No limits CNC

[Vixen]

The discussion regarding end stops, limit switches and 'home' switches has been moved here from the Mercedes W165 build thread.

It's quite an important subject and definitely one that needs it's own topic which members can refer to, read and perhaps contribute too.

Different machinists have conflicting views on the use of limit switches and stops, the discussion has been examining the pros and cons and the possible consequences.


My much modified Emco VMC, has a table movement of 200 x 100. I do not use limit switches, so I impose a soft limit of 190 x 90 instead. I see no sense in tap dancing on the limit switches or end stops. If you run into either, the job cannot be completed and is probably ruined. 190 x 90 is more than enough movement for most of the parts I need to make.

Mike

[kvom]

I do not use limit switches

Same here; soft limits work fine. 

[internal_fire]

I don't "use" limit switches, but I have them installed and functional. Hit one on rare occasions when something goes really wrong. Not sure anything would break, since the motors are not oversized, but it provides added safety.

Gene

[dieselpilot]

My much modified Emco VMC, has a table movement of 200 x 100. I do not use limit switches, so I impose a soft limit of 190 x 90 instead. There is no sense in tap dancing on the limit switches or end stops. If you hit either, the job cannot be completed and is probably ruined.

Do you not use home switches? Or are they not accurate enough to restart a job?

[Vixen]

Hello All,

I do not have, or use, any limit switches or 'Home' switches on my machines. They can be a source of unreliability and EMF interference. Any limit or home switch needs to be hermetically sealed to prevent the ingress of fine metal dust particles, otherwise they have the potential to cause nuisance tripping or failure to trip.  My philosophy has always been to keep it a clean and simple as possible.

So what do I do about 'Homing'?

Well, I do not use 'Home' switches to define a fixed point on the mill's table. Instead I use a digital touch probe (similar to a Renishaw) to find a corner, or a center,  or a defined position, such as a toolmakers button, on the piece of material to be machined. That position on the material becomes my Zero (Home??) point. My CAD CAM uses the same position to calculate the tool paths. It certainly simplifies tool offsets... there are none. 

This may not be how they do it in a professional machine shop: but it has worked well for me for the last twenty years. 

Mike

[steamer]

Thanks Dave, 

As an engineer, I like to be creative with the tools available to me. If they have limitations.... no problem.... I will try to find a work-round.

My much modified Emco VMC, has a table movement of 200 x 100. I do not use limit switches, so I impose a soft limit of 190 x 90 instead. There is no sense in tap dancing on the limit switches or end stops. If you hit either, the job cannot be completed and is probably ruined. 190 x 90 is more than enough movement for most of the parts I need to make.
I
The cam gear case cover is an exception, it measures approx 240 x 160. Being "T"  shaped I will be able to get away with three set-ups.

Cheers   

Mike

Oh Totally understand!   I was just curious.....

Dave

[kvom]

Same as Vixen.  Machine coords are ignored and part zero is determined for each part (usually wiggler).  If I need to leave the part overnight, I manually move to X0Y0 before shutting down.  The control doesn't move the table when referencing the axes.

My machine does have limit proximity switches, but I never found using them to be a benefit.

[Hugh Currin]

I typically set machine zero to be the corner of my vice and all the way up in Z. Then set work coordinates for each part. Setting machine zero this way is consistent enough, for me, that the soft limits mean something. I also haven't gotten around to putting on home or limit switches. I park the machine at machine zero when shutting down. This is consistent within a few thousands, close enough unless continuing to machine the same part.

Mike: Your work is amazing. I want to see the finished engine, but don't what the thread to end. Thanks.

[steamer]

For a critical part I'll fixture the part, and mark the zero from a specific corner, that way if I crash or lose power it's easy to pick back up.

Dave

[Vixen]

For a critical part I'll fixture the part, and mark the zero from a specific corner, that way if I crash or lose power it's easy to pick back up.

