[Coydog]

I have had some idea of making a CNC wood working router since 2000. I even bought the stepper motor, power supply unit and some XL belt drive.

I made my 1st machine some time last year it had a cutting area of about 15x18 inch. Had a 1 inch emt conduit for X rail the Y and Z was just roller skate bearing riding on the wood. With a 1/4x20tpi threaded rod for the drive system.

It was my first machine. It was slow at 15 ipm for some reason my 269 oz in Stepper will not go over about 300 rpm reliably, because every few minute it will just stop and buzz if I was moving over 300 rpm on the stepper. The machine was not rigid at all. Just from the flexing when I am cutting the head can move up to 1/8 of an inch from the force of the cutter in the wood material. if I forget to torque every thing up tight. and even then at best the cutter give about 1/16 on a cut with 1/4 cutter at 1/8 inch deep

My 2nd machine Is belt driven 2x4 ft cutting area . It is again build from scrap wood. This time scrap from some busted furniture and a 1.5 inch emt Conduit. The machine is faster. Capable of cutting at 80 ipm and rapid to 150 ipm. On this machine I still have problem with flex at the Cutter head with 1/4 bit cutting 1/4 inch deep it has a flex of about 1/32 inch. And it don't give a clean smooth cut no matter what the depth of cut is. It has some chatter mark on all cut.

This will be my 3rd machine. This one will be made with 2x4 lumber from Lowes and Home Deapot instead of scrap lumber. I am not a great wood worker. I might be able to put basic wood deck together but fine wood working is beyond me. With my lurking around CNCZone for the past couple of month to learn what I did wrong my hope is that this one will be stiff and solid enough to give me a clean cut and no chatter mark in my VCarve cuts.

[jhowelb]

From my experience, lumber form the home improvement stores has much water in the wood and will tend to warp, shrink and drive you nuts trying to achieve and keep accuracy.

May I suggest aluminum extrusions? They will cut and drill with the same tools as wood and then you only have to deal with heat exansion.

[Qicker306]

Your design looks good. However trying to maintain tight tolerances and accuracy with 2x4 lumber will be very difficult. Finding a completely true and square 2x4 in an enourmous stack at HD is a challenge in itself. I feel you would be better off by laminating mdf or plywood sheets together for your construction. Evidently you're trying to minimize costs, while plywood or mdf is more epensive than a bundle of 2x4s I'm sure it would be cheaper in the long run than having to build a 4th machine. Your design is very similar to the Joes 2006 design found on this site in respect to the use of conduit and skate bearings, they all use mdf or plywood construction with great results. Best of luck to you on your 3rd machine.

[jckstrthmghty]

I'm also going to recommend not going with building lumber. Even sealed lumber will expand and contract with temperature changes. Over time it will bend and warp. 1/10 of a inch may not be a big deal for a wall or a floor but for a precision cnc machine that is significant. In this case plywood and lumber are far better options. As mentioned metal is the best option.

[Coydog]

I agree with every one about plywood and aluminum It would be nice if I can afford it. But my budget is very very very tight for the new machine. I am reusing the barring, Conduit and Electronics from my current machine.

And yes Lumber store lumber can be CRAP the people at Home Depot and Lowes Lumber department are currently cursing my name. because I took one of there stack apart for 8 piece of 2x4.. got them for $2.15 each Southern yellow pine.

So far I spent $18.40 in lumber and $20 in hardware. and $6 on a bottle TightBound glue.

Tomorrow I start putting the Machine together.. Wish me luck.

[Coydog]

By the way This is a picture picture of the X axis carriage. It weight in at about 30 lb on my bath room scale. and this is the Y axis carriage and the Z slide assembly
Attachment 207162

[Coydog]

This is an example of what i mean by Chatter mark. You can see it in the number 6 The Cut shown is as it come of my old machine before any sanding, except for just enough to knock of the fuzzy. The wood is yellow pine.

[widgitmaster]

What software did u use to create the tool path?
I use VCarve Pro, and it allows editing & smoothing of vectors. This reduces or eliminates all the jagged curves that look like a pixels in an enlarged image!
No mater how sharp the cutter, or how slow the feed, it will follow the abrupt vectors!
Widgit

[Coydog]

Widgitmaster it was done with Aspire and it is from a Vector graphic. The jaggies that you are seeing is as far as i can determine the fault of my machine not the gCode. My machine currently have only 0.02 resolution per step of the stepper motor. That could be part of the problem. But not likely. This is because even cutting a straight line will product this chatter mark on the cut. And it don't seem to matter what tool I use. If the Tool is cutting anything on the side I get these marks. but it don't show up on the z axis. I can use the table and a 3/4 inch bit to face plain a piece of oak it it would require no sanding.. very smooth.. but cut edges always has jaggies.. :/

Note that if I cut a pocket it will be about +0.03 of from expected dimension on regular cut and will be -0.03 off from dimension if I do a climb cut. That why I say its my machine stiffness ? It don't seem to matter much if I am cutting at 80ipm and 1/4 deep or 15ipm at 1/16 deep either That why the new machine I hope to solve this issue.

[CarveOne]

My 1st machine was built from plans that called for 2x4 pine lumber. Knowing how that warps as the wood dries I spent a lot more money and built it with red oak, maybe about $120 worth. Where it called for 2x4 parts I laminated two layers of 1x4, and on the motor and belt drive end where it called for 1x4 I later added a second layer of 1x4 because the single 1x4 was flexing as the machine was operating. That machine worked pretty well after that and had no warping problems. After less than a year I went on to build more machines using steel tubing.

