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Topics - xxtoni

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1
Hello,

I've been a lurker for a while now and I have finally decided to make myself a CNC flatbed cutter.

First a little intro.

I own a signage company and we already have a pretty decent CNC router that we have bought from a local manufacturer and we are pretty happy with it.

Now however we want to build ourselves a CNC flatbed cutter.

In case some of you (probably most) don't know what a flatbed cutter is...it's basically a CNC gantry router that instead of having a spindle has various cutting heads, usually knives, that cut light materials like PVC foam board, lexan, vinyl, paper, rubber and so on. We actually consider/ed making these heads ourselves but it's a bit beyond us at this time so we've decided that for the time being we will buy them from
https://www.damencnc.com/en/tools/tangential-knife---accessories/tangential-knife/1583

We are looking for a travel speed of some 30m/min. I'm actually not sure if the oscillating knife will be able to keep up with it in thicker materials but as said, we will try to develop these tools in the future so we want the machine to be able to travel these speeds.

One advantage of a flatbed cutter is that there aren't as many resistance forces at work here as in a traditional CNC router as for say wood because most of the materials are very light so the cutter doesn't have to be as rigid as it would be if it needed to cut these heavier materials.

There are some things I've decided and the rest I don't really know a lot about and am still researching and hoping for advice here as well.



Size: 300x200cm

This is the standard size of most materials in our industry, I don't see why the size should be a problem in a CNC like this (because it doesn't have to be extremely rigid) but if it is I guess we could cut it down some if it's absolutely necessary.

Speed - Around 30m/min


Those are really our only requirements. The gantry needs to carry the 3 tools, they around 2.5kg a piece so a total of some 7,5kg which I think isn't that heavy.

The rest I am pretty clueless about to be honest.

For the bed we are going to be using a special vacuum foam for holding down stuff, I was planning on using side channel blowers to power the vacuum table but I am not sure what kind of table design to use for the mat, the seller of the mat told me to use a vacuum table with 5mm blind holes that let the vacuum through a 0,6mm opening in, according to him we would get the effective vacuum of a 5mm hole but only a loss of a 0,6mm hole once a cut in the material is made. Ideas ?


Regarding the rest, I honestly don't really know what to do.

I am currently looking at:

- Motors. Stepers vs servos ? Suggestions ?
- Rails - No clue in this regard
- Construction - What design and what material.  I have a team of pretty skilled welders so welding a sturdy construction together is no issue. My current CNC router is made mostly out of steel (the base anyway but a whole lot of steel on the gantry as well)
- Software - I was planning on using Mach3 because of it's wide support as well as having native tangential cutting support.


- Everything else [/B

This is the part that concerns me the most at this point to be honest. I am currently researching but it's a bit overwhelming right now, I do know a fair bit about CNC routers and have been doing research for years but now that it's coming all together it is a bit too much at once.

I would appreciate any advice you can give me, not just answers to these questions but these are some that come to mind right now:

- Belt vs  ball screw

I read somewhere and while doing research on the most prominent flatbed cutters like Zund and Konsberg found that most of the flatbed cutters use belt drives instead of ball screw drives. Any suggestions here ?

Stepper vs Servo

I know that steppers are cheaper and easier to setup because of the lack of encoders but I also know that servos are much better for high speeds so any suggestions here would be much appreciated.


The rest of the parts...

I am a bit clueless here in my mind the major things here are:

- Motors
- Drivers
- Cutting heads
- Construction
- Control Board


What about the rest though, the linear rails, the carriages, nuts, bolts and so on ?


For the end a flatbed cutter that seems to work quite well and seems DIY, I could show you a $200k Zund flatbed cutter but that would be unrealistic so here is a pretty good looking DIY one:

https://www.youtube.com/watch?v=H7s24MxNbDo

https://www.youtube.com/watch?v=a3hVeC1Ub1Y


I really hope that some of you guys can help me out with this.


Thanks in advance! 



2
Hi everyone,

So last year we bought a CNC router with a 3x2m table from a local manufacturer, when we ordered the machine we specified our requirements to the manufacturer in detail and he told us that he would make a top of the line machine for our application, which is signage. One of the requirements was that the machine be stable because we route a lot of thick acrylic (4cm) so that there would be no vibrations and that the cut would be as good as possible so that we don't a lot of manual labour with the finish of the acrylic. We were told to achieve that they would use top of the line components that are totally overkill for our application but just to make sure there would be no skimping on the parts. They used 25mm ballscrews (if I remember correctly) and the servos used are made by Schneider Electric with: 1.1kw of power,  IO 5.55 arms, MO - 3.4 Nm nN - 4000 rpm, lmax 17.84 Arms, nmax 8000 rpm

All in all it's a pretty nice machine, works well enough but there's a rub. For some reason the machine can only cut "well" at 2-2.5m/min. If you increase the speed any more than that you will get extremely rounded edges where they should be a straight edge (excluding the radius of the bit of course).

