Ideas on upgrading my mill to be more rigid

[johntech]

Hi Guys

Here are 3 pictures of my mill. The problem I'm having is the flex in the X axis front to back is enough to move the cutting bit by 1/4" by hand. For wood or plastic
it does ok but still moves a little.

By looking at the pictures, can you see any changes that I can make to stiffen up the X axis? Are the rods too close together? The machine is all aluminum
frame and weighs several hundred pounds or more. O bought it preassembled and ready to run. A few minor things were broken in shipping that have been
fixed or replaced.

Any ideas or suggestions are welcome.

John Frankforther

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[Bl@ckrat]

id say you need to change to supported rails ....

you will be amazed how much better thk rails will make your machine ...

[johntech]

Do you have any drawings or pictures I could look at to give me an idea what I need to change? Will I have to rebuild the entire X axis?

Thanks for the information!!

John

[cgo]

I agree supported rail could help.

Heres one type of supported rail I found on ebay, you will probably find out you need to replace x,y and z if there all unsupported.

Linear Bearing Slide SBR16 6 Supported Rails 12BLOCKS | eBay

This is another type of supported rail, but the prices may shock you.
SS15AL 370mm Used NSK Linear Guide Bearing LM THK SSR15XW CNC Route 2RAIL 4Block | eBay

[johntech]

So if I were to purchase these Linear Bearing Slide SBR16 6 Supported Rails 12BLOCKS | eBay, how would I mount them from the pictures I have shown?

John

[cgo]

You would need to have/or machine the blocks that are on the machine now (the part with the switches on it) or make a new one.
Looks like theres enough material to machine pockets out for the new bearings?

The plate behind (the plate below the 2 guide rails are hovering above) would also need precision drilled and tapped to fasten the new supported guide rails to it.

Would also point out that you will need to have the rails in the right length to match your machine.

[johntech]

You would need to have/or machine the blocks that are on the machine now (the part with the switches on it) or make a new one.
Looks like there's enough material to machine pockets out for the new bearings?

The plate behind (the plate below the 2 guide rails are hovering above) would also need precision drilled and tapped to fasten the new supported guide rails to it.

Would also point out that you will need to have the rails in the right length to match your machine.

So what you are saying, in the above picture, I would remove the original X axis support rails and mount the new support rails onto the back of the plate that ties the 2 sides together? Then I would have to figure out how to attach the spindle mount back on the new rail guides. Correct??

John

[cgo]

Yes, that is where the rails would go.

The red arrows you would remove ( current linear bearings )
The blue arrow is the part that will need machined or replaced so that 4x new linear bearings would go in place of the original bearings.

[Bl@ckrat]

I agree with cgo :-)

However , you must measure the diameter of the rails ... Those rails look like they are either 20 or 25mm ??

I wouldn't replace them with anything smaller than the diameter that's already on.

Before you click the buy button john , let is know what your plans are so we might be able to help you make more informed decisions

[johntech]

Well my initial reason for buying this mill is because it showed videos of it milling aluminum. That is not the only thing I'm going to use it for. I have used it on wood and plastic but have noticed the flexing more lately when I tried to mill out the chassis of my model train. Most of the milling will be for my model trains. I noticed the flex more so when I was trying to mill out a section of my engine frame and I had to go over the same section several times, without changing the depth, to get the depth I needed. I was taking very shallow cuts and noticed when the bit left the material it would slightly "spring" back into the non loaded position. It took almost 2 hours to remove 1/4" of material. As I mentioned before, this thing weighs 200 - 300 lbs and made of heavy aluminum so I thought it would be good for milling small stuff. Now I'm not so sure that I didn't waste my money on it and maybe spent a little more for something better. But my first mill was only $500, made of heavy PVC sheets and it cut wood and plastic accurate enough for some of the small stuff I was learning to make. Now I need to make some larger parts, which this one is 2' x 2' table which will allow me to make what I need.

Now finding out that I may need to re-engineer the darn thing to make it do what I need kind of bums me out for the money I already have in it. I am glad that you guys are willing to help me out. I was ready to sell it or scrap it out and take the losses. The other problem is I don't have the tools available to do the precision milling I need to fit ne rails to this. I just hope someone sells rails to fit this machine or cut to fit.