Dave

Corners are good.    They are easy to find and easy to return to. They give both the X and Y work datum (Work Zero)

Oh!! Don't machine off that corner until the last moment

Mike

[Jasonb]

Never found them that good on round parts I tend to use the top ctr on most jobs more than a corner but that's possibly just a carry on from what I tend to do on the manual mills. Also suits me on teh CNC as stock is usually a little oversize in both directions so using ctr ensures i'm not too tight on one or two faces.

The KX3 has home and limit switches but I don't have them enabled, just watch the simulation to make sure the machine is not moving too far. As for home it would probably be more useful if I were using quick change tooling as it takes the head up and gives you room to change but as I'm only going to be swapping a cutter in teh ER collet then I'll just raise the head as far as needed to do that and jog down to set the tool height.

[john mills]

with industrial machines in years of using and programming cnc and older nc machines
the  limits are important to protect the machine from over travel accidental movements and errors malfunctions.
soft limits are important too have used machines with chuck barrier and machine barrier protect the machine
if you hit a barrier and it stops from finishing that is what it is for .toprotect the machine i have had the service man go to another job to come back and say they had crashed the machine did not bother to have set chuck barrier took to much time .well the machine would be months before it would be repaired.it had ripped the tool holder off the cross slide.thousands of dollar cause didn't bother to set barriers.i have had the tail stock in the way
barrier set some how .but the machine did not have one.if you hit a stop you stop i had a day shift operator that didn't set no's of parts relying on barrier to stop .even with low power machines stopping when hitting end of travell can do lots of damage .as for where you put x and y 0  is a matter of when you program what suits the job.
you just need to know where it is.
john     

[steamer]

Wot John said......As a machine designer....I have to agree.   The limits are there to protect the machine

On my little mill, the limits are always active, and the software will flag me and prevent me from running if the program runs out of bounds either by capacity, or because of my zero location....   

Jason.   The point I was making was that two edges of the fixture plate are used as a zero, knowing that a set distance from these two edges is the program zero.    That way I can pick it back up very easily with an edge finder...as compared to sweeping in a round part.     By the way a edge finder can do very good job of picking up a round part....but it usually takes two goes from the X and Y to do it...

The reason for this is that zero on my machine is set from a rotary encoder reference to one of the limit switches, and those switches don't necessarily repeat that great...

Anyway....none of this matters, as I want to see how Mike the magnificent Vixen is going to finish this engine!   

[john mills]

the maximum travel limit switches are the same as maximum travel feed knock out stops on manual machines
there are plenty of good manual machines with power feed badly damaged by these stops removed to get a bit more travel .shear pins and slipping clutches are used as well but don't always work and the machine is still damaged.
John

[Vixen]

Thank you, John and Dave,

You make a very good point about the use of limit switches and stops. They are there to protect the machine from damage. You can avoid using them if you must, but the risk is yours alone.

Much like seat belts in a car. Nobody intends to have a car crash, but if they do, they have the protection of the seat belts to avoid serious injury.

Mike

[dieselpilot]

Hard limit switches are really only needed for DC servo machines where a drive failure can run an axis uncontrolled to the end stops. Stepper machines simply don't need limit switches, but accurate homing is a nice thing to have. Many newer machines don't have limit switches because failure modes of BLDC or AC drives and the types of signals used today mean that an axis simply can't run away.

If you aren't using tool offsets or don't have to shut down the machine before a part is finished, you can do without. I built my first machine with homing, and would never do without.

If using an encoder index pulse with a limit switch to home it will be as accurate as the resolution of the encoder. The accuracy of the switch doesn't come into play. Emco stepper machines have excellent homing with an index signal and a prox.

[Jasonb]

Not sure about stepper equipped machines not needing limit switches. This is the externally visible damage done to my machine by the previous owner when he ran  it past the x height stop, more damage inside



I must have  ago at enabling them again on mine, they were giving some issues when I first got the machine which I may be more able to sort out now having used it some more.

