Custom Production CNC design


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    Default Custom Production CNC design

    Hopefully this is an appropriate section to post this! However if it would fit better in another sub forum please feel free to move.

    I am looking to design(and hopefully build) a completely custom CNC vertical machining center that would have very specific and specialized purpose. This machine would be used in a production environment and be running at least 10 hours a day 5 days a week if not more and would optimally need to be operable via a few basic control buttons(i.e. Start, Stop, E-Stop). Obviously it would need standard CNC controls/interface for machine setup, switching from one part to another and maintenance, but my point is that it would need to be able to basically run the current program over and over at the push of a button. So the operator would open machine, remove last part, clamp new part, close machine, hit run, maybe work on secondary operation while program runs and when program finishes, inspect part and repeat.

    I am leaning toward a VMC because for me it is what I am most familiar with and seems like it would be the best fit but I would be open to something like water jet etc. if it was cost effective and meets the needs of the operation.

    The basic operation that I am trying to automate is the rough cleanup and removal of Non-ferrous sand castings from the 'tree"(all of the parts of the casting that are not the actual part).

    In the sand casting process, after the mold has cooled and the 'tree' has been removed from the sand mold, it is run through a Wheelabrator/shotblaster to remove most of the sand and then the individual parts are manually cut from the tree using an abrasive disk. After that, the individual castings are ground by hand to remove the 'gate' (part that connects the individual part casting to the rest of the casting tree) and any flashing or casting defects. Last, the cast parts are run through a vibratory tumbler and polisher before they go to machining or assembly.

    Because this process is so labor intensive I would like to design a CNC that one would basically clamp the casting tree into and the tool would go around the part cleaning up any flashing, then cutting the gate off, removing the part from the tree. My thought is that any holes that need to be drilled could also be drilled at this time and in fact almost any rough machining needed could be done at this time as long as the part is oriented properly.

    The reason I am posting this here is that I would like any advice on the general design and layout of the machine, any suggestions as far as what components to use and in general, how realistic this would be to build?

    Also just for a sense of scale, the mold size is roughly 2'x3' and 6" to 8" deep at extreme so that should give an idea of the size of the table and movement of the Z.

    Thanks in advance for any reply's!!!!!!

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  2. #2
    Registered Jim Dawson's Avatar
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    Default Re: Custom Production CNC design

    From what you describe it sounds like any appropriately sized VMC would work. As you stated a water jet might be an option, as might a laser or plasma torch. Any CNC controller would do exactly what you want as far as press GO and run.the part. As long as you can reach all of the areas that you want to machine vertically, then a 3 axis machine would work fine, if not then adding more axes might be in order.

    You would still have to run the tree through the shot blaster to remove the sand and other dross. I think the biggest challenge would be fixturing the tree. If you are going to use a rotary cutting tool (milling cutter), the the fixturing and clamping would have to be substantial to overcome the cutting forces. The parts would have to have some provision that would facilitate clamping, maybe to be removed in a subsequent operation. The individual parts would each have to be clamped in the fixture, and this will require that the tree is very consistent. There are all kinds of manual, pneumatic, and hydraulic clamping devices available. And it's practical to build your own clamping devices in some cases. The degree of sophistication and automation depends on your budget for this operation.



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    Default Re: Custom Production CNC design

    How many, how long is the run?
    How heavy is that casting? what material?
    What is the tool design and fab budget?
    ( Fixturing is identical to forgings, no problem)
    Calculated run time? between operator intervention?
    How about a HMC with pallet changer? Load and run simultaneous.
    An HMC has a chip conveyor.

    Load and push green button, simply done

    Been doing this too long


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    Default Re: Custom Production CNC design

    Yes, figuring out how to fixture and consistently get the individual parts on the tree to be in the exact right place every time is what I expect to be the biggest challenge. However this is an issue that comes up with every proposal to automate this process, so it is not a deal killer.
    We have looked at and been quoted on a few different commercially available systems that are available and designed specifically for this operation, but the initial investment in the equipment is mind blowing($300-$500k) and on top of that the cost of the specific tooling($10-$30k) needed for EACH individual part (pattern) is what really makes these solutions cost prohibitive for a company like ours.
    Obviously we could just buy a new VMC or convert one of our older ones, but after spending a good amount of time learning about CNC and working on and building my own machines I feel like I, along with other engineer’s etc. that are familiar with the details of out parts and manufacturing processes can design and build a machine that would as well or even better at a fraction of the cost.
    My thought is to come up with a way to fixture and locate the individual parts on the tree using some sort of universal feature on the tree. This feature would have to provide a way to clamp the part/tree so that it won’t move during marching, plus it would have to locate the part so that it is in the exact right place so the cutter only removes the unwanted material.
    I am also looking for input on specific spindles, motors, linear bearings and control boards that would be appropriate for the specifics of this build.
    As far as a budget, at this point I am really in the design proposal stage and I would kind of like to give a couple different options based on cost. So maybe a very low cost, med cost and top of the line option but the general idea is to make custom machine at a fraction of the cost of production made machine. With the little knowledge I have I was roughly thinking we could get there somewhere around $10 grand, but again that is just a big shot in the dark.
    Thanks Again
    Alan



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    Default Re: Custom Production CNC design

    Alan, unless this is a secret project, can you show us the problem part.?
    Are there "datum reference locating pads" built into the casting?
    (design change for manufacturing.)
    Sand or permanent mold?
    I have done many forgings with success.

