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phazertwo

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I think it's a killer idea. Honestly, I would offer up different levels of kits... Keep a hardware set on hand and have it ready to ship, just in case some one wants a more complete kit... Assuming you have the financial and storage means to carry some inventory. You could also provide a hardware list, so they can just order it themselves.

The parts themselves look pretty dang good. The only criticisms I have is (A) I would try to use a fly cutter, or face mill on the flat surfaces you get a super smooth finish. (B) come up with a logo/name, and etch it into the big parts. That's really just aesthetics though.

Last I would say find someone on the board here that would be willing to give it a try. Hopefully someone that is willing to help you out with pictures of install so you can build some good instructions (if you want to take it that far). Once that mill is up and running have him take a bunch of vids to send you so that you can post them, some with the thing just chewing the some Al.

I could see this being a nice little side business, and with your skills I bet you could build some cool fixturing to really save you time and make nice parts. If it works, you could branch out to other machines... A kit for a PM-833T would be killer. (https://www.precisionmatthews.com/shop/pm-833t/)

As always, solid work!

PZ
 

shooter123456

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I appreciate the feedback!

Honestly, I would offer up different levels of kits... Keep a hardware set on hand and have it ready to ship, just in case some one wants a more complete kit... Assuming you have the financial and storage means to carry some inventory.
There are a few reasons I wanted to offer only the machined hardware and not the ballscrews and bearings.
1. I couldn't buy anything in enough quantity to get a wholesale discount, so I would be paying the same price anyone else would, except I would need to pay for shipping twice.
2. I would need to support the ballscrews and bearings and make sure they were decent quality for a decent price. If a set is bad, then the purchaser has to ship them back to me, then I would need to ship them back. Again, paying for extra shipping.
3. I wouldn't be offering anything different than everyone else selling kits. Competing directly would be tougher than offering something different.
4. People can re-use ballscrews they already have, purchase used ones, or take advantage of any sales or discounts.
5. I don't really have the extra money and space to buy a few sets and store them.

The only criticisms I have is (A) I would try to use a fly cutter, or face mill on the flat surfaces you get a super smooth finish. (B) come up with a logo/name, and etch it into the big parts.
More good feedback, thank you. I have a face mill that creates fantastic finishes, but they are not perfectly flat. I figured the part being flatter would be better compared to looking nicer. Though for most of the parts, it doesn't matter how flat they are, so it looking better could be the better way to go. I have been thinking about a logo, but I am not the creative type. That is good advice though, I will try to come up with something.

Last I would say find someone on the board here that would be willing to give it a try. Hopefully someone that is willing to help you out with pictures of install so you can build some good instructions (if you want to take it that far). Once that mill is up and running have him take a bunch of vids to send you so that you can post them, some with the thing just chewing the some Al.
Is there any reason you would find someone else to do it, instead of just putting it on my machine and taking the pictures/videos with that?

Again thank you for the feedback!
 

phazertwo

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Those are 5 good reasons not to get into the hardware business lol. You have obviously thought this out! In this case I would say just provide a drawing of what the ball screw needs to be... MAYBE go so far as to provide some part numbers for ball screws you know will work.

As for flatness vs finish... As a general rule I tend to pick function over form each and every time, however if you can make it look significantly nicer and not detract from the function, or add significant cost... make stuff shinny. I would challenge you to evaluate your parts, and make drawings with realistic tolerances. Like you said, some of those surfaces don't need a flatness on them at all... better to make them look nice. Remember people on the interwebs make decisions based on pics they see... It's marketing really.

As for a logo... Start with just a name, and etch it, or an abbreviation into a few parts. More marketing really, you just need to make sure that if someone sees some pics of it on the interwebs they know how to find you.

Last, I was thinking that you would keep yours up and running, but if you're going to tear it down, DEFINITELY write the instructions as you are assembling (IMO no instructions is not an option). MUCH easier to do it all yourself. HOWEVER... I would still find a guinea pig and have them install and post all about it. Again, marketing.

PZ
 

bakrch

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Great thread!

I had similar issues with my ball screws, but they work ... for now.
 