   By the way a edge finder can do very good job of picking up a round part....but it usually takes two goes from the X and Y to do it...

That's what I normally use on the manual machines, not so much on the CNC as my usual electronic edge finder is not very flexible so don't want to jog too far or in the wrong direction I guess it all comes down to how an individual works, I'd mostly use a chuck or ER collet fixed to the mill table to hold a round part rather than a fixure plate

[Vixen]

......... I built my first machine with homing, and would never do without.

If using an encoder index pulse with a limit switch to home it will be as accurate as the resolution of the encoder. The accuracy of the switch doesn't come into play. Emco stepper machines have excellent homing with an index signal and a prox.

You say you built your machine with 'homing' and would never do without. Well, I have never had a 'homing' capability, therefore I dont know how to use the 'homing' facility or what advantage it would bring. Perhaps you would be kind enough to give me a short 'how and why' primer.

I have just checked my Emco VMC. It still has the magnetic index and proximity sensors and wiring for each of the X, Y and Z axes still in place, but they are not interfaced to my Linux CNC controller at the moment. Perhaps I am missing a trick by not using the 'homing' facility.

Mike

[Dave Otto]

I was going to comment before but didn't want to muck up Mike's thread.
I guess I'm in the minority here, I have working plus and minus limit switches on all three axes of my mill. I can full rapid into any switch and it slows and stops with out any issue; this is due to properly setup soft limits. It is also nice when loading a job file you know if there are boundary issues before you start cutting.
My machine is a converted knee mill so there are some extra variables that come in to play, I.E. knee position or ram position on the turret that may cause you not to be able to cut your entire job without repositioning something.
I'm using industrial quality snap action switches (Omron) with a spring loaded roller actuator. Testing has shown that these switches will repeat to within .001", plenty good considering the rest of the hardware.

Dave

[internal_fire]

You say you built your machine with 'homing' and would never do without. Well, I have never had a 'homing' capability, therefore I dont know how to use the 'homing' facility or what advantage it would bring.

I have active limit and homing switches. As I said previously I try very hard to avoid using the limit switches. 

The homing switch is never used (by me) for referencing the tool to the workpiece. Instead it allows the entire system to remain centered. If I continually reference the workpiece with an edge finder I can accidently make the machine start to work more and more off center. Eventually this could cause a run-in with the soft limit stops.

LinuxCNC requires homing before it will run, so I do not have much choice in any case. (Requirement probably can be defeated, but I have not tried.)

Gene

[Vixen]

You say you built your machine with 'homing' and would never do without. Well, I have never had a 'homing' capability, therefore I dont know how to use the 'homing' facility or what advantage it would bring.

I have active limit and homing switches. As I said previously I try very hard to avoid using the limit switches. 

The homing switch is never used (by me) for referencing the tool to the workpiece. Instead it allows the entire system to remain centered. If I continually reference the workpiece with an edge finder I can accidently make the machine start to work more and more off center. Eventually this could cause a run-in with the soft limit stops.

LinuxCNC requires homing before it will run, so I do not have much choice in any case. (Requirement probably can be defeated, but I have not tried.)

Gene

Thanks Gene, that helps my understanding of the 'home' function.

My LinuxCNC set-up does not try to automatically 'Home' during switch on. Thats probably because the 'home' sensors are not connected. LinuxCNC sees an open circuit and assumes it has reached the 'home' position.

I position the workpiece by eye between the max travel markers on the bed. I then reference the workpiece with an edge finder and press 'Home axis' to Zero each axis to the workpiece reference point. Much like you do with the DRO's on a manual machine.

We all have different way of working and our machines may be set up differently

Mike

[Hugh Currin]

Dave:

It sounds like you're using soft limits (limits imposed by software rather than physical switches). Then you have physical limit switches active but the machine never trips them as long as the soft limits work. I understand this to be correct and safest way to set up a CNC machine. I should put limit switches on my converted knee mill. However, the vast majority of my parts are too small to push the machine size limits. The few times I've pushed it the soft limits have prevented over travel. The soft limits do well as long as LinuxCNC knows where machine zero is. Oh, well yes, I'm lazy!

