[PaulMakesThings]

What I'm trying to learn more about in general
I'm working on a project that will use a sherline mill with the 4th axis add on attached and tilted at an angle, most likely 45º.

Can anyone suggest what software I should look at for creating G-code for this system? How does one go about getting cam software to work with a machine like this? It's basically a live tooling lathe at an angle. I've so far only worked with cam software for typical 3 axis mills, so I don't know how you get it to understand the tilted 4th axis.

For those who want more detail:
The project budget allows for the software used to prototype the system to cost at most around $2000, and that will have to cover CAD and CAM. Free open source would be best, something we could try out before we buy it would be good.

The parts we need to make are called dental abutments. Basically a cylinder with a contoured lower edge. The blank looks like this:

it's about 5 mm wide
and we need to provide the ability machine that tapered part to a custom contour mimicking the lower half of a tooth. CAD software to allow the dentist to easily customize this tooth blank is another part of the project, for now it's safe to assume that it will be something that can export the usual parametric modeling formats and that the model will not have any sharp angles or concavities in the region where material is to be removed.

[LongRat]

Interesting project. I am extremely familiar with these components as I work in the dental CAD-CAM industry myself. I think you might need to be clearer on how the part is being held, and from which end. Also the fact that the collar area you wish to machine is not necessarily rotationally symmetric, or else the lathe would be the obvious choice.
I guess it is a little strange why you would use a Sherline to do this sort of component. The enormous value of abutments means that surely you could afford to push out the budget a little further? Regarding your software question, this could be done with any of the big boys' systems (e.g. Delcam Powermill) but not for the budget you've mentioned. I'm sure someone will will suggest something that will work though.

[txcncman]

I assume you want to run the 4th axis at 45 degrees for clearance issues. Yes?

[PaulMakesThings]

This is a university project for mechanical engineering and it is being paid for by an individual dentist, so that's partially the reason for the low budget. I agree he probably could make money while funding us more.

You understood correctly, the collar won't be rotationally symmetric. It will be held, either by a lathe chuck or a custom clamping fixture, at the wide end. The cylindrical portion that is toward the top in the image I posted.

The angle might not be necessary, but it is for clearance. A custom clamping fixture might also solve that issue. I don't know enough about CNC software for machines with rotational axes to tell yet. But if getting software that can work with a tilted rotating axis (as opposed to one perpendicular to the tool) proves more difficult than making a custom clamping fixture, that route is an option.

[LongRat]

If you hold the part horizontal you'll still be able to access the geometry I think, without needing the 45 degree tilt. Certainly then you could use Meshcam to hit it from any number of discrete angles. 4 would almost certainly be enough. This might not be the most time-efficient method but it would get the job done, with VERY cheap software.

[awerby]

DeskProto is working on that issue, but it's not in the current 5.0 software. If you get on the beta program for DeskProto 6.0, though, you could try out the tilted fourth-axis feature. Send Lex a message at [email protected] and explain what you're interested in doing. When the program is released, it will be well within your budget.

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[txcncman]

My advice here is to try to NOT use true 4th axis. Use your 4th for position only, 0, 90, 180, 270 degrees. Create WCS for each poistion, on the 45 degree tilt. Then create tool paths for each. Then you can hand code in the A axis position with manual coding as needed. I do not know of any software that will for sure handle this any other way.

[PaulMakesThings]

My advice here is to try to NOT use true 4th axis. Use your 4th for position only, 0, 90, 180, 270 degrees. Create WCS for each poistion, on the 45 degree tilt. Then create tool paths for each. Then you can hand code in the A axis position with manual coding as needed. I do not know of any software that will for sure handle this any other way.

If you hold the part horizontal you'll still be able to access the geometry I think, without needing the 45 degree tilt. Certainly then you could use Meshcam to hit it from any number of discrete angles. 4 would almost certainly be enough. This might not be the most time-efficient method but it would get the job done, with VERY cheap software.

I can see how just using the 4th axis to index would make things a bit simpler and I'll consider this option too. I already would know enough about G-code to manually add the indexing. What software would you recommend for generating the code for between each index? I know many support a projection onto one face of a model.

DeskProto is working on that issue, but it's not in the current 5.0 software. If you get on the beta program for DeskProto 6.0, though, you could try out the tilted fourth-axis feature. Send Lex a message at [email protected] and explain what you're interested in doing. When the program is released, it will be well within your budget.