Karter44

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With all the photos of a dis-assembled mill in this post, how difficult is it to remove the head and table and then re-assemble? I have a basement workshop but there is no room on the basement stairs to take down a complete mill. I have restored a '40s Logan lathe but I have never worked with milling machines before. I do have a knock down engine hoist that can be used. Thanks for the help.
 

shooter123456

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Its not hard at all. The head is very easy to remove, but I would remove the spindle motor first, otherwise it is very top heavy and has a tendancy to swing around hard when you loosen it up.

To remove the head, there are just three nuts that need to be removed and it pops right off. It weighs around 60 lbs, so be ready for it. There is also a little spike at the bottom to point to the head angle, and its a bit hazardous.

The table is about 55 lbs if I remember right and also comes off pretty easy. You just need to run the table to the end of its travels, remove the end blocks and loosen the gib up and it slides right off. Be careful when it is at the end of the travel because it may tip a little, especially if the head is already off.

Reassembly isnt too bad. The tough parts are getting the X axis gib back in place. I needs to be wiggles and nudged to get it to sit right. The head can be a pain in the butt to get the screws lined back up, but that is the hardest part. Then it just needs to be trammed back in.
 

shooter123456

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Trying to make a lot of parts gave me a chance to push the machine harder and try to get even more out of it. I am making motor risers and at first it was taking about 10 minutes for the first operation for each part. I sped things up and got it down to about 5. I posted a video of it moving pretty quick if anyone wants to see.

 

phazertwo

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What is your max RPM right now? Looks like she was cooking!

Also, consider ditching the drill op... Looks like your pretty much machining it out with the end mill anyway.

PZ
 

shooter123456

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What is your max RPM right now? Looks like she was cooking!

Also, consider ditching the drill op... Looks like your pretty much machining it out with the end mill anyway.

PZ
Holding steady at 7500. Can't really push it higher without a good deal of spindle work.

I didn't really want the drilling operation in there, but without it, there was trouble getting into the corners. The 1/4" end mill doing and adaptive cut would leave a lot of material. Then doing a 2d contour to finish it, there would be a lot of chatter when it got to the corner. When I used a 1/8 end mill to do the adaptive, it got into the corners just fine, but took 4x as long to do it. The drill time for that operation is 32 seconds (and I have been running 2 parts at once and the other part needs holes drilled, so the drill will be in the spindle anyway) and so far is the best way I have been able to figure out how to do it. I think if I spent some time figuring out ideal feeds and speeds for drilling, I can speed it way up.
 

shooter123456

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I think it is time for the direction of this machine to change. I have been in college for the last 4 years and for the most part, I have had an abundance of time and a very limited budget. Well I am graduating in 2 weeks and I have started a new job. As the stars have aligned, those two have reversed. I now have an abundance (well compared to what I am used to... which was no money) of money to spend and limited time. So now, I need the machine to work faster and more reliably, even if that means some things will be more expensive.

So its time to re do the machine I think. I would like to tailor it more towards production and reliability so I can design a part and output some toolpaths, then stick a piece of stock in the vise and press start, then come back however many hours later and have a finished part waiting for me. Ideally, I could get the machine up and running in 10 minutes or less, and not have to worry about a thing, even if that means I don't come back to the machine until the next day (or next several days). So what will I need to accomplish this?

1. Servos. I just don't trust steppers to run that reliably for long amounts of time without me checking in on them. I also would like the increased speed from servo motors and the fact that servos are much smoother is a big plus. Right now I am looking at DMM 640-DST-A6HS1 motors and DYN4-L01A2-00 drives for X and Y, then 86M-DHT-A6MK1 and DYN4-H01A2-00 for the Z. All in, those would run $1415 and would give me (theoretically) 1000 IPM rapids (more likely 400 IPM rapids) and cutting feeds in the 200 IPM range. Alternatively, I am looking at clearpath servos, which I haven't been able to decide on a model, but it looks like it will be roughly the same price, but I would get to try them out for 3 months to see if I like them first. I could also put servos on X and Y just for the running smoothness and rapids, then if the machine makes any money, add a servo the Z.

