Z axis head supporting three types of functions

Hello

I would like to design a Z axis head that can do:
1. light weight cnc milling/drilling - This will only be used to mill PCB tracks and drill PCB boards
2. Solder paste dispatching - This is used to dispatch solder paste.
3. Pick and place actuator - This is used to pick and place SMT components

One option I have is to have three separately movable Z axis heads. This is costly as it needs three separate motors, linear rails and lead screws or belts. Other option is to have just one head plate which is driven by a lead screw and moves on a linear rail. This plate can have provisions to accept an extension which can have either the spindle (for 1 above), solder paste dispatcher (for 2 above) or pick n place actuator (for 3 above), one at a time. This extension has to be easily attachable/detachable from the main head. Obviously this will also involve electrical connections, but for the moment I just want to concentrate on mechanical aspect.

With this option, how do I make sure the attached extension positions it self consistently relative to the main head all the time? Are there any standard methods to achieve this?

Thanks

I was going to suggest using pneumatic cylinders and some small rail sections to extend your pick and place and solder dispenser when needed so that they were below your spindle bit, and retract them when not. That way the same screw driving the spindle could also drive those 2. However, this seems about the same complexity as having 2 extra screws and requires an air source, so probably not what you're looking for.

You could have manual clamps on the solder dispenser and pick and place that have their own short linear rail sections and that way they could be driven by the same screw and not have to be removable.

I found this pic online, but I've seen them before, they can be found in a number of varieties. I'm guessing you could even make some from inexpensive MGN12 linear rail parts.

Attachment 380396

I found this on YouTube and find it interesting the way the pick and place rotates the part and the X Y zeros are set.

Good Luck!

https://www.youtube.com/watch?v=CRSLbo_8nTQ

Quote:

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Originally Posted by NIC 77

I was going to suggest using pneumatic cylinders and some small rail sections to extend your pick and place and solder dispenser when needed so that they were below your spindle bit, and retract them when not. That way the same screw driving the spindle could also drive those 2. However, this seems about the same complexity as having 2 extra screws and requires an air source, so probably not what you're looking for.

You could have manual clamps on the solder dispenser and pick and place that have their own short linear rail sections and that way they could be driven by the same screw and not have to be removable.

I found this pic online, but I've seen them before, they can be found in a number of varieties. I'm guessing you could even make some from inexpensive MGN12 linear rail parts.

http://www.cnczone.com/forums/attach...d=380396&stc=1

I found this on YouTube and find it interesting the way the pick and place rotates the part and the X Y zeros are set.

Good Luck!

https://www.youtube.com/watch?v=CRSLbo_8nTQ

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Thank you for the suggestion about clamping heads to a rail. This seems to be a really good idea. Clamping is also much easier for the user than attaching and detaching heads. Only downside I see is head will be heavier, but with a decent motor and a ball screw this should not be an issue. I will search about these clamps, but in case you remember, I appreciate if you could let me know the general name of these clamps.

Thanks

Please have a look at the following image for a tentative design I came up with for extension attachment/de-attachment (Please note that the image has to be rotated by 90 clockwise). Essentially, the head plate has a single linear motion cartridge fitted permanently. Each extension unit has a matching rail fixed to it horizontally. Attaching the extension involves sliding extension's rail through the cartridge. Movement of the extension unit is blocked by a fixed wall made of aluminum (see the pic) which is fitted to the head plate permanently. I am planning to have electrical contacts attached to this blocking plate which will create necessary connections with the extension when slided in.

http://www.cnczone.com/forums/attach...d=380546&stc=1

I have couple of questions about this setup.

Firstly, would the linear rail or linear cartridge get damaged after continuous use? Each detachment involves taking the rail completely out of the cartridge and re-attachment involved putting it back. I am mostly concerned about rail's corners.

Secondly, how can I secure the extension firmly. I want the extension to press against the blocking wall with electrical connections firmly so that the position of the extension would be consistent after re-attachment.I considered linear rail clamps, but they do not create a force against the wall when clamped, so user would have to manually push the extension against the blocking wall when clamping. Also, these clamps are expensive, the cheapest one I found was for £90.

I have considered using a magnet in the blocking wall to pull the extension towards it. This magnet can be electrical, so that when the extension need to be removed, power can be cut. Alternatively I can use permanent magnet, which would require some mechanism to exert a force to extension when it needs to be removed.

I am new to mechanical design, so any advice and suggestions are very welcome.

The clamp idea I had was with the idea that all 3 would be permanently attached, but would give you the option to slide down below the spindle and clamp in place via a little lever, either the pick and place or solder dispenser when needed.

I think what you're suggesting is actually sliding the rail in each time, so that's not what I was thinking. I was thinking of two blocks each, but inexpensive ones, perhaps even MGN12 for the solder and pick and place, with a clamp on each, I bet you could modify a block yourself to add a clamp.

Yes, you can accidentally knock ball bearings out of your bearing blocks if you don't slide them in perfect, so probably you don't want to do it every time.

If you are going to do it this way, I would think one or two small screwless machinist vises mounted to the Z plate would be better. Just put your pick and place or solder dispenser in the vice and clamp it in when you need it. You could still have a plate at the bottom to help align it, but there is no need for a rail if you plan on taking it out each time. A vise and some quick disconnect wiring would be better IMO.

I guess I understood your suggestion correctly but changed it a bit to reduce cost because it required 2 new linear cartridges + clamps. These four would approximately cost around £250 based my findings.
https://www.mooreinternational.co.uk...Grp/MGN_Series

Cost of cartriges above is around £25 which is fine. I could not find any clamps under £90 however which is is too expensive. It is great if you could point me to a reliable supplier who got these for lower prices if you know any.

I will also research about screwless machine wises as it sounds like a good idea.

Thank you for the advice!

If I can depend on the weight of pickNplace module and solder paste dispensing module, I really don't need an expensive clamp. The machine you mentioned in the previous thread uses weight.
In this case all I need is a simple non precision clamp to hold extensions pulled to the top when not in use. A spring loaded clamp that has a slider to release would be enough. This also has the advantage that I can just use normal electrical connectors.

I was actually talking about the cheapo ones available on EBay, not genuine HiWin, and modifying two of them by drilling and tapping a hole in the top with a simple turn screw mechanism. As these aren't spindles, and wouldn't actually be providing linear motion when the machine is in use, I am guessing the cheapo generic ones would be just fine. Actually I'm thinking about using them on a 3d printer.

In retrospect, electrical quick disconnects = a couple of plugs, not a big deal, and the easiest thing you could do would be to drill some aligned holes and use a couple threaded pins (which you could make from long bolts that have an unthreaded area) and a couple of wing nuts. There. That would be simple and cheap. A couple of wing nuts and plug it in when you want to add the pick and place or solder dispenser. For the amount of effort that it will take to get everything working correctly, like the rotation of the pick and place, etc, it might be worth it to spend a bit more money and make it like the one in the video. The idea of having it spring loaded in conjunction with linear rails could also work.

Although I am building this for my self for now, I have a remote idea of selling these machines with a custom software if things work well. Therefore I would like to stick with source-able fairly good quality components. If I can get this spring loaded clamp working, I guess all is good even after considering the cost.

Thank you for your advice again.