Member postings for Mark Fry

Yes, units are in mm.

Does each die cost much to make? How is pressing compared to injection moulding (as plastic) in terms of tooling costs?

> However you might want to reconsider the design to eliminate the rolled section.

Will the rolled section be difficult?

Hi all,

I'm planning to have 1,000 pieces of the following made. Material is 304. Does it require several dies be made for multiple stage stamping? Is it even feasible?

I wonder if something like this could be made for less than £2,000 all up.

Any thought appreciated.

Edited By Mark Fry on 10/04/2017 13:22:38

Michael,

Do you mean a 0.5mm increase? That's quite significant - especially when the rod is only 2mm in diameter.

If a 2mm stainless steel rod is pressure knurled, could the height of the pattern be 0.025mm? Is a height increase of 1.25% reasonable? Like Clive pointed out, I wonder if the end of a 2mm rod can be made thicker (2.05mm) to give a tight fit.

Hi

Are knurling patterns always taller than the rod itself? For instance

In this photo, the pattern seems to be significantly taller. Are there ways to precisely control the height of the pattern?

Any help appreciated.

Edited By Mark Fry on 29/03/2017 10:30:59

@JasonB I think I forgot to mention that I'm hoping to achieve a tight fit. I was thinking a 7mm hole because I thought the rubber should be compressed a fair bit in order for it to grip on the plastic tube.

So I think a M5 in a 5.1mm hole would give it a somewhat loose fit.

Is ABS prone to cracks? Will PC be better?

Edited By Mark Fry on 08/05/2016 20:43:26

Hi all,

I wonder if there's a good way for quick-fitting a M5 screw into a piece of 2mm-thick, 10mm wide plastic tube. That is, the screw could be inserted and removed by just pushing and pulling the screw into/from a hole in the plastic piece.

The connection won't sustain high stress, as the screw part will be held fixed and it'll always be under the plastic piece.

I'm thinking of fitting a rubber sleeve over the screw, but I wonder if popping the plastic piece (with a 7mm hole, suppose the rubber is 2mm thick?) in and out would put too much stress on the plastic and eventually create cracks in it.

Any thought will be much appreciated.

Thanks

Edited By Mark Fry on 28/04/2016 10:19:28

That's not how patents work. An "invention" is patented (automated or not), and if you put those steps into practice, then you as a human being infringe the patent.

But often CAD like Solidworks is used to generate CNC code. You load the model in Solidworks, assess the parting line and all, and generate CNC code. Isn't that very much what's specified in the claim?

The patent says:

More specifically, the present invention relates to software supported methods, systems and tools used in the design and fabrication of molds for custom plastic parts.

So, as long as it's "software supported", it could infringe the patent. No?

Hi

I've just come across this patent which seems to encompass what machinists do everyday, i.e. take someone's CAD file, find parting line, etc.

Here's the claim:

1. A method of automated, custom mold manufacture for a part, the mold having a first half and a second half opposed to the first half, the first half and the second half together defining a cavity corresponding in shape to the part to be molded in the cavity, the method comprising:

• creating a collection of stored information of standard tool geometries indicating surface profiles machinable by each of the standard tool geometries;
• receiving a CAD file from a customer for the part to be molded, the CAD file defining a part surface profile;
• assessing the CAD file to determine a straight pull z-direction, a parting line and corresponding shutoff surfaces separating the first half and the second half of the mold, so that the parting line and corresponding shutoff surfaces are oriented with respect to the part to permit straight pull of the first half and the second half in a straight-pull z-direction during molding of the part;
• based upon the determined orientation of the straight-pull z-direction with respect to the part, processing the CAD file with a computer to automatically identify and locate a plurality of discrete machinable portions of the part surface profile, each machinable portion corresponding to a machining tool path machinable with a selected tool from within the collection of standard tool geometries, each of the machinable portions being tool accessible with the selected tool oriented in the straight-pull z-direction;
• based upon the plurality of discrete machinable portions, computer generating a series of CNC machining instructions corresponding to machining the mold with the selected tools and computed machining tool paths; and
• machining the cavity into the first and second halves of the mold with the selected tools and computed machining tool paths via the computer generated series of CNC machining instructions.

We practice the steps outlined, don't we?

Edited By Mark Fry on 24/04/2016 07:48:29

Sure. The block is just driven by a crank. Indeed, the crank can freely shift vertically. However, i'm hoping the block (along with the crank) to return to the home position whenever the cut points upwards.

Thanks

Hi all

I have a design with two parts (at the moment): a fixed 10cm ring with vertical tracks and a freely rotating block with a cut that slides along that tracks:

I'm trying to find a low profile way to ensure that whenever the cut in the moving block faces upward vertically, the block is pushed up (almost) touching the inner face of the ring. That is, it returns to its "home position" whenever the cut faces up:

The only way I could think of is to have a part like a leg sticking out from the bottom of the block so that it pushes against the ring or an external track (near the bottom of the ring) whenever the cut nears facing upward. The issue is that this leg will require quite a bit of extra space, e.g., when the cut faces down but the block is at the top, the leg will point upward. The method should not constrain the block's movement along the tracks or rotation.

Does anyone know of a better way?

Any thought appreciated.

Edited By Mark Fry on 11/04/2016 08:33:44

Hi Muzzer,

Indeed, reduction ratio isn't needed. The two wheels don't have to move continuously, but need to move in the same direction.

The Oldham coupling is certainly interesting! However, my understanding is that the misalignment between the input and output shafts needs to be defined so that the coupler is manually shifted accordingly. In my case, manual configuration isn't possible, so I was hoping for a mechanism that could self-adjust to the misalignment.

I wonder if there's a self-adjustable coupling mechanism.

Thanks

Mark

Edited By Mark Fry on 11/02/2016 18:46:46

Hi Ian,

Here are the answers to your questions:

- The green wheel is to be driven by the grey base wheel.

- The green spindle is about 3MM-5MM in diameter.

- The base grey wheel is the driver for the green wheel.

- The green wheel is to be rotated in circular motion. It will not orbit.

- The block in slot is part of the wheel. It's attached to the spindle, so it rotates with the spindle.

Cheers

Mark

Hi Tim,

Sorry, I certainly can provide more detail. I'm just trying to turn the green part/wheel using a base wheel. The rotational axis of the green part is eccentric w.r.t. the base wheel. Also, the position of the green part can be slightly adjustable along the X axis intersecting the centre of the grey wheel, i.e. the red line

Note that the red line doesn't span across the entire diameter of the grey wheel, as the allowed adjustment is relatively small.

As to your questions:

- No, the green wheel needs to turn in a circular motion.

- The green wheel could rotate at any speed and the speed could vary.

Hopefully my issue is better explained. Let me know if I'm missing anything.

Thanks

Mark

Well, I don't doubt that for a second. I'm very new and CAD's merely a tool.

Hi Jeff,

I've just looked it up. Are you referring to this?

But this slides the bar horizontally whereas I'm hoping to turn a wheel eccentrically, whose axis is adjustable.

Mark

Hi all

I have a small setup (~20cm) in which a wheel-like part (green) is turned with an eccentric drive (grey wheel) as below

The position of the green wheel is adjustable along the two grey points.

My current idea is to cut a radial slot on the wheel and design a planetary part with a slot and pin (yellow). The wheel turns the yellow part by the pin.

With the depicted position, the wheel can no longer turn anti-clockwise due to the wedge action of the yellow part.

Is it possible to have this adjusted such that the yellow part somehow gives way?

Here's the wireframe view, if it helps:

​

Mark