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Topics - grzgrz

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Hi guys,

I attempted to cut a spindle mount out of some scrap piece of 16mm sheet POM and the result was really poor.

Here's the setup:

The machine itself is a lightweight (ca 50kg) extruded aluminium profile router with a water-cooled 800W 1000-24000 RPM spindle and can supposedly feed up to 2500mm/min.

The stock had been drilled, placed on a wooden spoilboard and attached to the T-slot table by two screws.

I used a 6mm 1-flute, polished rake solid carbide end mill designed for machining aluminium/plastics. Not an Onsrud, but I fed their cutting data for soft plastics for a 1/4 inch diameter end mill (ChipLoad = .008-.012', or ,02-,03mm) to the CamBam's Feeds and Speeds Calculator, setting the RPM to 10000, F to 2000 (mm/min) and DOC to 6mm (=1D).

That's when black magic happened! The machine is not designed for running coolant, but I suppose chip evacuation wasn't an issue, as the black flakes flew everywhere. Also, the router itself began to dance on the table and the first half of the mount did not stay in place despite using some holding tabs. Needless to say, the end result was really poor and the surfaces really rough.

I remember machining POM before and encountering the opposite of this problem. The surface finish was better... until the plastic started to grow hair, so I imagine that the feeds were too slow back then.

Anyway, any words of advice on how to obtain a good finish on this router? Can it be achieved e.g. by reducing the feed and speed and/or DOC, better securing the workpiece, attaching the machine directly to the table (as it is, it stands on four rubber feet), all the three solutions combined, or something else?

Regards,

Grzegorz

2
Members Machines / Ideas for support and enclosure for a small CNC router?
« on: September 13, 2016, 08:42:08 am »
Dear fellow CamBam users,

I set about designing a proper support and an enclosure for my little Chinese CNC router (to be operated in a standing position). There are some constraints: I have limited space, so I'm aiming for the smallest possible footprint, and I cannot attach (i.e. screw) the support to the floor.

The router bed is 360 x 565 mm. The height of the bed is 95 mm (rubber machine feet excluded). The overall dimensions, including the gantry, are ca 550 x 565 x 535 mm, and the machine weighs 47 kg.

The machine is supposedly capable of 2500 mm/min (98 ipm) feeds and 5000 mm/min (196 ipm) rapids, uses 57 two-phase 3A stepper motors, and has a water-cooled, 800W, 1000-24000 RPM spindle.

I'd like the router bed surface to be at elbow height, or 1200 mm (+/- 40 mm, according to an OSH brochure; this was the recommended height for precision work at standing desks for tall people). I imagine that, for greater stiffnes, the router bed could be attached directly to the table top.

Disclaimer: I don't have any engineering background, but I thought of either an aluminium profile assembly or, if it weren't stiff enough, a welded steel tube frame. I only know that the support should eliminate the machine's jitter/wobble, but I have no idea how to match the right material to the right dimensions.

As for the enclosure, I need to solve the issue of chip removal first. For milling wood and plastics, if the machine is enclosed, do I need a dust collector, air blast, or both? And for aluminium, what would be the best solution: mist, flood coolant (though I don't know if it's suitable for this type of machine) or air blast?

I'll be grateful for your insight,

Grzegorz

3
Members Machines / Simple trunnion table design?
« on: February 18, 2016, 22:36:31 pm »
Hi guys,

After experimenting with my Chinese 4-axis CNC4030Z-S, I'm planning on adding a simple trunnion table to the current setup. As I don't have any experience in machine building and I couldn't find too many blueprints on the Internet, so I'll appreciate any advice!

My rotary unit has a three-jaw self-centering chuck and a tailstock (that I want to replace). The height of the rotary axis centre is 55 mm. My first concept is a 200x100x10 mm (steel/aluminum) plate with two shafts, one fixed in the chuck and the other in a (self-centering?) ball bearing.

My questions are:

- Would a single-piece trunnion (i.e. a plate with protruding shafts) be any good, or should the plate be milled separately, drilled from both sides, and then the shafts would be inserted, drilled and fixed with screws?

- Is one ball bearing (support) enough or do I need another one (close to the chuck; I suppose I'd need it anyway if I wanted the upper surface of the plate at the rotary axis centre, unlike in my draft, where the centre is in the middle)?

- Is there any way to calculate the right size of the components in relation to stepper motor/spindle output and/or structural rigidity? (E.g. minimum plate thickness, shaft and bearing size etc.)

- Similarly, how can I choose the maximum length of the trunnion table without the need for additional support from beneath (i.e. rollers, assuming that the lower part could be semi-cylindrical)?

- What about slots and/or holes in the plate for quick fixture/workpiece changes? Any recommended patterns for a versatile trunnion?

- Finally, is there any way to facilitate the homing of the Z axis and the rotary axis? Has anyone ever tried e.g. mounting a tool probe on a trunnion table?

I hope I'm not making the design process more complicated than it should be...

Regards,

Grzegorz

4
Feature Requests / Lofting, anyone? :-)
« on: December 16, 2015, 12:35:34 pm »
Hi there,

Correct me if I'm double-posting, but I couldn't find such a feature request in this section of the Forum: how about adding advanced solid creation, such as lofting, to CamBam?

CamBam's native 2D drawing features are a real time-saver for simple tasks. But for more complex solids, not every 3D modelling software has 3DS or quality STL file export options.

What do you think?

Grzegorz

5
CamBam help (General usage) / Indexed 4th axis + swarf/flank machining
« on: October 26, 2015, 15:25:41 pm »
Hi All,

I've just had an e-mail exchange with David about the CamBam's capacity for using the side of the cutter instead of its end. According to David's explanation, this can be done only for parts whose cross-section is symmetrical and circular. More complex 3D models would need to be wrapped, but the use of the cutter side is not available for such an approach.

Is there anyone out there who has a solution to this problem?

I know everything can be hand-coded, but the process would be very time consuming and would involve complex geometric calculations (of course, if you know some software that could help with that, do let me know).

Regards,

Grzegorz

6
Latest News / Polish CamBam translation
« on: August 20, 2015, 19:40:46 pm »
Dear Polish-speaking CamBam users,

I have uploaded a new version of the Polish CamBam interface. You are welcome to try it and let me know if the translation needs to be corrected.



Drodzy polskojęzyczni użytkownicy CamBam,

Zamieszczam nową wersję polskiego interfejsu CamBam. Przetestujcie i dajcie znać, gdyby tłumaczenie wymagało poprawek.


Grzegorz

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