On my knee mill it's the quill that is controlled. This does limit the Z axis travel. I usually break a program into two parts to get around any Z limits. For my small parts this is usually moving from end mills to drills/reamers.

What you have makes perfect sense.

Thanks.

I guess I'm in the minority here, I have working plus and minus limit switches on all three axes of my mill. I can full rapid into any switch and it slows and stops with out any issue; this is due to properly setup soft limits. It is also nice when loading a job file you know if there are boundary issues before you start cutting.
My machine is a converted knee mill so there are some extra variables that come in to play, I.E. knee position or ram position on the turret that may cause you not to be able to cut your entire job without repositioning something.
I'm using industrial quality snap action switches (Omron) with a spring loaded roller actuator. Testing has shown that these switches will repeat to within .001", plenty good considering the rest of the hardware.

Dave

[Hugh Currin]

Mike:

Let me try to explain homing as I understand it. This is usually where I learn a lot from more knowledgeable members telling me where I'm wrong. I look forward to this learning.

The commercial machines I've seen go through a homing routine upon startup. They then know where machine zero is and are ready to go. They move each axis until they trip the home switch(s) telling the software where that axis is sitting. Zero may not be at the switch but they apply an offset from the switch to know where zero is.

LinuxCNC can likewise be set up to search for home switches. Can even use a limit switch for a home switch. Many options are available such as. 1) Move axis ? in a given direction until it trips the switch and stops with slight overshoot but take it as set, 2) Move axis ? till switch is tripped with slight overshoot then reverse direction and move slowly till switch un-trips and call this set. 3) Move axis ? till switch trips with slight overshoot then reverse direction and slowly look for next rotary pulse and call this set. These are progresivly more accurate with the last requiring a secondary rotary pulse to pin down ball screw rotation. Accuracy, in the first two, will depend on the switch. Dave says he 's within 0.001" which sounds very good to me. For this it's important to have repeatability in the switch. The advantage is that home position is found automatically and consistently.

As I've said I don't have limit or home switches 'cuz I'm lazy. When I start up the machine I use a wiggler to zero in on my vice and call this X/Y machine zero. Then take the highest Z position as Z machine zero. When I turn off the machine I make sure it's parked at X/Y/Z machine zero. If this is done, and I'm extra lazy, I just home the machine on startup at this starting position. On LinuxCNC I just push X&Y&Z home buttons on start up. The wiggler is likely within 0.001" and the second process within the backlash, maybe 0.002".

Why? Well, the soft limits only work when the machine knows how far it can travel +/-. It measures +/- from machine zero and it knows this from homing. Commercial machines are set up to hit soft limits before hard (switch) limits. I depend on soft limits which depend on my homing the machine manually. I'd not give my machine to a student 'cuz I'm not confident they'd home it adequately. But it's my machine and this works well for me.

Why don't I have home switches, besides being lazy? Because I'm also impatient. Home switches are best at the far end of an axis, either + or -. If I set up a home switch at say the far + X axis the machine would search all the way to the end of the table before finding it. It would then know X machine zero and I'd likely ask it to move back there, near the middle of the table. With my slow machine that takes some time. Well, you say, just put the home switch closer to the middle of the table? Because, if the axis is somehow past the home switch it will search for it till it hits the limit switch. I don't have limit switches so that would be a crash. The only sure way to prevent this is to put any limit switches at the end of travel.

The home position, and machine zero, have little effect on parts. That at least the way I use it. After homing the machine to machine zero (G53) I use work coordinate G54 for part programs. I use a wiggler or CoAx indicator to set X/Y part zero. Then use tool length compensation to set tool height Z for the part. I don't know if commercial machines can home accurately enough to depend on. If they are you could set a fixture on the table and depend on homing to set work coordinates on that fixture. Just start the machine up in the morning and cut parts. I don't anticipate ever being pressed for time enough for this to matter. As long as set up is within my patience threashhold I'm OK.

