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Bridgeport Manual to CNC conversion...
Anyone here converted a manual Bridgeport mill to CNC?
After building my plasma table and my mini-mill, both of which are working lovely, I WANT MORE CNC ;) ;)
My old 9x48 Bridgeport is looking for some love but is it worth it?
It would need a ball-screw conversion kit, these are available, plus I am guessing servo drives on X, Y and Z so I have encoder display, the knee doesn't seem to get driven on the few vids i have watched so far.
On the plus side, it's already powered via a VFD :D and i could likely recoup some cash by selling the working power feeds, control box and new DRO i fitted last year.
Worth a look or too expensive/not good enough...
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Re: Bridgeport Manual to CNC conversion...
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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Re: Bridgeport Manual to CNC conversion...
Don't bother.
Sell the manual and buy a dead CNC.
You have a machine that's currently worth about £900 ? you throw close to 2K at it and have a machine worth £800
Look for a BOSS 1 to 4 or an MDI machine. These were made as CNC, ballscrews, pressure oiling, a really nice quill where the ball screw is actually around the quill and not an add on that just wants to lever the quill sideways.
Downside of these machine which is in your favour is the electrics were crap, sorry make that $hit. Result is the iron is very good as ost have stood the last 15 years acting a shelf somewhere.
Beaver V5 here sold for £650
http://www.ebay.co.uk/itm/Beaver-V5-...-/182111147591
TOS CNC mill sold for £460 OK not working but that doesn't matter for a refit.
http://www.ebay.co.uk/itm/Tos-CNC-Mi...-/252353975743
You could have got 1/2 of that back reselling the controller.
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Re: Bridgeport Manual to CNC conversion...
I think you might be right there John, it's being in the right place at the right time to catch the machines when they pop up, plus getting some transport arranged.
Will keep looking.
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Re: Bridgeport Manual to CNC conversion...
Am I right in my belief that if i want real-time display of position in Mach3, I need to use servo's and encoders?
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Re: Bridgeport Manual to CNC conversion...
Quote:
Originally Posted by
Davek0974
Am I right in my belief that if i want real-time display of position in Mach3, I need to use servo's and encoders?
No, you can use optical encoders too. There is a screen out there that allows you to have 2 DRO's. However, you cannot use these as positional feedback in Mach3
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Re: Bridgeport Manual to CNC conversion...
Hmm, just had a thought...
Instead of dropping around £2k on building a mini-mill/router, what I should have done is use that cash to convert the Bridgeport and fit an adaptor mount that enables me to hold the 24k water-cooled spindle - best of both worlds??
I could even mount a complete Z-axis on the rear of the ram where the slotting head should fit!
The BP has a lovely 48" bed, ok maybe it only has 9" of Y axis but thats still not too shabby I think, certainly I've done a hell of a lot of big jobs on the old girl.
So, what would the drawbacks be here?
The new spindle has the speed I need, I think a BP conversion can reach 4-5000 mm/min rapids which is where the mini-mill is set so thats no issue, ballscrews would provide the same accuracy as the mini-mill has presumably.
Hmmm......
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Re: Bridgeport Manual to CNC conversion...
You lose Z travel when you convert the bridgeport's quill and another bit more when you add the adapter to hold the high speed spindle. Apart from that, I cannot see any issues except the speed at which your motors are able to move the bed. Good lubrication is key here. 4-5000 is way to quick for stepper conversions but possible with good servos. I have restriced mine to 3000mm/min actually.
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Re: Bridgeport Manual to CNC conversion...
Ok, but by building a custom Z-axis and mounting it on the rear of the ram I would retain whatever travel I build into the new axis, it means swivelling the ram round to change from heavy to light milling but thats about it, plus would need two z-axis drives - heavy and light.
The Z on the heavy side is a pain, a couple that i have seen today - one replaced the quill lever with a toothed pulley and drove that via a planetary gearbox reduction - seemed ok, another replaced the fine-feed hand wheel and drove that, the ones that mount to the front of the quill I am not too impressed with, have read a few tales of quills being trashed by the single bolt pulling out.
As for speed, so far most of my mini-mill work ranges from 600mm/min to 150mm/min - hardly blistering, I'm sure the old girl can match that ;)
I think this may be an interesting project.
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Re: Bridgeport Manual to CNC conversion...
Yes, that would do it. I have gone with direct drive on the quill and do not over drive it. The fine feed goes through a clutch while the backlash on the lever is too much for CNC.
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Re: Bridgeport Manual to CNC conversion...
Good points, thanks.
By direct, I gather you have the screw nut coupled to the front where the depth-stop used to sit?