For example when routing the letter K at 2m/min with a 4mm bit you would get a 4mm radius but if you were to route at 5m/min with the same bit the radius is much larger.

Now here's my main question, as I don't understand as much about CNC mechanics as I probably should but why does this happen ?

I've never felt that the machine doesn't have enough power in the servos, I mean it has no problem jogging at 10-15m/min around the table when it's not cutting and these are all lightweight materials like 3mm acrylic and foamex so it's certainly not a issue with the spindle (3kw Teknomotor air cooled spindle with 24k RPM, not that it matters for this specific issue.)

I also have a theory as to why this happens, my guess is that the router can't change direction fast enough or rather that it can't stop abruptly and then start again to make the "sharp" edge and that it sort of just does a continued motion (if that makes sense) and that's why it leaves the very curved edge.

The reason I'm asking this is that it's pretty frustrating that the machine can't go faster accurately, I was expecting that a new machine with strong servos and good components would be able to do 10m/min. It's not a tragedy, we do good work with the machine but I'm trying to figure out if anything can be done to make it go faster and remain accurate.


Thanks in advance for any tips!




3
General Mach Discussion / Replacing electronics on a CNC
« on: January 12, 2014, 09:57:06 AM »
Hey peeps,

I've done a lot of work on my small 1000x600mm CNC router these last few days and during that last stretch of work it started freaking out. All of a sudden the Y motor starts going into random directions I tell it to go forward and it goes forward, and backwards and backwards and forwards...After a bit of fiddling I take out the breakout board, figure out where that motor is connected and I see that the part where it's screwed in has been burning. Thankfully I got it working and managed to finish the job.

Another thing is, my little router was rated 2000mm/min by the manufacturer but I can only get it to run around 800mm/min consistently. At first it works fine but after a few minutes the motors start stalling. At first I assumed that the motors just couldn't handle it but now I have a new theory...since it is manufacturer rated for 2000mm and it can perform like that for a while before they start stalling AND since I am having electronics problems I am guessing that the electronics are near death. So I guess when I try to get it to run at 2000mm the electronics just can't deliver enough power to the motors consistently cause they're old and worn out.

So I've decided to beef up my CNC by:

- Replacing the breakout board
- Adding limit switches on X, Y, Z
- Adding an estop button
- Adding one of those probes for setting the z zero (toolsetter probes or what)
- Adding a pendant


Right, so what's the problem then ? Why am I opening this thread ?

Well...I don't know a lot about CNC electronics so I thought I'd question a higher authority instead of buying a bunch of stuff and finding it doesn't work.

At first I thought that i would only need to buy a breakout board and plug my CNC motors and the rest of the stuff in, since my current router only has a single board where everything is connected (everything being the motors since it doesn't have limit switches and the spindle is a router that's manually turned on).

But (thankfully) I then did a bit of research and think that I may need a driver for each of the motors. Is that the case ?

My Y and X motors are VEXTA 2 Phase motors, 2A each and the Z motor is 1.2A

I don't know the voltage of the steppers, does it matter ?

The whole premise seems simple enough, and please correct me if I'm wrong but from what I know...plug power from transformer to the new breakout board, plug drivers into breakout board, plug parallel cable into computer. Add the rest of the stuff (estop, probe, limits) into the breakout board and configure all the pins in Mach3. Am I missing something ?

I also haven't figured out where to buy the breakout board, drivers and limit switches. I've looked around ebay and found some stuff but I'm not sure if it's any good or if it will even work together:

http://www.ebay.com/itm/USB-5-Axis-CNC-Breakout-Board-Interface-Adapter-For-Stepper-Motor-Driver-/321133023129?pt=LH_DefaultDomain_0&hash=item4ac5050f99
http://www.ebay.com/itm/CNC-Single-Axis-TB6560-3-5A-Two-Phase-Hybrid-Stepper-Motor-Driver-Controller-/321170671199?pt=LH_DefaultDomain_0&hash=item4ac743865f


Would this work ?


EDIT:

Forgot to include images:

http://imgur.com/a/uJrWj

4
General Mach Discussion / Optical Registration Mark Reading With Mach3
« on: January 06, 2014, 06:38:09 PM »
Hello everyone,

This is only my second post on here but this is something that has been on my mind for over a year now and I've finally decided to see if something can be done about it or not so here goes.

First a little background.

I am in the signage industry and also do the majority of my CNC work as part of that. Having a CNC machine in this work really isn't an option anymore and we can't really imagine doing most of our work without one.

