Small Composite Router Build 1000 X 600 X 300

[routalot]

Isn't it the case that Boeing are now using composites for more and more of their aircraft?It needs to be used with respect for it's properties and can be added to comparatively easily if more stiffness is needed.

It is a little monotonous reading accounts of the planning of machines intended for wood,plastics,alloy -oh and maybe some steel too.The whole forum is littered with those and really it would make more sense to buy a new Haas or retrofit a Bridgeport (or clone) if steel is likely to figure in future plans.

[MachineRising]

I may start a new thread. The machine has experienced extreme design and cost creep. What started out as an exercise in building an inexpensive "good enough" machine, has turned into several thousand dollars.

I saw a Shop Bot on Craig's List the other day for $5000. I think the guy has excessive expectations, but it did serve to provide a baseline for cost verses capability.
The latest machine is 1500 X 1000 X 500. It will include the original concept I mentioned in another thread, to include a 4th Axis. It will be constructed of various types of sheet goods, including Aluminum, FRP, Wood Cores, and Advantech, which is an engineered wood composite with some pretty radical properties.

So far spend an extra 300 or 400 dollars on things I don't need in this build. Maybe will be able to use some in other projects.

[MachineRising]

LOl are you saying I should shut up and just build this thing? I tell you this last couple of weeks has been full of surprises, and most of them have been very costly.

[routalot]

I would say go small,allow for upgrades if,or when, the machine fails to do what you need.Be sensible about what you really need and maybe send the bigger jobs to a pro with a big machine.Make some parts,get some experience and then use that experience to guide your future plans.

[Arjay]

Isn't it the case that Boeing are now using composites for more and more of their aircraft?

They've been using it for over 30 years. The tail section of the 777 was composite. The 787 structure was nearly all composite.

[wizard]

I may start a new thread. The machine has experienced extreme design and cost creep. What started out as an exercise in building an inexpensive "good enough" machine, has turned into several thousand dollars.

Many of us are very interested in new ways to build machine tools. There was a thread about a year a go that seems to have petered out exploring such a build. The problem for many of us is that we have no real experience with machine constructed this way. I've worked on more than a few epoxy granite machines which are a composite of a different type but they have nothing in common with what you propose.

My biggest problem here is that you have a tight time line and frankly I don't see it happening. If you go with a steel structure you are likely to be able to engage the help of any number of local machine shops to get things done in parallel. Even if you did it internally and had to hire a machinist there would be less effort needed to get him productive on the build. In a few days you will have aobut one month of build time left.

I saw a Shop Bot on Craig's List the other day for $5000. I think the guy has excessive expectations, but it did serve to provide a baseline for cost verses capability.

If the timing is right used machines can be huge bargains. Even so a Shop Bot is a lighter weight router which may or may not fit your needs.

The latest machine is 1500 X 1000 X 500. It will include the original concept I mentioned in another thread, to include a 4th Axis. It will be constructed of various types of sheet goods, including Aluminum, FRP, Wood Cores, and Advantech, which is an engineered wood composite with some pretty radical properties.

Sheet goods just expand your build times. I'd lean towards steel tubing or aluminum extrusions simply to get the build underway as fast as possible. I'm wondering just how hard is your February start of production, because right now I'd be focused on machine components that reduce my need to fabricate anything.

So far spend an extra 300 or 400 dollars on things I don't need in this build. Maybe will be able to use some in other projects.

Or just sell them.

[MachineRising]

It has evolved.

[peteeng]

Hi MR - Are you going to make moulds for these parts? Aluminium or steel is the stiffest and cheapest source of stiffness you will get. If you use fibreglass for instance it will be difficult to get to half the stiffness of aluminium. I'm involved with a project at the moment and we made FG parts in an autoclave and got to 30GPa which is less then half the stiffness of Al. These were for a structure that requires high voltage insulation so FG is the go. If you infuse FG you will get to 20-30Gpa. You can infuse in your garage. If you use carbon fibre and infuse or use autoclave you'll get to 60 or 70GPa which is same as AL. My point is that if you can machine the part out of Al or Steel there is no reason to go to a composite. If the shape is complex, difficult to machine then there are reasons to go to composites. By the shape of the original model is it going to be cast? Cheers Peter S

[MachineRising]

Hi MR - Are you going to make moulds for these parts? Aluminium or steel is the stiffest and cheapest source of stiffness you will get. If you use fibreglass for instance it will be difficult to get to half the stiffness of aluminium. I'm involved with a project at the moment and we made FG parts in an autoclave and got to 30GPa which is less then half the stiffness of Al. These were for a structure that requires high voltage insulation so FG is the go. If you infuse FG you will get to 20-30Gpa. You can infuse in your garage. If you use carbon fibre and infuse or use autoclave you'll get to 60 or 70GPa which is same as AL. My point is that if you can machine the part out of Al or Steel there is no reason to go to a composite. If the shape is complex, difficult to machine then there are reasons to go to composites. By the shape of the original model is it going to be cast? Cheers Peter S

When you compare stiffness there are many aspects that have to be considered. In every case sandwiched construction is lighter and stiffer than uncored structures. The final product is going to be as follows.

The bed will be Advantech Flooring which is dense, stiff, and dimensionally stable. More mass in the base is desirable as it absorbs vibrations.