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

That's interesting. How does it currently handle a normal lathe axis? If it can already do that I may be interested for that use as well. I see it has a free demo for 30 days.

[txcncman]

The only software I have used that I am sure can do what I described is MasterCAM. I am sure there are others. I just do not know what they are.

[LongRat]

I can see how just using the 4th axis to index would make things a bit simpler and I'll consider this option too. I already would know enough about G-code to manually add the indexing. What software would you recommend for generating the code for between each index? I know many support a projection onto one face of a model.

Meshcam will do this. It will handle all of the indexing moves too so there shouldn't be any manual cade chopping required. It's only $175 and you can get a free 30 day trial. Interestingly the multi-side machining feature doesn't seem to be mentioned on the web site, maybe that is because it is a fairly recent addition.

[PaulMakesThings]

Meshcam will do this. It will handle all of the indexing moves too so there shouldn't be any manual cade chopping required. It's only $175 and you can get a free 30 day trial. Interestingly the multi-side machining feature doesn't seem to be mentioned on the web site, maybe that is because it is a fairly recent addition.

Sounds like it might fit the bill, I'll check it out.

[awerby]

That's interesting. How does it currently handle a normal lathe axis? If it can already do that I may be interested for that use as well. I see it has a free demo for 30 days.[/QUOTE]

[DeskProto isn't lathe software; it assumes that things are being cut with an endmill of some sort. But it does support an A axis, and offers a few different approaches -with the Y axis at zero, moving the rotary A axis as the tool cuts around the workpiece with Z going up and down, then incrementally moving down X and taking another bite, or keeping the A axis fixed while the tool moves down the X axis, varying in Z, or using the indexing function to cut in 3-axis mode, then rotating in A a variable number of degrees and superimposing another 3-axis toolpath. Try the demo; it's pretty easy to get the idea...]

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[Fixittt]

actually, if your looking at the part as a whole, your over thinking it.
I did a proto type of one of these about 5 years ago. we cut it on a 4 axis machine with 3 different toolpaths. Machine the outside as a standard flip. Then had to rotate the part to get to the screw hole which was at an angle. The simple way to do this is to rotate the model in CAD and create the toolpath as a top down. Rotate the part on the machine to match and machine. I am trying to see if I still have the pictures of the one I cut. They are small, I want to think we cut it in corian (counter top material)

Dont over think it. Its actually pretty simple. Do it one step at a time. Rhino ($1000) to create the parts and STL files. Deskproto (995 euro I think) for the cam.

[PaulMakesThings]

I've been trying out meshcam and it seems to work well with this machine. The current problem I'm having is that Z is flipped. The machine plunges down and cuts rapid gashes in the part, then lifts up and cuts patterns in the air. Would I correct this in the tool path generating software (meshcam), or in the driving software (EMC2 for sherline)? And where would I find the setting? I'm not sure which part is unusual, is it more standard to take Z+ as being down into the part, or up away from it?

[Fastest1]

Z 0 is usually the surface and all cuts down are negative Z. There is no set way as long as you understand what is about to happen. Do the controls of your axis work as you expect otherwise? If so most likely just change your Z direction setting in Mach 3.

[Fastest1]

Sorry just saw your running EMC. I am sure the setting is similar, I am just not familiar with theirs. You could place the item in the opposite quadrant. Personally I think the Z is moving the wrong direction and just needs the directional change.

[PaulMakesThings]

It seems like EMC2 is probably wrong then, the jog controls also move the cutting head upward (toward the ceiling) when you press "Jog Z-" and since the machine is moving down for rapids and up for cuts, clearly this isn't want meshcam was expecting when it wrote the G-code.

Sorry for my newbness, but how do you reverse the Z axis, or any axis for that matter? Is it in calibration?

[rpovey]

In EMC you can either re run the setup and flip the Z or edit the machines XML file.

[PaulMakesThings]

In EMC you can either re run the setup and flip the Z or edit the machines XML file.

I had tried that but it didn't seem to work. Then I found that for some reason the settings weren't sticking. I'd change the conversion factor negative and it didn't work and when I went back it hadn't changed. Then I reset the computer and without starting any other programs I changed the settings and it worked. Odd.

[rpovey]

You just need to change the polarity of the Z Dir pin, I don't have a copy of EMC here right now, but if you haven't found it by the weekend I can take a look and tell you what the line in the XML file is.