That's great, when this actually gets built I'm sure I'll ber asking for more detailed advice. Just good to know it can be done.
Actually, that's running two motors from one drive, not two drives from one set of signals.
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Actually...my setup is simple...a lot more simple than what most of you use. My controller is an Arduino Uno which only has ports for an X, Y and Z. The two drivers for the motors that move the gantry in the Y axis get their signal from the single Y port on the Arduino. It was a setup that was on my Shapeoko 2 that I carried over to the machine I built.
I just wish I had all the info I have now at the start of my build. There are so many off the shelf options for used precision cnc parts if you know what to search for. I would have saved a ton a time and effort building parts that I could have bought better and cheaper.
I passed on the chance to buy something like this for $1500. I'm still kicking myself:
https://www.ebay.com/itm/2006-Integr...frcectupt=true
You won't achieve precision like that making diy parts on a cheap mini mill....
Well, I'll throw in my humble little project. Built this with 80/20. Made the gantry myself (on a mini mill) by drilling the mounting holes through both plates at the same time (stacked on top of each other). cheap Chinese ball screws. motor kit and controller from CNC router parts. 3HP 220v water cooled spindle. I made the bed out of wood so i could level it with the spindle. Seemed like the best way to get a level bed. Tapped all the screws by hand. This is still a new machine but I've done some diamond drag engraving in Al. the smallest letters at the bottom, in the pic are about 2mm. And making a fretboard for a guitar in hardwood. the fretslots are made using a .023" end mill and the cut was programmed to stop .07" from the ends. All 23 slots seem pretty good along the 18" of the board and the bit didn't break! These are about the most precise projects I've made so far. All in it was about $3000 CAD so maybe $2300 USD. 2' x 3' bed. Chasing zeros is great for rhetorical discussion but real world cuts on cheap machines require a different mind set. More setup time, strategic cutting with feeds and speeds (i.e. lighter), more trial and error. wasted time and material. I don't use this to make money or for production. If I did it would be a whole other machine and investment. I've already broken 2 couplers (those cheap spiral ones that came with the ball screws). It is what it is. Had a blast building it. Love running it. Learned a lot - and still learning. What else can you ask for? Do I expect .002" precision at 24"? hell no. What could you possibly be building that requires that accuracy at 2 feet - in wood??? Even with a 3hp motor, which is plently to cut Al, I wouldn't attempt to hog out a large piece like a manifold. Little parts are no problem. It's the same as a welder. You wouldn't try to weld 1/2" steel with 20% duty cycle.
Hi, that's a nice project build...…...that solves the table issue that dogs a lot of builds.....very practical too.
Ian.
I'm not so sure. In my experience, wood is one of the worst materials to use if precision is the goal. It bows, expands and contracts with changes in the weather. You could make it perfect today and find a dip in the center tomorrow. You'd have to go over it with a fly cutter before every job.
That's not to say that other materials don't have limitations. Metals can also bend with variances in temperature if the table is not sufficiently stiff. This is one of the reasons why granite and epoxy granite are favored for hyper precision machines.
Well, it was stated that .002" was not an expectation and it is a gantry router after all.
One of our DIY shops sells wood boards that are made up from thin slices of wood glued together and then machined flat...….that usually takes care of the wood grain structure pulling across the board as with many slices of wood the grain is non existent.
If wood is seasoned and dried properly and them machined and subsequently sealed, moisture can't get in and cause what you said......I suppose a few layers of thick MDF board glued together would also do the trick.
Ian.
Wood can be very flat and stable if done right.I'm not so sure. In my experience, wood is one of the worst materials to use if precision is the goal. It bows, expands and contracts with changes in the weather. You could make it perfect today and find a dip in the center tomorrow. You'd have to go over it with a fly cutter before every job.
I just built a wood table for a 4x8 machine last week. 7" thick torsion box, all baltic birch construction, assembled on the vacuum table of a 5x12 CNC router. It's as flat as you could possibly build it, and should stay that way forever.
You have to define "precision" to determine if it's usable for a given situation. While it's flat and stable, any time you use a spoilboard, you're subject to thickness variations.
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Hi All - Timber and wood (depends on how you were brought up) does change shape as the humidity changes. If it's in a stable environment then its as stable as the environment. If its used for a router base and you are not using coolants or need flood cooling etc then it can be an excellent base. To improve the stability it can be plasticised. This slows down the ingress/egress of water. This can be done by using PVA adhesive as a sealer/lacquer. Especially on end grain areas. White glue diluted 50:50 with water is a cheap excellent sealer for timber. Takes a few coats but its easy to apply and dries fast. Once you start getting a build on it you can stop. The other way is epoxy but do not use laminating epoxies as they are thickened and sit on the surface. Use an infusion grade epoxy and it will soak in and seal deeply. Again will take a couple of coats until you get a build or bring it to level. You can also laminate thin aluminium or plastic over the surfaces if you want to be more sophisticated. You can also use acrylic paint diluted 50:50 with water if you want it a nice colour. Neat acrylic paint is too thick to penetrate far. Cheers Peter
I have just made a temporary mdf table for my machine using 2 16mm pieces glued together then sealed with a pva product by bondcrete. Basically its a watered down pva glue but its also great for adding to cement to make a render and has many other uses. On mdf it aoaks in nicely and leaves a very flat surface.
Hi All- As V2 says "bondcrete" in Oz is PVA resin. A question for any chemists out there. I have not been able to determine the actual difference between internal and external PVA's except they tint the "external" yellow. The MSDS's read exactly the same and the chemistry seems to be the same. Although we use the term PVA this is actually the abbreviation for Polyvinyl alcohol which is different to the resin. The correct abbreviation for the glue polyvinyl acetate is PVAc. PVA is water soluble so we wouldn't want to use that! It is used as a release film for concrete moulds and composite moulds because as a film it is impermeable. It is also used for all those coatings for dissolvable medicines and laundry products. Interesting stuff.
https://en.wikipedia.org/wiki/Polyvinyl_acetate
Can't argue with that. A lot of people seem to worry about levels of precision that most of us could not even measure and certainly not see in the finished product.
My experience with wood has been different to yours but it could just be the type of work and the climate here. I make a lot of molds and if I use a wood plug in summer, it no longer fits the mold by fall. Also, every piece of MDF or wooden shelf I have owned has bowed within 12 months.
I'd like to see some pics of your wood table design if you have time. Maybe there are some pointers I could borrow to make wood mold blanks.
Here's a link
https://www.cnczone.com/forums/cnc-w...ml#post2298954
Baltic birch is much more stable than MDF. Because of the alternating grain direction, it doesn't change in width or length with humidty changes.
MDF will grow and shrink in all directions with moisture changes. Unless you live in the desert, where humidity is stable, it's going to move.
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
That's a good tip on the Baltic birch. I've not tried it before. In my world it's all about the figured walnuts with the occasional exotic hard wood. I wonder if Baltic Birch would make a good rifle stock. The basic desirable properties are broadly the same (i.e. stiffness, strength and stability).