    Noticed this was under engineering on the forum,
    Are you the decision maker for the boss?
    If so, with more info, you can do this waaaay under those estimate$.
    Show the part, us machinists / tooling guys are visual

    Been doing this too long


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    Registered Jim Dawson's Avatar
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    Default Re: Custom Production CNC design

    Back in my die casting days we used trim presses to roughly clean up the parts for subsequent operations. Basically pressed the part tree through a die with the shapes of the individual parts in it. This trimmed the parts and removed all of the excess material.

    Something like this Used 50 Ton B&T Trim Press No. 3878

    Last edited by Jim Dawson; 07-15-2017 at 12:09 PM.


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    Default Re: Custom Production CNC design

    Yep, there were always two dies one to form, one to trim-off look at a alternator housing edge where the ragged parting line exists.

    Been doing this too long


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    Default Re: Custom Production CNC design

    Let me try to answer some of the questions but first let me say that I am consistently surprised by the incredible willingness and true ability of members of this forum to respond to posts like mine with real well thought out and knowledgeable responses, regardless of how knowledgeable or green the original poster seems to be. I really look forward to using this forum as one of my go to resources as I start my new job.
    This also leads me to try to answer one of the questions below and clarify where I am coming from and why I am asking these questions. Also this next paragraph gets in the weeds a little so if you are just looking get the details about the main question you can skip it.
    “Are you the decision maker for the boss?”
    Here is the situation. This is a family owned and family run business. My grandfather actually started the company 50-60 years ago and after he passed away in the mid 90’s my mom took over with ZERO prior involvement and basically pulled a manufacturing business back from the brink and into the 21st century. Although at the time it was consistently chugging along and being fairly profitable, as anyone in manufacturing and especially the FOUNDRY business knows there was a cliff coming and those who didn’t make drastic changes in the way they did business done would not survive. We found a way to survive and thrive despite the massive amount of exact copies(literally exact copy’s as one of my grandfathers trusted executives was secretly working with a Chinese importer to bring in their own version of our product line) of our products coming in from China for pennies on the dollar. So basically with the use of diversification and innovation my mom has brought the company through the past 20 years, but now it’s time for her to start removing herself from the day to day operations so she can eventually retire and spend time with my kids and do the things she wants to do. I have been involved with the business my whole adult life, but do to an assortment of disagreements, personal issues and typical problems found within family run businesses I left about 5 years ago when my son was born. Now that my mom is trying to phase her day to day involvement out we are trying to find a way to bring me back into the business without just installing me in a position and creating a situation where the existing employees, who are a very trusted, valued and integral part to the business, feel like their position is threatened. In the past I have been deeply involved in process improvement and looking at how parts are made then trying to think outside the box to streamline and eliminate operations. Due to the fact that I am going to school for mechanical engineering and that I have been working with and learning about CNC for a few years now one of my first projects it to design and propose a solution to the manual cutoff and grinding of the rough cast parts.
    So to actually answer the question, I will not be making the final decision 100% myself, but I will be doing the research, design and creating the proposal and depending on what I come up with playing a big role in making the decision along with other engineers and decision makers.
    So let me try to answer some of the other more specific questions.
    “How many, how long is the run?”
    This would become the standard way of processing the majority of production castings obviously with the exception of custom castings with small or short runs. I don’t have exact current numbers but we are talking hundreds and hundreds of thousand of castings a year.
    “How heavy is that casting? what material?”
    White bronze, Red Bronze, yellow bronze and some Aluminum
    As far as the weight of the castings, once again I don’t have exact numbers but the majority of the individual castings are between 1/4lb and 1lb with a few weighing between 1 and 5lbs but the large volume is less than 1lb.
    ”Are there "datum reference locating pads" built into the casting?”
    No nothing like that built into the parts or casting tree, BUT I am fully expecting that this processes is going to require modification of the existing tooling to make it work.
    “Alan, unless this is a secret project, can you show us the problem part.?”
    Its not a secret project, but it is not just one part. This would apply to the majority of production line which is widow and door hardware with the large volume production being focused in the window hardware so you have a handle casting and then the ‘base’ casting which the handle operates on and mounts to the window.

    Just one more note to the poster that mentioned using presses to trim the castings. This is one of the options and in fact one of the process improvements that I played a part in implementing years ago. Although we don’t use the press to remove the casting from the tree we use it to clean out the mounting holes and trim the casting so that it is consistent.
    In fact one of the commercially available systems for doing what I am trying to accomplish here with a CNC uses this same concept but on a much larger scale, but the press itself is extremely expensive and then the dies, some of which as the poster mentioned are multi staged, are just too costly to be considered with such an extensive product line like ours.