2. Flood coolant and new enclosure. My enclosure was meant to be quick and easy to contain some of the mess. It did that for sure, but I want something that will be water tight (ish) and allow for flood coolant. I sort of like mist coolant, but it doesn't do a great job with pockets and holes, and it is a bit unreliable for me. It is also tough to get it to work with different tool lengths without adjustment. I am working on a design for an enclosure made of steel instead of wood (I got a welder a few months ago and messed with the exhaust on my car to learn to use it, now the car is louder and I sort of know how to use a welder) and sheet metal instead of MDF. It will also be stronger and more rigid so it doesn't shake like crazy when the machine accelerates hard with the servos.

3. Auto tool changer. There is only so much the machine can do without me changing tools constantly. I made an auto tool changer and it had a lot of problems. So much so that I decided not to show it at all and keep it to myself. I have tweaked the design and changed a ton on it, and once the stock and parts come in, I will try tool changer take 2. It will need sensors out the hoorah to make sure that if it fails, the machine doesn't continue running and break everything. I have nightmares thinking about a partial index causing the machine drop down and break the tool changer, then have it continue running and break something each time it smashes into the tool changer. Don't want that nonsense.

4. Ground ballscrews. My ballscrews are rough and I don't love them. If I can find ground ballscrews for a semi reasonable price, I will buy them in a heartbeat. This doesn't need much explanation.

5. Remote control. My house is wired with security cameras, and I can check on them with an app on my phone. I also learned how to use remote desktop at my old job. I feel like these can be combined so I can keep an eye on the machine when I am away, and maybe even have it do stuff remotely. This is just a nugget of an idea, but who knows...

6. Probe. I would like to make a probe so I can fixture something and tell the machine to do its thing. I think the most time consuming part at the moment besides work holding is using a wiggler to touch off the workpiece. A probe would speed this way up. If I can't make a probe that is reasonably accurate, I will look into buying one.

7. A new control computer. The one I have is an old work surplus machine that isn't all that great. It works but it has its glitches (for example, 1 in 10 times when I remove the USB drive, the computer restarts) and it isn't all that reliable. I want one that will work all the time and minimize the time I spend redoing set up work because it conked out for some reason.

8. Spindle work. The spindle on the machine is like a 4 out of 10. It needs to be balanced and have a few other improvements made so it can run fast without vibrating. I want a better surface finish that it just can't handle.

9. Head spacer. The machines spindle isn't centered over the Y axis travel, so in order to use the whole thing, parts need to hang off the front of the table. This often makes them run into the column. You also lose a lot of travel when you use a vise. I would like to fix that.

I would love some feedback on all this. If you have ideas for things I could get to improve it, I am all ears. My idea is to make it out perform a Tormach 440 (which I consider the closest competition, though my machine has more travels) by far, for less than half the price of an equivalent machine ($14,500 for the machine with tool changer and enclosure).

Like everything for this machine, I hope it will only take a few months, but I am sure I will be halfway done by next Christmas...
 

phazertwo

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I'm interested to see what you come up with... Servos and a encloser that can handle flood coolant are the things I dream about at night. If you and Jake both figure out servos, it should be a walk in the park for me!

We should compare spindles. Do you have a model of yours that I could compare to mine? I've been doing a lot of dreaming of a spindle that has stacked AC bearings and can turn 10k rpm... but this means a whole new spindle, and probably quill. I've been thinking about how to do this in a smaller lathe and hold everything as concentric as we would need it... if our spindles are the same, I'd be willing to split some of the development effort with you.

PZ
 

shooter123456

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I'm interested to see what you come up with... Servos and a encloser that can handle flood coolant are the things I dream about at night. If you and Jake both figure out servos, it should be a walk in the park for me!

We should compare spindles. Do you have a model of yours that I could compare to mine? I've been doing a lot of dreaming of a spindle that has stacked AC bearings and can turn 10k rpm... but this means a whole new spindle, and probably quill. I've been thinking about how to do this in a smaller lathe and hold everything as concentric as we would need it... if our spindles are the same, I'd be willing to split some of the development effort with you.

PZ
The DMM and clearpath servos are supposed to be very easy to set up and use. I anticipate clearpath being much easier then steppers from what I have seen. The reason I have never used them is just because of cost.

