did you buy your Panasonic servo motors and drives.

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Originally Posted by Colin Barron

Hi,
where did you buy your Panasonic servo motors and drives.

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Who are you asking?

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.

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.

Quote:

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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.

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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).

Quote:

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Originally Posted by Colin Barron

Hi,
where did you buy your Panasonic servo motors and drives.

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I was in a thread a few weeks ago and it was pointed out to me how much Yaskawa had come down in price. You can get 750W set for around £450-500 on Ebay just search Yaskawa Sigma. I'd use these over most other makes and DMM or Delta etc don't compare to Yaskawa, esp when it comes to tuning and software. They basically tune them selfs on the fly. Go to youtube and check out the Vides and the tuning software.

Quote:

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Originally Posted by JAZZCNC

I was in a thread a few weeks ago and it was pointed out to me how much Yaskawa had come down in price. You can get 750W set for around £450-500 on Ebay just search Yaskawa Sigma. I'd use these over most other makes and DMM or Delta etc don't compare to Yaskawa, esp when it comes to tuning and software. They basically tune them selfs on the fly. Go to youtube and check out the Vides and the tuning software.

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A good shout. The 'premium' brands are worth it if you can afford their kit.

You did a very positive youtube video on the BST servos/drives, how did they perform on the machine? The 750w Yaskawa drives at £500 is that second hand.

Quote:

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Originally Posted by Colin Barron

You did a very positive youtube video on the BST servos/drives, how did they perform on the machine? The 750w Yaskawa drives at £500 is that second hand.

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If you are talking about the 1.8Kw then yes they worked fine, they actually ended up on a Lathe. Well 2 did the third I still have waiting for a project.
I've also got some 600W 60mm here that I may do a video on as well.

The Yaskawa where new here a link for one I just did a quick search on Ebay, if you look around you may find them cheaper. They are fluctuating in price I've noticed, obviously because of the state of the markets.!

https://www.ebay.co.uk/itm/750W-YASK...f7dd09cee77dea

Colin if you use servos what controller are you going to use and how do you plan to run them.? Analog or Step/Dir.

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.

I have a Denford Easiturn 3 which had old electronics which did not work and i have removed them. I then thought i would reuse the steppers and drivers or steppers and the likes of the Leadshine 882 or if new servos are a direct replacement (mechanically) then the BST servos at about £250 each looks a decent bet.
On the controller front the Chinese controllers look a better bet than the mach3 bits and pieces which look like a project in themselves. A decision must be made before the controller is purchased as i believe i must specify incremental or absolute type (whatever that means?).
I was looking at the GSK clones such as Newker http://newker-cnc.com/index.php?m=co...=166&l=3&id=91

Quote:

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Originally Posted by Colin Barron

A decision must be made before the controller is purchased as i believe i must specify incremental or absolute type (whatever that means?).
I was looking at the GSK clones such as Newker http://newker-cnc.com/index.php?m=co...=166&l=3&id=91

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Yes, it's a bit of a mind field with these controllers so be careful, I've been looking for Mill controllers. Make sure you read all the tech spec because some have limited memory amongst other differences like how many simultaneous axis can be used at one time.

Regards Absolute and Incremental then it relates to the Encoder type used on the Servo. The BST uses incremental encoders as do most other types of servos unless you state you want Absolute.

The difference being that with incremental when you shut down the machine, the controller has no idea where the position of the machine is when it starts back up so you have to home the machine at the start of each day. (or if the servos are powered down) Just like you do with the stepper system.

Absolute Encoders retain the position of the servo even after shutdown, they do this by having a battery attached to the cable to power the memory of the encoder. This means you don't need to home the machine on startup and the drives/encoders know at all times where the machine is located, even if after power down someone manually moves an axis. (provided the battery power doesn't fail or the encoder cable is unplugged from the motor)
There is some setup I believe to be done when first installing because the drives/motors/encoders need to be told where Zero is located etc and the controller needs to support Absolute type but after that they work just like Incremental but without the need to home on startup.

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.

Quote:

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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.

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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.

How good are the BST servos and drives? Have you tried any other cheap servo motors/drives. Do the incremental controllers operate with stepper drives, for example the Leadshine am882?

Quote:

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Originally Posted by Colin Barron

How good are the BST servos and drives? Have you tried any other cheap servo motors/drives. Do the incremental controllers operate with stepper drives, for example the Leadshine am882?

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The BST servos are very good for the money they cost and well worth the price but don't be under any illusions that they are in the same league as Yaskawa or any of the leading brands because they are not. You really do get what you pay for when it comes to Servos.

Regards the controller then if it outputs Step/Dir then it doesn't matter what's on the other end ie: Steppers or Servos. it knows nothing about what's attached. All it does is send out pulses and receive feedback if your using encoders and fully closing the loop.

If you are unsure about Servos and don't need the speed they allow have you considered Closed loop stepper systems? I only use Closed steppers now on all the machines I build now and I can tell you they are much better than standard steppers. They are simple and accurate if sized correctly for the machine. They don't come with any of the issues that AC brushless servos have in that you need to tune the motors to the drives and controller etc. They also don't require the same high-frequency controller that servos need to get best from them.

The difference between servos and steppers in technical terms is quite large and much more costly. I would seriously ask my self if you need to take this route when in all probabilty Closed-loop steppers will serve you just as good with a lot less hassle and cost.!

New Yaskawa servos seem to be about two to three times the price of Delta servos.

Delta servos seem to be 1.5 to 2 times the price of the generic Chinese (e.g. BST).

I am considering 750w Delta servos for a new mill build. Possibly the newer B3 drives, a bit more expensive but look to have good features. I am encouraged by the manual in comprehensible English.

Check DMM servos

Quote:

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Originally Posted by pippin88

New Yaskawa servos seem to be about two to three times the price of Delta servos.

Delta servos seem to be 1.5 to 2 times the price of the generic Chinese (e.g. BST).

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Not really £400 for B3 Delta's on Ebay £525 for Yaskawa and can be found cheaper. While half decent the Delta's don't compare to Yaskawa and I'd gladly pay £100 more for Yaskawa.