Poplar is less expensive than oak and still has less warping problems because the wood has been kiln dried before the home centers get it. Construction lumber is received still wet from the sawmills. Clear pine has also been kiln dried and would be better than construction lumber. Personally, I would use MDF and even laminated OSB before using construction lumber when very low cost is a requirement. The key thing is to buy dry wood products.

Look at the vectors using Aspire's node editing tool and verify if it has "millions" of nodes and the vectors between nodes are black or blue in color. If all nodes are black the vectors are straight line vectors. If blue they are bezier curves or arcs. The straight lines can cause patterns like you are seeing. Check your acceleration rate in Mach3 (or LinuxCNC) and set it for something like 15 or 20. Your machine may not be able to handle faster acceleration rates without flexing too much.

[Coydog]

Hay CarveOne. The wood I am using is 2 x 4 x 92-5/8 Kiln-Dried Southern Yellow Pine Stud. They were very straight but I destroy a stack just looking for the best of the best.

Currently the 1x4 oak at hardware store is about $20 per board. and I would need 16 board Glued together for total of $320 which is well beyond my budget.

The nodes in aspire are correct. I did not use the Bitmap trace. The curve are hand traced by drawing point to point then Adjust the bezier curve handles to fit. The stuff that is out put by Bitmap tracer in Aspire,Xara, Corel are junk for the most part. Be careful of down loaded fonts too.. allot of them are just not Vcarve friendly and actually are jagged.

In the motor tuning of Mach3 I have acceleration on my X and Y axis at 5 in/Sec/Sec and Velocity at 150 ipm, My Z axis acceleration is at 10in/s/s and Velocity at 15 ipm.

And the machine bounce if I accelerate any more then this due to the Belt. The belt currently has about 150 lb of tension on it. I am going to be using a Belt on belt system on the new machine and Reduce the speed of the motor output of 4.33 inch per motor revolution down to something more reasonable.

The Old machine have a problem with accuracy because the Drive on it has a resolution of about 0.02 inch per step so average accuracy of 0.03 is not bad as far as it go. But it still not very good. The Chatter on the cut make fine detail cut of letters smaller then about 1/2 look very ugly. But For cutting parts that will Fit together it is OK. But I want to do more


Here is an Image of the Old Machine Drive System. The pulley diameter are around 1.4 inch at the belt forgot the exact dim. It is directly driven by the Stepper motor.

[widgitmaster]

One of the fundamental necessities in machining anything is rigidity, the other is repeat-ability. I've been cutting metal all my life, wood is something I started playing with after retirement! Most all metal cutting machines are made of heavy duty cast iron, and have precision dovetail slide ways. The machine's strength is far more than needed for most machining purposes, that's why the parts the machines make, can be made of tough steels and exotic metals!

With that said, I would suggest you put as large diameter pin in the spindle of your machine, and try to move it with your hand. This should show you where the looseness or slop is. Then you can see what needs to be beefed or tightened up!
Good luck!
Widgit

[Coydog]

I did that with my old one. I put a 1/4 inch rod and pulled with a fishing weight scale on it. I pulled in different direction +x -x +y -y cant really pull in the z with 20 lb of pull in the tool end the machine flex about .08 at the tool tip. This is while the machine is on and the stepper motor has locked down. with as little a 5lb of force it already flex to .03. It seem those unsupported 1.5 inch emt conduit are flexing. I will do this with the new machine when its assembled.

I worked in a machine shop in CA back when I was paying my my way trough collage. I know what you mean.

[Trotline]

One thing I'd strongly suggest is to throw out the EMT conduit. That stuff is thin-walled, is welded from strips, and is poorly dimensioned. Electricians don't even bother with power tools to cut it, until you get to the larger diameters. I could easily see it deforming under load. Heavier steel pipe is expensive, in terms of your budget, but you might well be able to scrounge some, if you keep an eye out. Dumpster diving and alley sweeping can yield some amazing results...

Luke

[Coydog]

Well did not get much done today. Finished off the Z axis tool carrier. And Temporary drive system until I get Gear for the Threaded rod drive.

Here the Tool (Spindle ?)l Holder. I am using a 19$ Harbor Freight trimmer or my old RotoZip. Been using the trimmer for over a year now. I got a Black Decker Router some where if i can find it..


And just for fun here is a picture of my Old Machine. I know some of you going to look at it and shake your head

Attachment 207304

[CarveOne]

In this DIY CNC game you do what you can with what you have to work with. It's about learning and getting better at it. For some, it's much more of a struggle than for others but it's all worth it. Winners don't let the struggles get in their way. 4-1/2 years or so ago I had no idea where this hobby was going to lead me, or if I could do it successfully at all.

[jckstrthmghty]

And just for fun here is a picture of my Old Machine. I know some of you going to look at it and shake your head

Attachment 207304

Love those rail sweeps.

[Coydog]

Well Finally got the machine together with the belt drive. Going to lvl the table next.. maybe tomorrow. Here is some pix.

Attachment 207718

[Qicker306]

Evidently you've had lots of building practice, your machine sure came together quickly. Have you had a chance to compare its capabilities to your previous machines?

[Coydog]

yes. The current machine is a lot stiffer. It don't have anywhere near the flex the old one had, which allows opportunity for deeper cuts. It still chatter a little on the X axis this is due to the belt drive. The belt is to long to be used on the X axis at nearly 6 feet it bounce and do the shimmies when it run. The belt is a .375L type belt even tho I have enough tension on the belt that it pluck like a guitar string it still chatter. My machine is currently drive the belt directly like the old one. I am going to experiment with Belt Rack system to see if it will eliminate that chatter on the X axis. Maybe I will make some head way on that tonight and post some pix.