I have a model that I can send to you tonight. I don't think the two are very similar though, yours is a whole lot bigger. Mine is really quite tiny and unimpressive. Ive considered making an entire new spindle, but I don't know that it would be worth it for this particular machine. I would need to replace the head as well, and I would probably want to change it to a BT30 instead of R8. I think I can get this spindle to run acceptably at 10,000. I will need to remachine the threads at the top and replace the r8 collet it is currently using (threads arent super straight on those either), then see if I can use a phones vibration sensor to get it balanced better. If that all works, it should run much smoother and vibrate less.
 

shooter123456

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I have been visiting my parents for Christmas, so I have been away from the shop for a few weeks. That means plenty of time to model and design stuff. I made a number of changes to the design of the tool changer because there were a few things that weren't quite working for me.

First was the tool fingers. They were a little bit over complicated, had very small parts that needed to be made, couldn't get enough spring tension in the space that I had left, and they required a very accurate tool holder geometry. The diameter of the groove had to be very specific and even when they were close, it would either be super tight, or somewhat loose. I didn't like that, so I changed the design to a 2 piece finger design that rotates on a shaft and are forced apart at one end by a spring so they grab the tool holder on the other end. I saw a very similar design on Haas tool changers so I figure it has to be a decent design. I started making some of those parts before I left and I think it should work just fine.

Here are is the updated version of the tool changer, from the bottom. You can also see some cut outs in the tool platter to try to reduce the weight.


I also decided to just buy an air cylinder instead of making one. I was having a heck of a time boring out a bar to use (accurately) and an already finished one made of stainless steel was only $24 brand new. Screw it, I bought it instead. It is a 2 stage cylinder with a 4" stroke. That will be plenty for the tool changer. It has a little over a 1" bore which will let me push it with 150lbs of force if I need to. I don't anticipate needing to use more than 30ish lbs.

I ran into some trouble with the motor that is used to rotate the tool changer. I was concerned that it wouldn't have enough torque to rotate the tools. The tools rotate on an axis with a diameter of 4.5". Considering only the weight of the tools, estimating 1 lb per tool (conservatively, more likely each tool will weigh less), that gives me 10 lbs (160 oz) rotating at 4.5". To move them, I would need 720 oz/in of torque (if my math is right, it is very possible that I am miscalculating completely). I am using a 400 oz in stepper, so it might struggle. To mitigate this, I made a 2:1 gear box that will double the torque and hopefully let me rotate the tool changer without trouble.



I am planning to make some changes to the pneumatic draw bar as well. Right now I am using a 3 stage air cylinder with 3" pistons. The springs I am using have a working load of 900 lbs and a flat load of 1200 lbs. I am running them in pairs giving me 1800 lbs of working force and 2400 lbs to release. At 115 PSI, that gives me enough force to release the tool. The plan now is to add another spring to give me 2700 lbs of holding force and 3600 lbs to release. This will let me push the tool a bit harder without worrying about it pulling out. To get the 3600 lbs of release force, I will add another stage to the air cylinder and push the pressure up to 130 psi. That will give me 3675 lbs of force to release the tool.

Last, I got a deal on some vises on ebay. I got 2 4" machine vises for $85 each that seem to be good enough for what I want to use them for. I now have 4 vises, and they should all fit on the table of the machine, letting me run 4 parts at the same time, or maybe run OP1 on 2 vises, then OP2 on the second 2 vises. I think this and the tool changer should let me really ramp up the production capabilities of the machine.

Here is a look at the 2 vises I received. They have the flat sides which should let me get them in much closer to each other and save some space. For what I paid, I am very pleased.



Here is how it should look when I get all 4 mounted with the tool changer.

 

macardoso

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Awesome job on the ATC! I can't wait to see the real deal. I have mine 90% built and laying in a corner. You're making me want to go finish it up.
 

macardoso

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Also, from having designed and built an ATC from the TTS system, be aware that the slot on the tool holder is very finicky and intolerant of misalignment. It has caused me a lot of problems in the past. I'm happy to share any design files for my ATC which might help you.
 