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Re: Bridgeport Manual to CNC conversion...
It's slippery slope and quickly your into it $$$ before too far to stop.!! . . . Don't Do it Listen to John S.
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Re: Bridgeport Manual to CNC conversion...
awww, bum, damn that cold hard logic JAZZ ;)
In my defence, it would pretty much fit in with exactly what i want though!
So, the alternatives then -
Find a donor machine and hopefully just fit the electrics?
Downsides I can see...
space - nowhere to put it.
would like a big table again - this seems to mean a big machine (see point above)
transport costs
unknown wear & tear
different tooling probably
This seems not too bad, but its bed is quite small, although it does have an ATC - would that be the sort of stuff to search for???
http://www.ebay.co.uk/itm/1821213470...%3AMEBIDX%3AIT
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Re: Bridgeport Manual to CNC conversion...
Yep I'd take that every time over converting BP.
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Re: Bridgeport Manual to CNC conversion...
Hmm, looks like a no-go then - it weighs 4,500kg and has a 7.5kw spindle - i could not get that sort of power in the shop and anything much heavier than BP would be a bitch to get into place.
The bed is poor too - 500x600 not much bigger than my mini-mill!
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Re: Bridgeport Manual to CNC conversion...
Quote:
Originally Posted by
Davek0974
Hmm, looks like a no-go then - it weighs 4,500kg and has a 7.5kw spindle
Can't beat fat lass with bit of muscle.!!! . . . . But ye got to be practicle. .:thumbdown:
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Re: Bridgeport Manual to CNC conversion...
That's the thing - I know mass rocks when it comes to machines, and also see the point of having a pre-ballscrewed donor but as you say - I need to be practical if I bother to do this.
It would have to be viewed as what it is - a computer controlled Bridgeport Knee Mill NOT a VMC wannabe. I really can't squeeze anything much bigger than a BP in and have no expansion options as we are residential so have to be careful a bit ;) There is no garden left to build a bigger shop.
In the past I have had bigger stuff - a Colchester Student lathe, a large horizontal mill and a vertical slotting machine - all the stuff i used when building traction engines for fun. Back then I would have killed for a CNC bridgeport but had neither the cash or the knowledge. Using a boring head to machine a 25mm hole out to 100mm and only being able to take small cuts gets old real fast - that job would be seconds with CNC ability.
I'm still not convinced and a bit pissed that the machine I linked to above costs less than the ballscrew kit alone :(
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Re: Bridgeport Manual to CNC conversion...
Why don't you trade your Bridgeport in for a Bridgeport interact and convert that to Mach3?
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Re: Bridgeport Manual to CNC conversion...
Quote:
Originally Posted by
jamesgates1000
Why don't you trade your Bridgeport in for a Bridgeport interact and convert that to Mach3?
Something like this???
http://www.ebay.co.uk/itm/Bridgeport...sAAOSwYmZXD2Iq
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Re: Bridgeport Manual to CNC conversion...
Looks like a pretty good deal, I have used them before with the heidenhain control and they are good machines. Best wait for some advice from the others regarding suitability for Mach3 conversion.
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Re: Bridgeport Manual to CNC conversion...
Luckily, I got the tape measure out last night.
I can't fit anything bigger than the standard Bridgeport in! That only fits because the head is between the roof trusses, so that rules out practically all others I think as even an Interact is 90" tall which i think is 12" more than a standard machine.
So my options now seem limited to converting my own BP, buying another BP and converting that then selling my on on or not bothering.
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Re: Bridgeport Manual to CNC conversion...
Just had a lengthy chat with my supplier of bits and they seem to favour heavily towards 8NM stepper-servo's for this task. The specs read well, basically a closed loop stepper and DSP drive with variable current etc. Price was about £250 per axis for motor and drive with cables.
Being stepper also means i can use my existing knowledge of BOB's and USB motion controller etc.
More options to throw in the pot.
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Re: Bridgeport Manual to CNC conversion...
Knowledge gap...
Stepper-servo motors, I know I need the drive plus a BOB plus a motion control - done that before and it works.
AC servo motors, I know I need the drive amp plus ? - what goes between the drive unit and the PC?
Just trying to price up, the price is identical between 8Nm stepper-servo motors and drives OR 750W servo motors and drives - I have no idea how to choose between one or the other, one I know the other I do not.
I am advised that 750W is ideal for the job so thats one decision, also the 8Nm step-servo is ideal it seems.
Anyone want to fill the gap?
I know the servo is rated to 3000rpm and the stepper to maybe 1000rpm?
