Frage Hello from a prospective Stepcraft owner

Hi all,

I've been reading through the forum (mostly using Google's translate function!) to research the Stepcraft, and thought I'd post a quick introduction.

I run a small business (Wolfram Slides) making specialist high-end guitar slides from solid tungsten carbide, and am in the process of expanding this product range in some new areas.

I'm considering purchasing a Stepcraft (I'm currently waiting for more information on the new 840 before I make a move) for prototyping new products, making molds for thermoset plastic and production of bespoke cardboard / foam packaging for my existing bespoke products. - No I'm not expecting it to be able to mill tungsten carbide!

I'm completely new to CNC, but am relatively experienced with 3D CAD and modelling. The Stepcraft machines with appropriate accessories appear to satisfy most of my requirements, and Rory of StoneyCNC here in the UK has been really helpful in answering my (many) questions.

However, while most of what I want to do is clearly within the envelope of the machine, not having any 'hands on' experience of CNC or these machines, I don't really have any intuition or feel for what I can and can't do with it when I start pushing the capabilities, and most of the online videos (with which I have entertained myself - and my fascinated four-year-old daughter - for hours) are focused mainly on cutting 2D shapes.

So, a couple of questions - I'd appreciate any input.

Firstly, what is the maximum size of workpiece that can be held by the Stepcraft fourth axis chuck? To do what I want, I really need to be able to clamp a 1" diameter solid plastic cylinder from the outside. I guess if the Stepcraft-supplied unit is too small for this, I'll have to investigate a third-party solution or make something.

Finally, just for fun, would the Stepcraft (with 500 watt HF spindle) be capable of replicating these projects: (I understand that the machine would have to be run more slowly, with a lower feed rate, but could it be done if I had sufficient patience?)

1. CNC Frog Table https://www.youtube.com/watch?v=TMG3mnlUimk

2. Electric guitar body https://www.youtube.com/watch?v=x5lp2Z6Qp2g (maybe would need to be machined two-sided if Stepcraft cannot hold cutters with sufficient diameter to cut to this depth?)

Thanks in advance for your input!

Cheers,
David

hi, i watched the video making the guitar body. i think this will be hard for a stepcraft machine cause of the cutting depth. the biggest diameter for routing bits for hf-spindle is 8 mm.
some weeks before i was cutting through 40 mm plastics (polyethylen). it was really hard work to get through cause of the clamping lenght of the used bit. till around 30 or 35 mm depth all is fine but then i lost the bit twice and damages the working part. i was using a bit with clamping diameter 8 mm and cutting diameter 10 mm.

with other and better cutting tools it will be better but for cutting depth around 40 mm (i think the guitar body thickness is around that) you will be at the limit of a sc hf spindle.

Hi DrillDevil!

Yes, I figured 40-45mm might be too much. I wonder whether it would be feasible to cut it two sided, so the maximum cut depth from either side would be about 25mm? I guess I'd need to work out a way to centre the origin on the workpiece for each side so the cuts meet in the middle close enough for sanding out any discontinuity...

drilldevil schrieb: hi, i watched the video making the guitar body. i think this will be hard for a stepcraft machine cause of the cutting depth. the biggest diameter for routing bits for hf-spindle is 8 mm.
some weeks before i was cutting through 40 mm plastics (polyethylen). it was really hard work to get through cause of the clamping lenght of the used bit. till around 30 or 35 mm depth all is fine but then i lost the bit twice and damages the working part. i was using a bit with clamping diameter 8 mm and cutting diameter 10 mm.

with other and better cutting tools it will be better but for cutting depth around 40 mm (i think the guitar body thickness is around that) you will be at the limit of a sc hf spindle.

WolframSlides schrieb: ...
Firstly, what is the maximum size of workpiece that can be held by the Stepcraft fourth axis chuck? To do what I want, I really need to be able to clamp a 1" diameter solid plastic cylinder from the outside. I guess if the Stepcraft-supplied unit is too small for this, I'll have to investigate a third-party solution or make something.
...

I don`t have any experience with the fourth axis, but I looked at the pictures on Stepcraft site: https://www.stepcraft-systems.com/en/accessories/system-accessories/cnc-accessories/circular-table-with-three-jaw-chuck . There is a Proxxon logo on the chuck. The only Proxxon chuck in that size and appearance seems to be the optional three jaw chuck (item 27026) for the lathe DB 250 seen here http://www.proxxon.com/en/micromot/27020.php?search#27026 . Capacity inside for this chuck is 1.5 to 32mm, but the ends of the jaws could hit the clamping surface when attaching max size. I could be wrong though. Maybe someone can confirm that.

drilldevil schrieb: ...
the biggest diameter for routing bits for hf-spindle is 8 mm.
some weeks before i was cutting through 40 mm plastics (polyethylen). it was really hard work to get through cause of the clamping lenght of the used bit. till around 30 or 35 mm depth all is fine but then i lost the bit twice and damages the working part. i was using a bit with clamping diameter 8 mm and cutting diameter 10 mm.

In the Stepcraft Operating Instructions under Intended Use it is said that "you should work using milling cutters with a diameter of up to 3mm". Aren`t larger ones risky to use?

WolframSlides schrieb: ...
Finally, just for fun, would the Stepcraft (with 500 watt HF spindle) be capable of replicating these projects: (I understand that the machine would have to be run more slowly, with a lower feed rate, but could it be done if I had sufficient patience?)...

Low feedrate or cutting depth and sufficient patience might not be good if you run a CNC machine for commercial purposes. Time cost and maintenance schedule is also to be considered here. If it takes a long time for the machine to make a single item then the number of maintenance procedures per detail will also be larger. More powerful and initally costly machine could actually prove cheaper pretty soon because of faster machining time and lower maintenance needs. Just something to think about. I am not involved in running a business myself.

tikka schrieb: In the Stepcraft Operating Instructions under Intended Use it is said that "you should work using milling cutters with a diameter of up to 3mm". Aren`t larger ones risky to use?

i didnt read something like this, so i cant say whether it s wrong or not but:
er 11 clamping

it sounds silly me to sell these er 11 clamps up to 8 mm and saying "you can buy these but you are not allowed to use them "

Hmm, I understand from one of the German posts on this forum that Stepcraft have confirmed that the forthcoming Stepcraft 2 range have a higher portal and can accommodate Kress and Suhner routers up to 1,000 watts.

The new machines must have been significantly beefed up - the Suhner weighs just under 3kg!

Think I need to wait until there's more official info on the 840 that's available from mid December.

Regarding cutting depth - can you not run a .5m depth then step down and repeat the path as in a CNC machine? Just copy the Gcode into the next path .5mm deeper until you get to the desires depth of cut. Then run a pressure pass (same tool path) around the cut at full depth to remove tool marks?
Do this on the big mills all the time.