Firstgear

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welcome to the land of tax payers!

I saw that your posting on the coolant lines that occasionally stopped flowing, that you had to turn the needle valve open and when it started flowing again you turned it back down. If you want this to run automatically that cant happen.

Couple of thoughts...
1. on the inlet side before the needle valve put an inline filter. You can get these at Tractor Supply or Rural King (or Ebay) for about $5-$8. Look for the filters that are used for home spraying systems (I have one I pull behind my garden tractor when I want to spray weed killer in the yard). I would start with the smallest screen mesh they have since the viscosity of what you are dealing with is just above water. This will eliminate any very small particles that get into the coolant as it wont take much across that needle valve to plug it enough that requires manual intervention. Another filter that would work would be a paint filter, like is used for a manual spray gun. This might be a better way to go since they may make them with smaller mesh size. At any rate you can try one of them.
2. After putting the filter in place, if you still have problems, get a more accurate regulator. if you are using 5psi, make sure that you are using a regulator that is 0-15psi....you want that regulator to not be sitting too close to off...that will raise hell with you too.
3. Not sure what you are using for a needle valve but the same issue here. If you cant control the pressure feeding it the needle valve will have to take the pressure drop meaning it will be hardly open, again, it wont take much to choke off the flow requiring you to open it and then after what ever it was cleared, then setting it back again....you might need a better needle valve....

Having built systems before in my work life, these were the kinds of things that often tripped me up. These systems were going into automated systems where there were no human eyes so they had to work. That is what you want.

Let me know your thoughts....
 

phazertwo

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That really looks great.

As far as torque is concerned for rotating the ATC when there is no external force being applied to the assembly (is spins free save friction): Torque=Angular Acceleration * Moment of Inertia (τ=αI). Moment of Inertia is a term takes into account size, shape, mass ect. of the object that is rotating. τ=αI is actually just the rotational equivalent of F=ma for linear motion. Except F is replaced with τ, m is replaced with I, and a is replaced with α.

I could go into more detail, if you like, but long story short, you won't need the gear box to spin the ATC. I think there is a way to get Fusion to tell you your moment of inertia, if not I think I can get it in SolidWorks. Or we can roughly calculate it and get close enough. OR I'll beat my inner nerd back to where he belongs.

As always, inspiring work. Your video "Pushing PM-25 CNC Faster" actually got me off my ass and working on my machine!

PZ
 

shooter123456

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welcome to the land of tax payers!

I saw that your posting on the coolant lines that occasionally stopped flowing, that you had to turn the needle valve open and when it started flowing again you turned it back down. If you want this to run automatically that cant happen.

Couple of thoughts...
1. on the inlet side before the needle valve put an inline filter. You can get these at Tractor Supply or Rural King (or Ebay) for about $5-$8. Look for the filters that are used for home spraying systems (I have one I pull behind my garden tractor when I want to spray weed killer in the yard). I would start with the smallest screen mesh they have since the viscosity of what you are dealing with is just above water. This will eliminate any very small particles that get into the coolant as it wont take much across that needle valve to plug it enough that requires manual intervention. Another filter that would work would be a paint filter, like is used for a manual spray gun. This might be a better way to go since they may make them with smaller mesh size. At any rate you can try one of them.
2. After putting the filter in place, if you still have problems, get a more accurate regulator. if you are using 5psi, make sure that you are using a regulator that is 0-15psi....you want that regulator to not be sitting too close to off...that will raise hell with you too.
3. Not sure what you are using for a needle valve but the same issue here. If you cant control the pressure feeding it the needle valve will have to take the pressure drop meaning it will be hardly open, again, it wont take much to choke off the flow requiring you to open it and then after what ever it was cleared, then setting it back again....you might need a better needle valve....

Having built systems before in my work life, these were the kinds of things that often tripped me up. These systems were going into automated systems where there were no human eyes so they had to work. That is what you want.