The stepper torque is way down where it's needed but the servo is where, linear spread?
Looks like a ballscrew kit is going to be around £1300 so thats a fair chunk of cash in one hit, the rest I need to get right first time.
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Re: Bridgeport Manual to CNC conversion...
Ok well in theory there's no difference in requiremnets between Servo and stepper for connecting to PC. However in practise there is specification difference.
Servo's require much higher Pulse frequency and much cleaner signals. Now your average £5 Bob doesn't cut it and the Parallel port is just doesn't cut the mustard.
The speed and resolution you get from Servo is dependant on the encoder fitted. The encoder also determines the pulse frequency required.
For instance most Servo come fitted with 2500 count encoders which are quadrature encoders so this number is *4 so 10,000 pulses required for one revolution at full speed. If 3000Rpm that's 30,000,000 pulses in 60s. Break this down to seconds and that's 500,000 pulse per second or 500Khz required to achieve full motor RPM.
Now PP is only 25Khz or at realistic best 45khz 45,000 pulses. At best this means you'll only get 270rpm out of your 3000rpm motor.
Now most servo drives provide a pulse multiplier so one pulse becomes 2, 4 etc depending on amount set. This however comes at the cost of Encoder resolution which gets reduced by the same amount. IE: 1:2 Multiplier 10,000 = 5000ppr 1:4 2500ppr etc.
Not problem your thinking I don't need all that resolution anyway but it's not just resolution that suffers, so does smoothness of the motor and really the whole point of servos is for there superior Resolution and smoothness along with linear torque.
So bottom line is if using servos then really you need an external motion control card that gives you required pulses of good quality.
On more positive note there are other advantages to servos than just resolution and linear torque. 3000Rpm often is too fast so you'll use ratio which increases torque so smaller cheaper servo can be used.
Torque is linear and the rated servo torque is when at full motor speed unlike steppers which is when at stand still and drops quickly when rpm rise. Large steppers drop very quickly and not much use after 900-1000rpm.
Servo drives are powered directly from mains so NO PSU required.
If I was converting a mill then I'd use servos because they are much stronger than Steppers and smoother in operation. Torque is linear so much stronger when your pushing hard and deep.
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Re: Bridgeport Manual to CNC conversion...
Thanks JAZZ,
The UC300 USB motion controller goes to 100kHz so that seems ok, I only suggest that one because I have used the smaller UC100 with total success and the price is pretty good too. However I do not know yet if that interfaces direct with the servo drive unit?
Not having a high power PSU is a big plus as well and as there is no price difference it looks like servos have won the toss :)
Would you go with 750W motors or smaller??
2:1 reduction for resolution & torque increase, more?
Servo drives seem to have lots of settings, what is used - speed & torque, positioning..... All new to me but i have the manual for the drives now.
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Re: Bridgeport Manual to CNC conversion...
Quote:
Originally Posted by
Davek0974
The UC300 USB motion controller goes to 100kHz so that seems ok, I only suggest that one because I have used the smaller UC100 with total success and the price is pretty good too. However I do not know yet if that interfaces direct with the servo drive unit?
Well not really 100khz is still 400khz short of full speed/res. Or 1:5 multiplier so only getting 5th of resolution. Plus it's USB rather than ethernet so wouldn't be my first choice.
Really Ethernet Smooth stepper is what you want or feeling really flush then go for Cslabs Controller.
Quote:
Originally Posted by
Davek0974
Would you go with 750W motors or smaller??
Probably 750W but really you should do some calcs to get better idea of size, inertia ratio etc. Like steppers Bigger isn't always better.
Quote:
Originally Posted by
Davek0974
2:1 reduction for resolution & torque increase, more?
Again depends on other things like screw pitch and what kind of speed/res/torque your looking for. Thou 2:1 with 5 or 4mm pitch screw sounds about right. My Big Semco CNC Mill uses 5mm pitch with 2:1 ratio and 1.8Kw servo's but it Dwarfs BP.
Matt (kingcreaky) on the Forum used 750W servos with 2:1 ratio on BP Interact sized mill and was happy with them. (He's got a video some where on this site)
Quote:
Originally Posted by
Davek0974
Servo drives seem to have lots of settings, what is used - speed & torque, positioning..... All new to me but i have the manual for the drives now.
If using Step Direction then you use Positioning. If using Analog +/-10v control then would use Speed. You'll be using Step & Dir so positioning.
Difference between Step/Dir and Analog is mostly how they are controlled and how the Closed loop works. With S/D the loop is closed only between drive and Motor. Analog the Loop is extended between Controller drive and Motor.