SO it sounds like I do about what you do. Set or more the machine to it's home position and press home buttons. That lets the soft limits work. Then accurately set the work coordinates to each part. I don't think you're missing anything.

At least that's my process from the last time we all went around this track. I may well change once I read all the comments which are sure to come. But if it does I'm ahead of where I was.

P.S. I'm not a CNC programmer, but I once stayed in a Holiday Inn. :-)

You say you built your machine with 'homing' and would never do without. Well, I have never had a 'homing' capability, therefore I dont know how to use the 'homing' facility or what advantage it would bring. Perhaps you would be kind enough to give me a short 'how and why' primer.

I have just checked my Emco VMC. It still has the magnetic index and proximity sensors and wiring for each of the X, Y and Z axes still in place, but they are not interfaced to my Linux CNC controller at the moment. Perhaps I am missing a trick by not using the 'homing' facility.

Mike

[john mills]

I have always worked with industrial machines and have always used home positions
the home position is the position the machine can find and is always the same.the first lines of the program tell it where you have made zero on the part you are doing .when you find your position on the part by what eva means you like to use the machine can find its home position so whenever you turn on the machine you go to the home position then you have told it where you have put it on the part .if the power goes of you don't know any more where it is so you go home and your ready to go .i used to use a vice a lot so i knew where the corner of the vice was so i could position the material from there and be ready to go without having to find that position again .
when doing lots of parts and the machine is not always on you can always turn on home the machine and be ready to go again.it is a constant reference position.the position on the part is where you make it from the home position
and can be found at any time .the home switch is position where the machine can go and find it home position
and is as accurate and repeatable as the machine.
John

[Hugh Currin]

I forgot to mention that I depend on machine zero for tool changes. The post processors I use take the machine to home position for a tool change. They have G53 Z0 , G53 X0 Y0 embedded in the tool changes.

From what John says, commercial machines home accurately enough for part location. That would be an advantage for production.

Thanks.

[Vixen]

Hello Hugh,

Thank you professor, for taking the time and effort to clearly explain the how and why of 'limit' and 'home' switches and how they should be used in an industrial setting. There it is important that all machines and all operators work in the same way, to the same set of rules.

I am well past the age of ever being invited to work in an industrial machine shop and selfish enough not to let anyone else use my CNC machines. So I can devise my own simplified way of working. I have physical markers on each axis to show the extent of travel, so it is easy to position the vice (or vertical chuck for round stuff) well within the available travel limits. I only use (workpiece) part zero, so dont need to bother with offsets (G5xxx etc) . I find it quicker (and safer??) to set Z zero, off the work, after a tool change. Again, this avoids  measuring and setting tool heights into a tool table, and yet more offsets.

Simple and lazy, yes. It works in my shop but I would be a disaster in another workshop.

Mike   

[steamer]

Alright.....Good morning to all.

Mike ....thank you so much for starting this thread and declutering yours.    As it should be    I'm enjoying your thread immensely!

Now....everyone here has a mill...most on this thread run CNC, or have a CNC mill

As you are president and CEO of your mill....feel free to run it however you like!    That would seem quite logical

That said....based on the volume and quality of the outcome,  I think Mike and dare I say myself and many others appear to be doing just fine by whatever unique or esoteric means at our disposal, whether it complies with industrial norms or not....as it would seem...as some of my Midwestern friends would say

"Its not our first rodeo"

So lets strap in and make some engines.....hmmm?

Steamer wants big Vroooom!

[Jasonb]

Hello Hugh,



I am well past the age of ever being invited to work in an industrial machine shop and selfish enough not to let anyone else use my CNC machines. So I can devise my own simplified way of working. I have physical markers on each axis to show the extent of travel, so it is easy to position the vice (or vertical chuck for round stuff) well within the available travel limits. I only use (workpiece) part zero, so dont need to bother with offsets (G5xxx etc) . I find it quicker (and safer??) to set Z zero, off the work, after a tool change. Again, this avoids  measuring and setting tool heights into a tool table, and yet more offsets.