Let me know your thoughts....
I hope uncle sam enjoys living large on my hard work :)

I will keep your thoughts in mind. I think a filter is probably a good idea, but the issue has largely gone away on its own. I switching to koolmist from WD-40 helped a bunch, and I think the WD-40 may have been clogging the lines a little bit for a while after. It is definetely a cheap thrown together system. The needle valve is one I found in the garage, probably form an old refrigerator and the mist system parts are almost completely from an RO water filter. The regulator is an inexpensive one and I am not sure what the rating on it is. If I redo the mister, I am going to follow your advice and add a filter and a better regulator.
 

Firstgear

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If you stated earlier, I am sorry if I missed it. What are you building this machine to make? Are you trying to get in the machine shop business? Make your own products you plan to sell?
 

shooter123456

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If you stated earlier, I am sorry if I missed it. What are you building this machine to make? Are you trying to get in the machine shop business? Make your own products you plan to sell?
The machine is for personal projects, I am just trying to make a few things to sell to fund more parts for the machine. Not planning to get into the machine shop business.
 

adhue587

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Hi,

You've done an awesome job at getting this designed. Any chance you would share your 3D models?
I have a PM-25MV and really want to get it CNC ready. The Power Drawbar and ATC are awesome too.
 

shooter123456

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The new servo motors got in. I got 2 CPM-SDSK-2321S-RLN motors for the X and Y axis and CPM-SDSK-3421P-RLN for the Z. Needless to say, they are quick! I am using the same 48V power supplies I used for the steppers, so the motors are limited slightly from their full ratings at 75V. I am probably going to buy a Clearpath power supply sometime soon to get them up a little bit and to run it off of 240v AC input since I have a 60 amp line for it.

I am now getting 400 IPM rapids on X and Y and 250 on Z. The set up was very easy and they are very smooth. They are also much quieter than steppers. You usually hear the ballscrew turning now instead of the stepper whine. They are plenty strong for this machine and I am very please.

Here is a video showing a short before and after.

 

phazertwo

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Very nice! I like the speed, it really is impressive. I'm very excited to see you tear up some Al.

Care to share why you went with Clear Path?

PZ
 

shooter123456

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Very nice! I like the speed, it really is impressive. I'm very excited to see you tear up some Al.

Care to share why you went with Clear Path?

PZ
Thank you!

I went with clearpath for a number of reasons. I was really only considering them and DMM because I wasn't aware of any others that weren't either no name Chinese imports or 3x+ the price.

Clearpath won because:
  1. The sales guy was very clear and straight forward, providing me with a ton of information and making it easy to choose which ones were best for me.
  2. The DMM sales guy just quoted me for the most expensive Nema 23 and Nema 34 items they had and didn't seem to think it was overkill even though they were 3x the power of what I have now. Ended up being more than $600 more expensive for very little gain.
  3. Clearpath lets you try their motors for 3 months and return them no questions asked if you are not impressed.
  4. Clearpath autotuning is simple and easy, the DMM ones were not nearly as straight forward.
  5. I can use the Clearpath motors on my machine without buying new power supplies. Saves me a few bucks for now.
  6. Drives are attached to the motors saving me space in the electronics box.
  7. The information available on the Clearpath motors was much more clear and thorough than DMM. They also seemed to have their stuff together a lot more (ie their site looks professional and is easy to navigate vs DMM which looks kinda like an ebay store selling rebranded motors.)
It wasn't a super tough decision really and I am happy with the performance.
 

phazertwo

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Good to hear they have some good customer service! A 3 month no questions asked return is a pretty sweet deal as well.

PZ
 

Larry42

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Motors are mounted and axes are moving. Looks like my careful measuring at the beginning paid off because every part went on without an issue and the machine moves smoothly.