The result is that Analog feeds the Encoder position back to the controller, which it must do to work, which then checks this position with the commanded position and if wrong sends corrective signals.
The upshot is that the DRO's always display the actual position of the table, no matter if mach or controller as commanded this or you whind it there by hand. In affect works just like Manual DRO's.
Step/Dir on the other don't do this. It sends commanded position to the drives and takes it on faith that it arrived there. The drive then takes control of getting to commanded position and any corrections needed.
So the DRO's only show the commanded position and if it's wrong or if for instance something is loose you'll never know your out of position. Essentially works just like your steppers now with the exception the drive is checking the motor actually moved the distance told.
Bottom line is S/D is easier to setup. Analog gives more feed back but takes more setting up and tuning of drives.
See this video I made showing 1.8Kw servos controlled via Analog.
https://www.youtube.com/watch?v=tW8knRAOr7s
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Re: Bridgeport Manual to CNC conversion...
Nice video, that would be what i would like ideally - feedback.
So The option is now ESS at about £150 and no feedback or CSMIO/A at about £490 with all the bells and whistles.
The motors I was looking at are from the same guy as in your video, drives the same too.
The 750W suggestion comes from the CNCZone where a builder mentions doing 30+ conversions of this type and always uses 750W, 1kw was too large and 400W too small.
He uses 1:1 or 2:1 but I favour 2:1 as I want to get the most torque I can and the machine won't handle massive rapids.
Ballscrew kits seem to be 5tpi so 5.08mm pitch
Question is - is the benefit of real-time position DRO worth the extra cash?
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Re: Bridgeport Manual to CNC conversion...
Quote:
Originally Posted by
Davek0974
Question is - is the benefit of real-time position DRO worth the extra cash?
Yes IMO but with the Cslabs controller there's more to it than just this. You also have very accurate Homing using the Index pulse of the Encoder. You can also Fit a Servo to the Spindle and control that just like an axis so can index to position or do things like ridged tapping etc.
Then you have 24V I/O etc not to mention you don't need a BOB. This Alone is BIG Plus, esp when using servo's. Don't confuse the IP-S with ESS they are completely differant animals.
While they seem expensive they are not actually that bad when you consider that it's one complete unit nothing else is required. It's also Industrial spec and high quality.
By the Time you have Bought ESS and Decent quality BOB like PMDX126, which about the only one I'd use with servo's plus Spindle speed Control board then your not long way behind the IP-S or IP-A.
They really do not compare other than both use Ethernet and provide 4Mhz after that it's all down hill for the ESS.!!
Quote:
Originally Posted by
Davek0974
The motors I was looking at are from the same guy as in your video, drives the same too.
Think you'll find 750W will be most likely be 80 frame(like Nema34) not 110 which will probably be better for you. Drives may be smaller too.?
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Re: Bridgeport Manual to CNC conversion...
Ok JAZZ, i'm sold on the CSMIO/A unit, does it have PWM output or is that an add-on? Controlling the VFD would be nice.
Will be reading up on that tonight.
Rigid tapping is a bugger because you need to get an encoder on the spindle - this is a nightmare the Bridgeport manual machines. Possible later add-on though.
Yes I think those motors will be Nema34 size.
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Re: Bridgeport Manual to CNC conversion...
Quote:
Originally Posted by
Davek0974
Ok JAZZ, i'm sold on the CSMIO/A unit, does it have PWM output or is that an add-on? Controlling the VFD would be nice.
Yes it as Analog 0-10V Output for spindle Control built into it. Also has few Analog Inputs so can use Pot to override spindle speed and feedrate if desired.
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Re: Bridgeport Manual to CNC conversion...
A couple things to remember with the CS-Lab controllers, is if you want rigid tapping, you need to add the ENC/threading module, although not really an issue if you're happy to use a tapping head or thread mill.
Also, if you want to add a MPG, you need to buy the MPG module.
I would of suggested a KFlop+Kanalog (+ a Konnect if you need more than 8 In or 16 Out) as they'll do whatever you program them to do without any additional modules, however you need to know at least a little bit about C programming to get them working.
I was advised for my big mill, that the larger motors would be a better match. I was looking at 1000W 80 frame motors, and 1050W 110 frame motors, although I think I'll have to get 1200W to get the 3000RPM now. However I do think you could probably get away with the smaller frame motors on a standard Bridgeport, as it's not that heavy a table.
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Re: Bridgeport Manual to CNC conversion...
fitting an encoder to a BP is going to be hard i think, not many places to access the spindle, I have tapping heads so not really a concern yet.