    Hopefully this gives a little better understanding on what I am looking for and what the parts are I am working with.

    Thanks Again
    Alan



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    Registered Jim Dawson's Avatar
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    Default Re: Custom Production CNC design

    Quote Originally Posted by JnkYrdCNC777 View Post
    I am also looking for input on specific spindles, motors, linear bearings and control boards that would be appropriate for the specifics of this build.
    As far as a budget, at this point I am really in the design proposal stage and I would kind of like to give a couple different options based on cost. So maybe a very low cost, med cost and top of the line option but the general idea is to make custom machine at a fraction of the cost of production made machine. With the little knowledge I have I was roughly thinking we could get there somewhere around $10 grand, but again that is just a big shot in the dark.
    Given that this machine will have to run reliably in a high production environment, it is going to have to be built heavier than the hobby class machine that your budget would indicate. Since you already have VMCs available, that would be the place to start. Building pallets of tooling specific to the the individual product trees would be the way to accomplish what you want. Then just load the pallet on the machine, load the parts and program. I suppose you could purchase a used industrial grade router and accomplish the same thing, but these are typically more expensive than used VMCs. To get the robust systems that you will need for this machine, buying new components is out of the question given your proposed budget. Your money would be better spent on the tooling side.

    The biggest challenge is going to be building the fixtures for the parts because of the volume of different products. Maybe it's possible to make changes to your patterns to make them more ''universal'' to facilitate fixturing. The downside of doing this is that it is going to require a massive retooling effort on the front end. I just don't see any way around expensive tooling costs either on the front end or the backend.



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    Default Re: Custom Production CNC design

    Nice Topic, Thanks for sharing your thoughts



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    Default Re: Custom Production CNC design

    I assume these parts are heat treated / artificially aged while they are still in the tree? I'm guessing fresh aluminum casings will be pretty gummy to machine.

    Quote Originally Posted by JnkYrdCNC777 View Post
    Also just for a sense of scale, the mold size is roughly 2'x3' and 6" to 8" deep at extreme so that should give an idea of the size of the table and movement of the Z.
    Quote Originally Posted by JnkYrdCNC777 View Post
    Obviously we could just buy a new VMC or convert one of our older ones, but after spending a good amount of time learning about CNC and working on and building my own machines I feel like I, along with other engineer’s etc. that are familiar with the details of out parts and manufacturing processes can design and build a machine that would as well or even better at a fraction of the cost.
    I'm not understanding what's going on here. You already have an older VMC? With the travels you need? What kind of conversion is required other than to come up with the appropriate fixturing? Perhaps if we could see some Cad files or photos that could help us understand? It seems like a no brainer to me to use an existing machine that you already have, so clearly, I am missing something. Sounds like a really interesting thing that you're doing, though. Wish I could come and work at your factory and help you sort it out.

    Quote Originally Posted by JnkYrdCNC777 View Post
    With the little knowledge I have I was roughly thinking we could get there somewhere around $10 grand, but again that is just a big shot in the dark.
    It's doable for that budget, depending. Steppers or servos? Ballscrews? It really depends on the components. Good linear rails, let's say $1300, Ballscrews and bearings and mounts, 1100 (that would get you Chinese ones, based on my build, good quality mounts and bearings already cost me over $500, that leaves 600 for ballscrews, ballnuts, ballnut housings, couplers), Steppers, good quality drivers, a board, control software, a computer, cables, $2000, servos would be more$$. So really, that's $4400 so far, so for the remaining budget, well, a good quality HSD ATC spindle is more than that, so you're looking at something else. How frequently would you want to do tool changes? If it was just a matter of cutting the parts from the tree, we could probably come up with a different solution, but you want to do machining on the parts also? An compromise solution could be a jig run on linear rails or even a two axis machine that just cuts the parts from the tree.

    You mention that you are a mechanical engineering student? well, that will take most of your time. You can't do that and run a business. How much is your time worth? Listen, it's easy to mess up on DIY CNC designs. If you do, boom, money and time is wasted. Plus, are you going to be making this, or is an employee on wages? The time factor is a big component to cost. This will take alot of time to make from scratch.

    So you have a factory, and factory power, can you find a used Biesse router? They can cut aluminum pretty well, you could load up a dozen trees and cut them at once. Seriously. Think of some better options.

    In order to give you some better advice, I'd need to see the parts and know exactly what you want to do. Other than perhaps a jig, that is manually operated, or a two axis machine running a cutoff wheel, the idea of building your own, in order to keep the business running profitably is problematic. There are too many ways to waste time and money doing it this way. The design and execution would need to be perfect.

    If you can give some more info, I am happy to think of better ways to help you out, if I can. Right now, my best advice is DON'T. Find some good used machinery and adapt it, or think outside of the box. I am happy to think outside of the box with you, but like I said, I don't have enough info.



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