There is a problem though - of course.

A big part of the work that we do is made up of printing a graphic, laminating (applying) it to a hard substrate like foamex (PVC foam board) and then contour cutting it out to a shape, that usually looks something like this -

The problem here is that we usually do the cut with a jigsaw manually because it is much faster and safer (for the workpiece) than trying to do it our CNC.

Obviously doing complex contour cuts on the CNC router would save a lot of time and just be all around much easier than doing it by hand but right now that usually entails that you make some kind of registration mark in the artwork during preparation for print. Then you would have to export the outline of the artwork, as well as the registration mark, DFX/DWG/whatever and use that to generate your g-code for cutting later on. Then you apply the print to the board substrate and put it on the CNC for cutting, and here's the rub. At this point your work piece has to be perfectly aligned with the machine so that when you set your zeros on the registration mark, which serves as a reference to where the artwork is, that it cuts exactly along the contour. Doing this once or twice isn't that challenging but having to do it all day long quickly becomes tedious.


Now if it could be somehow accomplished that a camera reads those registration marks and that then software adjusts the angle of the registration marks in the g-code accordingly to the ones that the camera read then this whole problem would be eliminated. Initially I just assumed that doing this was far too complex to be attempted by a hobbyist but lately I noticed that Mach3 seems to have video capabilities and based on Tweakie's replies on a thread that someone else made to this question it seemed to me that it was implied that this wouldn't be too hard to do.

If all of this was too convoluted to understand I apologise but this video should explain in a few seconds what I tried to explain in 500 words here

http://www.youtube.com/watch?v=s3MeHLluzC0
(tried embedding this but didn't work)


Systems like this certainly exist but they cost thousands to tens of thousands of dollars which is not viable for me.


I do hope that someone with deeper understanding of these things can shed some light if doing this is possible or not.


In any case I'm looking forward to the replies.

5
Hello everyone.

I've only recently (few weeks back) switched a small mill I have to Mach3 and it is working wonderfully since then. I do have one question though.

The mill I have is a relatively old Haase mill, 1.6m x 0.6m in dimensions and while I'm not exactly sure what it's steppers are they're relatively small. On it I have a 900w (if anyone could explain to me what the advantage of wattage is I would appreciate it, what does it matter if you have 900w or 3kw if you have 26k RPM, bear with me, I'm new in this) milling motor with 26k RPM.

A project I currently have (it's pretty awesome and I'm sure more of the like will follow soon so this is important for me) requires me to cut 8mm thick acrylic. I had a custom two spiral carbide bit made for me specifically for this purpose, 8mm in diameter and it works perfectly.

The one problem I have with it is that I think that I'm forcing the machine. The first thing I do is mill a small channel into the acrylic, 8mm wide and 3mm deep I try to do this at 800mm/min and 26k RPM. This works almost perfectly the only problem is that the spindle/mill motor carriage starts shaking from time to time which is a bit alarming to me, holding it for a few seconds with my hand will usually stabilize it and that tends to be the end of it. Another thing I need to do on this project is cut through the acrylic, so for that I go 8.5mm deep into the acrylic and set the speed to 400mm/min and it works well enough for a while but soon afterwards it starts shaking again, the only thing that will prevent this, other than holding it with my hand, is setting the feed speed to 120mm/min which seems ridiculously slow to me.

What bothers me with this whole situation is that my guess is that the motors shouldn't have any resistance whatsoever while going through the material. That's at least how I always imagined it, I thought that the mill/spindle would take care of all the materials and that the motors would basically have the same resistance as when going through the air.


Another issue I have is when jogging at some points the mill seems to encounter some resistance and I hear a screaching noise and sometimes it even gets stuck during jogging (just pressing the jogging button in that direction will get it going again). My first thought was of course lack of lubrication so I got out and got myself an entire can of machine grease but that didn't really help as I still have the same problem after putting lots of grease on it. Grease actually made it worse as it got stuck at all the places where I put huge lumps. I set the job speed from 2000mm/min to 800 mm/min and I don't seem to be having problems anymore during jogging but the max of the X motor as far as I could determine is around 2500mm/min so running it at 800 is less than ideal.

I really hope that someone can help me with my issues, any replies are greatly appreciated.

Regards

6
Hello everyone,

Since I got my first mill a few months back I've:

- Successfully switched my machine over from some DOS control software to Mach3 (which was the hardest step by far)
- Gained some basic knowledge about tools
- Established a few supplier relationships (for tools (bits) mainly). I now have a supplier for the cheaper HSS tools and have a company that customs makes carbide tools for me. Interestingly enough it's both faster and cheaper for me to have them made instead of ordering them to be delivered (they make them for me in 2-3 days).
- Started basic usage of the mill (mostly for cutting plexiglass/acrylic and forex/pvc foam sheets)


Things are pretty great so far and I've come a long way but there is one part in my workflow that is particularly annoying and I'm sure there is some other way to go about it.