Here is the Y axis motor mount. The ballscrew I have on the Y is about an inch too short so I am down to 6" of travel. When the funds allow, that will be replaced with a longer double nut screw.
View attachment 257206

Here is the X axis mount. The picture isn't very good because the lighting is bad. I need to get some more light over in that corner of the garage. The X axis loses 5" travel with the current ballscrew. This one will also be replaced with a longer double nut screw when the funds allow for it.
View attachment 257207

Here is the Z axis. This unfortunately isn't going to last as long as I hoped it would. The 400 oz in motor didn't have the torque to reliably move the head. The motor would not lift the head under 60 IPM or over 120. At 50 IPM, it would try to move it, maybe make a quarter of an inch, then the head would fall as the motor strained. At 75 IPM, it would move the head well, but would stall roughly 10% of the time when it was lifted. I am looking at Nema 34 motors and drives now to replace it. I think I will make a simple adapter plate to allow the Nema 34 to mount to the Nema 23 mount. I am thinking somewhere in the 900-1200 oz in range. Since there will be a pneumatic cylinder and potentially a larger motor on the head, I want to have a little extra power so I can move it quickly without needing any counter weight or spring helping to push the head up.
View attachment 257208

I was hoping the 400 oz in motor would last a little while on the Z axis, but my hand has been forced. I was getting set up to do some test cuts when something exploded inside the power box. The Z axis drive ate it, potentially from the current being drawn holding the head up. So until I get the new motor and drive, I won't be doing any cutting on the machine.
View attachment 257209

I have started the design work for the tool changer and have plans for a pneumatic cylinder, so hopefully those will be next. I am also getting the planning for the enclosure started. I got used to it with the X2 and doing the manual machining made such a mess I don't know how long I will last without one.
To take some strain off the Z-axis system you might install a couple of pneumatic cylinders, one on each side for balance. The regulator would maintain the same force through out the travel range. Mount the cylinders rod up to get maximum force from the piston. This is a common system on industrial CNC machines that carry much heavier loads.
 

Larry42

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I made some new lock nuts and machined some spacers for the AC bearings. I suspect some of the .008" backlash was coming from the bearings I was using and I don't think they were preloaded properly. I made 2 piece nuts with screws that can be tightened to lock the nut down on the threads. These are much better than the lock nuts that came with the ballscrews and in my opinion, they are better than the nylon lock nuts. Since it was an M12x1 thread, I couldn't commercial nuts for it anywhere anyway. They use 3 4x40 screws to lock and I cut the holes so there was just a little bit of space between the nuts when the holes are aligned. I have always had trouble with the regular lock nuts occasionally loosening up and it has ruined parts before. I am confident that these won't move once locked.
View attachment 259216

Here it is installed on the X axis with the new coupler on the motor.
View attachment 259217

I machined some spacers so I could preload the AC bearings as well. That was pretty straight forward but I don't have any pictures of it. Essentially I machined a bar to the right inside and outside diameter, then parted off 3 pieces, then super glued each to a piece of steel in the spindle, and faced it until it was about .05" thick. Using the lock nuts, I can adjust the preload on the bearings without needing shims.

I have the tool changer mostly designed now. It will be a little while before I am ready to start making parts for it, but I will start ordering stock and parts soon. The plan is to use a Nema 23 motor, a deep groove ball bearing, some round linear rails, and a pneumatic cylinder to run it. I think I will use an arduino to control the changer if I can figure out how to interface it with LinuxCNC. The plan is to have several sensors checking each step of the tool change to ensure reliability.

The tool change will go like this:
  1. Z axis return to home position (Home switch confirm head in position)
  2. Spindle motor off (Relay on spindle power to ensure spindle motor off)
  3. Tool changer move into position below spindle (sensor to confirm changer in position)
  4. Z axis lower tool to tool changer (sensor confirm head lowers to tool tray)
  5. Pneumatic cylinder release tool (sensor to confirm cylinder actuates)
  6. Z axis return to home position (home switch confirm head in position)
  7. Tool changer rotate to the next tool (sensor to confirm position of carousel and proper tool selected)
  8. Z axis lower spindle to tool (sensor to confirm head lowers to tool tray)
  9. Release pneumatic cylinder (sensor to confirm cylinder releases)
  10. Retract tool changer (sensor to confirm tool changer fully retracted)
  11. Z axis return to home position (home switch confirm head in position)
  12. Confirm new tool in spindle (not sure how I will do this yet)
Here is the tool changer with all of the covers removed.
View attachment 259218

Other side.
View attachment 259219

On the mill.
View attachment 259220

I used Fusion360s FEA to make sure the changer wouldn't deflect too much under the weight of all the tools. It gave me a deflection value of .0002" at the worst position so I am confident the structure is strong enough.
View attachment 259221