I greatly appreciate any help you can share before I scrap this thing or sell it.

John Frankforther

[cgo]

Maybe with some creative steps you can do everything with that machine you want. What I am talking about is the methods you use to cut different materials and within the limits of your machine.
This is done even on larger or better made machines to improve accuracy, steps like roughing and finish cuts. Could be as simple as using a band saw to trim away material so that you only need to cleanup the surfaces, or a drill press to remove bulk material out of the center of a pocket cut. Can even use a roughing cut with the router itself and then go back for a finish cut.

If you go though some of the builds in this forum you will see people retro fitting cnc parts to manual machines, they add parts that end up costing more than the machine does.
Most of the router builds Ive seen are one offs but Im sure theres a few people that upgraded a machine similar to yours.
If you do take this path then just dont go too far, such as trying to put a 3hp router on a 500watt machine, thats throwing away money.

Your machine could be made better and it does look like a good start if you decide to upgrade it.
If you dont have access to a machine shop you could try to find a local shop that maybe reasonable and willing to help you upgrade your machine, and if your good with blue printing and layouts you could do some of the work yourself.

Lastly I cant tell what that router is able to do even without flex (Ive probably seen that video), you would have a better idea after using the machine.
Obviously selling or scrapping is the worst case, then getting something to replace it with, without actually looking the machine over and up close, I wouldnt want to say anything to influence you either way.

[johntech]

cgo

Thank you for your input!! As far as the X and Y movement, the machine is fairly accurate. I have cut bearing inserts to a snug fit in PVC and other plastics with no problems. It's just when I need to do a little bit of Aluminum milling is where the machine fails. I currently have a 48 volt dc motor for the spindle but in the video they show a Dewalt or similar router mounted on the machine doing the milling. So maybe just stiffing up the flex in the X axis will be ok for now and maybe upgrading to a better spindle motor. I mean with the spindle I have now, about 8K rpm is tops. That's what you get for a free add on..... I think I can handle getting the new rails mounted and I'm pretty handy at making things, it would be better if I had the right tools to make the parts. I'll have to talk to the maintenance guy at work to see where they get their custom parts made. Maybe it won't be that expensive to get a few custom parts made.

John Frankforther

[UA_Iron]

While linear bearings would be an improvement over your current setup, they won't solve your problem completely. You need to add material perpendicular to the cutting forces, then it would help to box in that profile to stiffen up the gantry against torsion/moments.

Replace that floppy center aluminum plate with an aluminum rectangular tube section
Aluminum Supplier | Aluminum Supply | Industrial Metal Supply

Get that rectangular section ground flat on both sides

Use a linear bearing
NSK LS25AL 1250L Used LM Guide THK SR25W Linear Bearing CNC Route 2RAIL 4Block | eBay
(I'm a fan of NSK over THK, but probably just preference)

You'll want to reconfigure your ball screw and rail setup - probably would be best to have it on the same side as the z-axis instead of cantilevered over like it is. Like this guy:
http://www.cnczone.com/forums/diy-cn...yy-budget.html

Beef up the side supports of your X-axis - they appear to be the same aluminum plate as the X-axis.

You'll be adding weight, make sure that it's within the power budget of your drive system.

[johntech]

UA_Iron

Thanks for the suggestions.... What size rectangular tube section would you suggest? I can post measurements of the machine or if I can find the link, point you to the Site where I bought it. Here: KL6060 Desktop CNC Router with 3 Stepper motors | Automation Technology Inc

They have a forum on here And several people have had the same issues with poor workmanship and design of this machine. Since there was a problem with things being broken during shipping, I had to fight to get it fixed on their dime. Since then they will no longer answer my emails or phone calls. All water under the bridge now..... So the only way to get this into a worthwhile machine is to upgrade it myself.

So any help along the way in what to do to fix it and what materials to use will be helpful. I talked to the maintenance guy at work today and he gave me the name of a machine shop they work with. He said they are reasonable and just down the street from where I work. So if I need anything machined I can go there!!



John Frankforther

[wizard]

Well my initial reason for buying this mill is because it showed videos of it milling aluminum.