My machine doesn't have home switches so more or less every time I add a new workpiece onto the machine I have to zero the home positions to match new workpiece. I know a lot of people will keep telling me that I don't actually have to zero all to each workpiece and that I could instead just do that with the workpiece coordinates. Here's the thing though, I like having maximum usability of the material I'm milling and usually that's within 10mm of the edge of the workpiece and since I don't have end/home switches my soft limits are based around the ref all home as well.
I am guessing however that there isn't a way around this one without installing home switches, if there is please let me know.


Now to the main issue. I don't have materials or tools setup in my CAM software (CamBam) so when I'm milling a new piece I do the following: measure the thickness of the material I am about to mill, select the tool and setup everything in CamBam. Now instead of selecting a material or a pre-defined tool I just enter the depth I want to cut, so for example if I'm cutting 3mm acrylic I just set the depth in cambam to -3.5mm and export it to g-code. Then when I import that into Mach3 I just select the x,y zeros for the workpiece, activate the spindle and jog the z so it touches the material a bit, then I just set that as the z and start milling. Mach3 will lift the tool to 3.0 with G3, go to the starting point of the cut and lower it to -3.5mm as defined in CamBam.

The problem here is, it's pretty annoying having to do this every time but that's not even the main issue. The main issue here is the all important z soft limit. I defined the z limit (soft) with one tool and set it at -57 for example, then if I change the tool then I have to change the z limit again. This quickly becomes annoying but that's not even the worse of it. I usually know right away what the issue is but my employees, who I'm also teaching to operate the mill, probably won't know the solution and will just turn of soft limits and continue machining. As you can imagine that can have serious consequences if someone made a mistake in the CAM part and it's inevitable that someone will make a mistake and that something will happen.

I think that this part can be solved with tool offsets but I have no idea how to setup these because as said, I'm pretty new to the world of CNC machining.


Looking forward to your replies and thanks in advance!

7
Greetings,

I'm a newcomer in CNC-land.

A few weeks back we bought ours a small Haase mill. It is a sturdy little thing. At first we used it with an ancient computer that came with it and with a software called CNCProfi. However the computer was really old, didn't even have USB so I was worried that it might burn out any day now. Instead of waiting for that to happen I tried transferring the software to a new PC. The problem was that the software was DOS based and modern OS' don't give DOS apps direct access to the paralel port. I tried installing DOS and Windows 98 but to no avail, constant error and after a few frustrating days I just thought screw it and decided to switch to Mach3. After a few daunting hours I managed to get the motors to move, oh what joy. Of course when you're a beginner one solved problem creates two more.

We are a signage company so we do most of our work in Adobe Illustrator and a bit in CorelDraw as well (but we're trying to kick the habit). The previous software we used (CNCProfi) had the CAM built in it seems, I would just import a PLT file and it would automatically convert that to g-code without even prompting me to do anything. When I tried to do that with Mach3 I realized that I would need another tool to convert the drawing to g-code.

At this point I bought BobCad as it seemed to be the best tool for my needs, using it however was completely overwhelming for me. After trying to get it setup for a few days I just gave up from it and found out that LazyCam exists. I've started experimenting with LazyCam yesterday and it's the easiest software so far.

I would however like to learn how to use BobCad in the future so if someone can guide me on how to just setup the Drawing to G-code conversion I would be very thankful.



Problems

Larger in Mach3 than in CAD


When I try to export something from CorelDraw or Illustrator and import it into LazyCam the file looks fine in LazyCam and shows the right dimensions. When I import the same file into Mach3 it should up 10 times bigger in the preview. Obviously since we're talking about 10x I automatically assumed that its a centimeter/milimiter thing. I've tried changing both the working units and the export units in both Illustrator and Corel but to no avail, it is always 10x bigger. In Mach3 the units are mm. My workaround so far has been to just scale this in LazyCam to 10% that way when I import it into Mach3 I get the desired dimensions but I'd rather not have to do that.

Square-y In DFX

Another problem that has forced me to use CorelDraw is that when I import a DXF file into LazyCam it becomes all square-y (please see the attachments for more details). The only workaround for this I've found so far is to export the drawing from CorelDraw in a PLT file (which Illustrator doesn't support) then the drawing looks as it should (please see attachement #2).


Any help with these would be greatly appreciated. I've already learned a lot from this forum and the tutorial videos and I must say Mach3 is a fantastic software. I was weary of using it because of the design (I know, I know, it's all about the functionality) but it turns out that it's a great piece of software.

I want to thank everyone in advance for their help.

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