I'm fairly well recommended from previous converters that 750w is a good match for this job, 3:1 reduction should help too.
I really don't want to get into C programming ;)
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Re: Bridgeport Manual to CNC conversion...
Then put an AC servo on the Spindle? I have done this on my MDI.
Its 3KW and 4KRPM. Bit small but i will see how it goes.
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Re: Bridgeport Manual to CNC conversion...
Control options...
Not sure we need a alpha keyboard for a mill, hows about a touch-screen monitor to do away with the mouse and a small numeric USB keypad?
Or
normal monitor (cheaper/stronger) and a track-ball and numeric keypad?
Looking at controls..
X/Y joystick
Z joystick
Knee up/down buttons
Speed override knob
Feed override knob
Cycle start
Feed-hold
Stop
Spindle motor...
This is currently run from a VFD but only at 50Hz, the head is the vari-speed unit with back-gear so i have 50-3000rpm but in two ranges and manual speed control. Whats a good option here - using the VFD won't address the variable torque ability of the vari-speed unit so can't just lock it in one spot.
Any cool options here to play with?
With a bit of fiddling the vari-speed changer could probably be motorised with a stepper and gearbox, not sure it's worth it?
Mach can obviously take over the Fwd/Rev function - still using the old switch but I wired it to the VFD so I can plug-reverse for tapping;) That was before i got the tapping head.
Any cool ideas?
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Re: Bridgeport Manual to CNC conversion...
Z axis...
It looks like I have four options here...
1 - Drive the Quill direct from the bolt point where the depth gauge mounts at the front.
2 - Drive the manual lever shaft on the right side
3 - Drive the power-feed clutch shaft on the left side
4 - Drive the knee lift
Points -
Option 1 seems to be the most common but adds a lot of bulk to the front of the head and costs a little Z axis travel.
Options 2 & 3 are similar, both will suffer from the rack backlash but option 3 is the neatest one, backlash can be reduced with the clock-spring.
Option 4 is a contender I think, it gives a massive 300mm Z travel, but suffers from stickiness and has backlash in the bevel gears. The force is reasonable - I measured my one and if my figures are correct, it needs approx 1Nm to lift the knee based on the handle length of 160mm and 6kg force on that handle 6kg / (1000/160) = 0.96Nm
The backlash is a factor but the Z is usually used to plunge or position - both of these are done in the positive direction so maybe backlash does not matter here?
Thoughts?
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Re: Bridgeport Manual to CNC conversion...
Based on advice, 750w AC servos and 2:1 is ideal on a bridgeport so that is whats going in, totally overkill for the Z axis but the price of smaller motors is higher so i cant see the point really, keep it all the same.
Got a few parts on the way - stainless panel mount keyboard, stainless panel mount trackball, some bits from the box at work - nice 10-turn pots and dials for FRO & SPO controls, a few spare relays and other bits and bobs.
Just about got a source lined up for a ballscrew kit - this bit really hurts the wallet :(
Does anyone have a drawing or sketch that would give me the dimensions of the right table (X) bearing bracket and the front (Y) bearing plate??
Mine will be missing as I have the original 6F power-feeds which will be taken off when i convert.
I can get the parts but the prices seem silly and they surely must be an easy enough part to make up from steel or aluminium?
Thanks
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Re: Bridgeport Manual to CNC conversion...
Drive belts - HTD5mm x 15mm wide big enough?
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Re: Bridgeport Manual to CNC conversion...
Quote:
Originally Posted by
Davek0974
Drive belts - HTD5mm x 15mm wide big enough?
They'll work ok but i'd be more inclined to go with 25mm for Mill with heavy bed.
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Re: Bridgeport Manual to CNC conversion...
Quote:
Originally Posted by
JAZZCNC
They'll work ok but i'd be more inclined to go with 25mm for Mill with heavy bed.
Hmm, will have to check pulley dimensions will fit machining on shafts, there is a conversion kit which uses 1/2" belts, I thought that was a little weak so went for the 15mm size as i used before.
Will look into the 25mm size
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Re: Bridgeport Manual to CNC conversion...
Drive belts, just had a chat with a very knowledgeable guy and it seems HTD is the best option here, GT is better but more expensive all round. The backlash concern is valid but equates to approx 0.25mm linear which if i have my sums right on 5mm pitch screws and a 75mm pulley will give me an error of 0.0053mm - I think thats acceptable on a 30+ year old machine ;)
He did however strongly recommend going for 8mm pitch and 20-30mm wide belts.
Can't use 8mm pitch as you can't get the needed ratio in as the pulleys are so much bigger so will have to be 5mm pitch.