Simple and lazy, yes. It works in my shop but I would be a disaster in another workshop.

Mike   

That's just what I do too and have the Sharpie marks on the machine to prove it:) I decide on the datum point in F360 which is usually top ctr of part be it round, square, rectangular or part machined and locate that position when the stock or part is placed on the machine. Each tool height is set from the part usually with a 20mm block so I just enter Z as +20mm after touching off a new or changed tool.

The only thing I need to do about the code is delete the three instances that F360's post processor for mach3 puts G28 into the list of code and it's ready to run.

I'd like one of these then you could machine whole crankcases in short time and bring back all those long lost designs where castings are no longer available. He uses a novel way to separate the parts from the block in several of his videos - a reverse chamfer tool and then a slitting saw to cut almost through then the part can be snapped off, not sure I'd trust my machine to leave a whisker thin piece of metal as I'd probably launch the part across the workshop!

<a href="https://www.youtube.com/watch?v=I--_63_wysk" target="_blank">http://www.youtube.com/watch?v=I--_63_wysk</a>

[stevehuckss396]

I'd like one of these then you could machine whole crankcases in short time and bring back all those long lost designs where castings are no longer available.

You don't need all that fancy stuff to machine a crankcase. With a little planning and careful setup you can do  a crankcase fairly easy.

This was 6 setups, no homing switches, manual tool changes on a $1300 scratch built milling machine.

[kvom]

On my mill homing to find machine 0 would move the table and spindle at a moderate rate.  As each access sensed its limit switch it would stop and reverse several though.  In theory this was repeatable to +/- .001".

With Mach3 it was never necessary to home, and with soft limits the machine is protected.  With a switch to PathPilot I need to reference each axis (i.e., click a button for each axis), but a configuration option lets this happen with no table motion.  However, referencing changes the values in the DRO.  For that reason, I shutdown the machine at the x0y0 position so that after referencing I can rezero the X and Y DROs.  I rarely leave a tool after shutdown, so the Z axis isn't an issue when referenced.  However, referencing Z sets its limit, so I'll typically jog it near to its upper limit before referencing.

No limit switch is provided for negative Z, but there's a rubber cushion at the bottom of the ball screw.

[Jasonb]

Yes Steve I know it can be done with a lot less I've done them myself even ones with just manual machines and mike Certainly does not have a fancy setup but it would be ideal for teh more rounded designs with thin tapering webs and fillets. I was thinking more that a small run could be done as there are many designs about that I'm sure people would make but don't due to the castings not being available, just look at something like the Motorboys plans books and you hardly see any of those being made. Same would go for the old Wall & Westbury designs

This is my Wall, crankcase two setups and each cutter changed manually (only got the one holder) Also base, manifold, flywheel, endplates, milled cylinder features, etc

[dieselpilot]

With Mach3 it was never necessary to home, and with soft limits the machine is protected.

This simply isn't the case. If the machine was configured to not require homing, you are taking a risk as to whether or not soft limits are within the machine's physical travels. Moving to X0.,Y0.(or any position) only helps if you have some physical reference you check. Linuxcnc stores the position on shut down. If the machine moves while the control is powered down the control has no idea where it is the next time it's powered up. This is where the risk is. If the machine hits a physical stop before the soft limit because the physical position and control position aren't aligned..... Forced homing prevents this issue.

  With a switch to PathPilot I need to reference each axis (i.e., click a button for each axis), but a configuration option lets this happen with no table motion.  However, referencing changes the values in the DRO.  For that reason, I shutdown the machine at the x0y0 position so that after referencing I can rezero the X and Y DROs.  I rarely leave a tool after shutdown, so the Z axis isn't an issue when referenced.  However, referencing Z sets its limit, so I'll typically jog it near to its upper limit before referencing.

