CAM Assist's cycle time is a calculated estimate, so it can run shorter or longer than the real time on your machine. The Scale factor on each machine corrects it: a percentage that CAM Assist multiplies every machining time estimate by. This article explains what the estimate covers, how to work out the right scale factor, and what the other cycle time fields mean.
What the estimate covers
CAM Assist calculates the machining time of each operation from the planned cuts and their cutting parameters:
- Roughing: the volume of material to remove divided by the material removal rate.
- Finishing: the estimated cutting distance divided by the feed rate in the tool's cutting parameters.
The estimate leaves out machine effects such as acceleration and deceleration, and lead-in, lead-out and linking moves. That's the gap the scale factor closes.
The scale factor adjusts:
- Cycle time in the program summary at the top of the Program stage. See The Program stage.
- The time shown for each setup, section and operation in the Program stage, and Cycle time in the operation panel.
- The machining time in the Cycle Time Estimate Report. See Estimate cycle time and export a cycle time report.
It doesn't change toolpaths, feeds, speeds or anything the machine does. It only changes the times CAM Assist reports.
How the scale factor works
| Scale factor | Effect on a 20:00 estimate |
|---|---|
| 100%, or left blank | No change: 20:00 |
| 150% | Multiplied by 1.5: 30:00 |
| 80% | Multiplied by 0.8: 16:00 |
Work out your scale factor
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Open the machine in My Shop > Machines, and set Scale factor under Cycle time adjustment to 100 or leave it blank. See Add or edit a machine in CAM Assist.
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Run CAM Assist on a part you often make on that machine. With every operation included, note the Cycle time in the program summary at the top of the Program stage. This is the CAM Assist estimate.
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Get a reference time you trust for the same part: the cycle time your CAM package reports for the posted program, or a timed run on the machine.
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Convert both times to the same unit, seconds or decimal minutes. For example, 9:36 is 576 seconds, or 9.6 minutes.
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Work out the scale factor:
Scale factor (%) = reference time ÷ CAM Assist estimate × 100
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Enter the result in Scale factor and click Done.
The next time you run CAM Assist with that machine, the estimate should be close to your reference time.
Worked examples
| CAM Assist estimate | Reference time | Calculation | Scale factor |
|---|---|---|---|
| 20:00 | 30:00 (timed on the machine) | 30 ÷ 20 × 100 | 150% |
| 24:00 | 30:00 (from your CAM package) | 30 ÷ 24 × 100 | 125% |
| 12:00 | 9:36 (9.6 minutes) | 9.6 ÷ 12 × 100 | 80% |
| 18:45 (1,125 s) | 22:30 (1,350 s) | 1,350 ÷ 1,125 × 100 | 120% |
If the estimate runs short, the scale factor is above 100%. If it runs long, it's below 100%.
Tips for a reliable scale factor
- Set it per machine. A fast, powerful machine and an older, slower one need different values. That's why the scale factor is stored on the machine.
- Use a typical part. A value tuned on an unusual part won't suit your everyday work.
- Average two or three parts for a steadier number.
- Check it again when you change the machine, your tooling or your approach to feeds and speeds.
- Pick one kind of reference time. A posted CAM package time is the easiest to repeat. A timed run on the machine is the most accurate.
Change the scale factor for one report
The Cycle Time Estimate Report starts with the machine's scale factor (or 100% if it has none). You can change Scale factor in the report for that estimate. In the report it must be at least 1%. To change it for every part, set it on the machine instead.
Other cycle time fields
The machine's Cycle time adjustment section and the Cycle Time Estimate Report also hold times that aren't machining:
| Field | What it is | Where it's set |
|---|---|---|
| Tool change time (MM:SS) | Average time for one tool change on this machine. The report multiplies it by the number of tool changes. | On the machine |
| Set up time / Setup time (MM:SS) | Time to get the machine ready before the first part: loading tools, fixtures and programs, and setting work and tool offsets. Counted once per batch. | On the machine; the report starts with it |
| Part to part time (MM:SS) | Time to unload a finished part and load the next stock. Counted between parts in a batch. | In the report |
| Part quantity | How many parts are in the batch. | In the report |
The report then works out:
- Total non machining time = part quantity × tool change time for part + (part quantity − 1) × part to part time + setup time
- Total time = total non machining time plus the machining time
For the steps, see Estimate cycle time and export a cycle time report.
Questions
What if I leave the scale factor blank? CAM Assist uses 100%, so you see the calculated estimate unchanged.
Can the scale factor be below 100%? Yes. Use a value below 100% when CAM Assist overestimates. On the machine it can't be negative.
Does the scale factor change my program? No. It only changes the cycle times CAM Assist shows and exports.