RF-31 milling problems

[unco]

Hi all, I have a RF-31 mill which I have used for quite a few years as a manual machine. Recently I converted the machine to cnc via the cnc masters retrofit kit. After all the expected teething dramas I got the machine working well and was quite pleased with the practice pieces I was doing on the bakerlite panels I acuired. However when I moved to working on aluminium I encountered problems with inconsistency in cuts. For example if I made 10 identicle cuts of a 1mm depth using a 10mm end mill I'd get to the 3rd or 4th cut and it looks as though the tool has been pulled in on a 20-30 degree angle then the following cuts appear to be ok. I use climb milling technique with hss four flute end mills. Ive checked the quill for play but there doesnt appear to be much there. Any help would be fantastic. While Im here does anyone have a RF-31 manual I could get a copy of Ive been looking for one now for ages without any luck, thanks guys

[Torsten]

Not sure what exactly you meant by pulled in 20-30 degr., are you saying you encountered Tool deflection meaning the tool gets pushed away from the surface?
Are you using the stock leadscrews?
A 2 flute or a 4 flute, carbide or hss cutter?
What feedrate did you use, and coolant or dry?
What was the Spindle Speed?
If you give us some more info we may be able to make some suggestions.
Congratulation on getting your mill converted, is this stepper or servos.
How did you do you Z-Axes?
I converted the same Machine, actually still finishing up on it.

[Bubba]

unco,
I agree with Torsten that more info is needed. And for cutting Aluminum, I use a 2 flute as you can't really get proper rpm out of a stock RF31 setup (approximately 2500 rpm) and for proper chip loading, you need a lot more.
I can help you on the manual part though and attached are a few that I have accumulated for my RF31

[Bubba]

OK, lets try the attachments again. Had a problem with the upload

[irving2008]

Originally Posted by Bubba OK, lets try the attachments again. Had a problem with the upload

Thanks for that Bubba... I have a Warco MD30 which is very similar and I've been looking for a manual for it... Warco can't supply one!

[dgoddard]

Welcome to the RF-31 world. Several years ago I converted my RF-31 to CNC (with the help of Bubba) and been having fun every since. Agree with the others, need more info such as feed, speed, depth of cut, etc. Prehaps you could attach a copy of the g-code for the part you were machining. Also suggest, if you haven't already done so, is do a backlash check on the X and Y axis.

[unco]

Originally Posted by Torsten Not sure what exactly you meant by pulled in 20-30 degr., are you saying you encountered Tool deflection meaning the tool gets pushed away from the surface? Are you using the stock leadscrews? A 2 flute or a 4 flute, carbide or hss cutter? What feedrate did you use, and coolant or dry? What was the Spindle Speed? If you give us some more info we may be able to make some suggestions. Congratulation on getting your mill converted, is this stepper or servos. How did you do you Z-Axes? I converted the same Machine, actually still finishing up on it.

The Z-Axes is belt driven in the cnc masters retro-fit kit. They supply replacement ballscrews for the x and y axes' as well which makes for a top class mill.

[unco]

Sorry about the lack of info, I'm a novice forum poster, I was machining a piece of 20mm 7075 aluminium flat bar. I had the speed set at 1540 rpm. I was using a four flute end mill and taking a 1mm deep cut. I had the coolant pump on and quite a strong stream of coolant,I use Rocol ultracut cutting fluid. This is a bit difficult to explain but when you look at the machined surface it looks as though the piece had been tilted on a angle for about 8mm. So there is an angular cut which goes from nothing at the top down approx 8mm and in to a depth of approx 1.5-2mm. The job profile below this depth is OK. You can see the depth of each cut but Its not a bad finish. This fault occurred on cuts that where both curved and straight The cutter was pulling into the job not away from the job. The feed rate I set was 125mm per minute or about 5 inches per minute. Hope you have enough to go on thanks for your time and experience

[Bubba]

OK, the first thing I see is that your feed and speed for this cutter are probably way off.

You should be according to my calculator be running about 4800 rpm and 950 mm/min feed rate! It also sounds like you "may" be getting deflection of the tool.

[dblox]

At first I thought you had described the cutter as ramping down, I.E. the cutter was being pulled out of the collet.
Now I think you mean the workpiece has an angled move where there should be a straight one.
I dont know if it's the same issue but when I first started out in CNC I had a similar problem, where the corner of a part I was making kept getting "gouged" by the cutter and I couldnt figure out why.
In the end it was bad fixturing, I was using counter sunk screws in non countersunk holes to hold my aluminium down.
(I figured the countersunk screws would "center" the work exactly where the holes were)
The screws were allowing the work to move around and flex when the cutter entered the work.
How are you holding your part?

[unco]

Thanks Bubba The JET manual in particular is a huge help to me. Its not exactly the same but its very close. I have been tossing up whether to try and replace the quill bearings or not and now with your manual I might give it a go.

[unco]

Originally Posted by Bubba OK, the first thing I see is that your feed and speed for this cutter are probably way off. You should be according to my calculator be running about 4800 rpm and 950 mm/min feed rate! It also sounds like you "may" be getting deflection of the tool.

Thanks again Bubba, the physical limitations of my machine dictate a possible max spindle speed of 2500 rpms. Is there an alternative strategy you would recommend IE shallower cuts slower feed rate etc.