The DRO changes depending on which work offset is active and how you're you're setting them. If the machine was homed when the work offset was set, homing again would not change the DRO for that offset. That is the function of work offsets. You can set one, and at any point later set the same values, and the machine goes to the same position.

No limit switch is provided for negative Z, but there's a rubber cushion at the bottom of the ball screw.

With homing and soft limits there is no need for hard limit switches when the control failure modes won't result in axis runaways. This machine design take that into account(hopefully).

[steamer]

The PCNC 440 does not have linear scales, or even motor encoders.  it only has limit switches, which is how it homes.   It counts stepper motor pulses and that is it.

Dave

[dieselpilot]

The PCNC 440 does not have linear scales, or even motor encoders.  it only has limit switches, which is how it homes.   It counts stepper motor pulses and that is it.

Dave

Yes.

[steamer]

And?

[stevehuckss396]

JasonB

I hear you. About 5 years ago I toyed with the idea of "electronic casting kits". You would get the basics in the form of Gcode and a setup guide for the block, heads, and oil pan and a set of drawings for the rest. If you had a machine run by Mach3 or compatible software you could simply setup your part exactly like the manual says and press cycle start and wait for the tool changes. I thought it would be a good way for hobbyist to make fancy things without buying fancy software or having fancy machines like that one. The crankcase on the engine in your photo would be a good example of what could have be done. It was not a well received idea so I forgot all about it. 

[Jasonb]

I was thinking more along the lines of the machined parts, at least the overall shape of major components  machined much like a casting but still leaving the builder the boring, turning and drilling to do. I other words a CNC machined "casting" set. Though an option at additional cost could be fully machined parts such as CNC cut cam profiles or finish machined castings.

I'm sure it would be a small market and maybe not worth the bother but if the CAD and CAM has been done then machining a second or six will be no more than the basic material and machining time and a bit of tool ware. A tool changer would help with reducing machining time or simply no need to stand around in front of the machine so you could be getting on with something else and getting a modest return from an otherwise unused machine. I expect farming it out to a small CNC shop would put the price to high but have no idea of their charges.

I you are aiming at those who already have a CNC then a step file of the assembly may be the better bet then they can access each part, decide how they want to machine it and run it trough their own CAM and Post processor to suit their machine and tooling complete with limits and stops as desired (keeping the thread on topic!). I did this with my Midget engine and the guy increased it back to the original size and has been machining the various bits on his own CNC.

[Hugh Currin]

Steve & Jason:

Alternately you could provide solid models and tool paths for the complex parts, such as the crank case. The purchaser would use their CAD/CAM program to produce the G-code, and/or make any modifications he wanted (feed speed etc). I'm thinking of Fusion 360 which has a minimal hobby package for free. If you sell the models you'd have to purchase a license for Fusion but that's not exorbitant.

It would probably take 10-12 hours before bootleg models apeard on the net though. Ya, not a great business model. But maybe something there for distributing model plans?

Just random thoughts.

[stevehuckss396]

Hello Hugh

Providing solids would be just a step above 2D plans. May as well just draw the part yourself from the plans.

[kvom]

Regardless of how they are set, I have the maximum X and Y motion +/- configured, and these are relative to the part x0y0.  These limits are large enough to cover 99% of parts I'd make and 100% of parts in the vise.

If I have a part mounted that might conceivably exceed a limit, I'll jog to the outer limit of the toolpaths as shown on the control.

[dieselpilot]

As we are all happy with the efficacy of our machines and practices, I have nothing else.

[Vixen]

What we are attempting to do is actually quite simply, it's to place the work on the table within the tables travel envelope.

There are many ways to do this, as we have read. Some methods use limit or home sensors, some do not.

There is no right way and no wrong way, as long as it works.

The discussion has been interesting and useful. Many methods have been described, We can now make our own minds up as to which way we want to go.

Thank you all

Mike