Unless you are focused on thin sheet metal a machine with unsupported rails is not suitable for machining aluminum. This has already been pointed out but I thought I would highlight it again. If you intend ay amount of serious machining of aluminum you need to consider either a new machine or an extensive rebuild of this one.

That is not the only thing I'm going to use it for. I have used it on wood and plastic but have noticed the flexing more lately when I tried to mill out the chassis of my model train. Most of the milling will be for my model trains. I noticed the flex more so when I was trying to mill out a section of my engine frame and I had to go over the same section several times, without changing the depth, to get the depth I needed.

Realize that all machines flex and are subject to the same physical forces we have to live with such as gravity. However if you can see the deflection in this machine that is a pretty significant problem.

I was taking very shallow cuts and noticed when the bit left the material it would slightly "spring" back into the non loaded position. It took almost 2 hours to remove 1/4" of material. As I mentioned before, this thing weighs 200 - 300 lbs and made of heavy aluminum so I thought it would be good for milling small stuff. Now I'm not so sure that I didn't waste my money on it and maybe spent a little more for something better. But my first mill was only $500, made of heavy PVC sheets and it cut wood and plastic accurate enough for some of the small stuff I was learning to make. Now I need to make some larger parts, which this one is 2' x 2' table which will allow me to make what I need.

More details on your current machine would help as we can't see much from the pics. The problem you may have is that you may need to rebuild more than the gantry to get the results you want. It may come to the point that you need to or end up building a completely new machine.

Now finding out that I may need to re-engineer the darn thing to make it do what I need kind of bums me out for the money I already have in it. I am glad that you guys are willing to help me out. I was ready to sell it or scrap it out and take the losses. The other problem is I don't have the tools available to do the precision milling I need to fit ne rails to this. I just hope someone sells rails to fit this machine or cut to fit.

There are ways around needing to mill some parts or you can simply find a local machine shop to help out. Beyond that you may be able to get to the point where You have the machine rebuilt good enough that you can use it to machine parts for itself or a new machine.

I greatly appreciate any help you can share before I scrap this thing or sell it.

John Frankforther

I don't want to mislead you, you could have a lot of work ahead of you! Most likely the gantry is only part of your problem. Are the other axis riding on unsupported rails? Honestly before you make a decision one way or the other I'd suggest reading this entire thread from here back through 2013 to get a feel for what is involved in such a rebuild. You should also get a feel for what is required mechanically to make a machine rigid.

[wizard]

UA_Iron

Thanks for the suggestions.... What size rectangular tube section would you suggest? I can post measurements of the machine or if I can find the link, point you to the Site where I bought it. Here: KL6060 Desktop CNC Router with 3 Stepper motors | Automation Technology Inc

There was an excellent thread a few months back, which sadly I can't find, which in part went into depth about gantry beams and linear rails. One guy commenting obviously had a strong engineering background and even posted a few spread sheets. Unfortunately I can't find the thread at the moment, it should have been made a sticky as it has some great information in it. <<<<--- Whoops scratch that, fine tuned the search request and came up with this: http://www.cnczone.com/forums/diy-cn...thickness.html. It is a very informative thread

In any event consider how much clearance you expect to have under that gantry to the end of the cutter. A rough way to figure out beam size is to take that dimension and implement a square beam of that size. So if you expect six inches of clearance under the beam then you need to consider a beam of six inches square. A machine of 2 ft by 2 ft though isn't really a long span to cover so that might be an excessive rough figure for a wood working machine. If you want to machine metal though it is pretty hard to have to much mass or material.

They have a forum on here And several people have had the same issues with poor workmanship and design of this machine. Since there was a problem with things being broken during shipping, I had to fight to get it fixed on their dime. Since then they will no longer answer my emails or phone calls. All water under the bridge now..... So the only way to get this into a worthwhile machine is to upgrade it myself.

Does this manufacture have a name or do you prefer not to say?

Note that a machine may be perfectly suitable for one set of uses and terrible for another. When it comes to machining metals, even aluminum, I would suggest that many manufactures and even owners over state how well their machines handle machining aluminum. You can machine aluminum with a router based on a Dremel if you really wanted too. But I don't think anybody seriously would suggest such a machine for what most people consider to be milling operations. In any event it appear that you expect to be doing milling operations on your machine, that takes a substantial machine.