With a vise installed, there will only be about 5.5" between the bottom of the tool holders and the top of the vise jaw. I am considering a few alternatives such as adding a Z axis to the tool changer so it lifts up and out of the way when not in use, and the table can move all the way forward (closest to me) when changing tools, so hopefully it will be mostly out of the way. I don't think it will be too much trouble though, since I don't plan to have any tools sticking out more than 2 inches, and I don't often work with parts sticking more than 3.5" out of the vise. Im pondering the idea of some kind of quick release for the tool changer so I can lower the tool carousel out and remove it completely for when I work with taller parts.

If anyone has any ideas or suggestions, I am all ears. I have never tackled a project like this and could use all the help I can get.
Some machines mount the tool changer separate from the head. Off to the side. The machine then transverses to the end of its (X) travel to pick up tools.
 

shooter123456

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To take some strain off the Z-axis system you might install a couple of pneumatic cylinders, one on each side for balance. The regulator would maintain the same force through out the travel range. Mount the cylinders rod up to get maximum force from the piston. This is a common system on industrial CNC machines that carry much heavier loads.
That seems to be a common solution for this sort of problem. That motor was swapped for a 1200 oz in stepper, then swapped again for a servo. Now the motor is more than capable of moving the head.

I still considered going that way to relieve strain on the system and prevent unnecessary wear, but when I did the math, it wasn't really worth it. The head weighs about 75 lbs with everything on it. The air cylinders would only be able to counteract gravity, otherwise they would be pushing up against the motor and the head would be floating. Not ideal. At 75 lbs, the head experiences 333N pushing down. The ballscrew is rated for 9800N. So really nothing to worry about there.

Some machines mount the tool changer separate from the head. Off to the side. The machine then transverses to the end of its (X) travel to pick up tools.
I also considered doing that, but elected not to for a few reasons. First, it takes up table space, which this machine does not have much to spare. I think on the one I modeled up, to get 9 tools on the table, I lost 6" of travel in the X, then a little more to keep the tool from hitting the rack when it was cutting. The other issue I had with that is keeping chips away from the tools. I wanted to keep the tools up out of the way to keep them a bit cleaner and hopefully prevent chip build up from gumming up the works.

I am very close to done with a rotating tool changer that will be mounted on the column. It is a very common design on industrial machines, so in theory it is a tried and true method.

I appreciate your input though for sure!
 

Larry42

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Jun 22, 2016
Messages
76
That seems to be a common solution for this sort of problem. That motor was swapped for a 1200 oz in stepper, then swapped again for a servo. Now the motor is more than capable of moving the head.

I still considered going that way to relieve strain on the system and prevent unnecessary wear, but when I did the math, it wasn't really worth it. The head weighs about 75 lbs with everything on it. The air cylinders would only be able to counteract gravity, otherwise they would be pushing up against the motor and the head would be floating. Not ideal. At 75 lbs, the head experiences 333N pushing down. The ballscrew is rated for 9800N. So really nothing to worry about there.



I also considered doing that, but elected not to for a few reasons. First, it takes up table space, which this machine does not have much to spare. I think on the one I modeled up, to get 9 tools on the table, I lost 6" of travel in the X, then a little more to keep the tool from hitting the rack when it was cutting. The other issue I had with that is keeping chips away from the tools. I wanted to keep the tools up out of the way to keep them a bit cleaner and hopefully prevent chip build up from gumming up the works.

I am very close to done with a rotating tool changer that will be mounted on the column. It is a very common design on industrial machines, so in theory it is a tried and true method.

I appreciate your input though for sure!
I've got two CNC's with tool changers. One is a ride-along with 8 tools that is located just in front of the spindle. The other is mounted at the end of the moving gantry and holds 18 tools. It has a cover built in. 8 tools isn't enough. If an operator has to put a different tool on the changer, he has to be sure to have told the machine the diameter and length or bad things happen. I can see where adapting a manual mill to a tool changer in a way that wouldn't limit the table movement would add design complications. It could be done by having the tool carousel move into and out of it's tool changing location.
 
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