& todays random 'wet behind the ears' questions are....

[HankMcSpank]

How do I measure how much backlash my homemade machine has (don't laugh!), so I can then enter a compensation in Mach? (as it goes - don't laugh - using delrin nuts on M8 there doesn't seem to be a huge amount!)

My Dremel is starting to get on my tits (too whiney & too feeble), so I was pondering has anyone used/seen/heard the Proxxon BFW 40/E

http://www.kdntool.com/_sgt/m5m4_1.htm

It seems to fit the bill (quietish - so they say), more power (rock 'n roll, rock ....rock 'n roll), a 1/4" collet holder (so I can start hanging out with the big lads).

The down side is that it only goes up to 5,000RPM......how much of a hinderance is that going to be (say for 'playing grown ups' & attempting to mill aluminium)...most of my cutting will be acrylic, so the lower speeds (vs the Dremel) should be handy.

Becuase I'm a bit of an electronics anorak, I'd also like eventually to be able to mill pcbs.... does the runout increase with router size? Am I likely to get runout 'for better', for worse until parts do me death?

Would 5,000RPM even do PCB milling well?

The ideal solution woud be to have two cutting spindles...the Proxxon for the chunkier jobs & something like the wolfgang for the PCB jobs....does anyone operate in this manner (ie a quick spindle changing option?)


Oh yeah...one last question, Two sided milling - how can I flip a part over to mill the other side, yet still have it lined up ok ...so that the tool ends up in the right place on the board vs the other (original) side - presumably some form of keying comes into play?

[Robin Hewitt]

How do I measure how much backlash my homemade machine has

You either measure it directly with a dial test indicator, or, you cut something then measure it with calipers.

S'easy

[audioandy]

Hi Hank

I have a BWF 40E, I have just purchased a VFD and water cooled spindle so at the moment in the process of rebuilding my machine.
I have not used the Proxon in anger, if you go to my build thread there is a video of mine pocketing out some MDF,might give you a better idea.

Andy

[John S]

Oh yeah...one last question, Two sided milling - how can I flip a part over to mill the other side, yet still have it lined up ok ...so that the tool ends up in the right place on the board vs the other (original) side - presumably some form of keying comes into play?

Make a sacrificial plate up, MDF or alloy and put a hole in at 0,0 say 3mm [ up to you.] Now put two holes in on the Y 1.5mm to the left of the 0,0 point about 30 to 50 mm apart [ depends on size of board ]
Do same in X with the holes 1.5mm lower than 0,0
You now have 4 contact points that are on Y 0 and X 0 you can butt your board up against.

If you program everything from 0,0 it will be in the correct relation, now if you program the other side again from 0,0 remembering to take mirroring into account [ don't ask ] just flipping the board will allow you to pick position up again.

Next time you use the jig, square it up on the bed, drop a 3mm peg into the 0,0 hole, zero your controller and you can re run pre programmed codes again with no trouble.

You could do the same with a corner machined out to form an L but they are prone to getting dust and crap in the edges that hold the board off.
using pins gives an edge contact that's easy to keep clean and free from obstructions.

Often on a simple one off job I'll code the drilling of the 5 holes then the part.
Fit the sacrificial plate, drill the holes and before the part code starts bale out of the program with e-stop.
Edit the 5 holes out of the program then run the program for the part.

Hope this helps.

.

[HankMcSpank]

Hi Hank

I have a BWF 40E, I have just purchased a VFD and water cooled spindle so at the moment in the process of rebuilding my machine.
I have not used the Proxon in anger, if you go to my build thread there is a video of mine pocketing out some MDF,might give you a better idea.

Andy

I'm a little puzzled with your videos. You bought a VFD spindle & then posted up a virtually silent CNC machine doing it's stuff!

[ame="http://www.mycncuk.com/forums/showpost.php?p=5675&postcount=25"]MYCNCUK - View Single Post - Machine Build My Build[/ame]

Is that the Proxxon *or* is that the VFD Spindle? (I can';t believe how quiet that is! - like astoundingly quiet ...very anti-ASBO ish)

You say you've not used it in anger...do you mean, not used it much or not used it at all). I just wanted to canvass your opinion on whether it seems like quailty. I think I read somewhere there are problems with the Proxon not have a standard collet ...has this hampered you?

Also, if you've upgraded...do you wanna sell me the proxxon?!!

[HankMcSpank]

Hmmm...re that Proxxon...it seems I wouldn't joining the big lads with proper 6.35mm cutting bits after all!

An owner/user on his site (below), reckons there's no 6.35mm collet available for it. there is a 6mm collect...but I guess that extra .35mm counts?!

http://www.tea-with.me.uk/index.php?cid=3114

[audioandy]

Hi Hank

The video showing the MDF being cut is the Proxon not the spindle.

The Proxon was one of the first things I purchased when I first started with this CNC bug!
but the machine I have built is much bigger than I first planned and the Proxon is dwarfed, so thats why I decided to buy the 3HP spindle.

When I say its not been used in anger, all I have done with it is the MDF in the video and some engraving thats it.

The build of it feels good and I was very pleased with the engraving I did,if you are serious about getting one, you are more than welcome to borrow this one (I have the clamps for it) and try it to see if it will do what you intend to use it for.

Regards

Andy

[HankMcSpank]

Hi Hank

The video showing the MDF being cut is the Proxon not the spindle.

The Proxon was one of the first things I purchased when I first started with this CNC bug!
but the machine I have built is much bigger than I first planned and the Proxon is dwarfed, so thats why I decided to buy the 3HP spindle.

When I say its not been used in anger, all I have done with it is the MDF in the video and some engraving thats it.

The build of it feels good and I was very pleased with the engraving I did,if you are serious about getting one, you are more than welcome to borrow this one (I have the clamps for it) and try it to see if it will do what you intend to use it for.

Regards

Andy

Andy what a marvellous offer (& very trusting of you to!).

I'll drop you a PM.

[HankMcSpank]

Well, what can I say...a big thanks to Andy for allowing me to trial this. It's mounted & boy compared to my dremel it's a beast on this small CNC I've built. It's actually too heavy for my present asthmatic steppers (ex dot matrix printer steppers)...



but fortunately, at the weekend I bought some new steppers. The problem is they have an 8mm shaft - and my jaw couplers will need boring out more...



Anyway, too late tonight to trial it (unless I want to be slapped with an ASBO) - but it's *so* quiet in comparison to my screeching Dremel!

[audioandy]

Looking good Rob