So any help along the way in what to do to fix it and what materials to use will be helpful. I talked to the maintenance guy at work today and he gave me the name of a machine shop they work with. He said they are reasonable and just down the street from where I work. So if I need anything machined I can go there!!

John Frankforther

Having a local machine shop that is reasonable is a good thing as it frees you up design wise. Basically you can have anything you may need made but remember one thing, what is reasonable to a guy keeping a plant running may not be reasonable to you. Also if you expect reasonable work and costs you will have to do the design work yourself. if the machinist has to figure out what you want or need expect costs to balloon. Also it might pay to find out what this shops capabilities are.

That being said much can be done that doesn't require a machine shop. As you read though the threads here you will find that there are some interesting solutions out to be had.

One thing to consider here is that you can improve the gantry but that is the top of the stack so to speak. So consider starting your rebuild from the ground up even if you need to do a little at a time. I'd start with the fabrication of a robust frame for the base of the machine to mount your X-Axis on. (by the way I'm calling the axis on the gantry beam the Y-Axis). Depending upon your funds you could drop the gantry you currently have on top of this base to get by until more funds come in or redo the machine completely in one shot. I just think from a machine tool building back ground that it makes more sense to get your base structure right first. In this regard you will want a strong rigid frame to mount the linear rails to support your gantry.

[johntech]

Wizard

Thank you for the links and the information. I did post a link to the machine I purchased and the company is Automation Technology Inc. As far as milling the Aluminum, I wasn't planning on high speed milling like you would see in a typical machine shop. For the piece of my model train frame I was milling, the size I was trying to cut was 1" long by 1/2" wide by 1/4" deep. A standard mill would have probably cut that in 2 passes. Since the spindle I got would only hold 1/8" bits and ran a max of about 8K, it took over and hour to cut. I have seen lots of videos of homemade cnc machines cutting thick plates of aluminum but that is not what I'm looking for. I just want this to cut small pieces or trim down parts with out taking forever. Most of the milling will be wood and plastics but I would like to do small things in aluminum if needed. If I could have done the above cut in 15 - 20 minutes that would have been fine. If I get a chance I will try and get pictures of the frame and rails under the machine so I can find out if this is worth pursuing any further or just selling it and take my losses.

If I can make this work without too much more expense, I would at lease like to put a better spindle on it. Maybe a water cooled one if it would handle it. I mean basically I have a 48 volt DC motor with a 1/8" chuck on it. I don't even know what the run out is on it. As I mentioned in my previous posts I have cut wood and plastics with reasonable accuracy. Here is a rotary coal dumper that I designed from scratch and milled to fit my American Flyer trains. I think that only took me about an hour to mill the front and back sides. I didn't "push" the bit too hard because of the flimsy spindle would get hot!!



SO If I could upgrade this to hold a better spindle, stiffing it up to the point it doesn't flex or the flex is much much less that the 1/4" I have now and doesn't cost the price of the original machine then I would probably pursue the upgrade.

[johntech]

Here are a few pictures of the Y axis lead screw drive and the right rail.


The Y axis drive lead screw


The Y axis drive lead screw and the right rail


A closer view of the right rail.

After talking to you guys, it looks like the base of this machine is kind of beefy, IMHO!

So maybe all I need to do is rebuild the X axis to make it stiffer!

What do you guys think, is it worth pursuing this project??

John Frankforther

[dbsharp]

The best thing you could do for this machine is to scrap the linear bearings it has and look on ebay for some thk rails or similar. You will need to check the mounting height so that everything will fit, the bearing spacing is gonna limit rigidity even if you have really good bearings. Expect to have to add holes and possibly counterbores for the bolts. You might have to have some adapter blocks machined for the x axis.

You want something like this:

[johntech]

Hi Guys

Just a quick update on the mill situation..... It seems the cheap lead screw bearings AND the cheap couplers have decided to turn to junk also!! I was milling a plastic game box for my son and I started hearing a clicking sound. It seems that the cheap bearings and motor couplings can't handle .125 depth cut in plastic at anything over 20 ipm!! So it looks like I will be rebuilding from the ground up!! Heavy duty bearings and motor couplers are on order so I can start redesigning for them.

John