The bridge will be cored aluminum skinned structures with a total of 1/2' of aluminum skins and 1.5 inches of end grain western red cedar. Some people have expressed concerns about thermal expansion differentials but this machine will be in a controlled environment.
The YZ plate is 1/2 aluminum, and the Z Plate is 1/2 aluminum.

The construction is coming along well. Using aluminum plating for the skins is good, as you all know it utilizes the natural flatness of aluminum extrusions.

We have a lathe, a mill and a shop full of industrial tools. I really have to give credit to people that build theses things in a home garages. You can see why so many of them are built using T Slot extrusions.



I will be posting some pics soon.

[peteeng]

Hi MR - Al skins over timber core is an excellent construction method for stiffness and lightweight. Will be good to see some images. Are you contact cementing the skins on or epoxy? cheers Peter S

[MachineRising]

West System Q Flex Epoxy. West System Used to recommend their aluminum etch solution prier to developing the G Flex products they remove the etch from the market because they achieved 2600 pis adhesion on sanded aluminum surfaces. I've been using West System epoxies since the 90s and have always had good results. They're a little pricey, but worth it.

We have a granite table that we are going to use to vacuum bag the assemblies. I haven't decided if we are going to add a layer of glass under the aluminum, part of my thinking is that the glass will wet out and then retain an even film of epoxy. What do you thick about that?

[peteeng]

Hi MR- I'd not use the glass underneath as it will wrinkle and give you an inconsistent thickness and it does not contribute to the structure. Is the Q flex runny ? I use a runny epoxy as a primer so you can brush, or blade it on thin. Wait until it gets tacky then lay on the sheet. For the application if you have not bought the epoxy use contact cement. Easy to use and cheaper then epoxy. Still vac bag it down though. Don't go full bore with the pressure 50% vac is good for the job. 5T/m2 if you go full bore on vacuum you can bleed all the epoxy out. Peter

[routalot]

When you describe 1/2 inch of total thickness and 1 1/2 inches of end grain cedar,will you be using two 1/4 inch skins?Its normally regarded as good practice in composite work to use a balanced laminate.

[peteeng]

Hi MR - If in interprete the info correctly you are using two pieces of 1/4" plate, one each side of a 1.5" piece of timber. This is equivalent to a bending stiffness plate of 42mm (1.67") see calc attached. The weight of a 42mm plate is 113kg for a meter sq but the composite is 43kg for the alum and 10kg for the board so 53kg for a sq meter which is less than half the weight. So it's very attractive in a bending application. Is this going to be used for the gantry? A single vertical piece? Peter.

[peteeng]

Hi MR - 50kgf is huge for cutting wood. My machine I've measured at 20kgf at stall and its cuts plastic, timber and thin aluminium very easily. Peter

[davida1234]

Great to see this valuable info.

Peter, you say that the proposed layout equals to a bending stiffness plate of 1.67".

I assume an aluminum plate. In that case, wouldn't that be insufficient for a gantry beam?

It is incredible that simple contact cement would be able to transfer all the sheer forces between the skin and core.

Also, you seem to have experience with cored composites.
Would this layout be prone to delamination in a non-controlled environment over time?

Thank you. David

[peteeng]

Hi David - If non-controlled environment you mean in a shed and not in the snow or rain it will outlast you. Good quality contact or epoxy provided its done right. Most insulated panels used on houses are contact, product can't afford epoxy and can't make it fast enough with epoxy. Just seal edges with epoxy or with aluminium to prevent moisture ingress in end grain and glue lines.

Now is it stiff enough?? depends on your beam span and expected load so I've done a quick calc based upon 800mm wide and 50kgf applied in the middle. Plus I assume its 100mm deep. As calculated this deflects 0.12mm which for signage is fine as you won't get to 50kgf. If you use 2x 1.5" in the middle it deflects 0.040mm which is more like you want maybe. Just keep in mind this sandwich is the same stiffness as a 100x100x6mm thick square tube (6"x6"x1/4" SHS) so if this is at your metal dealer you save some effort by buying this vs making it. Unless the design takes advantage of the sandwich somehow or you want a very big gantry that is too big to get as a tube but then it would need to be thin to get the weight down..... 1/4" is a very thick material in my world. Unless you need it for threads. A 100x100x2mm steel tube will be same weight and 3x stiffer as steel is 200GPa stiffness vs Al at 70GPa.

So you do need to think through why you are using the composite... If there us a design feature that you can take advantage of using the sandwich then its good to go... eg thin your skins down to say 1/8" (1.6mm or 2mm in my world) and use 2x1.5" ply or OSB so its still really stiff and use the timber as a thread foundation and your good to go...

Cheers Peter S

edit - here's a discussion on machine stiffness in a UK forum. stiffness measurements cnc mk3 - Page 2

[MachineRising]

When you describe 1/2 inch of total thickness and 1 1/2 inches of end grain cedar,will you be using two 1/4 inch skins?Its normally regarded as good practice in composite work to use a balanced laminate.

Yes both skins will be 1/4" 6061 plate.

[davida1234]

Thanks Peter, great insight.

[MachineRising]

Been distracted, but I'm back . Lost a year.