Messages

1181

General Mach Discussion / Re: Muti-start threading....

« on: April 20, 2009, 05:17:30 AM »

Hi Andy,

Yes. If you set the pitch in Mach3 to 2.8mm (which is actually has to be called "lead") and advance the Z axis by 0.7mm for each start, then you would get a 4 start thread with a PITCH of 0.7mm and a LEAD of 2.8mm.

Prior to getting a new belt, check how it runs on the pulley - on mine I could actually see it going up and down when looking at a fixed point just above the pulley.

Daniel

1182

General Mach Discussion / Re: Muti-start threading....

« on: April 20, 2009, 02:21:43 AM »

Hi Guys,

About a month ago I decided to try to cut a double start thread on my Emco lathe. I chucked a 15mm dia aluminum bar stock and gave it a go... and it worked perfect right on the first attempt.

I think that in order to cut multi start thread it's necessary to first understand the nomenclature and how it works. Pitch, P, is defined as the distance between two adjacent crests (for metric threads). Lead, is the distance the screw advances when it's turned one revolution. For a single start thread, lead and pitch are equal.

Thus, when you cut a (multi start) thread what you have to consider is the LEAD and NOT the PITCH. So if you want to cut a 1mm pitch double start thread, you have to program a feed of 2mm/Rev for each of the starts. Obviously, the two starts are 1mm apart, so after cutting the first lead you have to move the tool 1mm in Z and start the move from there for the second lead. Note that the depth of thread has to be the same as if you were cutting a single start thread with the same pitch (which is 1mm for this example).

Like was noted in the previous posts here, the end of cut (in Z direction) has to be adjusted for each lead so that that they end in the same point along Z.

Hope it helps

BTW, Andy, both the threads on your picture above look messy. The single start thread looks awful - like mine used to be with the DC spindle motor that was not rotating steadily in the same RPM. Turned out my belt was worn out unevenly along the perimeter and was causing fluctuations in the spindle speed.

Daniel

1183

Show"N"Tell ( What you have made with your CNC machine.) / Re: Boxford Tooling Plate, 4th Axis & CoolJet

« on: April 18, 2009, 02:37:37 PM »

Simon,

Yes the rotor core is made in one setup on the mill. The blank is turned onthe lathe to prepare the bottom diameter and that is used to hold it for all the other operations.

It proves what a powerful tool a 4th axis is! Think could make the part without using a 4th axis?

I would really like a through bored spindle and I prefer a one that I can mount a chuck on. Know where I can find such?

If you say aluminum housing works well for you, then I think I'll go for aluminum as well.

Daniel

1184

Show"N"Tell ( What you have made with your CNC machine.) / Re: Boxford Tooling Plate, 4th Axis & CoolJet

« on: April 18, 2009, 02:07:32 AM »

Simon,

Thanks for the details!

Wow... and that tiny rotor core... is it nice... Well done! I liked id. Was it fully made on the 4th axis with one setup?

How do you generate the gcode for the 4th axis?

What is the bore diameter through spindle? Did you make the housing out of steel?

I plan do build a 4th axis as well (to be used with my Emco F1), but I want to design it such that I can mount it both vertical and horizontal. I want the horizontal mounting mainly because I had to machine large disks few times, that were beyond the travel of my F1's Y axis (100mm).

What belt tooth profile did you use? I used Gates GT2, 5mm pitch on my Compact 5 servo spindle, and was stunned to discover it had backlash. I don't know if it's the way it should be. You can actually see the air gaps between the meshed teeth of the belt and pulley, which is not the case with MXL belts for example.

Daniel

1185

Show"N"Tell ( What you have made with your CNC machine.) / Re: Boxford Tooling Plate, 4th Axis & CoolJet

« on: April 17, 2009, 08:10:24 AM »

Hi Simon,

Nice work! Did you make the 4th axis from scratch? How about sharing some details about how you made it? Is it stepper driven? what is the max RPM?

Did you make the spindle yourself? Did you use angular contact ball bearings?

Have you tried it yet? What is held in the collet there?

What is the table travel of your Boxford?

Thanks.
Daniel

1186

General Mach Discussion / Re: Opinion and advice - explain relationship of encoder to kernel speed

« on: April 17, 2009, 07:40:22 AM »

Hood,

Thanks for the insight... and I was wondering why no one is using it with Mach3...

Daniel

1187

General Mach Discussion / Re: Opinion and advice - explain relationship of encoder to kernel speed

« on: April 17, 2009, 07:18:25 AM »

The CNC Brain is a pretty expensive motion controller, that can be interfaced with Mach3 (like the SmoothStepper), and has yet to prove itself being worth the money. It is supposed to provide double closed loop control. I think, if it proves itself, it's going to be the next thing for many CNC builders and OEMs that use Mach3.

You can check it here http://www.safeguardrobotics.com/default.aspx?tab=cncbrain

Daniel

1188

General Mach Discussion / Re: Opinion and advice - explain relationship of encoder to kernel speed

« on: April 15, 2009, 02:26:37 PM »

You are right, but arranging a hardware solution would also take time...

As I said, I think it should be an easy fix for Greg to enable setting same pins for two axes. I will see first how it goes with this software fix...

Daniel

1189

General Mach Discussion / Re: Opinion and advice - explain relationship of encoder to kernel speed

« on: April 15, 2009, 12:14:12 PM »

You're right, I could use a hardware relay to switch from A axis to Spindle, but I don't want to do this at this point. I want to find a software solution to this. The problem is that the software guys keep saying they are just about to fix the problem, causing us not to want to do any fancy hardware changes. If someone of them were to tell us it isn't going to happen, I'm sure everyone were looking for other solutions.

Daniel

1190

General Mach Discussion / Re: Opinion and advice - explain relationship of encoder to kernel speed

« on: April 15, 2009, 06:00:16 AM »

Yes, I know, it's OEMbutton 253 to disable A axis. It does disable the axis but the spindle still won't work - you must go to Ports&Pins and disable it from there.

Any other ideas? Another OEMbutton?

Daniel